WO2024136723A1

WO2024136723A1 - A transmission arrangement and control of the transmission arrangement

Info

Publication number: WO2024136723A1
Application number: PCT/SE2023/051249
Authority: WO
Inventors: Mikael Bergquist
Original assignee: Scania Cv Ab
Priority date: 2022-12-21
Filing date: 2023-12-13
Publication date: 2024-06-27
Also published as: SE2251515A1; SE546268C2

Abstract

A transmission arrangement (200) including a first planetary gear (210), including a first ring gear (R1/211), a first sun gear (S1/212), and a first planet gear carrier (C1/213), and a second planetary gear (220), including a second ring gear (R2/221), a second sun gear (S2/222), and a second planet gear carrier (C2/223). A first electrical machine (101) is coupled to the first ring gear, the first sun gear is coupled to the second sun gear, the second electrical machine (102) is coupled to the second ring gear, and the second planet gear carrier is coupled to the at least one drive wheel. The transmission arrangement includes a first freewheel arrangement (231) and a second freewheel arrangement (232) arranged such that: -- when a first rotation direction of the first ring gear is provided: --- the first freewheel arrangement locks the first planet gear carrier against rotation; and --- the second freewheel arrangement allows the first ring gear and the first sun gear to rotate in relation to the first planet gear carrier; and -- when a second opposite rotation direction of the first ring gear is provided: --- the first freewheel arrangement allows the first planet gear carrier to rotate; and --- the second freewheel arrangement locks the first planet gear carrier to one of the first ring gear and the first sun gear.

Description

A TRANSMISSION ARRANGEMENT AND CONTROL OF THE TRANSMISSION ARRANGEMENT Technical field The present invention relates to a vehicle, such as e.g. a truck, a bus, a car, or another type of vehicle, being driven by at least by two electrical machines. The present invention relates in particular to a transmission arrangement, and to methods and control units for controlling the transmission arrangement. The present invention also relates to a computer program and a computer-readable medium that implement the methods according to the present invention. Background The following background description constitutes a description of the background to the present invention, which does not, however, necessarily have to constitute prior art. Many vehicles of today, such as electric and/or hybrid vehicles, comprise one or more electrical machines arranged for driving the vehicle forwards and/or backwards. An electrical machine can, depending on operating conditions of the vehicle, work both as an engine, which provides torque to one or more drive wheels of the vehicle to propel the vehicle, or as a generator, which stores electrical energy in at least one energy storage when braking the vehicle. The electrical machine may therefore comprise and/or be coupled to at least one energy storage, e.g. an electromechanical energy storage. The electrical machine and/or the at least one energy storage may also comprise and/or be coupled to control equipment arranged for controlling a flow of electrical energy between the at least one energy storage and the electrical machine. Hereby, electrical energy is controlled to flow from the electrical machine to the at least one electrical storage when the vehicle is being braked, which is commonly known as regenerative braking. Thus, when the electrical machine is used for regenerative braking, it is used as a generator charging the at least one energy storage by a flow of electrical energy from the electrical machine to the at least energy storage. When the electrical machine is used as an engine to propel the vehicle, on the other hand, electrical energy is controlled to flow from the at least one energy storage to the electrical machine, whereby the electrical machine utilizes the electric energy for producing a torque driving the at least one drive wheel of the vehicle, i.e. for providing a torque at the at least one drive wheel causing it to rotate. Thus, the electrical machine may be controlled to alternate between consuming electrical energy, when driving the at least one drive wheel, and generating electrical energy, when braking the vehicle. An electrical machine generally has a maximum torque which is dependent on its rotational speed. In other words, the maximum torque being providable by an electrical machine is a function of its rotational speed. An electrical machine can generally provide a higher maximum torque at lower rotational speeds, and can provide relatively lower maximum torques at higher rotational speeds, due to its maximum torque function. The maximum torque function may, for example, have a torque plateau for lower rotational speeds, and decreasing maximum torques outside this plateau, e.g. for higher rotational speeds. Thus, without proper gearing, an electrical machine would be able to provide higher torques at lower vehicle speeds, but would only be able to provide lower torques at higher vehicle speeds, i.e. lower torques than it could provide at lower vehicle speeds. Therefore, due to the maximum torque function of the electrical machines, and since a reasonably high torque must be provided also for higher vehicle speeds, some kind of gearing should be provided between the electrical machine and the at least one drive wheel. The gearing should then transform the power of the electrical machine into a desired torque and rotational speed at the at least one drive wheel. Such gearings have in vehicles traditionally been provided by conventional gearboxes. Brief description of the invention Conventional gearboxes are expensive, complex and space consuming. Many mechanical parts, such as gear wheels and shafts, need to be designed to be able interact with each other in complicated and differing ways, in order to provide various gear ratios and corresponding gear shifts. This results in a space consuming gearbox housing, inside of which many of these mechanical parts must be able to move, e.g. both around their respective shafts and in relation to each other. In vehicles having more than one source of power, such as in a vehicle comprising at least two electrical machines, conventional gearboxes would become even larger in size than for the traditional setup with only one engine, because both the complexity and the number of mechanical parts are then increased. Also, a number of mechanical parts of the conventional gearboxes must be controlled for the gearboxes to work at all. For this reason, the gearboxes are conventionally equipped with a number of actuators being used for providing gearshifts. These actuators are arranged to move gear sleeves or the like, thereby causing movements of gear wheels such that various gear wheels engage each other, whereby various gear ratios are provided by the gearboxes, respectively. The movements of these actuators are often achieved by usage of hydraulics and/or pneumatics. Thus, control systems for providing hydraulics and/or pneumatics to move these actuators also have to be included in the conventional gearboxes. These actuators and control systems add to both the size and the complexity of these gearboxes. It is therefore an objective of the present invention to provide a less expensive, smaller, and less complex way to provide a suitable gearing between two electrical machines and at least one drive wheel in a vehicle comprising at least two electrical machines. According to an aspect of the present invention, this objective is achieved by the above-mentioned transmission arrangement for transferring torque between one or more of a first electrical machine and a second electrical machine, and at least one drive wheel of a vehicle, the at least one drive wheel having a positive rotation direction when the vehicle is moving forward; the transmission arrangement including: - a first planetary gear including a first ring gear, a first sun gear, and a first planet gear carrier; and - a second planetary gear including a second ring gear, a second sun gear, and a second planet gear carrier; wherein - the first electrical machine is coupled to the first ring gear; - the first sun gear is coupled to the second sun gear; - the second electrical machine is coupled to the second ring gear; - the second planet gear carrier is coupled to the at least one drive wheel; - a first freewheel arrangement and a second freewheel arrangement are arranged such that: -- when the first electrical machine provides a first rotation direction of the first ring gear, which would cause a negative rotation direction of the at least one drive wheel if the first sun gear would rotate in a first direction equal to the first rotation direction of the first ring gear and if the second ring gear would stand still: --- the first freewheel arrangement locks the first planet gear carrier against rotation; and --- the second freewheel arrangement allows the first ring gear and the first sun gear to rotate in relation to the first planet gear carrier; and -- when the first electrical machine provides a second rotation direction of the first ring gear, being opposite to the first rotation direction: --- the first freewheel arrangement allows the first planet gear carrier to rotate; and --- the second freewheel arrangement locks the first planet gear carrier to one of the first ring gear and the first sun gear. The herein presented transmission arrangement provides for an uninterrupted torque supply to the at least one drive wheel, which is of course useful in many situations. The proposed transmission arrangement uses a first and a second planetary gear, and a second freewheel arrangement, to provide a second operation mode M2, i.e. to provide a second mode of operation M2 for the transmission arrangement. The two planetary gears are coupled together such that a suitable gear ratio for the second operation mode M2 is achieved between the first and second electrical machines and the drive wheels, respectively. The transmission arrangement further uses a first freewheel arrangement to provide a third operation mode M3 for the transmission arrangement. The two planetary gears are coupled together such that a suitable gear ratio for the third operation mode M3 is achieved between the first and second electrical machines and the drive wheels, respectively. The transmission arrangement is controlled to provide the third operation mode M3 simply by controlling the torques and rotational directions provided by the first and second electrical machines. Hereby, an uninterrupted torque may be achieved with few mechanical parts, whereby a small, lightweight and cost effective transmission arrangement is provided. In this document, the modes of operation are sometimes called operation modes or transmission modes, or simply modes, and/or are sometimes denoted with an abbreviation, such as M1, M2, M3, MR and MB. The use of two planetary gears coupled according to this proposed transmission arrangement provides for a solution with low mechanical complexity, which is also considerably less space consuming than a conventional gearbox solution. The present solution, using two planetary gears, involves a lower number of mechanical parts, and therefore reduces the needed size, weight and cost for the transmission arrangement, in relation to a conventional gear box. Also, the control of the present transmission arrangement, utilizing a double planetary gear solution, is less complex than the control of a conventional gearbox. The second freewheel arrangement is coupled to the first planetary gear such that the rotational directions of the first and second electrical machines set up the transmission arrangement for a wanted mode of operation. Such rotational directions include positive rotational directions, negative rotational directions, and standstill of one or more of the first and second electrical machines. For example, different and suitable gear ratios are provided for the second mode of operation M2 and the third mode of operation M3, respectively, when the first and second electrical machines are controlled appropriately. Thus, simply by controlling the torques, rotational speeds and rotational directions of the first and second electrical machines, the transmission arrangement is, due to its inventive design, controllable to provide the wanted modes of operation, and their respective gear ratios, between the first and second electrical machine and the at least one drive wheel. Since modes of operation for the transmission arrangement, and their respective corresponding gear ratios, are achievable simply by controlling the torques and rotational directions provided by the first and second electrical machines, there is according to various embodiments for the herein presented transmission arrangement no need for mechanical actuators conventionally having been used within the gearboxes for physically moving gear sleeves, gear wheels, or the like, at gear shifting. The omission of such conventional actuators, and their respective hydraulic or pneumatic control systems, greatly reduces the complexity and cost of the transmission arrangement, as well as increases the robustness and reliability for the transmission arrangement. Thus, by usage of the herein presented solution, which utilizes two planetary gears coupled as described herein, uninterrupted torque and a large ratio or difference between the highest and the lowest gear ratios, may be achieved with few mechanical parts. Hereby, it is possible to design a small, lightweight and cost- effective transmission arrangement, which is still able to provide the needed difference between the highest and the lowest gear ratios and torque capacities for various vehicle applications, with low control complexity. According to an embodiment of the present invention, the transmission arrangement includes - a third freewheel arrangement coupled between the second electrical machine and the second ring gear, and arranged such that: -- when a first rotation direction would be provided at the third freewheel arrangement, where the first rotation direction would have been the result if the second planet gear carrier would rotate with a rotation direction corresponding to a positive rotation direction at the at least one drive wheel, and the second sun gear would rotate with a rotation direction which would cause the positive rotation direction of the at least one drive wheel if the second ring gear would stand still: --- the third freewheel arrangement locks the second ring gear against rotation; and -- when a second rotation direction is provided at the third freewheel arrangement, being opposite to the first rotation direction: --- the third freewheel arrangement allows the second ring gear to rotate. The third freewheel arrangement makes it possible to provide a first mode M1 of operation with the transmission arrangement, where the first mode M1 supplies a high/maximum torque and a relatively low rotational speed at the at least one drive wheel. The first operation mode M1 may typically be used at takeoff from standstill, or when shunting, such as during parking or in connection with loading of the vehicle. The usage of the third freewheel arrangement in the first operation mode M1, results in an increased freedom in choice regarding the power and/or capacity of the first and electrical machines, respectively. This is possible since the second electrical machine does not itself have to be able to counteract the reaction torque resulting from the first electrical machine in the first mode M1. Instead, if the second electrical machine does not counteract the reaction torque itself, the third freewheel arrangement locks the second ring gear against rotation. Thus, the third freewheel arrangement can by its own counteract the reaction torque. It is therefore possible to use a second electrical machine being weaker, i.e. less powerful, than the first electrical machine, since the third freewheel arrangement locks the second ring gear in the first mode M1 if the second electrical machine is not powerful enough to counteract the reaction torque from the second planetary gear. This increased freedom of choice results in a flexible use of the transmission arrangement, which may be easily adapted to various implementations. The possibility to use a less powerful second electrical machine may also reduce the cost and complexity of the vehicle. According to an embodiment of the present invention, the transmission arrangement includes - a brake coupling arrangement arranged to: -- when a first torque difference provided/present over the brake coupling arrangement acts on the brake coupling arrangement in a first direction which would, if the second ring gear would stand still, result in a forward driving torque on the at least one drive wheel: --- couple the second sun gear to the first electrical machine via the first planetary gear, thereby functionally utilizing the first planetary gear, a first freewheel arrangement and the second freewheel arrangement; and -- when a second torque difference provided/present over the brake coupling arrangement acts on the brake coupling arrangement in a second direction being opposite to the first direction: --- functionally bypass the first planetary gear, and a first arrangement and the second freewheel arrangement. The brake coupling arrangement makes both regenerative braking and backwards driving of the vehicle possible. The brake coupling arrangement is automatically controlled by the torque provided over it, i.e. by the torque difference/direction applied to it. The brake coupling arrangement either utilizes or bypasses the functionality of the first planetary gear and the first and second freewheel arrangements, i.e. does not utilize their functions/features. When the vehicle is braked in the regenerative brake mode MB, or is driven backwards in the reverse mode MR, the brake coupling arrangement functionally bypasses the first planetary gear in the sense that the torque and rotation relationships of the first planetary gear are not utilized/enabled, i.e. the first planetary gear is functionally bypassed/disabled and does not provide any up gearing or down gearing. The second planetary gear, i.e. the second sun gear, is thus functionally coupled directly to the first electrical machine, as if the first planetary gear would not have been located between the first electrical machine and the second planetary gear. In other words, the brake coupling arrangement provides for a 1:1 gearing over the first planetary gear during braking or backwards driving of the vehicle. However, in the forward operation modes, i.e. in the first M1, the second M2 and third M3 operation modes, the brake coupling arrangement does not bypass the first planetary gear, and the above mentioned first and/or second freewheel arrangements. The first planetary gear, and the above mentioned first and/or second freewheel arrangements are thus utilized as described in this document, i.e. the first and/or second freewheel arrangements are used to control the function of the first planetary gear. Based on the rotation direction of the first electrical machine, the first and/or second freewheel arrangements control the first planetary gear such that a 1:1 gearing is utilized for the first M1 and second M2 operation modes, and such that another gearing is utilized in the third operation mode M3. The brake coupling arrangement is a low complexity and low cost device which contributes to the transmission arrangement being able to provide both regenerative braking MB and backward driving MR operation modes. It should especially be noted that, according to some embodiments, no actuators are needed for controlling the brake coupling arrangement, since it is then instead controlled via the control of the first and second electrical machines. More specifically, the brake coupling arrangement, and the whole transmission arrangement, is then controlled by the torques, rotational speeds and rotation directions provided by the first and second electrical machines. According to an embodiment of the present invention, the brake coupling arrangement comprises: - a first shaft coupled to the electrical machine at a first end and to the first ring gear at a second end; - a second shaft coupled to the second sun gear at a second end; and - a sleeve arranged to interact with both the first sun gear and the second shaft, and arranged to be movable between a first and a second position; wherein: -- the sleeve is arranged to be moved towards the first position when the second shaft, by the first torque difference, is rotated in a first direction relative to the sleeve, where the first ring gear, the first sun gear and the first planet gear carrier are unlocked in relation to each other when the sleeve is in the first position, such that the first shaft is coupled to the second shaft via the first ring gear, the first sun gear and the sleeve; and -- the sleeve is arranged to be moved towards the second position when the second shaft, by the second torque difference, is rotated in a second direction relative to the sleeve, where the sleeve locks the first sun gear to the first planet gear carrier, when the sleeve is in the second position, such that the first shaft and the second shaft corotate. By this mechanical implementation of the brake coupling arrangement, a low complexity and automatic brake coupling arrangement is provided, which is controlled simply by the torque, i.e. the first and second torque differences/directions, respectively, being provided over it. The features/characteristics/properties of the first torque difference are such that the relative rotation of the shaft in relation to the sleeve in the first direction is caused by them, and the features/characteristics/properties of the second torque difference are such that the relative rotation of the shaft in relation to the sleeve in the second direction is caused by them. The brake coupling arrangement may hereby either enable or bypass/disable the function of the first planetary gear and the first and/or second freewheel arrangements, as explained above and below, such that regenerative braking in a regenerative brake mode MB, and backwards driving of the vehicle in a reverse mode MR, are made possible. The movement of the sleeve may, according to various embodiments, be provided by spline arrangements comprising e.g. spiral splines, which is a low complexity mechanical solution for which no control logic in addition to the control logic for the first and second electrical machines is necessary. Also, for the first M1, second M2 and third M3 modes of operation, being used for driving the vehicle forward, the herein described utilization of the functionality of the first planetary gear, and the above mentioned first and/or second freewheel arrangements, is enabled by the brake coupling arrangement, whereby these components are utilized as described in this document. According to an embodiment of the present invention, the transmission arrangement includes - a reverse coupling arrangement, arranged at a third freewheel arrangement coupled between the second electrical machine and the second ring gear, and arranged to: -- when a first torque difference provided/present over the reverse coupling arrangement acts on the reverse coupling arrangement in a first direction which would, if the second sun gear would stand still, result in a backward driving torque on the at least one drive wheel: --- decouple the third freewheel arrangement from the second ring gear; and -- when a second torque difference provided/present over the reverse coupling arrangement acts on the reverse coupling arrangement in a second direction being opposite to the first direction: --- couple the third freewheel arrangement to the second ring gear. The reverse coupling arrangement makes it possible to utilize the transmission arrangement for driving the vehicle backwards. The second electrical machine is, by usage of the reverse coupling arrangement, able to help driving the vehicle both forwards and backwards. This is made possible by the presented reverse coupling arrangement. The transmission arrangement is also able to provide the first mode of operation M1 using the third freewheel arrangement mentioned above. This is made possible by the presented reverse coupling arrangement being implemented in the transmission arrangement. The reverse coupling arrangement is automatically controlled by the torque provided over it, i.e. by the torque difference/direction over it, such that the third freewheel arrangement is decoupled from the second ring gear if the torque difference would result in a backwards driving torque on the drive wheels. The locking function of the third freewheel arrangement is thus disabled when the vehicle is driven backwards by the second electrical machine. If the vehicle is not driven backwards, such as in the first M1, second M2 or third M3 operation modes, the third freewheel arrangement is, however, coupled to the second ring gear and the locking function of the third freewheel arrangement is enabled. The reverse coupling arrangement is a low cost mechanical device which contributes to the transmission arrangement being able to provide both forward and backward operation modes. It should especially be noted that, according to an embodiment, no conventional mechanical actuators are needed for controlling the reverse coupling arrangement, since it is then controlled via the control of the first and second electrical machines only. The enabling and disabling of the function of the third freewheel arrangement is thus automatically provided through the torque differences being provided over the reverse coupling arrangement by the first and second electrical machines. Thus, the reverse coupling arrangement does not add to the complexity of the control system. According to an embodiment of the present invention, the reverse coupling arrangement comprises: - a first shaft coupled to the second electrical machine; - a second shaft coupled to the second ring gear; and - a sleeve arranged to be: -- interacting with the first shaft at a first end; -- engaged with the second shaft at a second end; and -- movable between a first and a second position; wherein: - the sleeve is arranged to be moved towards the first position when the first shaft, by the first torque difference, is rotated in a first direction relative to the sleeve, where the second shaft, via the sleeve, is engaged with the first shaft, but is disengaged from the third freewheel arrangement, when the sleeve is in the first position; and - the sleeve is arranged to be moved towards the second position when the first shaft, by the second torque difference, is rotated in a second direction relative to the sleeve, where the second shaft, via the sleeve, is engaged with both the first shaft and the third freewheel arrangement when the sleeve is in the second position. By this mechanical implementation of the reverse coupling arrangement, a low complexity and automatic reverse coupling arrangement is provided, which is controlled simply by the torque, i.e. the torque difference/direction, being provided over it. The reverse coupling arrangement may hereby either enable or disable the function of the third freewheel arrangement. Backwards driving of the vehicle in a reverse mode MR is made possible when the third freewheel arrangement is decoupled/disabled. For other operation modes, such as for the forward first M1, second M2 and third M3 operation modes, the third freewheel arrangement is enabled, i.e. the third freewheel arrangement is then coupled to the second ring gear. The movement of the sleeve, which causes the enabling and disabling of the third freewheel arrangement, may, according to various embodiments, be provided by spline arrangements comprising e.g. spiral splines. This is a torque driven mechanical solution for which no control logic is necessary. According to an embodiment of the present invention, the second freewheel arrangement comprises one in the group of: - a second freewheel arrangement arranged to be able to either lock the first planet gear carrier and the first sun gear to each other, or allow the first planet gear carrier and the first sun gear to rotate in relation to each other; and - a second freewheel arrangement arranged to be able to either lock the first planet gear carrier and the first ring gear to each other, or to allow the first planet gear carrier and the first ring gear to rotate in relation to each other. The second freewheel arrangement may thus be arranged in two different ways, either between the first planet gear carrier and the first sun gear, or between the first planet gear carrier and the first ring gear. An implementation freedom is hereby provided, since the most suitable solution, i.e. the most suitable location of the second freewheel arrangement, may be chosen for the specific implementation of the transmission arrangement. According to an aspect of the present invention, a vehicle comprising the herein described transmission arrangement is presented. A vehicle comprising the transmission arrangement provides for a low complexity transmission solution, which is low at cost and small in size. The herein described first mode M1, second mode M2, third mode M3, regenerative brake mode MB, and reverse mode MR of operation may hereby be utilized with very low control complexity. According to an aspect of the present invention, the objective is achieved by a method for controlling a herein described transmission arrangement for providing a second mode of operation of the transmission arrangement. The method includes: - controlling the first electrical machine to cause the second rotation direction of the first ring gear, whereby: -- the first freewheel arrangement allows the first planet gear carrier to rotate; and -- the second freewheel arrangement locks the first planet gear carrier to one of the first ring gear and the first sun gear; and - controlling the first electrical machine to cause the at least one drive wheel to move in a positive rotation direction; and - controlling the second electrical machine to cause the at least one drive wheel to move in the positive rotation direction. The proposed method for controlling the herein described transmission arrangement provides for a low complexity control. The second operation mode M2, and its corresponding gear ratio, are achievable simply by controlling the torques and rotational directions provided by the first and second electrical machines. Thus, the transmission arrangement may, by simple control of the first and second electrical machines, provide the second operation mode M2. By controlling the torque and rotational directions of the first and second electrical machines, the transmission arrangement, including the second freewheel arrangement, is thus controlled to provide the second operation mode M2. Especially, there is no need for any complex control of mechanical actuators as the ones conventionally being used for moving gear sleeves and/or cog/gear wheels in conventional gearboxes. The mechanical complexity and costs are therefore minimized. Thus, the control method used for controlling the transmission arrangement utilizes the control system already used for controlling the first and second electrical machines, and does thus neither add to the mechanical complexity nor add to the production costs for the vehicle. Hereby, the already existing robust control system used for controlling the first and second electrical machines is adapted for also being used for providing a robust and low- complexity control of the transmission arrangement. According to an embodiment of the present invention, a first mode of operation of the transmission arrangement is provided by: - controlling the first electrical machine to cause the second rotation direction of the first ring gear, whereby -- the first freewheel arrangement allows the first planet gear carrier to rotate; and -- the second freewheel arrangement locks the first planet gear carrier to one of the first ring gear and the first sun gear; and - controlling the first and second electrical machines such that they try to cause the first rotation direction at the third freewheel arrangement; whereby: -- the third freewheel arrangement locks the second ring gear against rotation; and - controlling the first electrical machine to cause the at least one drive wheel to move in a positive rotation direction. By controlling the first and second electrical machines, according to this method embodiment, such that the third freewheel arrangement locks the second ring gear against rotation, and thereby counteracts the reaction torque from the second planetary gear when the first electrical machine provides a torque, the first operation mode M1 is provided. The first operation mode M1 may be useful e.g. at takeoffs or when driving slowly with the vehicle, e.g. by shunting. This control of the transmission arrangement makes it possible to use identical first and second electrical machines, or even to use a second electrical machine being less powerful than the first electrical machine. Hereby, a low cost and flexible vehicle may be produced. According to an embodiment of the present invention, a third mode of operation of the transmission arrangement is achieved by: - controlling the first electrical machine to cause the first rotation direction of the first ring gear, whereby -- the first freewheel arrangement locks the first planet gear carrier against rotation; and -- the second freewheel arrangement allows the first ring gear and the first sun gear to rotate in relation to the first planet gear carrier; - controlling the first electrical machine to cause the at least one drive wheel to move in a positive rotation direction; and - controlling the second electrical machine to cause a positive rotation direction of the at least one drive wheel. According to this embodiment of the method, the transmission arrangement is controlled to provide the third mode M3. The control of the first and second electrical machines is here used for setting the transmission arrangement up for achieving the third mode M3. There is here no need for conventional actuators, which minimizes the mechanical complexity and production costs. According to an embodiment of the present invention, the first electrical machine is, when switching between the second and third modes of operation, controlled to: - switch its rotational speed from a previous rotation direction to a subsequent rotation direction being opposite to the previous rotation direction. According to this embodiment of the method, the transmission arrangement is controlled to switch between the second M2 and third M3 modes. The first electrical machine here switches both rotation direction and torque direction, for causing switching between the second M2 and third M3 modes, while the transmission arrangement continues to provide torque to the at least one drive wheel. Switching between the second M2 and third M3 modes is hereby achieved without conventional actuators and conventional control of such actuators. According to an embodiment of the present invention, the switching from the previous rotation direction to a subsequent rotation direction includes controlling the first electrical machine to: - reduce an absolute value of a rotational speed of the previous rotation direction to zero, while providing a torque having a non-zero absolute value; - switch to the subsequent rotation direction; and - increase the absolute value of the rotational speed of the subsequent rotation direction. Hereby, mode switching, corresponding to conventional gear shifting, between the second mode M2 and the third mode M3 may be easily and smoothly achieved, possibly taking driving comfort into consideration, simply by controlling the electrical machines. The mode switching may thus be performed without actuators and while continuing to provide torque to the at least one drive wheel. According to an embodiment of the present invention, the method further includes providing a regenerative brake mode of operation of the transmission arrangement by: - controlling the first and second electrical machines such that the second torque difference is provided/present over the brake coupling arrangement; whereby -- the first planetary gear, a first freewheel arrangement and the second freewheel arrangement are functionally bypassed by the brake coupling arrangement; and - controlling the first and second electrical machines to brake the vehicle and to thereby generate energy. By this control of the first and second electrical machines, the regenerative brake mode MB is easily provided, without any need for conventional actuator control. In the regenerative brake mode MB, energy is produced by the first and/or second electrical machines during regenerative braking. The energy may then be stored in the at least one energy storage, which may be a combined energy storage for the first and/or second electrical machines, for later use by the first and/or second electrical machines. According to an embodiment of the present invention, the method further includes providing a reverse mode of operation of the transmission arrangement by: - controlling the first and second electrical machines such that the first torque difference is provided/present over the reverse coupling arrangement; whereby -- the third freewheel arrangement is decoupled from the second ring gear; and - controlling the first and second electrical machines such that the vehicle is driven backwards. By this control of the first and second electrical machines, the reverse mode MR is easily provided, without any need for conventional actuator control. Hereby, the vehicle may be driven backwards, which is useful in many situations, such as when shunting. According to an aspect of the present invention, the objective is achieved by a control unit implementing the method and its embodiments described herein. According to an aspect of the present invention, the above-mentioned computer program and computer-readable medium are configured to implement the method and its embodiments described herein. It will be appreciated that all the embodiments described for the method aspects of the invention are applicable also to the control unit aspect of the invention. Thus, all the embodiments described for the method aspects of the invention may be performed by at least one control unit, which may also be a control device, i.e. a device. The control unit and its embodiments have advantages corresponding to the advantages mentioned above for the methods and their embodiments. The transmission arrangement herein described is arranged such that the herein described method aspects and embodiments may be performed by the transmission arrangement, whereby the transmission arrangement then provides corresponding advantages as mentioned for the method aspects and embodiments. Correspondingly, the herein described method aspects and embodiments may control the transmission arrangement such that the herein described transmission arrangement usages are provided, resulting in corresponding advantages. Brief list of figures Embodiments of the invention will be illustrated in more detail below, along with the enclosed drawings, where similar references are used for similar parts, and where: Figure 1 schematically shows an example vehicle, in which embodiments of the present invention may be implemented, Figures 2a-b schematically show some parts of an example vehicle and a transmission arrangement according to some embodiments of the present invention, Figures 3a-b schematically illustrates a brake coupling arrangement according to some embodiments of the present invention, Figures 4a-b schematically illustrates a reverse coupling arrangement according to some embodiments of the present invention, Figure 5 shows a flow chart for a method according to some embodiments of the present the invention, Figure 6 shows a flow chart for a method according to some embodiments of the present the invention, Figure 7 shows a flow chart for a method according to some embodiments of the present the invention, Figures 8a-b show flow charts for methods according to some embodiments of the present the invention, Figure 9 shows a flow chart for a method according to some embodiments of the present the invention, Figure 10 shows a flow chart for a method according to some embodiments of the present the invention, Figures 11a-b show torque and engine speed diagrams for takeoff according to some embodiments of the present the invention, Figures 12a-b show torque and engine speed diagrams for change from first M1 to second M2 modes according to some embodiments of the present the invention, Figures 13a-f show torque and engine speed diagrams for change from second M2 to third M3 modes according to some embodiments of the present the invention, Figures 14a-d show torque and engine speed diagrams for change from third M3 to regenerative brake mode MB according to some embodiments of the present the invention, Figures 15a-b show torque and engine speed diagrams for change to reverse mode MR according to some embodiments of the present the invention, Figure 16 shows a control unit, in which a method according to any one of the herein described embodiments may be implemented. Description of preferred embodiments Figure 1 schematically shows an exemplary heavy vehicle 100, such as a truck or a bus, which will be used to explain the herein presented aspects and embodiments. The embodiments are, however, not limited to use in a vehicle as the one shown in figure 1, but may also be used in other vehicles, such as lighter vehicles, e.g. in smaller trucks or buses, or in cars. A vehicle 100, in which embodiments of the present invention could be implemented and being shown schematically in Figures 1, comprises at least one drive wheel 111, 112, for example a pair of drive wheels, and at least one other pair of wheels. The vehicle 100 furthermore comprises a drivetrain configured to transfer a torque between at least two power sources 101, 102, such as e.g. at least a first 101 and a second 102 electrical machine, and the drive wheels 111, 112. The first electrical machine 101 may also be equipped with, or may be coupled/connected to, at least one energy storage 104, arranged for storing electrical energy e.g. generated by the first electrical machine 101, and for providing electrical energy to the first electrical machine 101 being used for creating torque provided to the at least one drive wheel 111, 112. Correspondingly, the second electrical machine 102 may also be equipped with, or may be coupled/connected to, the at least one energy storage 104, arranged for storing electrical energy provided e.g. by the second electrical machine 102 and/or providing electrical energy to the second electrical machine 102. The at least one energy storage 104 may comprise multiple portions/cells, and may be arranged as a combined energy storage for both the first 101 and second 102 electrical machines, as schematically illustrated in figure 1. The at least one energy storage 104 may also, according to some embodiments, comprise separate energy storages for the first 101 and second 102 electrical machines, such that each one of the first 101 and second 102 electrical machines are equipped with, or may each be coupled/connected to, separate energy storages. A first output shaft/axle 106 of the first electrical machine 101 and a second output shaft/axle 107 of the second electrical machine 102 are coupled, respectively, either directly or indirectly, to a transmission arrangement 200 according to various aspects and embodiments of the present invention. In this document, the notations shaft and axle are both used for describing a rotatable element used for transmitting torque. An output shaft/axle 108 of the transmission arrangement 200 is coupled to the at least one drive wheel 111, 112, either directly or indirectly, possibly via a central gear 109, such as e.g. a differential gear, and/or possibly via first 113 and second 114 drive shafts connected with the central gear 109. The output shaft 108 of the transmission arrangement 200 may be coupled to the at least one drive wheel 111, 112 in essentially any way known for a skilled person, as long as this coupling provides the resulting output torque from the transmission arrangement 200 to the at least one drive wheel 111, 112. Also, the first 101 and second 102 electrical machines, and the transmission arrangement 200, may be arranged essentially anywhere in the vehicle, as long as torque is provided to the at least one drive wheel 111, 112 via the transmission arrangement 200. This could e.g. be closer to the at least one drive wheel 111, 112 than illustrated in Figure 1 and/or without any intermediate central gears 109 or drive shafts 113, 114, as is understood by a skilled person. The transmission arrangement 200 according to the embodiments of the present invention utilizes planetary/epicyclic gears. A planetary gear normally comprises three gear components that are arranged in a manner that allows rotation relative to each other. These components are a sun gear S, a planet wheel carrier C and a ring gear R. Knowledge of the numbers of teeth on the gear components of a planetary gear allows the mutual rates of revolution of the three components during operation to be determined. Generally, the function of a planetary gear is defined by its torque equation/relationship and its rotational speed equation/relationship. These specific functions of two planetary gears are utilized by the embodiments of the present invention, by coupling these two planetary gears together as herein described, thereby forming the presented inventive transmission arrangement 200. Also, some specific features of planetary gears in general are utilized in the transmission arrangement 200. One such feature is that when one of the components, i.e. one of the sun gear S, the planet wheel carrier C and the ring gear R, is prevented to rotate, the other two components are still allowed to rotate. These two components are then rotating at different speeds depending on the cogs/teeth relationship between the two components, whereby, depending on the number of cogs/teeth of the components, respectively, a gear ratio other than 1:1 is provided. For example, if the planet gear carrier C is locked against rotation, then the ring gear R and the sun gear S will rotate with different speeds, and in different rotational directions. Thus, both a shift in rotational direction and a gearing, i.e. a gear ratio, is then provided between the ring gear R and the sun gear S. However, if the ring gear R is instead locked against rotation, then the planet gear carrier C and the sun gear S will rotate with different speeds, but in the same rotational direction. Thus, only a gearing is then provided between the ring gear R and the sun gear S, without any shift in rotational direction taking place. Further, if two of the components, i.e. if any pair of the sun gear S, the planet gear carrier C and the ring gear R, are locked to each other, then all components, i.e. all of the sun gear S, the planet gear carrier C and the ring gear R, will rotate in the same direction and at the same speed. Thus, a gearing 1:1 and no shift in rotational direction takes place between the components of the planetary gear. The transmission arrangement 200, and its utilization of planetary gears, is explained in detail below. Figures 2a-b schematically illustrate a transmission arrangement 200 according to some embodiments of the present invention. The transmission arrangement 200 is arranged for transferring torque between one or more of a first electrical machine 101 and a second electrical machine 102, and at least one drive wheel 111, 112 of the vehicle 100. The at least one drive wheel 111, 112 here rotates in a positive rotation direction Dout_pos when the vehicle is moving forward, as indicated with the symbol “ω +” at the arrow to the right in figures 2a-b. As mentioned above, the transmission arrangement 200 includes a first planetary gear 210 comprising a first ring gear R1/211, a first sun gear S1/212, and a first planet gear carrier C1/213. The transmission arrangement 200 also comprises a second planetary gear 220 including a second ring gear R2/221, a second sun gear S2/222, and a second planet gear carrier C2/223. The first electrical machine 101 is coupled to the first planetary gear 210, more precisely to the first ring gear R1/211 by a shaft 251. The first sun gear S1/212 is coupled to the second planetary gear 220, more precisely to the second sun gear S2/222. The second electrical machine 102 is coupled to the second planetary gear 220, more precisely to the second ring gear R2/221. The second planet gear carrier C2/223 is coupled to the at least one drive wheel 111, 112. Here, and in this whole document, the notation that two entities/components are “coupled” to each other means that these two entities/components are either directly connected to each other, i.e. without any further intermediate entities/components, or are indirectly connected to each other, i.e. via one or more intermediate entities/components. Thus, the two entities/components are then arranged/coupled to be able to transfer a torque between them, either directly or indirectly. Also, in this document, the notation that two entities/components are “engaged” with each other, or are “locked” to each other, means that these entities/components are connected such that they are non-rotatable in relation to each other, i.e. that they are rotatably locked to each other and therefore are arranged to corotate, or to both stand still. Thus, two such engaged/locked entities/components rotate in conjunction with each other, and therefore rotate at the same rate. Conversely, if two entities/components are “unlocked” or “disengaged”, then these entities/components are allowed to rotate in relation to each other. Further, when an entity/component is stated to be “locked” or “engaged” to a housing 235, it is locked/engaged to e.g. a housing of a powertrain component, such as an engine, an electrical machine, a gearbox or another component, or any other fixed, i.e. non-rotating, body, component, entity, arrangement or element. This means that the entity/component is then also fixed, i.e. non-rotating. For example, if an entity/component is locked/engaged to such a non-rotating housing, then this entity/component is prevented from rotating, because the entity/component is non- rotatable in relation to the fixed housing. Further, the notation that an entity/component is “locked” or “locked from/against rotation” means that this entity/component is prevented/restrained/stopped from rotating. Conversely, an “unlocked” entity/component is free to rotate in the meaning that it is released, i.e. is rotatable and not prevented from rotating. The transmission arrangement 200 further comprises a second freewheel arrangement 232 and a first freewheel arrangement 231. A freewheel arrangement is a component which allows rotation in one rotational direction, but prevents/blocks rotation in the opposite rotational direction. Freewheel arrangements may be mechanical components being independent from control logic, as the ones used in e.g. bicycle hubs for allowing the bike to roll freely when the rider stops treading, or may be controllable components, controlled by control logic utilizing e.g. hydraulics and/or pneumatics, for only allowing rotation in one rotational direction. Freewheel arrangements may also be electrically controlled arrangements, e.g. including electric actuators. The first freewheel arrangement 231 is arranged at the first planetary gear 210, such that the first planet gear carrier C1/213 is locked against rotation in a certain rotational direction. The first freewheel arrangement 231 may here e.g. be arranged to lock the first planet gear carrier 213 to the housing 235 of the transmission arrangement 200 when the first planet gear carrier C1/213 tries to rotate in a certain direction, such that the first planet gear carrier C1/213 then is held fixed. More in detail, the first freewheel arrangement 231 is arranged such that it locks the first planet gear carrier C1/213 against rotation when the first electrical machine 101 is controlled such that it provides a first rotation direction DR1_1 of the first ring gear R1/211, where this first rotation direction D_{R1_1} would cause a negative rotation direction Dout_neg of the at least one drive wheel 111,112, if the first sun gear S1/212 would rotate in a first direction DS1_1 equal to the first rotation direction DR1_1 in which the first ring gear R1/211 rotates, provided that the second ring gear R2/221 would stand still, i.e. if the electrical machine 102 would stand still. Thus, if the rotation direction would be unaltered/unchanged/kept between the first ring gear R1/211 and the first sun gear S1/212, and if the second ring gear R2/221 would stand still, then a first rotation direction DR1_1 of the first ring gear R1/211, provided by the first electrical machine 101, and causing a negative rotation direction Dout_neg of the at least one drive wheel 111, 112, should lock the first planet gear carrier C1/213 against rotation. This function is achieved by the first freewheel arrangement 231, which thus prevents the first planet gear carrier C1/213 to rotate under these conditions. Conversely, the first freewheel arrangement 231 is arranged such that it allows the first planet gear carrier C1/213 to rotate when first electrical machine 101 provides a second rotation direction DR1_2 of the first ring gear R1/211, where this second rotation direction DR1_2 is opposite to the first rotation direction DR1_1 of the first ring gear R1/211. The first freewheel arrangement 231 is thus arranged such the first planet gear carrier C1/213 is engaged with the housing 235, such that it blocks/locks/prevents/forbids/counteracts/disallows rotation of the first planet gear carrier C1/213, when the first electrical machine 101 causes the first rotation direction DR1_1 of the first ring gear R1/211, and such that it allows rotation of the first planet gear carrier C1/213 when the first electrical machine 101 causes the second opposite rotation direction D_{R1_2} of the first ring gear R1/211, whereby the first planet gear carrier C1/213 is released/unblocked/unlocked. In other words, the first freewheel arrangement 231 is arranged to allow rotation of the first planet gear carrier C1/213 in only one direction. The second freewheel arrangement 232 is arranged at the first planetary gear 210, such that the first planet gear carrier C1/213 is lockable to one of the first ring gear R1/211 and the first sun gear S1/212. The second freewheel arrangement 232 is then arranged such that the first planet gear carrier C1/213 is locked to either the first ring gear R1/211 or the first sun gear S1/212 when the first ring gear R1/211 would rotate in the second direction DR1_2, where this second direction DR1_2 is opposite to the first rotation direction DR1_1 which would cause the first freewheel arrangement 231 to lock the first planet gear carrier C1/213 against rotation. According to an embodiment, the second freewheel arrangement 232 may be designed as a second freewheel arrangement 232a (illustrated in figure 2a) arranged to be able to either lock the first planet gear carrier C1/213 and the first sun gear S1/212 to each other, or allow the first planet gear carrier C1/213 and the first sun gear S1/212 to rotate in relation to each other. More in detail, the second freewheel arrangement 232a is then arranged such that it allows the first sun gear S1/212 and the first planet gear carrier C1/213 to rotate in relation to each other when the first electrical machine 101 provides the above mentioned first rotation direction DR1_1 of the first ring gear R1/211. On the other hand, the second freewheel arrangement 232a locks the first sun gear S1/212 to the first planet gear carrier C1/213 when the first electrical machine 101 provides the above mentioned second rotation direction DR1_2 of the first ring gear R1/211, being opposite to the first rotation direction DR1_1. According to an embodiment, the second freewheel arrangement 232 may be designed as a second freewheel arrangement 232b (illustrated in figure 2b) arranged to be able to either lock the first planet gear carrier C1/213 and the first ring gear R1/211 to each other, or to allow the first planet gear carrier C1/213 and the first ring gear R1/211 to rotate in relation to each other. The second freewheel arrangement 232b is then arranged such that it allows the first ring gear R1/211 and the first planet gear carrier C1/213 to rotate in relation to each other when the first electrical machine 101 provides the above mentioned first rotation direction D_{R1_1} of the first ring gear R1/211. Conversely, the second freewheel arrangement 232b locks the first ring gear R1/211 to the first planet gear carrier C1/213 when the first electrical machine 101 provides the above mentioned second rotation direction D_{R1_2} of the first ring gear R1/211, being opposite to the first rotation direction DR1_1. The second freewheel arrangement 232 may thus, according to various embodiments, be implemented as one of the two alternative second freewheel arrangements 232a and 232b illustrated in figures 2a and 2b, respectively. Except for the two alternative second freewheel arrangements 232a and 232b, the transmission arrangements 200 shown in figures 2a and 2b are identical. Thus, for any given rotation direction of the first ring gear R1/211, only one of the first 231 and second 232 freewheel arrangements allows the planetary gear components connected to it to rotate freely and/or in relation to each other, whereas the other one locks one or more components. These features of the first planetary gear 210, and of the first 231 and second 232 freewheel arrangements are utilized for providing various modes when using the transmission arrangement 200. Each one of these modes provides a specific gearing, i.e. a specific gear ratio, between the first 101 and/or second 102 electrical machines and the at least one drive wheel 111, 112. The first 101 and/or second 102 electrical machines generate torques, and these torques are in each such mode geared up or down by the transmission arrangement 200 and are provided to the at least one drive wheel 111, 112. A second mode M2 is provided by the transmission arrangement 200 when the first electrical machine 101 is controlled to provide the above defined second rotation direction D_{R1_2} of the first ring gear R1/211. This second rotation direction D_{R1_2} causes the second freewheel arrangement 232 to lock the first planet gear carrier C1/213 together with either of the first sun gear S1/212 (illustrated in figure 2a) and the first ring gear R1/211 (illustrated in figure 2b). Hereby, no shift in rotation direction occurs over the first planetary gear 210, and no gearing takes place, i.e. the gear ratio is 1:1 over the first planetary gear 210. The second rotation direction DR1_2 also causes the first freewheel arrangement 231 to allow the first planet gear carrier C1/213 to rotate. The first sun gear S1/212 is coupled to the second sun gear S2/222 of the second planetary gear 220, whereby the torque T101 and rotation speed ω101 provided from the first electrical machine 101, being non-geared by the 1:1 gear ratio of the first planetary gear 210, is provided to the second planetary gear 220. A reaction torque Treact provided to the second ring gear R2/221 from the second sun gear S2/222 and the second planet gear carrier C2/223 will here be counteracted by the second electrical machine 102, providing a second torque T₁₀₂ and second rotational speed ω102 to the second ring gear R2/221 of the second planetary gear. The at least one drive wheel 111, 112 will therefore be provided with a torque Tout and a positive rotational speed ω_out, being a combination of a second torque T_S2 and a second rotational speed ωS2 of the second sun gear S2/222, originating from the first electrical machine 101 and being geared by the first 210 and second 220 planetary gears, and a second torque T_R2 and a second rotational speed ω_R2 of the second ring gear R2/221, provided from the second electrical machine 102 and being geared by the second planetary gear 220, respectively. The torque T_out at the at least one drive wheel 111, 112 may here have a value between zero and a maximum torque value T_{out_max_M2}, depending on the torques provided by the first 101 and second 102 electrical machines, respectively, and on the setting of the transmission arrangement 200 in the second operation mode M2. As mentioned above, the torques provided by the first 101 and second 102 electrical machines are limited at a certain rotational speed by the maximum torque functions for the first 101 and second 102 electrical machines, respectively. Thus, when utilizing the second operation mode M2, a certain maximum torque T_{out_max_M2} can be provided at the at least one drive wheel 111, 112 for a certain rotational speed ωout of the at least one drive wheel 111, 112, which is lower than a corresponding maximum torque T_{out_max_M1} possible for the first operation mode M1, but is higher than a corresponding maximum torque T_{out_max_M3} possible for the third operation mode M3. Correspondingly, the rotational speed ωout of the at least one drive wheel 111, 112 may here have a value between zero and a maximum rotational speed value ω_{out_max_M2}, depending on the rotational speeds provided by the first 101 and second 102 electrical machines, respectively, and on the setting of the transmission arrangement 200 in the second operation mode M2. Thus, when utilizing the second operation mode M2, a certain maximum rotational speed ω_{out_max_M2} can be provided at the at least one drive wheel 111, 112, which is higher than a corresponding maximum rotational speed ωout_max_M1 possible for the first operation mode M1, but is lower than a corresponding rotational speed ωout_max_M3 possible for the third operation mode M3. Mode Freewheel Freewheel Freewheel Reverse Brake Result 231 232 233 coupling coupling T_{out_max_M2}, 241 242 ω_{out_max_M2}, D_out M2 Released Locked Released Enable No bypass Tout_max_M2: 233 210 Middle ω_{out_max_M2}: Middle Dout: Pos Table: M2 Table “M2” indicates the conditions for the first 231, second 232, and third 233 freewheel arrangements, the reverse coupling arrangement 241 and the brake coupling arrangement 242 for the second mode M2. Table “M2” also indicates the resulting maximum torque Tout_max_M2, maximum rotational speed ωout_max_M2 and rotation direction D_out at the at least one drive wheel 111, 112 in the second mode M2. The functions of the third freewheel arrangement 233, the reverse coupling arrangement 241 and the brake coupling arrangement 242 are explained below. According to an embodiment, the transmission arrangement 200 further includes a third freewheel arrangement 233 (see figures 2a-b) coupled between the second electrical machine 102 and the second ring gear R2/221 of the second planetary gear 210. In figures 2a-b, component 245 indicates that there might be one or more gear wheels arranged between the second ring gear R2/221 and the third freewheel arrangement 233. Thus, the number of gear wheels arranged between the second ring gear R2/221 and the third freewheel arrangement 233 may be zero, or may be an odd or even number of gear wheels. Therefore, the shaft 255 at the third freewheel arrangement 233 may rotate in the same direction or in the opposite direction as the second ring gear R2/221, depending on the number of gear wheels therebetween. The third freewheel arrangement 233 is arranged such that it locks the second ring gear R2/221 against rotation when a first rotation direction D233_1 would be provided at the third freewheel arrangement 233 if it had not been locked, i.e. had been unlocked, against rotation. Thus, essentially immediately when the second ring gear R2/221 tries to rotate the shaft 255 to which the third freewheel arrangement 233 is engaged in this first rotation direction D_{233_1}, the third freewheel arrangement 233 locks the shaft 255 against the housing 235, such that it cannot rotate. The first rotation direction D233_1 is the direction in which the shaft 255 at the third freewheel arrangement 233 would have been rotated if the following two conditions were fulfilled: - the second planet gear carrier C2/223 would rotate with a rotation direction DC2 corresponding to a positive rotation direction Dout_pos at the at least one drive wheel 111, 112; and - the second sun gear S2/222 would rotate with a rotation direction DS2, which would cause the positive rotation direction Dout_pos of the at least one drive wheel 111, 112 if the second ring gear R2/221 would stand still. In other words, if it is assumed that the second ring gear R2/221 would stand still, then a certain rotation direction DS2 of the second sun gear S2/222 would cause the at least one drive wheel 111, 112 to drive the vehicle forward. If the first electrical machine 101 attempts to cause a first rotation direction D_{233_1} at the third freewheel arrangement 233 being the same as this certain rotation direction DS2 of the second sun gear S2/222 (which would cause a positive rotation direction Dout_pos of the at least one drive wheel 111, 112), then the third freewheel arrangement 233 locks the second ring gear R2/221 against rotation. This attempted first rotation direction D233_1 at the third freewheel arrangement 233 may be caused by the first electrical machine 101 when the second freewheel arrangement 232 locks the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212, and when the first electrical machine 101 provides such a high reactional torque Treact at the second ring gear R2/221 that the second electrical machine 102 cannot counteract it itself. The third freewheel arrangement 233 is conversely arranged such that it allows the second ring gear R2/221 to rotate freely when a second rotation direction D233_2 is caused by the second electrical machine 102 at the third freewheel arrangement 233. This second rotation direction D233_2 is opposite to the above defined first rotation direction D233_1. These features of the first planetary gear 210, of the second 232 and third 233 freewheel arrangements, and of the second planetary gear 220, are utilized for providing a first mode M1. The first mode M1 is provided by the transmission arrangement 200 when the first electrical machine 101 is controlled to provide the above defined second rotation direction DR1_2 of the first ring gear R1/211 and to attempt to provide the above defined first rotation direction D233_1 at the third freewheel arrangement 233. This will cause the second freewheel arrangement 232 to lock the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212, and will cause the third freewheel arrangement 233 to lock the second ring gear R2/221 against rotation as well. The torque T101 provided from the first electrical machine 101 then passes through the first planetary gear 210 without being geared, due to the 1:1 gearing of the first planetary gear 210, and is then increased by the gearing of the second planetary gear 220. Correspondingly, the rotational speed ω₁₀₁ is kept unaltered through the first planetary gear 210 and is then reduced by the gearing of the second planetary gear 220. The at least one drive wheel 111, 112 will therefore be provided with a high possible maximum torque T_{out_max_M1} and a low possible maximum positive rotational speed ωout_max_M1 resulting from the torque T101 and the rotational speed ω101 of the first electrical machine 101. The possible maximum torque Tout_max_M1 for the first mode M1 is higher than the corresponding possible maximum torques for the second M2 and third M3 modes Tout_max_M2, Tout_max_M3, and the possible maximum positive rotational speed ωout_max_M1 for the first mode M1 is lower than the possible maximum positive rotational speeds for the second M2 and third M3 modes ωout_max_M2, ω_{out_max_M3}. Mode Freewheel Freewheel Freewheel Reverse Brake Result 231 232 233 coupling coupling T_{out_max_M1}, 241 242 ω_{out_max_M1}, D_out M1 Released Locked Locked Enable 233 No bypass Tout_max_M1: 210 High ω_{out_max_M1}: Low Dout: Pos Table: M1 Table “M1” indicates the conditions for the first 231, second 232 and third 233 freewheel arrangements, the reverse coupling arrangement 241 and the brake coupling arrangement 242 for the first mode. Table “M1” also indicates the resulting possible maximum torque T_{out_max_M1}, possible maximum rotational speed ω_{out_max_M1} and rotation direction D_out at the at least one drive wheel 111, 112 in the first mode M1. The functions of the reverse coupling arrangement 241 and the brake coupling arrangement 242 are explained below. A third mode of operation M3 is provided by the transmission arrangement when the first electrical machine 101 is controlled to provide the above defined first rotation direction DR1_1 of the first ring gear R1/211. This first rotation direction DR1_1 causes the first freewheel arrangement 231 to lock the first planet gear carrier C1/213 against rotation. The first rotation direction D_{R1_1} also causes the second freewheel arrangement 232 to allow the first sun gear S1/212 (illustrated in figure 2a) and the first ring gear R1/211 (illustrated in figure 2b) to rotate in relation to the first planet gear carrier C1/213. Hereby, a shift in rotation direction occurs over the first planetary gear 210, and a gearing of the torque and the rotational speed take place over the first planetary gear 210. Thus, due to the shift in rotation direction over the first planetary gear 210, the first sun gear S1/212 rotates in a direction DS1 being opposite to the rotation direction DR1 of the first ring gear R1/211. Also, there is an increase in rotational speed ω over the first planetary gear, such that the rotational speed ω_S1 of the first sun gear S1/212 is higher than the rotational speed ωR1 of the first ring gear R1/211; ωS1 > ωR1. Further, the torque is decreased by the gearing of the first planetary gear 210, such that the torque T_S1 at the first sun gear S1/212 is lower than the torque T_R1 at the first ring gear R1/211; TS1 > TR1. In the third mode M3, the second electrical machine 102 provides a second torque T_R2 and second rotational speed ω_R2 to the second ring gear R2/221 of the second planetary gear 220, that will contribute to propelling the vehicle 100, together with the torque TS2 and rotational speed ωS2 provided from the first electrical machine 101 to the second sun gear S2/222 via the first planetary gear 210. In order to utilize the first 101 and second 102 electrical machines optimally, these rotational speeds ω_S2, ω_R2 may be balanced. Generally, each one of the first 101 and second 102 electrical machines has an efficiency varying over its rotational speed range, where its maximum efficiency is often provided somewhere around the middle of its rotational speed range. When two electrical machines are used, i.e. when the first 101 and second 102 electrical machines are used, there is only one point of operation which provides a maximum combined power for the two machines together. Thus, maximum power can then only be reached with one specific absolute value of the first rotational speed |ω101| for the first electrical machine 101 in combination with one specific absolute value of the second rotational speed |ω₁₀₂| for the second electrical machine 102. However, for non-maximum combined power, there are a plurality of possible operation points. Thus, various combinations of first |ω101| and second |ω102| absolute values of the rotational speeds for the first 101 and second 102 electrical machines, respectively, may be used to provide non-maximum power. For example, if the first electrical machine 101 runs at an absolute value of the first rotational speed |ω101| being lower than the absolute value of the second rotational speed |ω₁₀₂| of the second electrical machine 102, then the absolute value of the first rotational speed |ω101| of the first electrical machine 101 may be increased. Since the first 101 and second 102 electrical machines are coupled together by the transmission arrangement 200, such an increase of the absolute value of the first rotational speed |ω₁₀₁| would then reduce the absolute value of the second rotational speed |ω₁₀₂| of the second electrical machine 102 at a certain vehicle speed. Thus, an increased absolute value of the first rotational speed |ω101| of the first electrical machine 101 causes a reduction of the absolute value of the second rotational speed |ω102| of the second electrical machine 102. Conversely, a reduced absolute value of the first rotational speed |ω101| of the first electrical machine 101 causes an increase of the absolute value of the second rotational speed |ω₁₀₂| of the second electrical machine 102. It is therefore possible to balance the absolute value of the first rotational speed |ω101| of the first electrical machine 101 and the absolute value of the second rotational speed |ω₁₀₂| of the second electrical machine 102 for a certain vehicle speed, corresponding to a non-maximum combined output power, with the aim of achieving that neither the first 101 nor the second 102 electrical machine has to work at a rotational speed being inefficient or otherwise unsuitable for that electrical machine. As stated above, a non-maximum combined power may be provided by various combinations of absolutes value of the first rotational speed |ω101| of the first electrical machine 101 and the second rotational speed |ω₁₀₂| of the second electrical machine 102. The combined efficiency for these various combinations may be determined, e.g. by suitable calculations, and a combination that provides for high combined efficiency, e.g. a maximum combined efficiency, for the first 101 and second 102 electrical machines may be chosen. In comparison to the second mode M2, the at least one drive wheel 111, 112 will in the third mode M3 thus be provided with a lower possible maximum torque Tout_max_M3 and a higher possible maximum positive rotational speed ω_{out_max_M3}, being combinations of a first torque T101 and a first rotational speed ω101 originating from the first electrical machine 101, and a second torque T102 and a second rotational speed ω₁₀₂ originating from the second electrical machine 102, respectively. The possible maximum output torque Tout_max_M3 for the third mode M3 is thus also lower than the corresponding possible maximum torque Tout_max_M1 for the first mode M1, and the possible maximum positive output rotational speed ω_{out_max_M3} for the third mode M3 is higher than the corresponding possible maximum positive rotational speed ω_{out_max_M1} for the first mode M1. Mode Freewheel Freewheel Freewheel Reverse Brake Result 231 232 233 coupling coupling T_out, ω_out, 241 242 D_out M3 Locked Released Released Enable No bypass Tout_max_M3: 233 210 Low ω_{out_max_M3}: High Dout: Pos Table: M3 Table “M3” indicates the conditions for the first 231, second 232, and third 233 freewheel arrangements, the reverse coupling arrangement 241 and the brake coupling arrangement 242 for the third mode M3. Table “M3” also indicates the resulting maximum torque T_{out_max_M3}, maximum rotational speed ω_{out_max_M3} and rotation direction D_out at the at least one drive wheel 111, 112 in the third mode M3. The functions of the reverse coupling arrangement 241 and the brake coupling arrangement 242 are explained below. According to an embodiment, the transmission arrangement 200 further includes a brake coupling arrangement 242 illustrated in figures 2a-b. The brake coupling arrangement 242 is arranged to couple the second sun gear S2/222 to the first electrical machine 101 via the first planetary gear 210, thereby functionally utilizing the first planetary gear 210, and the first 231 and second 232 freewheel arrangements, when a first torque difference T242_diff_1 provided over the brake coupling arrangement 242 acts on the brake coupling arrangement 242 in a first direction D_{242_1}. This first torque difference T_{242_diff_1} in the first direction D_{242_1} over the brake coupling arrangement 242 would, if the second ring gear R2/221 would stand still, result in a forward driving torque T_forward on the at least one drive wheel 111, 112. The brake coupling arrangement 242 is also arranged to functionally bypass the first planetary gear 210, and the first 231 and second 232 freewheel arrangements, when a second torque difference T242_diff_2 provided over the brake coupling arrangement 242 acts on the brake coupling arrangement 242 in a second direction D242_2 opposite to the first direction D_{242_1}. Hereby, the brake coupling arrangement 242 makes it possible for the first electrical machine 101 to brake the vehicle in the regenerative brake mode MB, and to assist the second electrical machine 102 in the reverse mode MR. Thus, the brake coupling arrangement 242 is, according to the embodiment, arranged to couple the second sun gear S2/222 to the first electrical machine 101 via the first planetary gear 210, when a first torque difference T_{242_diff_1} is provided over the brake coupling arrangement 242. This first torque difference T_{242_diff_1} would, if the second ring gear R2/221 would stand still, result in a forward driving torque Tforward on the at least one drive wheel 111, 112. In other words, if the torque over the brake coupling arrangement 242 is a torque attempting to move the vehicle forward, if the second ring gear R2/221 would stand still, then the first planetary gear 210, and the first 231 and second 232 freewheel arrangements will be functionally utilized, as herein described. If the first planetary gear 210 is initially functionally bypassed (as described below) when this occurs, then the second sun gear S2/222 goes from being coupled to the first electrical machine 101, without using the functionality of the intermediate first planetary gear 210, to being coupled to the first electrical machine 101 via the intermediate first planetary gear 210, thereby using the functionality of the first planetary gear 210. Hereby, the brake coupling arrangement 242 makes it possible for the first electrical machine 101 to drive the vehicle forward in the above described first M1, second M2 and third M3 modes. The brake coupling arrangement 242 is further arranged to functionally bypass the first planetary gear 210, and the first 231 and second 232 freewheel arrangements, when a certain second torque difference T242_diff_2 is provided over the brake coupling arrangement 242. Thus, the brake coupling arrangement 242 is able to couple the second sun gear S2/222 to the first electrical machine 101 without functionally utilizing the first planetary gear 210, and the first 231 and second 232 freewheel arrangements, if the second torque difference T242_diff_2 is provided over the brake coupling arrangement 242. In this document, bypassing the first planetary gear 210, not functionally utilizing the first planetary gear 210, and functionally disabling the first planetary gear 210 are three ways of expressing the same thing, i.e. that the up- and down-gearing properties of the first planetary gear 210 are not used. Such bypassing may be achieved e.g. by causing all the components of the planetary gear to corotate with the same rotational speed, such that there is a 1:1 rotational relationship between each of the components. In other words, when the first planetary gear 210 is not functionally utilized/enabled, it does not provide an up-gearing or a down-gearing, and instead provides a 1:1 gearing, since all of the first ring gear R1/211, the first sun gear S1/212 and the first planet gear carrier C1/213 corotate. Correspondingly, to bypass, or to not functionally utilizing, the first 231 and second 232 freewheel arrangements means that the functionality of the first 231 and second 232 freewheel arrangements is disabled, such that they cannot block rotations in any direction. The second torque difference T242_diff_2 acts on the brake coupling arrangement 242 in a second direction D242_2, which is opposite to the above mentioned first direction D_{242_1}. Thus, the second torque difference T_{242_diff_2} occurs when the vehicle is being regeneratively braked or is driven backwards, i.e. when a non-forward driving torque Tnon-forward is provided to the drive wheels 111, 112. If the brake coupling arrangement 242 experiences this second torque difference T242_diff_2, then the first planetary gear 210, and the first 231 and second 232 freewheel arrangements are bypassed functionally by the brake coupling arrangement 242, as schematically indicated by the dashed line 244 from the brake coupling arrangement 242 to the first electrical machine 101 and the first ring gear R1/211 in figures 2a-b. Since the first ring gear R1/211 is coupled to the first electrical machine 101, the second sun gear S2/222 is hereby, i.e. by this functional bypass 244, coupled to the first electrical machine 101. Thus, the second planetary gear 220 is then coupled to the first electrical machine 101, without functionally utilizing the first planetary gear 210, and the first 231 and second 232 freewheel arrangements. The use of the brake coupling arrangement 242 hereby makes regenerative braking possible, since it solves the problem that the first planet gear carrier C1/213 would otherwise rotate freely. Thus, if the brake coupling arrangement 242 had not been arranged in the transmission arrangement 200 in this way, such free rotation of the first planet gear carrier C1/213 would occur when a non-forward driving torque Tnon- _forward is provided on the at least one drive wheel 111, 112, i.e. when the second torque difference T242_diff_2 is provided over the brake coupling arrangement 242. This is because of the fact that the first planet gear carrier C1/213 is in this direction not capable to counteract the torque provided from the second sun gear S2/222. The first planet gear carrier C1/213 is in other words not prevented to rotate in this direction, and would thus spin freely. In other words, depending on the direction of the torque, i.e. the difference in torque, over the brake coupling arrangement 242, the brake coupling arrangement 242 switches between coupling the second sun gear S2/222 to the first sun gear S1/212 and coupling the second sun gear S2/222 to the first ring gear R1/211 and the first electrical machine 101. The brake coupling arrangement hereby switches between functionally enabling/utilizing or functionally disabling/bypassing 244 the first planetary gear 210, respectively. By usage of the brake coupling arrangement 242, the first electrical machine 101 will be able to perform regenerative braking of the vehicle 100, whereby electrical energy may be stored in the at least one energy storage 104. The second electrical machine 102 will also be able to perform regenerative braking of the vehicle 100, whereby electrical energy may be stored in the at least one energy storage 104. Thus, the first 101 and the second 102 electrical machines may then regeneratively brake the vehicle, possibly all the way down to a rotational speed of zero, i.e. to a speed of 0 km/h, i.e. to standstill. According to an embodiment, regenerative braking is achieved by controlling the first 101 and second 102 electrical machines such that the second torque difference T242_diff_2 in the second direction D242_2 occurs over the brake coupling arrangement 242. The brake coupling arrangement 242 hereby functionally bypasses the first planetary gear 210 and couples the first electrical machine 101 to the second planetary gear 220, i.e. to the second sun gear S2/222, without functionally utilizing the first planetary gear 210 and its first 231 and second 232 freewheel arrangements. The second electrical machine 102 is also coupled to the second planetary gear 220, i.e. to the second ring gear R2/221. By the control of the first 101 and second 102 electrical machines, both of the first 101 and second 102 electrical machines may be used for regeneratively braking the vehicle 100. In the regenerative brake mode MB, a braking torque Tout is provided at the at least one drive wheel 111, 112, such that their rotation speed ω_out in the positive rotation direction D_out may be decreased if the vehicle should be retarded. Mode Freewheel Freewheel Freewheel Reverse Brake Result 231 232 233 coupling coupling T_out, ω_out, 241 242 D_out MB N.A. N.A. Released Enable 233 Bypass 210 Tout: (Bypassed) (Bypassed) Braking ω_out: Possibly ↓ Dout: Pos Table: MB Table “MB” indicates the conditions for the first 231, second 232 and third 233 freewheel arrangements, the reverse coupling arrangement 241 and the brake coupling arrangement 242 for the regenerative brake mode MB. Table “MB” also indicates the resulting torque T_out, rotational speed ω_out and rotation direction D_out at the at least one drive wheel 111, 112 in regenerative brake mode MB. The function of the reverse coupling arrangement 241 is explained below. In figures 3a-b, some embodiments of the brake coupling arrangement 242 are schematically illustrated. The brake coupling arrangement 242 comprises a first shaft 310, which, when implemented in the transmission arrangement 200, is coupled to the electrical machine 101 at a first end 311 and to the first ring gear R1/211 at a second end 312. The brake coupling arrangement 242 further comprises a second shaft 320 coupled to the second sun gear S2/222 at a second end 323. The brake coupling arrangement 242 also comprises a sleeve 330 arranged to interact with both the first sun gear S1/212 and the second shaft 320. The sleeve 330 is arranged to be movable between a first position 337 illustrated in figure 3a, and a second position 338 illustrated in figure 3b. More in detail, the sleeve 330 is arranged to be moved towards the first position 337 when the second shaft 320, by the first torque difference T_{242_diff_1}, is rotated in a first direction ΔD_{320_330_1} relative to the sleeve 330. In this first position 337, the first ring gear R1/211, the first sun gear S1/212 and the first planet gear carrier C1/213 are unlocked in relation to each other. The first shaft 310 is coupled to the second shaft 320 via the first ring gear R1/211, the first sun gear S1/212, and the sleeve 330. Thus, the first planetary gear 210 is functionally utilized when the sleeve 330 is in the first position 337, such that the first shaft 310 is coupled to the second shaft 320 via the first ring gear R1/211, the first sun gear S1/212, and the sleeve 330. Conversely, the sleeve 330 is arranged to be moved towards the second position 338 when the second shaft 320, by the second torque difference T242_diff_2, is rotated in a second direction ΔD_{320_330_2} relative to the sleeve 330. According to the embodiment illustrated in figure 3b, the sleeve 330 then locks the first sun gear S1/212 to the first planet gear carrier C1/213 in the second position 338. Hereby, since the first sun gear S1/212 and the first planet gear carrier C1/213 are locked together, the first planetary gear 210 provides a 1:1 gearing such that all of the first ring gear R1/211, the first sun gear S1/212, and the first planet gear carrier C1/213 corotate. The second shaft 320 is, via the sleeve 330, engaged with the first sun gear S1/212, which means that it also corotates with the first ring gear R1/211 due to the 1:1 gearing. Thus, the second shaft 320 also corotates with the first shaft 310, which is engaged with the first ring gear R1/211. Thus, the first planetary gear 210 is functionally bypassed when the sleeve 330 is in the second position 338. As explained above, when the coupling arrangement shown in figures 3a-b is utilized in the transmission arrangement 200 as a brake coupling arrangement 242, the first shaft 310 is coupled to the first ring gear R1/211 and to the first electrical machine 101, and the second shaft 320 is coupled to the second sun gear S2/222. The sleeve 330 is movable between the first 337 and second 338 positions, as explained above. The sleeve 330 moves towards the first position 337, which in this document means both that it moves in the direction of the first position 337, and that it may also reach and stay at the first position 337, when the second shaft 320 rotates in a first direction ΔD320_330_1 in relation to the sleeve 330. This relative rotation of the second shaft 320 in the first direction ΔD320_330_1, in relation to the sleeve 330, is in the transmission arrangement 200 caused by a first torque difference T_{242_diff_1} being present over the brake coupling arrangement 242. Thus, if the first torque difference T_{242_diff_1} is present over the brake coupling arrangement 242, this causes the second shaft 320 to rotate in a first direction ΔD320_330_1 in relation to the sleeve 330, and therefore causes the sleeve 330 to move towards the first position 337. The first torque difference T242_diff_1 acts on the brake coupling arrangement 242 in a first direction D242_1, which would, if the second ring gear R2/221 would stand still, result in a forward driving torque T_forward on the at least one drive wheel 111, 112. When being implemented in the transmission arrangement 200, the brake coupling arrangement 242 in the first position 337 then functionally utilizes the first planetary gear 210 and the first 231 and second 232 freewheel arrangements. Conversely, the second torque difference T_{242_diff_2} acts on the brake coupling arrangement 242 in a second direction D242_2, which would, if the second ring gear R2/221 would stand still, result in a non-forward driving torque Tnon-forward on the at least one drive wheel 111, 112. Thus, the second torque difference T_{242_diff_2} would, if the second ring gear R2/221 would stand still, result in a braking torque Tbrake or a backward driving torque Tbackward on the at least one drive wheel 111, 112. In the transmission arrangement 200, this second torque difference T_{242_diff_2} being present over the brake coupling arrangement 242 causes the above mentioned relative rotation of the second shaft 320 in the second direction ΔD320_330_2. The sleeve 330 moves towards the second position 338, which in this document includes both that it moves in the direction of the second position 338 and that it also may reach, and stay at, the second position 338, when the second shaft 320 rotates in the second direction ΔD320_330_2 in relation to the sleeve 330, i.e. when the above mentioned second torque difference T_{242_diff_2} is present over the brake coupling arrangement 242. In other words, when implemented in the transmission arrangement 200, the brake coupling arrangement 242 functionally bypasses the first planetary gear 210 when the second torque difference T242_diff_2 acts on the brake coupling arrangement 242, i.e. when the second shaft 320 rotates in the second direction ΔD320_330_2 in relation to the sleeve 330. As mentioned above, figures 3a-b illustrate various possible embodiments for the brake coupling arrangement 242, and figures 2a-b show a possible implementation of the brake coupling arrangement 242 in the transmission arrangement 200. Figure 3a shows an embodiment of the brake coupling arrangement 242 in the first position 337, in which the first planetary gear 210 is functionally engaged/utilized. Figure 3b shows the brake coupling arrangement 242 in the second position 338, in which the first planetary gear 210 is functionally bypassed. As shown in figures 3a-b, the first shaft 310, the sleeve 330 and the second shaft 320 are, according to an embodiment, arranged coaxially in relation to an axis 313. The first shaft 310, the sleeve 330 and the second shaft 320 are also arranged rotatable around that axis 313. Thus, all of the input shaft 310, the sleeve 330 and the second shaft 320 are coaxially arranged to be rotatable. The first shaft 310 and the second shaft 320 are axially fixed, whereas the sleeve 330 is axially movable between the first position 337 and the second position 338. According to an embodiment, the sleeve 330 at least partially surrounds a first end 322 of the second shaft 320. The sleeve 330 further comprises a first spline arrangement 331, arranged to interact with a component spline arrangement 341, which is arranged on, or coupled to, the first sun gear S1/212. The first spline arrangement 331 and the component spline arrangement 341 are here either both axially oriented, as illustrated in the figures, or are both spiral splines. The sleeve 330 further comprises a second spline arrangement 332 arranged to interact with a shaft spline arrangement 321 arranged at the first end 322 of the second shaft 320. The second spline arrangement 332 and the shaft spline arrangement 321 are here both spiral splines. For those embodiments wherein both of the first spline arrangement 331 and the second spline arrangement 332 are spiral splines, these two spiral splines are arranged in mutually different directions. Thus, if the first spline arrangement 331 comprises a spiral spline having a right-hand thread, then the second spline arrangement 332 comprises a spiral spline having a left-hand thread, or vice versa. The directions of the component spline arrangement 341 and the shaft spline arrangement 321 are arranged accordingly, such that they are complementary to the first spline arrangement 331 and the second spline arrangement 332, respectively. According to a non-limiting example shown in figures 3a-b, the first spline arrangement 331 may be arranged on the inside of the sleeve to engage with the component spline arrangement 341 arranged on the outside of the first sun gear S1/212, or on the outside of a component coupled to the first sun gear S1/212. Thus, the component spline arrangement 341 may be a part of the first sun gear S1/212 itself, or may arranged on a component coupled to the first sun gear S1/212. According to an embodiment, the interaction between the shaft spline arrangement 321 and the second spline arrangement 332, both being spiral splines, causes the above described movements of the sleeve. Thus, this interaction causes the movement of the sleeve 330 towards the first position 337, when the second shaft 320, relative to the sleeve 330, rotates in the first direction ΔD320_330_1. Conversely, the interaction causes the movement towards the second position 338, when the second shaft 320, relative to the sleeve 330, rotates in the second direction ΔD320_330_2. According to an example embodiment shown in figures 3a-b, the second spline arrangement 332 is arranged on the inside of the sleeve 330 to interact with the shaft spline arrangement 321 being arranged on the outside of the second shaft 320. According to another non-limiting example embodiment, which is not shown in figures 3a-b, the second shaft 320 is at its first end 322 provided with a circular hollow section, at least partially surrounding the sleeve 330, which has a diameter such that the sleeve 330 fits within the hollow section. The second spline arrangement 332 is then arranged on the outside of the sleeve 330 to interact with the shaft spline arrangement 321 being arranged on the inside of the hollow section of the second shaft 320. According to various embodiments, the first spline arrangement 331 and the second spline arrangement 332, respectively, may be arranged at the first end 335 of the sleeve, at the second end 333 of the sleeve, at least partially between the first 335 and second 333 ends of the sleeve, or from the first end 335 to the second end 333 of the sleeve. According to an embodiment, the interaction between the shaft spline arrangement 321 and the second spline arrangement 332 utilizes a momentum of inertia of the first planetary gear 210 for causing the movement of the sleeve 330 towards the first position 337. Here, the sleeve 330 may be helped to start moving by providing an increased torque on the second shaft 320, e.g. by a torque pulse or another suitable torque increase provided by the second electrical machine 102. Such a torque pulse causes, due to the momentum of inertia, the relative rotation of the second shaft 320 in relation to the sleeve 330, since the sleeve 330 is held by the momentum of inertia of the first planetary gear 210 via the interaction of the first spline arrangement 331 and the component spline arrangement 341. Thus, the components of the first planetary gear 210 do, due to the inertia of the first planetary gear 210, not move immediately when the torque is increased, e.g. as a pulse, via the second shaft 320, which causes the rotation of the second shaft 320 in the first direction ΔD_{320_330_1} relative to the sleeve 330, and thus causes the movement of the sleeve 330. According to an embodiment, the first spline arrangement 331 and the component spline arrangement 341 are also spiral splines. Hereby, the interaction between the first spline arrangement 331 and the component spline arrangement 341 contributes to the movement of the sleeve 330 towards the first position 337, due to the rotation of the second shaft 320 in the first direction ΔD_{320_330_1} relative to the sleeve 330, when the sleeve 330 has reached a third position, between the first 337 and second 338 positions. In this third position, the sleeve 330 is disengaged from the first planet gear carrier C1/213, i.e. the sleeve 330 lets the first planet gear carrier C1/213 loose. Also, the interaction between the first spline arrangement 331 and the component spline arrangement 341 contributes to the movement of the sleeve 330 towards the second position 338, when the second shaft 320 rotates in the second direction ΔD320_330_2 in relation to the sleeve 330. According to an embodiment, the interaction between the first spline arrangement 331 and the component spline arrangement 341 also utilizes the above mentioned momentum of inertia of the first planetary gear 210 when it contributes to the movement of the sleeve 330 towards the second position 338. As explained above, a torque pulse provided on the second shaft 320 may here be used, together with the momentum of inertia, for causing the rotation in the second direction ΔD320_330_2 in relation to the sleeve 330 and thus for causing the movement towards the second position 338. According to some embodiments, the first planet gear carrier C1/213 comprises, or is coupled to, at least one component engaging member 314, and the sleeve 330 comprises, or is coupled to, at least one sleeve engaging member 334. These at least one component engaging member 314 and the at least one sleeve engaging member 334, respectively, are arranged to be engaged with each other in the second position 338, and to be disengaged from each other, i.e. to let loose, when the sleeve 330 is in the third position, between the first 337 and second 338 positions. Thus, the at least one component engaging member 314 and the at least one sleeve engaging member 334, are arranged to, when the sleeve 330 moves towards the second position 338, become engaged in the third position and to then be engaged in the second position 328. Conversely, when the sleeve 330 moves towards the first position 337, the at least one component engaging member 314 and the at least one sleeve engaging member 334 are arranged to become disengaged in the third position and to then be disengaged in the first position 237. As shown in figure 3a-b, such at least one component engaging member 314 and at least one sleeve engaging member 334 may include coupling cogs arranged on, or coupled to, the first planet gear carrier C1/213 and the sleeve 330, respectively. According to an embodiment, the first planet gear carrier C1/213 comprises component coupling cogs 314 arranged at its second end 315 towards the sleeve 330. Also, the sleeve 330 comprises corresponding sleeve coupling cogs 334 at its first end 335 towards the first planet gear carrier C1/213. These component 314 and sleeve 334 coupling cogs are arranged to be complementary and to be engaged with each other in the second position 338, and to be disengaged, i.e. to let loose from each other, when the sleeve 330 is in the third position, and thus to also be disengaged in the first position 337. Depending on the axial position of the sleeve 330 in relation to the first planet gear carrier C1/213, the component and the sleeve coupling cogs are either engaged or disengaged. In this document, the notation complementary cogs means that the two cogs are matching each other, such that the two cogs can interact/cooperate with each other. According to an alternative embodiment not shown in figures 3a-b, the at least one component engaging member 314 and at least one sleeve engaging member 334 may include spline arrangements being axially oriented on the first planet gear carrier C1/211 and the sleeve 330, respectively. Thus, according to this embodiment, complementary axially oriented splines are arranged on the first planet gear carrier C1/213 and on the sleeve 220, respectively, instead of the above mentioned component 314 and sleeve 334 coupling cogs. In this document, the notation complementary splines means that the two splines are matching each other, such that the two splines can interact/cooperate with each other. Thus, there are, according to various embodiments, a number of ways possible for engaging and disengaging the first planet gear carrier C1/213 and the sleeve 330 to and from each other, respectively. In the first position 337 of the sleeve 330 shown in figure 3a, the sleeve engaging member 334 is disengaged from the component engaging member 314. Also, the second shaft 320 is, via the sleeve 330, coupled to the first sun gear S1/212, i.e. via the interaction of the first spline arrangement 331 and the component spline arrangement 341, and via the interaction of the second spline arrangement 332 and the shaft spline arrangement 321. Thus, in the position 337, the first electrical machine 101 is coupled to the second planetary gear 220 via the functionally utilized first planetary gear 210. In the second position 338 of the sleeve 330 shown in figure 3b, the sleeve engaging member 334 is engaged with the component engaging member 314, such that the first sun gear S1/212 is locked to the first planet gear carrier C1/213 via the sleeve. Therefore, the first planetary gear 210 is functionally bypassed, because it only provides a 1:1 gearing, and does not provide any up- or down-gearing of the torque transferred between the first electrical machine 101 and the second planetary gear 220. Thus, the input shaft 310 and the output shaft 320 are engaged via the sleeve 330 and the corotating components of the first planetary gear 210, such that they move together, i.e. corotate. The sleeve 330 may further, according to some embodiments, comprise at least one stopper arrangement, which is arranged for stopping the sleeve 330 in the first position 337 and/or in the second position 338. For example, two or more stoppers may be arranged such that movements of the sleeve 330 beyond the first 337 and/or second 338 positions are prevented. The above described first freewheel arrangement 231 and second freewheel arrangement 323; 232a are also schematically illustrated in figures 3a-b. The first freewheel arrangement 231 is, in this non-limiting embodiment, arranged between the first planet gear carrier C1/213 and the housing 235, whereas the second freewheel arrangement 232; 232a is arranged between the first sun gear S1/212 and the first planet gear carrier C1/213. As mentioned above in connection with figure 2b, the second freewheel arrangement 232 may, according to an embodiment not shown in figures 3a-b, alternatively be implemented as a freewheel arrangement 232b between the first ring gear R1/211 and the first planet gear carrier C1/213. Thus, In the first position 337 of the sleeve 330 shown in figure 3a, the sleeve coupling cogs 334 are disengaged from the component coupling cogs 314, i.e. the sleeve 334 and component 314 engaging members are disengaged. Also, the second shaft 320 is, via the sleeve 330, engaged/coupled to the first sun gear S1/212, i.e. via the interaction of the first spline arrangement 331 and the component spline arrangement 341, and via the interaction of the second spline arrangement 332 and the shaft spline arrangement 321. Thus, in the position shown in figure 3a, the first electrical machine 101 is coupled to the second planetary gear 220 via the first planetary gear 210. More in detail, the first electrical machine 101 is coupled to the first ring gear R1/211 of the first planetary gear 210. The first sun gear S1/212 of the first planetary gear 210 is further, by the brake coupling arrangement 242, coupled to the second sun gear S2/222 of the second planetary gear via the sleeve 330 and the second shaft 320. Torque may hereby be provided from the first electrical machine 101, through the first planetary gear 210, to the second planetary gear 220, i.e. by functionally utilizing the first planetary gear 210. Conversely, in the second position 338 of the sleeve 330 shown in figure 3b, the sleeve coupling cogs 334 are engaged with the component coupling cogs 314, i.e. the sleeve 334 and component 314 engaging members are engaged, such that the first sun gear S1/212 and the first planet gear carrier C1/213 are locked to each other via the sleeve 330. Thus, the input shaft 310 and the output shaft 320 are engaged via the sleeve 330 and the first planetary gear 210, since all components of the first planetary gear 210 then corotate due to its 1:1 gearing. Hereby, the input shaft 310 and the output shaft 320 move together, i.e. corotate. Since the input shaft 310 is coupled to the first ring gear R1/211 and to the first electrical machine 101, the second planetary gear 220 is here coupled to the first electrical machine 101 in this position without functionally utilizing the first planetary gear 210. Thus, the first planetary gear 210 is functionally bypassed and does not provide any up- or down- gearing of the torque transferred between the first electrical machine 101 and the second planetary gear 220. According to another embodiment, the brake coupling arrangement 242 is an actuator-controlled coupling arrangement. The coupling arrangement 242 is then controlled by at least one actuator to couple the the second sun gear S2/222 of the second planetary gear to the first sun gear S1/212, thereby functionally utilizing the first planetary gear 210, when the first torque difference T_{242_diff_1} present over the brake coupling arrangement 242. Correspondingly, the coupling arrangement 242 is then controlled by the at least one actuator to functionally bypass the first planetary gear 210, when the second torque difference T242_diff_2 is present over the brake coupling arrangement 242. The at least one actuator is, according to this embodiment, controlled by a control system, for example the control system arranged for controlling the transmission arrangement 200. The at least one actuator may e.g. be moved by usage of hydraulics and/or pneumatics, and/or may be an electric actuator. According to an embodiment, the transmission arrangement 200, schematically illustrated in figures 2a-b, further includes a reverse coupling arrangement 241, arranged at the third freewheel arrangement 233. The reverse coupling arrangement 241 is arranged to decouple the third freewheel arrangement 233 from the second ring gear R2/221 when a first torque difference T241_diff_1 present over the reverse coupling arrangement 241 acts on it in a first direction D241_1 which would, if the second sun gear S2/222 would stand still, result in a backward driving torque T_backward on the at least one drive wheel 111, 112. Conversely, the reverse coupling arrangement 241 is arranged to couple the third freewheel arrangement 233 to the second ring gear R2/221 when a second torque difference T241_diff_2 present over the reverse coupling arrangement 241 acts on it in a second direction D241_2, which is opposite to the first direction D241_1. Thus, the transmission arrangement 200 here includes a reverse coupling arrangement 241 arranged at the third freewheel arrangement 233. More in detail, the reverse coupling arrangement 241 is arranged at the shaft 255, which the third freewheel arrangement may 233 lock or release, and is arranged adjacent to the third freewheel arrangement 233. It should be noted that the first torque difference T241_diff_1 herein defined, which would, if the second sun gear S2/222 would stand still, result in that the vehicle 100 is driven backwards, would be created by the second electrical machine 102. Since the first electrical machine 101, according to the definition, would stand still, which would obviously be the case if the second sun gear S2/222 would stand still, the torque over the reverse coupling arrangement 241 may only be caused by the second electrical machine 102. In other words, the first torque difference T_{241_diff_1} and the direction with which it acts on the reverse coupling arrangement 241 would here be caused by the second electrical machine 102. When the third freewheel arrangement 233 is decoupled from the second ring gear R2/221, the third freewheel arrangement 233 is not able to lock the second ring gear R2/221 against rotation, i.e. is not able to block rotation of the shaft 255 at the third freewheel arrangement 233. Thus, the second electrical machine 102 and the second ring gear R2/221 may then rotate freely in relation to the housing 235. These features of the third freewheel arrangement 233 and of the reverse coupling arrangement 241, are utilized for providing a reverse mode MR. The reverse mode MR is provided by the transmission arrangement 200 when the second electrical machine 102 is controlled to provide the above defined first torque difference T241_diff_1 over the reverse coupling arrangement 241. The reverse coupling arrangement 241 thereby disables the locking function of the third freewheel arrangement 233, which is illustrated by the dashed line 243 in figures 2a-b. A torque T102 and a rotation direction D102 provided by the second electrical machine 102, that would drive the vehicle 100 backwards, may hereby be transmitted via the second planetary gear 220 to the at least one drive wheel 111, 112. It should be noted that if the reverse coupling arrangement 241 would not have been arranged in the transmission arrangement 200 as explained above, then the rotation direction D₁₀₂ originated from the second electrical machine 102, which would have caused the above defined first rotation direction D233_1 and which would have driven the vehicle 100 backwards, would have caused the third freewheel arrangement 233 to essentially immediately lock the second ring gear R2/221 against rotation. The reverse coupling arrangement 241 thus makes it possible to drive the vehicle 100 backwards, by inhibiting/bypassing/disabling the anti-rotation function of the third freewheel arrangement 233 in the first rotation direction D_{233_1}. The rotational speed ω102 provided by the second electrical machine is then reduced by the gearing of the second planetary gear 220. The at least one drive wheel 111, 112 will therefore be provided with a medium possible maximum torque Tout_max_MR and a relatively low maximum rotational speed ω_{out_max_MR} in the negative/backward direction Dout, resulting from the second torque T102 and the second rotational speed ω102 provided by the second electrical machine 102. In the reverse mode MR, the first planetary gear 210, and the first 231 and second 232 freewheel arrangements are bypassed functionally by the brake coupling arrangement 242, as indicated by the dashed line 244 from the brake coupling arrangement 242 to the first ring gear R1/211 and the first electrical machine 101 in figures 2a-b. Thus, the second sun gear S2/222 is then coupled to the first electrical machine 101 without functionally utilizing the first planetary gear 210, and the first 231 and second 232 freewheel arrangements. The first electrical machine 101 may here provide a smaller torque T₁₀₁ than the torque T102 provided by the second electrical machine 102. Typically, the torque T101 provided by the first electrical machine 101 should be big enough to counteract a reaction torque T_react at the second sun gear S2/222 caused by the second electrical machine 102. The first electrical machine 101 may, according to an embodiment, hold the second sun gear S2/222 still, i.e. may provide zero (0) rotational speed; ω₁₀₁=0. According to other embodiments, the first electrical machine 101 may, however, provide a non-zero rotational speed; ω101≠0; in the reverse mode MR. Mode Freewheel Freewheel Freewheel Reverse Brake Result 231 232 233 coupling coupling T_{out_max MR}, 241 242 ω_{out_mmax} _MR, D_out MR N.A. N.A. N.A. Disable Bypass 210 Tout_max_MR: (bypassed) (bypassed) (Disengaged) 233 Middle ω_{out_max_MR}: Low D_out: Neg Table: MR Table “MR” indicates the conditions for the first 231, second 232 and third 233 freewheels, the reverse coupling arrangement 241 and the brake coupling arrangement 242 for the reverse mode MR. Table “MR” also indicates the resulting possible maximum torque Tout_max_MR, possible maximum rotational speed ωout_max_MR and rotation direction D_out at the at least one drive wheel 111, 112 in reverse mode MR. Conversely, the reverse coupling arrangement 241 is arranged such that it couples the third freewheel arrangement 233 to the second ring gear R2/221 when a second torque difference T_{241_diff_2} is present over the reverse coupling arrangement 241. The second torque difference T241_diff_2 acts on the reverse coupling arrangement 241 in a second direction D241_2 being opposite to the first direction D241_1. Thus, the second torque difference T_{241_diff_2} in the second direction D_{241_2} would result when a non- backward driving torque T_non-backward is provided on the at least one drive wheel 111, 112 if the second sun gear S2/222 would stand still. Thus, the second torque difference T_{241_diff_2} would, if the second sun gear S2/222 would stand still, result in a torque T_non-backward which would hold the vehicle 100 still or would drive the vehicle 100 forward. This second torque difference T241_diff_2 thus has a direction opposite to the direction of the above mentioned first torque difference T_{241_diff_1}, which would drive the vehicle 100 backwards if the second sun gear S2/222 would stand still. The second torque difference T241_diff_2 present over the reverse coupling arrangement 241 may be created by the second electrical machine 102, as correspondingly explained for the first torque difference T_{241_diff_1} above. When the third freewheel arrangement 233 is coupled to the second ring gear R2/221, due to the second torque difference T_{241_diff_2}, the third freewheel arrangement 233 may either lock the second ring gear R2/221 against rotation, i.e. may block rotation of the shaft 255 at the third freewheel arrangement 233, or may let the second ring gear R2/221 rotate freely. Thus, the locking and releasing function of the third freewheel arrangement 233, as described above, is then performed by the third freewheel arrangement 233. Thus, a torque T102 and a rotation direction D102 provided by the second electrical machine 102, that would drive the vehicle 100 forward, may hereby be transmitted, via the second planetary gear 220, to the at least one drive wheel 111, 112. This is utilized in the second M2 and third M3 modes, as explained above. These forward operation modes may therefore be provided by the transmission arrangement 200 when the second electrical machine 101 is controlled to provide the above defined second torque difference T241_diff_2 over the reverse coupling arrangement 241, such that it acts on the reverse coupling arrangement 241 in the above defined second direction D_{241_2}. This will cause the reverse coupling arrangement 241 to enable the function of the third freewheel arrangement 233, which will then not lock the second ring gear R2/221 against rotation in the second M2 and third M3 modes, but will lock the third freewheel arrangement 233 in the first mode M1, as explained above. Thus, as explained above, the transmission arrangement 200 according to an embodiment, comprises a reverse coupling arrangement 241, which is arranged at the third freewheel arrangement 233, as illustrated in figures 2a-b. When the first torque difference T241_diff_1 present over the reverse coupling arrangement 241 acts on the reverse coupling arrangement 241 in a first direction D_{241_1} which would, if the second sun gear S2/222 would stand still, result in a backward driving torque T_backward on the at least one drive wheel 111, 112, then the third freewheel arrangement 233 is decoupled from the second ring gear R2/221, i.e. the function of the third freewheel arrangement is disabled. When, on the other hand, the second torque difference T241_diff_2 present over the reverse coupling arrangement 241 acts on the reverse coupling arrangement 241 in a second direction D241_2, which is opposite to the first direction D_{241_1}, then the third freewheel arrangement 233 is coupled to the second ring gear R2/221, i.e. the function of the third freewheel arrangement is enabled. In figures 4a-b, a coupling arrangement 241 according to some embodiments is schematically illustrated. When the coupling arrangement shown in figures 4a-b is utilized in the transmission arrangement 200 as a reverse coupling arrangement 241, the first shaft 410 is coupled to the second electrical machine 102, and the second shaft 420 is, via the component 245, coupled to the second ring gear R2/221. The sleeve 430 of the reverse coupling arrangement 241 is movable between the first 437 and second 438 positions, as explained above. The sleeve 430 is arranged to interact with the first shaft 410 at its first end 433, and to engage with the second shaft 420 at its second end 434. The sleeve 430 moves towards, i.e. moves in the direction of, and also may reach and stay at, the first position 437, when the first shaft 410 rotates in a first direction ΔD_{410_430_1} in relation to the sleeve 430. This relative rotation of the first shaft 410 in the first direction ΔD410_430_1, in relation to the sleeve 430 is caused by the above mentioned first torque difference T241_diff_1 being present over the reverse coupling arrangement 241. In this first position 437, the second shaft 420 is, via the sleeve 430, engaged with the first shaft 410, but is disengaged from the third freewheel arrangement 233. As mentioned above, the first torque difference T_{241_diff_1} acts on the reverse coupling arrangement 241 in a first direction D241_1 which would, if the second sun gear S2/222 would stand still, result in a backward driving torque Tbackward on the at least one drive wheel 111, 112. In other words, when implemented in the transmission arrangement 200, the reverse coupling arrangement 241 decouples the third freewheel arrangement 233 from the second ring gear R2/221 when a backward driving torque Tbackward is provided to the at least one drive wheel 111, 112. Correspondingly, the sleeve 430 moves towards, i.e. moves in the direction of, and also may reach and stay at, the second position 438, when the first shaft 410, relative to the sleeve 430, rotates in the second direction ΔD410_430_2. This relative rotation of the first shaft 410 in the second direction ΔD_{410_430_2}, in relation to the sleeve 430, is caused by the second torque difference T241_diff_2 being present over the reverse coupling arrangement 241. Thus, when the second torque difference T241_diff_2 acts on the reverse coupling arrangement 241, this causes the relative rotation of the first shaft 410 in the second direction ΔD_{410_430_2} in relation to the sleeve 430. In this second position 438, the second shaft 420 is, via the sleeve 430, engaged with both the first shaft 410 and the third freewheel arrangement 233, i.e. the function of the third freewheel arrangement 233 is enabled. As mentioned above, the second torque difference T241_diff_2 acts on the reverse coupling arrangement 241 in a second direction D241_2, which would, if the second sun gear S2/222 would stand still, result in a non-backward driving torque T_non-backward on the at least one drive wheel 111, 112. In other words, when implemented in the transmission arrangement 200, the reverse coupling arrangement 241 couples the third freewheel arrangement 233 to the second ring gear R2/221, i.e. enables the function of the third freewheel arrangement 233, when a non-backward driving torque Tnon-backward is provided to the at least one drive wheel 111, 112. According to an embodiment, the first shaft 410, the sleeve 430 and the second shaft 420 are arranged coaxially in relation to an axis 414, and are arranged for being rotatable around the axis 414. Thus, they are arranged coaxially with each other and are rotatable. The first shaft 410 and the second shaft 420 are further axially fixed, whereas the sleeve 430 is arranged axially movable between its first position 437, shown in figure 4a, and its second position 438, shown in figure 4b. According to an example embodiment shown in figures 4a-b, the sleeve 430 is arranged as at least partially surrounding a second end 412 of the first shaft 410, and a first end 422 of the second shaft 420. The sleeve 430 further comprises a first spline arrangement 431 on the inside of the sleeve 430, at its first end 433, to interact with a first shaft spline arrangement 411 on the outside of the first shaft 410, at its second end 412. The first spline arrangement 431 and the first shaft spline arrangement 411 here both comprise complementary/matching spiral splines. According to another non-limiting example embodiment, which is not shown in figures 4a-b, the first shaft 410 is at its second end 412 provided with a circular hollow section, which has an inner diameter such that the sleeve 430 fits within the hollow section. The first spline arrangement 431 is then arranged on the outside of the sleeve 430, at its first end 433, to interact with the first shaft spline arrangement 411 being arranged on the inside of the hollow section of the second shaft 420. The first spline arrangement 431 and the first shaft spline arrangement 411 here both comprise complementary/matching spiral splines. According to various embodiments, the first spline arrangement 431 may be arranged at the first end 433 of the sleeve, at the second end 434 of the sleeve, at least partially between the first 433 and second 434 ends of the sleeve, or from the first end 433 to the second end 434 of the sleeve. The interaction between the first shaft spline arrangement 411 and the first spline arrangement 431 causes the movements of the sleeve 430. Thus, this interaction causes its movement towards the first position 437, when the first shaft 410 rotates in the first direction ΔD_{410_430_1} relative to the sleeve 430 due to the first torque difference T241_diff_1. This interaction also causes its movement towards the second position 438, when the first shaft 410 rotates in the second direction ΔD410_430_2, relative to the sleeve 430 due to the second torque difference T_{241_diff_2}. The sleeve 430 may further, according to an embodiment shown in figures 4a-b, comprise a second spline arrangement 432 on the inside of the sleeve 430, at its second end 434, to engage with a second shaft spline arrangement 421 arranged on the outside of the second shaft 420, at its first end 422. The second spline arrangement 432 and the second shaft spline arrangement 421 both comprise complementary/matching axially oriented splines. The engagement of the axially oriented second spline arrangement 432 and second shaft spline arrangement 421 allows the sleeve 430 to move between its first 437 and second 438 positions. According to another non-limiting example embodiment, which is not shown in figures 4a-b, the first end 422 of the second shaft 420 is provided with a circular hollow section. This circular hollow section is arranged such that it at least partially surrounds the sleeve 430 and such that it has a diameter of the hollow section which allows the sleeve 430 to fit within it. The second spline arrangement 432 is then arranged on the outside of the sleeve 430 to interact with the second shaft spline arrangement 421 arranged within the hollow section. The second spline arrangement 432 and the second shaft spline arrangement 421 both comprise complementary/matching axially oriented splines, allowing the sleeve 430 to move between its first 437 and second 438 positions. According to various embodiments, the second spline arrangement 432 is arranged at the first end 433 of the sleeve, at the second end 434 of the sleeve, at least partially between the first 433 and second 434 ends of the sleeve, or from the first end 433 to the second end 434 of the sleeve. According to an embodiment, the third freewheel arrangement 233 is coupled to at least one component engaging member 441. The sleeve 430 also comprises matching at least one sleeve engaging members 435 at its second end 434. The at least one component engaging member 441 and the at least one sleeve engaging member 435 are arranged to be engaged with each other, in the second position 438, shown in figure 4b, and to be disengaged from each other when the sleeve 430 is in a third position, between the first 437 and second 438 positions, i.e. between the positions shown in figures 4a-b. When the sleeve 430 moves towards the second position 438, the at least one component engaging member 441 and the at least one sleeve engaging member 435 become engaged in the third position and are then engaged in the second position 328. When the sleeve 430 moves towards the first position 437, they become disengaged in the third position and are then disengaged in the first position 327. Thus, the at least one sleeve engaging member 435 is arranged for engaging and disengaging the sleeve 430 to and from, respectively, corresponding at least one component engaging member 441 coupled to the third freewheel arrangement 233, depending on the axial movements of the sleeve 430. According to a non-limiting embodiment shown in figures 4a-b, both of the least one component engaging member 441 and the at least one sleeve engaging member 435 comprise coupling cogs. Thus, the third freewheel arrangement 233 is coupled to component coupling cogs, and the sleeve 430 also comprises matching sleeve coupling cogs at its second end 434. According to another non-limiting embodiment, not shown in figures 4a-b, both of the least one component engaging member 441 and the at least one sleeve engaging member 435 comprise axially directed splines. Thus, the third freewheel arrangement 233 is coupled to a component spline arrangement, and the sleeve 430 also comprises a matching sleeve spline arrangement at its second end 434. The sleeve 430 may further, according to an embodiment, comprise at least one stopper arrangement 436, which is arranged for stopping the sleeve 430 from further movement towards a first end 413 of the first shaft 410 when it has reached its first position 437. Correspondingly, the sleeve 430 may comprise at least one stopper arrangement 436 arranged for stopping the sleeve 430 from further movement towards a second end 423 of the second shaft 420 when it has reached the second position 438. In the second position 438, the engagement of the at least one component engaging member 441 and the at least one sleeve engaging member 435 also prevent further movement. Also, the at least one stopper arrangement 436 may, although it in the non-limiting example in figures 4a-b is illustrated as one stopper 436, according to various embodiments, comprise two or more such stoppers, such that one or more stoppers are arranged for preventing further movement beyond the first position 437 and one or more other stoppers are arranged for preventing further movement beyond the second position 438. In the non-limiting embodiment shown in figures 4a-b, the stopper arrangement 436 is arranged on the inside of the sleeve 430, e.g. as a stopper sleeve, a stopper ring or a stopper lip, where it stops against the first 410 and second 420 shafts, respectively. According to other embodiments, the stopper 436 arrangement may, however, also be arranged somewhere else on the sleeve 430, e.g. on the outside of the sleeve, or at the first 433 or second 435 ends of the sleeve. As shown in figure 4a, the sleeve 430 has been moved axially to the first position 437, because the first torque difference T_{241_diff_1} has been present over the reverse coupling arrangement 241. This movement is caused by the interaction of the first spline arrangement 431 and the first shaft spline arrangement 411, both comprising spiral splines. In the first position 437 shown in figure 4a, the at least one sleeve engaging member 435 is disengaged from the at least one component engaging member 441. The output shaft 420, and therefore also the second ring gear R2/221, is therefore not lockable against rotation by the third freewheel arrangement 233 in the first position 437. The function of the third freewheel arrangement 233 is thus disabled in the first position 437. As shown in figure 4b, the sleeve 430 has been moved axially to the second position 438 because the second torque difference T241_diff_2 has been present over the reverse coupling arrangement 241. This movement is caused by the interaction of the first spline arrangement 431 and the first shaft spline arrangement 411, both comprising spiral splines. In the second position 438, the at least one sleeve engaging member 435 is engaged with the corresponding component engaging member 441. Thus, the output shaft 420, and therefore also the second ring gear R2/221, is via the sleeve 430 and the component engaging member 441, coupled to the third freewheel arrangement 233. The second ring gear R2/221 is therefore in this position lockable to the housing 442, i.e. is lockable against rotation, by the third freewheel arrangement 233. The third freewheel arrangement 233 is thus functionally enabled, and may be utilized as explained above. According to another embodiment, the reverse coupling arrangement 241 is an actuator-controlled coupling arrangement. The coupling arrangement 241 is then controlled by at least one actuator to decouple the the third freewheel arrangement 233 from the second ring gear R2/221 when the first torque difference T_{241_diff_1} is present over the reverse coupling arrangement 241. Conversely, the coupling arrangement 241 is then controlled by the at least one actuator to couple the third freewheel arrangement 233 to the second ring gear R2/221 when the second torque difference T_{241_diff_2} is present over the reverse coupling arrangement 241. The at least one actuator is, according to this embodiment, controlled by a control system, such as for example the control system arranged for controlling the transmission arrangement 200, and may be moved by usage of hydraulics and/or pneumatics, and/or may be an electric actuator. Mode Freewheel Freewheel Freewheel Reverse Brake Result 231 232 233 coupling coupling 241 242 M1 Released Locked Locked Enable 233 No bypass T_{out_max_M1}: 210 High ωout_max_M1: Low D_out: Pos M2 Released Locked Released Enable No bypass T_{out_max_M2}: 233 210 Middle ωout_max_M2: Middle D_out: Pos M3 Locked Released Released Enable No bypass T_{out_max_M3}: 233 210 Low ωout_max_M3: High D_out: Pos MB N.A. N.A. Released Enable 233 Bypass 210 T_out: (Bypassed) (Bypassed) Braking ωout: Possibly ↓ D_out: Pos MR N.A. N.A. N.A. Disable Bypass 210 T_{out_max_MR}: (Bypassed) (Bypassed) (Disabled) 233 Middle ωout_max_MR: Low D_out: Neg Table: All modes In Table “All modes”, all the conditions for the first 231, second 232 and third 233 freewheels, the reverse coupling arrangement 241 and the brake coupling arrangement 242, as well as corresponding possible output values at the at least one drive wheel 111, 112, are indicated for all of the first M1, second M2 and third M3 modes, and for the brake MB and reverse MR modes, respectively, that have all been described above. Figure 5 shows a flow chart for a method 500 for controlling a transmission arrangement 200 according to an embodiment described above such that a second mode of operation M2 of the transmission arrangement 200 is provided. It should be noted that the method steps illustrated in figures 5-10, and described herein, do not necessarily have to be executed in the order illustrated in these figures. The steps may essentially be executed in any suitable order, as long as the physical requirements and the information needed to execute each step is available when the step is executed. In a first step 510 of the method 500 illustrated in figure 5, the first electrical machine 101 is controlled to cause the above defined second rotation direction DR1_2 of the first ring gear R1/211. Hereby, i.e. when the first electrical machine 101 attempts to rotate the first ring gear R1/211 in the second rotation direction DR1_2, the first freewheel arrangement 231 allows the first planet gear carrier C1/213 to rotate, and the second freewheel arrangement 232 locks the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212. A 1:1 gearing over the first planetary gear 210 is then provided, as explained above. Thus, if the first electrical machine 101 is controlled to perform the first step 510, the transmission arrangement 200 is set for providing the second mode M2. In a second step 530, the first electrical machine 101 is controlled to cause the at least one drive wheel 111, 112 to move in a positive rotation direction Dout_pos. In a third step 540, the second electrical machine 102 is controlled to cause the at least one drive wheel 111, 112 to move in a positive rotation direction Dout_pos. Thus, by performing the first 510 step, the second operation mode M2 of the transmission arrangement is chosen via the control of the first electrical machine 101. Hereby, the second 232 freewheel arrangement is locked to provide the second operation mode M2. Also, the first 101 and/or second 102 electrical machines may, by performing the second 530 and third 540 steps, drive the vehicle 100 forward by providing a positive torque Tout, and a rotational speed ωout in a positive rotation direction Dout at the at least one drive wheel 111, 112. As is realized by a skilled person, the steps 510, 530, 540 of the method 500 do not have to be performed in sequence as illustrated in figure 5. For example, the second 530 and third 540 steps may be performed in parallel with each other, i.e. at essentially the same time, and may also be performed in parallel with the first 510 step. Figure 6 shows a flow chart for a method for controlling a transmission arrangement 200 according to an embodiment described above in order to provide the first mode of operation M1. In a first step 510, the first electrical machine 101 is controlled to cause the above defined second rotation direction DR1_2 of the first ring gear R1/211. Hereby, the first freewheel arrangement 231 allows the first planet gear carrier C1/213 to rotate, and the second freewheel arrangement 232 locks the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212, such that a 1:1 gearing over the first planetary gear 210 is provided. In a second step 550, the first 101 and second 102 electrical machines are controlled such that they attempt to cause the first rotation direction D_{233_1} at the third freewheel arrangement 233. Hereby, i.e. when the first 101 and second 102 electrical machines try to rotate the first ring gear R1/211 in the second rotation direction D_{R1_2}, and also try to cause the first rotation direction D233_1 at the third freewheel arrangement 233, the second freewheel arrangement 232 locks the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212, and the third freewheel arrangement 233 also locks the second ring gear R2/221 against rotation. Then, in a third step 560, the first electrical machine 101 is controlled to cause the at least one drive wheel 111, 112 to move in a positive direction D_{out_pos}, to cause the vehicle to move forward. Thus, if the first 101 and/or second 102 electrical machines are controlled to perform the first 510 and second 550 steps, the transmission arrangement 200 is set for providing the first mode M1 of operation. Then, the vehicle 100 is propelled forward in the first mode M1 of operation in the third step 560, which has the advantages mentioned above. Figure 7 shows a flow chart for a method for controlling a transmission arrangement 200 according to an embodiment described above in order to provide the third mode of operation M3 of the transmission arrangement 200. In a first step 520, the first electrical machine 101 is controlled to cause the above defined first rotation direction DR1_1 of the first ring gear R1/211. Hereby, the first freewheel arrangement 231 locks the first planet gear carrier C1/213 against rotation, and the second freewheel arrangement 232 allows the first ring gear R1/211 and the first sun gear S1/212 to rotate in relation to the first planet gear carrier C1/213. Thus, the transmission arrangement 200 is set up for providing the third mode of operation M3. In a second step 530, the first electrical machine 101 is controlled to cause the at least one drive wheel 111, 112 to move in a positive rotation direction Dout_pos. In a third step 540, the second electrical machine 102 is controlled to cause the at least one drive wheel 111, 112 to move in a positive rotation direction D_{out_pos}. Thus, by performing the first 520 step, the third operation mode M3 of the transmission arrangement is chosen via the control of the first electrical machine 101. Hereby, the first freewheel arrangement 231 locks the first planet gear carrier C1/213 against rotation and the second 232 freewheel arrangement is released. Also, the first 101 and/or second 102 electrical machines may drive the vehicle 100 forward by providing, by performing the second 520 and third 530 steps, a positive torque T_out, and a rotational speed ωout in a positive rotation direction Dout at the at least one drive wheel 111, 112. According to an embodiment, the above described second mode M2 is achieved by controlling 510, 530 the first electrical machine 101 to cause the second rotation direction D_{R1_2} of the first ring gear R1/211, which causes a positive rotation direction Dout of the at least one drive wheel 111, 112, and by controlling 540 the second electrical machine 102 to also cause a positive rotation direction Dout of the at least one drive wheel 111, 112. Correspondingly, according to an embodiment, the above described third mode M3 is achieved by controlling 520, 530 the first electrical machine 101 to cause the first rotation direction D_{R1_1} of the first ring gear R1/211, which also causes a positive rotation direction D_out of the at least one drive wheel 111, 112 due to the rotation direction switch in the first planetary gear 210 when the first freewheel arrangement 231 is locked, and by controlling 540 the second electrical machine 102 to cause a positive rotation direction D_out of the at least one drive wheel 111, 112. Thus, the second M2 and third M3 modes are chosen by the controlled rotation direction of the first electrical machine 101. According to some embodiments, the rotation direction D₁₀₁ of the first electrical machine 101 is controlled for performing switching between the second M2 and third M3 modes. The first electrical machine 101 is then controlled to switch its rotational speed ω₁₀₁ from a previous rotation direction D_{101_previous} to a subsequent rotation direction D_{101_subsequent}, where the subsequent rotation direction D_{101_subsequent} is opposite to the previous rotation direction D101_previous, to provide switches between the second M2 and third M3 modes, and vice versa. The rotational speed ω₁₀₁ may, according to an embodiment, be controlled to, as quick as possible, switch from a non-zero rotational speed ω101 in the previous rotation direction D101_previous to a non-zero rotational speed ω101 in the subsequent rotation direction D_{101_subsequent}. This control of the rotational speed ω₁₀₁ of the first electrical machine 101 results in the fastest direction switch being possible to provide, i.e. in a quickest possible reduction of the absolute value of the rotational speed |ω₁₀₁| in the previous rotation direction D_{101_previous}, and a quickest possible increase of the absolute value of the rotational speed |ω101| in the subsequent rotation direction D_{101_subsequent}. However, fast changes in rotation direction may in many situations cause comfort problems, such as jerking, and/or powertrain problems, such as e.g. component wear. According to an embodiment, which takes such problems into account, the first electrical machine 101 is controlled to be switched between causing the first rotation direction DR1_1 and the second rotation direction DR1_2 of the first ring gear R1/211, and vice versa, in a certain way to provide for a smooth mode shift. The first electrical machine 101 is therefore, according to an embodiment illustrated by the flow chart diagram in figures 8a-b, controlled 510, 520 to reduce 511, 521 an absolute value of the rotational speed |ω₁₀₁| of a previous rotation direction D_{101_previous} to zero, while still providing a torque T₁₀₁ having a non-zero absolute value; |T₁₀₁|≠0. Then, the rotation direction D101 is switched 512, 522 to a subsequent rotation direction D101_subsequent being opposite to the previous rotation direction D101_previous. Thereafter, the absolute value of the rotational speed |ω₁₀₁| of the first electrical machine 101 is increased 513, 523 to a non-zero rotational speed ω101, now in the subsequent rotation direction D101_subsequent. Here, the reduction 511, 521 of the absolute value of the rotational speed |ω₁₀₁| in the previous rotation direction D_{101_previous} and/or the increase 513, 523 of the absolute value of the rotational speed |ω101| in the subsequent rotation direction D101_subsequent may be controlled 510, 520 such that they fulfil suitable comfort and/or other powertrain requirements. Thus, in order to provide smooth, comfortable and low wear switching between the second M2 and third M3 modes, the absolute value of the rotational speed |ω101| may be decreased to zero in a more controlled manner. Then, after the switch from the previous rotation direction D_{101_previous} to the subsequent rotation direction D_{101_subsequent}, the absolute value of the rotational speed |ω101| is increased in a controlled manner. Such control of the first electrical machine 101 mitigates e.g. jerking and component wear, and results in a smooth transition between the second M2 and third M3 modes. For example, figure 8a illustrates smooth switching from the second M2 to the third M3 mode, i.e. in a situation where the first electrical machine 101 has previously been controlled 510 to cause the second rotation direction D_{R1_2} of the first ring gear R1/211, as explained above in connection with figure 5. The first electrical machine 101 is then controlled 521 to reduce the absolute value of its rotational speed |ω₁₀₁| in this second rotation direction DR1_2, in a controlled manner, down to zero rotational speed ω101, while still providing a torque having a non-zero torque absolute value; |T₁₀₁|≠0. This reduction may be more or less aggressively performed, depending on possible comfort and/or other powertrain requirements, as explained above. After the reduction to zero rotational speed ω101, the rotation direction D101 is controlled to be switched 522 such that the first electrical machine 101 causes the opposite first rotation direction DR1_1 of the first ring gear R1/211. Then, the absolute value of the rotational speed |ω101| of the first electrical machine 101 is increased 523, more or less aggressively, in a controlled manner to a non-zero rotational speed ω₁₀₁ in this rotation direction D₁₀₁ causing the first rotation direction D_{R1_1} of the first ring gear R1/211. Generally, the time periods used for the above described rotational speed reduction 521 and increase 523 steps may be adjusted, depending on possible comfort and/or powertrain demands. For example, the speed reduction and/or increase control may be adjusted according to a suitable linear or non-linear function, algorithm or curve, which may be predetermined or estimated/calculated in real time, or may be predicted for upcoming/future switching between the second M2 and the third M3 modes. As shown in figure 8b, when performing smooth switching from the third M3 to the second M2 mode, the first electrical machine 101 has previously been controlled 520 to cause the first rotation direction DR1_1 of the first ring gear R1/211, as explained above in connection with figure 7. It is then controlled 511 to reduce the absolute value of its rotational speed |ω₁₀₁| to zero while still providing a torque having a non- zero absolute value; |T101|≠0. After the reduction, its rotation direction D101 is controlled to be switched 512 such that it causes the second rotation direction DR1_2 of the first ring gear R1/211, being opposite to the first rotation direction D_{R1_1}. Then, the absolute value of the rotational speed |ω101| of the first electrical machine 101 is in a controlled manner increased 513 to a non-zero rotational speed ω101 in this rotation direction D₁₀₁ causing the second rotation direction D_{R1_2}. As mentioned above, the switch of rotation directions may also here be performed more or less smoothly, by adjusting the time periods used for the above described rotational speed reduction 511 and increase 513, depending on possible comfort and/or powertrain requirements. For example, the time periods may be adjusted according to a suitable linear or non-linear function, algorithm or curve, which may be predetermined or estimated/calculated in real time, or may be predicted for upcoming switching between the second M2 and the third M3 modes. Both the first 101 and the second 102 electrical machines are then controlled 530, 540 to provide a positive rotation direction Dout of the at least one drive wheel 111, 112 in the second M2 and third M3 modes, respectively, as explained above in connection with figures 5 and 7. Figure 9 shows a flow chart for a method for controlling a transmission arrangement 200 according to an embodiment described above in order to provide the regenerative brake mode MB operation of the transmission arrangement 200. In a first step 571, the first 101 and second 102 electrical machines are controlled such that the second torque difference T242_diff_2 is provided/present over the brake coupling arrangement 242. Hereby, the first planetary gear 210, and the first 231 and second 232 freewheel arrangements are functionally bypassed 244 by the brake coupling arrangement 242, and the second sun gear S2/222 is coupled to the first ring gear R1/211 and thus to the first electrical machine 101, without functionally utilizing the first planetary gear 210. Also, the second electrical machine 102 is coupled to the second planetary gear 220. In a second step 572, the first 101 and second 102 electrical machines are controlled to brake the vehicle 100, to generate energy during braking. The first 101 and second 102 electrical machines and the battery system are then controlled to store this generated energy in the at least one energy storage 104. Thus, if the first 101 and second 102 electrical machines are controlled to perform the first 571 and second 572 steps, the transmission arrangement 200 is set for providing the regenerative brake mode MB of operation, and regenerative braking is also performed/provided. Figure 10 shows a flow chart for a method for controlling a transmission arrangement 200 according to an embodiment described above in order to provide the reverse mode MR operation of the transmission arrangement 200. In a first step 581, the first 101 and second 102 electrical machines are controlled such that the first torque difference T241_diff_1 is provided/present over the reverse coupling arrangement 241. Hereby, the third freewheel arrangement 233 is decoupled 243 from the second ring gear R2/221, and is thus functionally disabled. In a second step 582, the second electrical machine 102 is controlled to drive the vehicle 100 backwards, which is possible since the third freewheel arrangement 233 is decoupled and therefore cannot block the rotation of the second ring gear R2/221. Also, the first electrical machine 101 is controlled to counteract the reactional torque Treact provided by the second sun gear S2/222. Thus, if the first 101 and second 102 electrical machines are controlled to perform the first 581 and second 582 steps, the transmission arrangement 200 is set for providing the reverse mode MR, and the vehicle 100 is also caused to be propelled backwards by the second electrical machine 102. According to various embodiments, the first 101 and/or second 102 electrical machines are controlled to switch between and initiate various operation modes in the transmission arrangement 200, and for propelling the vehicle 100 in these operation modes. In the following, it is further explained how this control is achieved. Below are some examples presented for how the first 101 and/or second 102 electrical machines are to be controlled in order to initiate various operation modes and/or to propel the vehicle 100 in these chosen operation modes, respectively. The herein presented examples, illustrated in figures 11-15, cover an example of a driving cycle, which is of course non-limiting, and which includes a takeoff using the first mode M1 to move the vehicle forward from standstill, then switching from the first mode M1 to the second mode M2 during acceleration of the vehicle, then switching from the second mode M2 to the third mode M3 during further acceleration, then switching from the third mode M3 to the regenerative brake mode MB and decelerating the vehicle to standstill, and finally switching to reverse mode MR and moving the vehicle backwards. A skilled person understands that the first 101 and/or second 102 electrical machines may be controlled correspondingly for other driving cycles, including switches between operation modes in another order than for the herein described example. Essentially any mode may be entered from any one of the other modes. However, if an acceptable driving comfort is to be provided for the driver and/or passengers, some operation mode switches are more suitable to perform than others. Thus, driving comfort parameters may add conditions for switching between operation modes, such that the number of possible switches in a given situation are restricted. The following examples are thus not intended to be a complete presentation of all possible controls providable by use of the first 101 and/or second 102 electrical machines. The herein given examples are based on a transmission arrangement 200 as the one schematically illustrated in figures 2a-b, and where component 245 comprises an odd number of gear/cog wheel engagements arranged between the second ring gear R2/221 and the third freewheel gear 233, whereby the second ring gear R2/221 rotates in a direction opposite to the rotation direction of the shaft 255 at the third freewheel arrangement 233, i.e. the shaft 255 between the reverse coupling arrangement 241 and the component 245. As understood by a skilled person, if one or more gear/cog wheels, or any other device that would shift/alter/switch the rotation direction of a shaft/axle/cog wheel/gear wheel, would be arranged in addition to the components of the transmission arrangement 200 shown in figures 2a-b, e.g. at the shaft 251 between the first electrical machine 101 and the first planetary gear 210, at the shaft 252 between the first planetary gear 210 and the brake coupling arrangement 242, at the shaft 253 between the brake coupling arrangement 242 and the second planetary gear 220, at the shaft 256 between the second electrical machine 102 and the reverse coupling arrangement 241, at the shaft 255 between the reverse coupling arrangement 241 and the component 245, at the shaft 254 between the component 245 and the second planetary gear 220, and/or at the shaft 257 between the second planetary gear 220 and the at least one drive wheel 111, 112, then the herein presented rotation and/or torque directions of the first 101 and/or second 102 electrical machines would be altered correspondingly. Thus, depending on the design of the transmission arrangement 200, the first 101 and/or second 102 electrical machines may be controlled in different ways in order to provide a certain operation mode or a certain switch between operation modes, as is understood by a skilled person. In summary, to perform the above mentioned driving cycle example; M1 ^M2 ^M3 ^MB ^MR; for a transmission arrangement 200 as the one shown in figures 2a-b, where component 245 causes one shift in the rotation direction, the first 101 and second 102 electrical machines are controlled according to the following. In figures 11a-b, and in the following figures showing torque and rpm diagrams, the dashed circles “101” and “102” schematically illustrate conditions for an initial or previous state of the first 101 and second 102 electrical machines, respectively. Correspondingly, the solid circles “101” and “102” schematically illustrate conditions for a subsequent or resulting state of the first 101 and second 102 electrical machines. The bold arrows schematically illustrate how the conditions change between the states. As illustrated in figures 11a-b, at takeoff from standstill, i.e. in order to initiate the first mode M1 when both of the first 101 and second 102 electrical machines stand still and do not provide any torques or rotational speeds; T₁₀₁=T₁₀₂=0 and ω₁₀₁=ω₁₀₂=0; the first electrical machine 101 is controlled to provide a positive torque; T101=positive; and a positive rotation direction; D101=positive, corresponding to ω₁₀₁=positive, i.e. ω₁₀₁>0. This causes the first freewheel arrangement 231 to allow the first planet gear carrier C1/213 to rotate, but also causes the second freewheel arrangement 232 to lock the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212. Hereby, no shift in rotation direction occurs over the first planetary gear 210, and no gearing takes place, i.e. the gear ratio is 1:1 over the first planetary gear 210. The second electrical machine 102 is not able to counteract the reaction torque Treact from the second ring gear R2/221, whereby the first electric machine 101 attempts to cause a negative first rotation direction D233_1 at the third freewheel arrangement 233. The third freewheel arrangement 233 then locks the second ring gear R2/221 against rotation in order to block such a negative first rotation direction D_{233_1} at the third freewheel arrangement 233. There may be various reasons for why the second electrical machine 102 is not able to counteract the reaction torque Treact. One such reason could be that the second electrical machine 102 is too weak to counteract the reaction torque Treact, which may e.g. be due to dimensioning and/or cost reasons. Another reason could be that the second electrical machine is controlled to provide a torque being too weak to counteract the reaction torque T_react, or is controlled to not provide any torque at all. To propel the vehicle 100 forward in the first mode M1, the first electrical machine 101 is controlled to continue to provide a positive rotation direction; D101=positive; as illustrated in figure 11a. The second electrical machine 102 is controlled not to contribute to the propelling of the vehicle, as illustrated in figure 11b. Hereby, the at least one drive wheel 111, 112 will, after the first planetary gear 210 has provided a 1:1 gearing and the second planetary gear 220 has geared up the torque and geared down the rotational speed in the first mode M1, be provided with up to a maximum first mode torque Tout_max_M1 and up to a maximum first mode rotational speed ω_{out_max_M1} in a positive direction D_out, originating from the torque T₁₀₁ and rotational speed ω₁₀₁ from the first electrical machine 101. The possible maximum first mode torque Tout_max_M1 is higher than the above and below described possible maximum second mode torque Tout_max_M2 and possible maximum third mode torque T_{out_max_M3}, respectively; T_{out_max_M1} > T_{out_max_M2} > T_{out_max_M3}. The possible maximum first mode rotational speed ωout_max_M1 is lower than the above and below described possible maximum second mode rotational speed ωout_max_M2 and possible maximum third mode rotational speed ω_{out_max_M3}, respectively; ω_{out_max_M1} < ωout_max_M2 < ωout_max_M3. The vehicle speed may then be increased by controlling the first electrical machine 101 to further increase the value of the positive rotational speed ω₁₀₁. The conditions of the takeoff from standstill, and for propelling of the vehicle 100 in the first mode M1, are given in the below Table “Takeoff using M1”. Electrical M1 initiation Vehicle propelling machine (Rotation directions and Torque) 101 D101: Positive D101: Positive T101: Positive T101: Positive 102 D102: Zero D102: Zero T102: Zero T102: Zero Table: Takeoff using M1 As illustrated in figures 12a-b, to initiate the second mode M2, when being in the first mode M1, the first electrical machine 101 is controlled to provide a continued positive torque; T101=positive; and a positive rotation direction; D101=positive, i.e. ω₁₀₁=positive; as illustrated in figure 12a, which causes the second freewheel arrangement 232 to lock the first planet gear carrier C1/213 to one of the first ring gear R1/211 and the first sun gear S1/212, and causes a release of the first freewheel arrangement 231. In the first mode M1, the third freewheel arrangement 233 locks the second ring gear R2/221 against rotation, as explained above. When the vehicle accelerates in the first mode M1, i.e. before the initiation of the second mode M2, the first electrical machine 101 provides an increasingly positive rotational speed ω₁₀₁; D₁₀₁=positive, as illustrated with the horizontal arrow in figure 11a. At these higher rotational speeds ω₁₀₁, the first electrical machine 101 often cannot provide torques as high as it normally can provide at lower rotational speeds ω₁₀₁, as illustrated in figure 12a.This is due to the above mentioned maximum torque/power function of the first electrical machine 101, i.e. due to the fact that the torque provided by the first electrical machine 101 is today often limited for higher rotational speeds ω₁₀₁. For electrical machines having other maximum torque/power functions, the control of the first 101 and second 102 electrical machines may be correspondingly adjusted, in relation to what is herein described. The second electrical machine 102 is then, as the torque T101 provided by the first electrical machine 101 decreases with the increased rotational speed ω101, without help from the third freewheel arrangement 233, able to itself counteract the reaction torque Treact provided to the second ring gear R2/221 from the second sun gear S2/222 with its own provided second torque T102. Thereafter, the torque T101 provided by the first electrical machine 101 is further reduced with its increasing rotational speed ω101. The second electrical machine 102 is then able to contribute to the output torque Tout and rotational speed ωout with its own torque T102 and rotational speed ω₁₀₂. Therefore, the second electrical machine 102 is then controlled to provide a negative torque; T₁₀₂=negative; and an increasing rotational speed ω₁₀₂ in a negative rotation direction; D102=negative; as illustrated in figure 12b. To propel the vehicle 100 forward with increasing vehicle speed in the second mode M2, the first electrical machine 101 is controlled to provide an increasing rotational speed ω101 in a positive rotation direction; D101=positive; and the second electrical machine 102 is controlled to provide an increasing rotational speed ω102 in a negative rotation direction; D₁₀₂=negative; i.e. to provide an increasing absolute value of the negative rotational speed |ω102|. The rotational speed ω101 of the first electrical machine 101 and the rotational speed ω102 of the second electrical machine 102 may here be controlled to be balanced, such that the first electrical machine 101 and/or the second electrical machine 102 may be operated at for them suitable rotational speeds, respectively. In the second mode M2, the at least one drive wheel 111, 112 will be provided with up to a maximum second mode torque T_{out_max_M2} and up to a maximum second mode rotational speed ωout_max_M2 in a positive direction Dout, being a combination of the torque T101 and rotational speed ω101 originating from the first electrical machine 101, and the torque T₁₀₂ and rotational speed ω₁₀₂ originating from the second electrical machine 102, respectively. The possible maximum second mode torque Tout_max_M2 is lower than the above described possible maximum first mode torque T_{out_max_M1} and higher than the above and below described possible maximum third mode torque Tout_max_M3; Tout_max_M1 > Tout_max_M2 > Tout_max_M3. The possible maximum second mode rotational speed ω_{out_max_M2} is higher than the above described possible maximum first mode rotational speed ωout_max_M1 and lower than the above and below described possible maximum third mode rotational speed ωout_max_M3; ω_{out_max_M1} < ω_{out_max_M2} < ω_{out_max_M3}. The conditions of the shift from the first mode M1 to the second mode M2, and for propelling of the vehicle 100 in the second mode M2, are given in the below Table “Shift from M1 to M2”. Electrical M1 ^ M2 initiation Vehicle propelling machine (Rotation directions and torque) 101 D₁₀₁: Positive D₁₀₁: Positive T101: Positive T101: Positive 102 D102: First zero (counteract), D102: Negative then negative (contribute) T102: Negative T₁₀₂: Negative. First counteract, then contribute Table: Shift from M1 to M2 As illustrated in figures 13a-f, to initiate the third mode M3 from the second mode M2, the first electrical machine 101 is controlled to provide a negative rotation direction; D₁₀₁=negative; which releases the second freewheel arrangement 232 and locks the first freewheel arrangement 232. More in detail, as shown in figures 13a-b, to be able to switch the rotation direction D₁₀₁ of the first electrical machine 101, from positive; D₁₀₁=positive; in the second mode M2 to negative; D101=negative; in the third mode M3, the balance between the rotational speed ω101 of the first electrical machine 101 and the rotational speed ω102 of the second electrical machine 102 is first altered/adjusted. Hereby, the rotational speed of ω₁₀₁ the first electrical machine 101 is reduced from its value in positive direction to zero; ω101=0; while the second electrical machine 102 is controlled to increase its rotational speed of ω₁₀₂ to a higher rotational speed in the negative direction; D102=negative. The first electric machine 101 provides a positive torque; T101=positive, and the second electrical machine 102 provides a negative torque; T₁₀₂=negative; when these rotational speed adjustment take place. Thereafter, as illustrated in figures 13c-d, the first electrical machine 101 is controlled to provide a negative torque; T101=negative; and a negative rotational speed ω101<0, having an absolute value increasing from zero; |ω₁₀₁|>0, such that the rotation direction has negative value; D101=negative. As explained above, the first electrical machine 101 may be controlled to go very quickly from the positive; D101=positive; to the negative; D₁₀₁=negative; rotation direction. However, it may, due to comfort and/or other powertrain requirements, be preferable to provide a more smooth rotation direction switch by a more controlled decrease and increase of the absolute value of the rotational speed. Meanwhile, the second electrical machine 102 is controlled to reduce its absolute value of the rotational speed |ω₁₀₂| in the negative direction D102=negative, as illustrated in figure 13d. By controlling the first 101 and second 102 electrical machines this way, they may be balanced, i.e. operated at for them suitable rotational speeds, respectively, in the third mode M3. Alternatively, the second electrical machine 102 may be controlled to keep its absolute value of the rotational speed |ω102| in the negative direction; D102=negative; while the first electrical machine 101 is controlled to increase the absolute value of the negative rotational speed |ω₁₀₁| to provide acceleration of the vehicle and to balance the first 101 and second 102 electrical machines. Alternatively, the second electrical machine 102 may be controlled to slowly increase its absolute value of the rotational speed |ω₁₀₂| in the negative direction D₁₀₂=negative, while the first electrical machine 101 is controlled to more quickly increase the absolute value of its negative rotational speed |ω101| to provide acceleration of the vehicle and to balance the first 101 and second 102 electrical machines. As illustrated in figures 13e-f, to further increase the vehicle speed in the third mode M3, the first electrical machine 101 is controlled to a higher absolute value of the rotational speed |ω₁₀₁| in the negative direction; D₁₀₁=negative; and with a negative torque; T101=negative; whereas the second electrical machine 102 is controlled to a higher absolute value of the rotational speed |ω₁₀₂| in the negative direction; D102=negative; and with a negative torque; T102=negative. Thus, in the third mode M3, both the first 101 and the second 102 electrical machines are controlled to contribute with up to a maximum third mode torque T_{out_max_M3} and up to a maximum third mode rotational speed ωout_max_M3 in a positive direction Dout at the at least one drive wheel 111, 112, by a combination of the torque T101 and rotational speed ω₁₀₁ originating from the first electrical machine 101, and the torque T102 and rotational speed ω102 originating from the second electrical machine 102, respectively. The possible maximum third mode torque Tout_max_M3 is lower than the above described possible maximum first mode torque T_{out_max_M1} and possible maximum second mode torque T_{out_max_M2}, respectively; T_{out_max_M1} > T_{out_max_M2} > Tout_max_M3. The possible maximum third mode rotational speed ωout_max_M3 is higher than the above described possible maximum first mode rotational speed ωout_max_M1 and possible maximum second mode rotational speed ω_{out_max_M2}, respectively; ωout_max_M1 < ωout_max_M2 < ωout_max_M3. The absolute value of the rotational speed |ω101| of the first electrical machine 101 and the absolute value of the rotational speed |ω₁₀₂| of the second electrical machine 102 may be controlled such that a balance between their respective suitable rotational speeds is achieved. The conditions of the shift from the second mode M2 to the third mode M3, and for propelling of the vehicle 100 in the third mode M3, are given in the below Table “Shift from M2 to M3”.

Electrical M2 ^ M3 initiation Vehicle propelling machine (Rotation directions and torque) 101 D101: Switch from positive to T101: Negative negative D₁₀₁: Negative T101: Switch from positive to negative 102 D102: Negative T102: Negative T102: Negative D102: Negative Table: Shift from M2 to M3 As shown in figures 14a-d, to initiate the regenerative brake mode MB, when being in the third M3 mode, it is in this example assumed that the driver first lifts his foot off the accelerator pedal. Thus, both of the first 101 and second 102 electrical machines then provide a torque being zero; T₁₀₁=T₁₀₂=0. The first electrical machine 101 initially runs at a negative rotational speed ω101, and the second electrical machine 102 runs at a negative rotational speed ω102. As illustrated in figures 14a-b, the second 102 electrical machine is then controlled to increase the absolute value of the negative rotational speed |ω₁₀₂|, which causes reduction of the absolute value of the negative rotational speed |ω101| of the first electrical machine 101. One way of facilitating for the brake coupling to be able to move to its second position 338 is to control the first electrical machine 101 to standstill, since all of the components in the first planetary gear 210 then also stand still and are possible to be engaged with each other. Therefore, the absolute value of the negative rotational speed |ω₁₀₁| of the first electrical machine 101 may be controlled to zero by increasing the absolute value of the negative rotational speed |ω102| of the second electrical machine 102. As illustrated in figures 14c-d, the second 102 electrical machine is then, when the first electrical machine 101 stands still, controlled to provide a positive torque pulse T102, such that the brake coupling arrangement 242 is moved to its second position 338, shown and explained in connection with figure 3b, and thereby functionally bypasses the first planetary gear 201. Hereby, the brake coupling arrangement 242 couples the first electrical machine 101 to the second planetary gear 220, i.e. to the second sun gear S2/222, without functionally utilizing the first planetary gear 210 and its first 231 and second 232 freewheel arrangements, which makes braking possible. Thus, the mode MB for regenerative braking is hereby initiated. The second electrical machine 102 is coupled to the second planetary gear 220, i.e. to the second ring gear R2/221. Hereby, both of the first 101 and second 102 electrical machines may be used for regenerative braking of the vehicle 100. During regenerative braking, the first electrical machine 101 is controlled such that its torque T₁₀₁ is increased from zero to a for regenerative braking suitable negative value. Also, the second electrical machine 102 is controlled such that its torque T102 is increased from zero to a for regenerative braking suitable positive value, causing a corresponding rotational speed ω₁₀₂. In this example, the absolute value of the negative rotational speed |ω102| is reduced to a lower value, possibly to zero, as illustrated in figure 14d. Hereby, the vehicle 100 is regeneratively braked and electrical energy is generated. The generated electrical energy is provided from the second electrical machine 102 to the at least one energy storage 104 during regenerative braking. As mentioned above, since the first 101 and second 102 electrical machines are coupled to each other via the transmission arrangement, their respective rotational speeds ω101, ω102 influence each other. Thus, at a certain vehicle speed, a reduced absolute value of the first rotational speed |ω101| of the first electrical machine 101 causes an increase of the absolute value of the second rotational speed |ω₁₀₂| of the second electrical machine 102, and vice versa. The first rotational speed ω101 of the first electrical machine 101 and the second rotational speed ω102 of the second electrical machine 102 may therefore be balanced, such that both of the first 101 and second 102 electrical machine can perform regenerative braking at suitable rotational speeds, respectively. In the regenerative brake mode MB, a braking torque Tout and a possibly decreasing rotation speed ω_out in a positive rotation direction D_out are caused at the at least one drive wheel 111, 112. For example, the rotation speed ωout may be reduced to zero, i.e. to a standstill for the vehicle 100. The regenerative brake mode MB may be initiated from any one of the herein described modes, i.e. from the first mode M1, the second mode M2, the third mode M3, or the reverse mode MR, as long as it is possible to move the brake coupling 242 to its second position 338, e.g. by controlling the first electrical machine 101 to a standstill. Also, any other mode may be initiated from the regenerative brake mode. Above is described how the first 101 and second 102 electrical machines are controlled for entering the regenerative brake mode MB from the third mode M3. Corresponding control of the first 101 and second 102 electrical machines are utilized for initiating the regenerative brake mode MB from the other modes, and for exiting the regenerative brake mode MB and returning to any of the herein described modes, as is understood by a skilled person. The conditions for the shift from the third M3 mode to the regenerative brake mode MB are given in the below Table “Shift M3 to MB”. Electrical M3 ^ MB initiation Vehicle braking machine (Rotation directions) 101 D101: Negative T101: Negative |ω₁₀₁|: ↓ to zero 102 D102: Negative T102: Positive |ω₁₀₂|: ↑ |ω₁₀₂|: Possibly ↓ T102: Positive torque pulse D102: Negative Table: Shift M3 to MB As illustrated in figures 15a-b, to initiate the reverse mode MR from standstill, i.e. when both of the first 101 and second 102 electrical machines stand still; ω₁₀₁=ω₁₀₂=0; after braking the vehicle, the first 101 and second 102 electrical machines are controlled such that the second electrical machine 102 goes from providing zero torque to providing a positive torque; T₁₀₂=positive, as shown in figure 15b. The positive torque T102 causes the above described first torque difference T241_diff_1, acting in the above defined first direction D241_1, over the reverse coupling arrangement 241, whereby the third freewheel arrangement 233 is decoupled from the second ring gear R2/221, i.e. whereby the third freewheel arrangement 233 is disabled. The second electrical machine 102 is also controlled to provide a rotational speed ω₁₀₂ in the positive direction D₁₀₂=positive. The control of the second electrical machine 102 results in a reactional torque Treact between the second sun gear S2/222 and the first sun gear S1/211, which causes the above described second torque difference T_{242_diff_2} over the brake coupling arrangement 242. The brake coupling arrangement 242 therefore functionally bypasses the first planetary gear 210, i.e. couples the second sun gear S2/222 to the first ring gear R1/211, and thus to the first electrical machine 101, without functionally utilizing the first planetary gear 210 and its first 231 and second 232 freewheel arrangements. The first electrical machine 101 is controlled to provide a negative torque T₁₀₁=negative, which counteracts the reactional torque T_react from the second sun gear S2/222, such that the second sun gear S2/222 is held still, as illustrated in figure 15a. The second electrical machine 102 is controlled to drive the vehicle 100 backwards, i.e. is controlled to provide a positive torque; T₁₀₂=positive; and a positive rotational speed; ω₁₀₂=positive. As is understood by a skilled person, the vehicle 100 does not have to stand still when the reverse mode MR is initiated, as in this non-limiting example. It is also possible for the vehicle 100 to be moving forward when the reverse mode is entered, whereafter the speed forward is then reduced in the reverse mode MR. At some point, the vehicle speed then becomes zero, i.e. as in the initial state of the above non-limiting example, whereafter the vehicle 100 is driven/moved backwards if the reverse mode MR is still utilized. When propelling the vehicle backwards, the first electrical machine 101 should provide enough torque to counteract a reaction torque T_react at the second sun gear S2/222 caused by the second electrical machine 102. This causes the first planetary gear 210 and its first 231 and second 232 freewheel arrangements, to stay functionally bypassed/disabled. The conditions of the shift from Standstill to the reverse mode MR are given in the below Table “Standstill to MR”. Electrical Standstill ^ MR initiation Reverse propelling machine (Rotation directions and torques) 101 D₁₀₁: zero T₁₀₁: Negative T₁₀₁: Counteract ω₁₀₁: Zero 102 D₁₀₂: Zero to positive T₁₀₂: Positive T102: Zero to positive D102: Positive Table: Standstill to MR Above, the control of the first 101 and second 102 electrical machines during an example of a driving cycle including takeoff/M1 ^ M2

MB ^ MR has been described. This is, as is understood by the skilled person, only a non-limiting example of one possible driving cycle. Theoretically, the transmission arrangement 200 may, simply by controlling the first 101 and second 102 electrical machines, be utilized in any driving cycle involving the herein described operation modes. Corresponding control of the first 101 and second 102 electrical machines may then be used for shifting/switching between the operation modes included in such other driving cycles. It is thus at least theoretically possible to go from any one of the operation modes to any other one of the operation modes. In practical implementations, however, limitations of the first 101 and second 102 electrical machines and/or driving comfort may have to be taken into consideration. It may also be noted that “upshifting” is described above, e.g. from the first mode M1 to the second mode M2; M1 ^M2; and from the second mode M2 to the third mode M3; M2 ^M3. Of course, corresponding “downshifting”, e.g. from the third mode M3 to the second mode M2; M3 ^M2; and from the second mode M2 to the first mode M1; M2 ^M1; may also be performed with corresponding control of the first 101 and second 102 electrical machines. Also, a two step “upshifting” from the first mode M1 to the third mode M3; M1 ^M3; and a two step “downshifting” from the third mode M3 to the first mode M1; M3 ^M1; may be performed. For example, a “downshift” from the third mode M3 to the second mode M2, may be needed when the vehicle reaches an uphill, e.g. a long uphill or a steep uphill, in which the vehicle loses speed in the third mode M3. Such a downshift is then achieved by essentially reversing the above described control steps used for the upshift from the second mode M2 to the third mode M3. Thus, such a downshift is then achieved by switching the rotation direction D₁₀₁ of the first electrical machine 101, from negative to positive, possibly by utilizing preferred decreases and increases for the absolute value of the rotational speed at the switch e.g. for comfort and/or component wear reasons, essentially in a reversed manner in relation to what is described in connection with figures 13a-f above. A “downshift” from the second mode M2 to the first mode M1, may for example occur automatically when the vehicle speed is reduced, e.g. by an uphill, such that the first electrical machine 101, due to its torque function, provides such a high torque T101 that the second electrical machine 102 cannot counteract the reaction torque Treact from the second ring gear R2/221 anymore, whereby the third freewheel arrangement 233 locks the second ring gear R2/221 against rotation, and the first mode M1 is entered. The vehicle 100 illustrated in figure 1 and/or the transmission arrangement in figures 2a-b may, according to an embodiment, include at least one control unit/device 600, 900, which may also be denoted processing arrangement, being arranged for executing the above described method 500. The at least one control unit/device 600, 900 may include control entities functions 610, 620, 630, 640 arranged for performing the herein described method steps, respectively, as explained below. The control unit/device 600, 900 and/or one or more another control units/devices may further be configured for controlling one or more of the at least one energy storage/source 104, and/or any other units/devices/entities of the vehicle. However, in figure 1, only the units/devices/entities of the vehicle useful for understanding the present invention are illustrated. The vehicle 100 may also include at least one first input device 701, 702 arranged for receiving an input from the driver, regarding e.g. a requested vehicle speed, a requested vehicle acceleration, a requested vehicle deceleration, or a requested regenerative braking. The at least one input device may include at least one pedal, at least one button, at least one knob, at least one lever, at least one touch screen, or any other suitable input device, and may provide the input information either directly or indirectly, e.g. via a cruise control system or the like, to the control unit 600/900. The control unit 600/900 may also comprise and/or be connected to other control systems and/or functions of the vehicle, such as systems and/or functions for speed control, e.g. cruise control utilizing vehicle positioning and/or map data, AiCC (Autonomous intelligent Cruise control), or any other type of cruise control, systems and/or functions for controlling braking, and/or systems and/or functions for controlling gear shifting or gearboxes. The person skilled in the art will appreciate that the herein described method aspects and embodiments for controlling the transmission arrangement 200 may also be implemented in a computer program, which, when it is executed in a computer, instructs the computer to execute the method. The computer program is usually constituted by a computer program product 903 stored on a non-transitory/non- volatile digital storage medium, in which the computer program is incorporated in the computer-readable medium of the computer program product. The computer- readable medium comprises a suitable memory, such as, for example: ROM (Read- Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit, etc. Figure 16 shows in schematic representation a control unit 600,900, which may also be denoted processing arrangement, and which may correspond to or may include the above-mentioned control units 600, 900, illustrated in figures 1 and 2. The control unit 600,900 may be arranged/configures for performing/executing one or more of the above-mentioned method steps 510, 511, 512, 513, 520, 521, 522, 523, 530, 540, 550, 560, 571, 572, 581, 582. The control unit 600, 900 comprises a computing unit 901, which can be constituted by essentially any suitable type of processor or microcomputer, for example a circuit for digital signal processing (Digital Signal Processor, DSP), or a circuit having a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 901 is connected to a memory unit 902 arranged in the control unit 600, 900, which memory unit provides the computing unit 901 with, for example, the stored program code and/or the stored data which the computing unit 901 requires to be able to perform computations. The computing unit 901 is also arranged to store partial or final results of computations in the memory unit 902. In addition, the control unit 600, 900 is provided with devices 911, 912, 913, 914 for receiving and transmitting input and output signals. These input and output signals may comprise waveforms, impulses, or other attributes which, by the devices 911, 913 for the reception of input signals, can be detected as information and can be converted into signals which can be processed by the computing unit 901. These signals are then made available to the computing unit 901. The devices 912, 914 for the transmission of output signals are arranged to convert signals received from the computing unit 901 in order to create output signals by, for example, modulating the signals, which can be transmitted to other parts of and/or systems in the vehicle. Each of the connections to the devices for receiving and transmitting input and output signals can be constituted by one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated Systems Transport bus), an Ethernet connection, or some other bus/connection configuration; or by a wireless connection. A person skilled in the art will appreciate that the above-stated computer can be constituted by the computing unit 901 and that the above- stated memory can be constituted by the memory unit 902. Control systems in modern vehicles commonly comprise communication connections, such as e.g. bus systems comprising one or more communication buses for linking a number of electronic control units (ECU's), or controllers, and various components arranged in the vehicle together. Such a control system may comprise essentially any number of control units, and the responsibility for a specific function can be divided amongst more than one control units. Vehicles of the shown type thus often comprise significantly more control units than are shown in figures 1, 2 and 16, which is well known to the person skilled in the art within this technical field. However, a vehicle 100 may also include less control units than herein described, such as one single control unit. Various control units distributed in the vehicle 100 may also be seen as at least logically comprised within one control unit. In a shown embodiment, the aspects and embodiments of the present invention may be implemented by the one or more above mentioned control devices/units 600, 900. The herein described aspects and embodiments may also, however, be implemented wholly or partially in one or more other control units already present in the vehicle, or in some control unit dedicated to the present invention. Here and in this document, control units are often described as being arranged for performing steps of the method according to the herein described aspects and embodiments. This also includes that the control units are designed to and/or configured to perform these method steps. For example, the control units may comprise one or more control entities 610, 611, 612, 613, 620, 621, 622, 623, 630, 640, 650, 660, 671, 672, 681, 682 arranged for performing one or more of the herein described method steps 510, 511, 512, 513, 520, 521, 522, 523, 530, 540, 550, 560, 571, 572, 581, 582, respectively. These control entities may for example correspond to groups of instructions, which may be in the form of programming code, that are input into, and are utilized/executed by the processor/computing unit 901 of the control unit 600, 900 when the entities are active and/or are utilized for performing their method steps, respectively. Such control entities may be implemented as separate entities in multiple control units, or may be logically separated but physically implemented in the same control unit, or may be both logically and physically arranged together. Of the one or more control entities mentioned above 610, 611, 612, 613, 620, 621, 622, 623, 630, 640, 650, 660, 671, 672, 681, 682, only some of the control entities 610, 620, 630, 640 are schematically illustrated in figure 1 for readability reasons, whereas the rest are indicated by dots (…). The present invention is not limited to the above described embodiments. Instead, the present invention relates to, and encompasses all different embodiments being included within the scope of the independent claims.

Claims

Claims 1. A transmission arrangement (200) for transferring torque between one or more of a first electrical machine (101) and a second electrical machine (102), and at least one drive wheel (111, 112 ) of a vehicle (100), the at least one drive wheel (111, 112) having a positive rotation direction (D_{out_pos}) when the vehicle is moving forward; the transmission arrangement (200) including: - a first planetary gear (210) including a first ring gear (R1/211), a first sun gear (S1/212), and a first planet gear carrier (C1/213); and - a second planetary gear (220) including a second ring gear (R2/221), a second sun gear (S2/222), and a second planet gear carrier (C2/223); characterized in that - the first electrical machine (101) is coupled to the first ring gear (R1/211); - the first sun gear (S1/212) is coupled to the second sun gear (S2/222); - the second electrical machine (102) is coupled to the second ring gear (R2/221); - the second planet gear carrier (C2/223) is coupled to the at least one drive wheel (111, 112); - a first freewheel arrangement (231) and a second freewheel arrangement (232) are arranged such that: -- when the first electrical machine (101) provides a first rotation direction (DR1_1) of the first ring gear (R1/211), which would cause a negative rotation direction (Dout_neg) of the at least one drive wheel (111, 112) if the first sun gear (S1/212) would rotate in a first direction (D_{S1_1}) equal to the first rotation direction (D_{R1_1}) of the first ring gear (R1/211) and if the second ring gear (R2/221) would stand still: --- the first freewheel arrangement (231) locks the first planet gear carrier (C1/213) against rotation; and --- the second freewheel arrangement (232) allows the first ring gear (R1/211) and the first sun gear (S1/212) to rotate in relation to the first planet gear carrier (C1/213); and -- when the first electrical machine (101) provides a second rotation direction (DR1_2) of the first ring gear (R1/211), being opposite to the first rotation direction (DR1_1): --- the first freewheel arrangement (231) allows the first planet gear carrier (C1/213) to rotate; and --- the second freewheel arrangement (232) locks the first planet gear carrier (C1/213) to one of the first ring gear (R1/211) and the first sun gear (S1/212).

2. The transmission arrangement (200) as claimed in claim 1, including - a third freewheel arrangement (233) coupled between the second electrical machine (102) and the second ring gear (R2/221), and arranged such that: -- when a first rotation direction (D233_1) would be provided at the third freewheel arrangement (233), where the first rotation direction (D233_1) would have been the result if the second planet gear carrier (C2/223) would rotate with a rotation direction (DC2) corresponding to a positive rotation direction (Dout_pos) at the at least one drive wheel (111, 112), and the second sun gear (S2/222) would rotate with a rotation direction (D_S2) which would cause the positive rotation direction (D_{out_pos}) of the at least one drive wheel (111, 112) if the second ring gear (R2/221) would stand still: --- the third freewheel arrangement (233) locks the second ring gear (R2/221) against rotation; and -- when a second rotation direction (D_{233_2}) is provided at the third freewheel arrangement (233), being opposite to the first rotation direction (D233_1): --- the third freewheel arrangement (233) allows the second ring gear (R2/221) to rotate.

3. The transmission arrangement (200) as claimed in any one of claims 1-2, including - a brake coupling arrangement (242) arranged to: -- when a first torque difference (T_{242_diff_1}) present over the brake coupling arrangement (242) acts on the brake coupling arrangement (242) in a first direction (D242_1) which would, if the second ring gear (R2/221) would stand still, result in a forward driving torque (T_forward) on the at least one drive wheel (111, 112): --- couple the second sun gear (S2/222) to the first electrical machine (101) via the first planetary gear (210), thereby functionally utilizing the first planetary gear (210), a first freewheel arrangement (231), and the second freewheel arrangement (232); and -- when a second torque difference (T242_diff_2) present over the brake coupling arrangement (242) acts on the brake coupling arrangement (242) in a second direction (D_{242_2}) being opposite to the first direction (D_{242_1}): --- functionally bypass the first planetary gear (210), a first freewheel arrangement (231) and the second freewheel arrangement (232).

4. The transmission arrangement (200) as claimed in claim 3, wherein the brake coupling arrangement (242) comprises: - a first shaft (310) coupled to the first electrical machine (101) at a first end (311) and to the first ring gear (R1/211) at a second end (312); - a second shaft (320) coupled to the second sun gear (S2/222) at a second end (323); and - a sleeve (330) arranged to interact with both the first sun gear (S1/212) and the second shaft (320), and to be movable between a first (337) and a second (338) position; wherein: -- the sleeve (330) is arranged to be moved towards the first position (337) when the second shaft (320), by the first torque difference (T242_diff_1), is rotated in a first direction (ΔD320_330_1) relative to the sleeve (330), where the first ring gear (R1/211), the first sun gear (S1/212) and the first planet gear carrier (C1/213) are unlocked in relation to each other when the sleeve (330) is in the first position (337), such that the first shaft (310) is coupled to the second shaft (320) via the first ring gear (R1/211), the first sun gear (S1/212) and the sleeve (330); and -- the sleeve (330) is arranged to be moved towards the second position (338) when the second shaft (320), by the second torque difference (T242_diff_2), is rotated in a second direction (ΔD_{320_330_2}) relative to the sleeve (330), where the sleeve (330) locks the first sun gear (S1/212) to the first planet gear carrier (C1/213) when the sleeve (330) is in the second position (338), such that the first shaft (310) and the second shaft (320) corotate.

5. The transmission arrangement (200) as claimed in any one of claims 3-4, including - a reverse coupling arrangement (241), arranged at a third freewheel arrangement (233) coupled between the second electrical machine (102) and the second ring gear (R2/221), and arranged to: -- when a first torque difference (T241_diff_1) present over the reverse coupling arrangement (241) acts on the reverse coupling arrangement (241) in a first direction (D241_1) which would, if the second sun gear (S2/222) would stand still, result in a backward driving torque (T_backward) on the at least one drive wheel (111, 112): --- decouple the third freewheel arrangement (233) from the second ring gear (R2/221); and -- when a second torque difference (T_{241_diff_2}) present over the reverse coupling arrangement (241) acts on the reverse coupling arrangement (241) in a second direction (D241_2) being opposite to the first direction (D241_1): --- couple the third freewheel arrangement (233) to the second ring gear (R2/221).

6. The transmission arrangement (200) as claimed in claim 5, wherein the reverse coupling arrangement (241) comprises: - a first shaft (410) coupled to the second electrical machine (102); - a second shaft (420) coupled to the second ring gear (R2/221); and - a sleeve (430) arranged to be: -- interacting with the first shaft (410) at a first end (433); -- engaged with the second shaft (420) at a second end (434); and -- movable between a first (437) and a second (438) position; wherein: - the sleeve (430) is arranged to be moved towards the first position (437) when the first shaft (410), by the first torque difference (T_{241_diff_1}), is rotated in a first direction (ΔD410_430_1) relative to the sleeve (430), where the second shaft (420), via the sleeve (430), is engaged with the first shaft (410), but is disengaged from the third freewheel arrangement (233), when the sleeve (430) is in the first position (437); and - the sleeve (430) is arranged to be moved towards the second position (438) when the first shaft (410), by the second torque difference (T241_diff_2), is rotated in a second direction (ΔD410_430_2) relative to the sleeve (430), where the second shaft (420), via the sleeve (430), is engaged with both the first shaft (410) and the third freewheel arrangement (233) when the sleeve (430) is in the second position (438) .

7. The transmission arrangement (200) as claimed in any one of claims 1-6, wherein the second freewheel arrangement (232) comprises one in the group of: - a second freewheel arrangement (232a) arranged to be able to either lock the first planet gear carrier (C1/213) and the first sun gear (S1/212) to each other, or allow the first planet gear carrier (C1/213) and the first sun gear (S1/212) to rotate in relation to each other; and - a second freewheel arrangement (232b) arranged to be able to either lock the first planet gear carrier (C1/213) and the first ring gear (R1/211) to each other, or to allow the first planet gear carrier (C1/213) and the first ring gear (R1/211) to rotate in relation to each other.

8. A vehicle (100) characterized in that it comprises a transmission arrangement (200) as claimed in any one of claims 1-7.

9. A method (500) for controlling a transmission arrangement (200) according to any one of claims 1-7 for providing a second mode of operation (M2) of the transmission arrangement (200), the method including: - controlling (510) the first electrical machine (101) to cause the second rotation direction (D_{R1_2}) of the first ring gear (R1/211), whereby: -- the first freewheel arrangement (231) allows the first planet gear carrier (C1/213) to rotate; and -- the second freewheel arrangement (232) locks the first planet gear carrier (C1/213) to one of the first ring gear (R1/211) and the first sun gear (S1/212); and - controlling (530) the first electrical machine (101) to cause the at least one drive wheel (111, 112) to move in a positive rotation direction (D_{out_pos}); and - controlling (540) the second electrical machine (102) to cause the at least one drive wheel (111, 112) to move in the positive rotation direction (Dout_pos).

10. The method (500) as claimed in claim 9, the method further including controlling a transmission arrangement (200) according to claim 2 for providing a first mode of operation (M1) of the transmission arrangement (200) by: - controlling (510) the first electrical machine (101) to cause the second rotation direction (D_{R1_2}) of the first ring gear (R1/211), whereby -- the first freewheel arrangement (231) allows the first planet gear carrier (C1/213) to rotate; and -- the second freewheel arrangement (232) locks the first planet gear carrier (C1/213) to one of the first ring gear (R1/211) and the first sun gear (S1/212); and - controlling (550) the first (101) and second (102) electrical machines such that they try to cause the first rotation direction (D_{233_1}) at the third freewheel arrangement (233); whereby: -- the third freewheel arrangement (233) locks the second ring gear (R2/221) against rotation; and - controlling (560) the first electrical machine (101) to cause the at least one drive wheel (111, 112) to move in a positive rotation direction (D_{out_pos}).

11. The method (500) as claimed in any one of claims 9-10, the method further including controlling a transmission arrangement (200) according to claim 1-7 for providing a third mode of operation (M3) of the transmission arrangement (200) by: - controlling (520) the first electrical machine (101) to cause the first rotation direction (D_{R1_1}) of the first ring gear (R1/211), whereby -- the first freewheel arrangement (231) locks the first planet gear carrier (C1/213) against rotation; and -- the second freewheel arrangement (232) allows the first ring gear (R1/211) and the first sun gear (S1/212) to rotate in relation to the first planet gear carrier (C1/213); - controlling (530) the first electrical machine (101) to cause the at least one drive wheel (111, 112) to move in a positive rotation direction (Dout_pos); and - controlling (540) the second electrical machine (102) to cause a positive rotation direction (Dout_pos) of the at least one drive wheel (111, 112).

12. The method (500) as claimed in any one of claims 10-11, wherein the first electrical machine (101) is, when switching between a second (M2) and third (M3) mode of operation, controlled (510, 520) to: - switch (512, 522) its rotational speed (ω101) from a previous rotation direction (D101_previous) to a subsequent rotation direction (D101_subsequent) being opposite to the previous rotation direction (D_{101_previous}).

13. The method (500) as claimed in claim 12, wherein the switching (512, 522) from the previous rotation direction (D101_previous) to a subsequent rotation direction (D_{101_subsequent}) includes controlling (510, 520) the first electrical machine (101) to: - reduce (511, 521) an absolute value of a rotational speed (|ω101|) of the previous rotation direction (D_{101_previous}) to zero, while providing a torque having a non-zero absolute value (|T101|≠0); - switch (512, 522) to the subsequent rotation direction (D_{101_subsequent}); and - increase (513, 523) the absolute value of the rotational speed (|ω101|) of the subsequent rotation direction (D101_subsequent).

14. The method (500) as claimed in any one of claims 9-13, the method further including controlling a transmission arrangement (200) according to any one of claims 3-4 for providing a regenerative brake mode of operation (MB) of the transmission arrangement (200) by: - controlling (571) the first (101) and second (102) electrical machines such that the second torque difference (T242_diff_2) is present over the brake coupling arrangement (); whereby -- the first planetary gear (210), a first freewheel arrangement (231) and the second freewheel arrangement (232) are functionally bypassed by the brake coupling arrangement (242); and - controlling (572) the first (101) and second (102) electrical machines to brake the vehicle (100) and to thereby generate energy.

15. The method (500) as claimed in any one of claims 9-14, the method further including controlling a transmission arrangement (200) according to any one of claims 5-6 for providing a reverse mode (MR) of operation of the transmission arrangement (200) by: - controlling (581) the first (101) and second (102) electrical machines such that the first torque difference (T_{241_diff_1}) is present over the reverse coupling arrangement (241); whereby -- the third freewheel arrangement (233) is decoupled from the second ring gear (R2/221); and - controlling (582) the first (101) and second (102) electrical machines such that the vehicle (100) is driven backwards.

16. A control unit (600/900) characterized in that it is configured to perform the method as claimed in any one of claims 9-15.

17. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of claims 9-15.

18. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 9-15.