SE2250483A1

SE2250483A1 - Method and control arrangement for controlling a vehicle during a speed reduction

Info

Publication number: SE2250483A1
Application number: SE2250483A
Authority: SE
Inventors: Manne Held; Mikael Alenius
Original assignee: Scania Cv Ab
Priority date: 2022-04-22
Filing date: 2022-04-22
Publication date: 2023-10-23
Also published as: DE102023107814A1

Abstract

A method performed by a control arrangement, for controlling an electrical machine of a vehicle, the electrical machine being configured to apply a propelling power for propelling the vehicle, the method comprising, when a speed of the vehicle is being reduced from an initial speed to a target speed:applying a propelling power by means of the electrical machine prior to the speed of the vehicle reaching the target speed, wherein the speed of the vehicle is reduced while the propelling power is applied.Hereby, the duration of the speed reduction is extended, and the peak power applied during the speed reduction is lower compared to the power required to maintain the target speed once the target speed is reached. This results in decreased heat losses in the electrical machine. Hence, increased engine efficiency is achieved.The invention relates also to a control arrangement, a vehicle comprising the control arrangement, a computer program and a computer-readable medium.

Description

METHOD AND CONTROL ARRANGEMENT FOR CQNTRÛLLÉN§ A VEHICLE DURING A SPEED REDUCTION Technical field The invention relates to a method and a control arrangement for controlling a vehicle during a speed reduction.

The invention also relates to a computer program and a computer-readable medium and a vehicle comprising such a control arrangement.

Background The following background description constitutes a description of the background to the invention, which does not, however, necessarily have to constitute prior art.

One of the major global challenges today is reducing the negative impacts of road transportation on the environment due to greenhouse gas emissions. Moreover, the efficiency of a vehicle's energy consumption is one of the major factors inﬂuencing the cost, performance, and competitiveness of the vehicle. This has led to an increased interest in solutions aiming to improve energy efficiency in vehicles.

Vehicles, including heavy motor vehicles, such as trucks and busses, may vary in speed when travelling on a section of road. Today, the speed of vehicles is often controlled automatically by means of speed control systems. Usually, a driver of the vehicle selects a set speed, which is thereafter automatically maintained. When the vehicle is coming from an overspeed, for example when gravity has increased the speed of the vehicle in a downhill, or if the set speed has been lowered, automatically or by the driver, to keep a legal speed limit, the speed of the vehicle needs to be reduced such that the target speed is reached.

An optimized and energy efficient deceleration strategy is an important factor contributing to improved vehicle economy.

Summaﬂ lO lt is an objective of the present invention to provide a method and a control arrangement for mitigating and/or solving drawbacks of conventional solutions. ln particular an objective of the present invention is to provide a solution for controlling an electrical machine of a vehicle in overspeed such that an improved energy efficiency in the vehicle is obtained.

According to a first aspect of the invention, the aforementioned and further objectives are achieved through a method, performed by a control arrengement, for controlling an electrical machine of a vehicle, the electrical machine being configured to apply a propelling power for propelling the vehicle, the method comprising, when a speed of the vehicle is being reduced from an initial speed to a target speed: applying a propelling power by means of the electrical machine prior to the speed of the vehicle reaching the target speed, wherein the speed of the vehicle is reduced while the propelling power is applied.

The invention relates thus to a method for controlling an electrical machine in an electrical vehicle, i.e., a vehicle that uses one or more electrical machines for propulsion. Examples of such vehicles are battery electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles. lt is to be understood that the electrical machine may be controlled automatically such that a propelling and/or brake power are provided when the vehicle is in motion to control the speed of the vehicle. The propelling power may here be understood as a power which, when applied, accelerates the vehicle in its direction of travel. ln similar fashion, the braking power relates to a power which, when applied decelerated the vehicle. The initial speed may be the actual speed which the vehicle is maintaining when the method of the invention is executed. The target speed may be understood as a desired speed, lower that the initial speed. Thus, the method of the invention is executed when the speed of the vehicle is being reduced.

According to the invention a propelling power is applied by means of the electrical machine during the speed reduction. When said propelling power is applied, the vehicle decelerates due to the aerodynamic drag, rolling friction, and other forces that lO oppose the movement of the vehicle. However the vehicle decelerates more slowly because of the applied propelling power compared to if no propelling power would have been applied or if a brake has been activated. The vehicle travels thereby a longer distance prior to completing the speed reduction. The method of the invention may be applied when the deceleration of the vehicle is performed on an uphill section of a road or on a section of the road which is generally level or other situations where the vehicle is not accelerated by means of gravity. Since the speed reduction from the initial speed to the target speed will take a longer period of time in comparison to when no power is applied by the electrical machine during the speed reduction, the vehicle will have travelled a longer distance prior to applying the power required to maintain the target speed once the target speed is reached. Consequently, the peak power applied during the reduction of the speed of the vehicle may be lower compared to the power required to maintain the target speed once the target speed is reached. This results in decreased heat losses in the electrical machine. Hence, increased engine efficiency is achieved.

Moreover, executing the method of the invention may lead to increased average speed when the speed is reduced from the initial speed to the target speed which may result in a reduced travel time of the vehicle. ln an embodiment of the invention, the propelling power applied by means of the electrical machine when reducing the speed of the vehicle from the initial speed vin: to the target speed is lower compared to a propelling power that would have been applied to maintain the target speed.

Thus, the peak power that would have been applied to maintain the target speed during the speed reduction from the initial speed vin: to the target speed is reduced. Hereby, increased efficiency of the electric engine components and batteries is obtained. ln addition, by reducing the applied peak power, the temperature of the electric engine components and batteries is reduced. Hence, a risk of overheating of the electric engine components and batteries is decreased. lO ln an embodiment of the invention, the duration of the speed reduction from the initial speed to the target speed when the propelling power is applied by means of the electrical machine is controlled to amount to at least a first period of time.

The first period oftime may correspond to the time period when a propelling power is applied by means of the electrical machine during the total time the speed reduction from the initial speed to the target speed is ongoing.

By applying said propelling power during at least a first period oftime of the total time the speed reduction is performed, the duration of the speed reduction is increased and thereby the time until the power required to maintain the vehicle speed needs to be applied. Hence, the peak power being utilised in the reduction of the speed of the vehicle from the initial speed to the target speed is lower compared to the power required to maintain the target speed once the target speed is reached which will result in similar advantages as described above with reference to the first aspect of the invention.

Moreover, the speed reduction may be performed also in situations when it may, for example, be favourable, or even necessary, to suddenly reduce the vehicle's speed and thus it is not possible to apply the propelling power during the entire duration when the vehicle speed is reduced from the initial speed to the target speed. ln some situations, the applied propelling power may need to change dynamically when the speed of the vehicle is reduced due to e.g., traffic conditions within the travelled section of the road. Hereby, the speed of the vehicle, and the applying of the propelling power, may be controlled dynamically in a flexible and reliable way. ln an embodiment of the invention, the method further comprises: determining the first period of time at least partly based on a speed difference between the initial speed and the target speed. lO By taking into account the speed difference between the initial speed and the target speed when determining the first period of time, a smooth speed transition may be obtained when the vehicle speed is reduced. This may contribute to an improved driving comfort.

Hereby, it may become attractive for the driver to use the automatic method of controlling the electrical machine in situations when the speed of the vehicle is to be reduced leading to increased energy efficiency. Also, the speed difference may be utilized to optimize energy consumption by suitably extending the period of time of speed reduction. ln an embodiment of the invention, the determining of the first period of time is further based on a total period of time during which the reduction in speed of the vehicle from the initial speed to the target speed is ongoing.

Hereby, the total period of time during which the vehicle speed is above a target value may be controlled. ln an embodiment of the invention, the vehicle speed is controlled by means of a cruise control function being set to maintain the target speed while the vehicle speed is being reduced from an initial speed toa target speed.

Hereby, the energy efficiency of the cruise control function may be further improved in situations where the speed of the vehicle is being reduced. Moreover, controlling the vehicle speed by means of a cruise control function may lead to increased use of the energy-saving functionality according to the invention when the speed of the vehicle is being reduced. ln an embodiment of the invention the method further comprises; applying the propelling power when the vehicle speed is reduced from the initial speed, the initial speed being an overspeed in relation to the target speed, the overspeed resulting from the vehicle being accelerated by a downhill section of road. lO Hereby, an improved energy efficiency is obtained when the speed of the vehicle is reduced from a speed increased due to gravity during downhill driving. ln an embodiment of the invention the method further comprises; applying the prope||ing power when the vehicle speed is reduced from the initial speed, the initial speed being a current target speed of the vehicle, the speed reduction resulting from the current target speed of the vehicle being decreased.

Hereby, an improved energy efficiency is obtained also in other situations where the vehicle speed is decreased, e.g., when the target speed of the vehicle has been decreased by a driver or automatically, for example due to changed speed limit on the travelled section of the road. A target speed may be automatically decreased based on e.g., speed sign recognition or information from map data. Moreover, when an approaching reduction of the current target speed is determined in the vehicle, the speed reduction of the vehicle may, at least partly, have been carried out when the reduced target speed takes effect. ln an embodiment of the invention, the method further comprises: determining a prope||ing power to be applied by the electrical machine during the reduction of the vehicle speed from the initial speed to the target speed, prior to applying the prope||ing power by the electrical machine, wherein the applying of the prope||ing power comprises applying by the electrical machine the determined prope||ing power.

Hereby, the prope||ing power can be calculated such that, for example, the speed reduction will amount to a predetermined period of time, and/or a predetermined power level is utilized while still ensuring that the speed reduction is accomplished in a desired manner. ln an embodiment of the invention the determining of the prope||ing power is at least partly based on information related to the section of the road in which the speed is reduced. The information related to the section of the road in which the speed is reduced comprises, in an embodiment, at least one of: lO - an inclination of said section of the road, - a traffic situation within said section of the road.

Hereby, the propelling power may be determined in a reliable way with a high degree of accuracy and the speed reduction may be adapted to road and traffic conditions in front of the vehicle. ln an embodiment of the invention the determining of the power level of the electrical machine is at least partly based on the first period of time during which the propelling power is to be applied.

Hereby, the propelling power may be determined such that the speed of the vehicle is reduced in an energy efficient manner, e.g. by ensuring that the speed reduction will take at least a predetermined period of time until the propelling power must be increased to maintain the vehicle speed.

According to a second aspect, the invention relates to a control arrangement for controiiing an electrical machine of a vehicle, the electrical machine being configured to apply a propelling power for propelling the vehicle, the control arrangement being configured to, when a speed of the vehicle is being reduced from an initial speed to a target speed: apply a propelling power by means of the electrical machine prior to the speed of the vehicle reaching the target speed, wherein the speed of the vehicle is reduced while the propelling power is applied. lt will be appreciated that all the embodiments that have been described for the method aspects of the invention are applicable also to at least one of the control arrangement aspects of the invention. Thus, all the embodiments described for the method aspects of the invention may be performed by the control arrangement, which may also be a control device, i.e. a device. The control arrangement and its embodiments have advantages corresponding to the advantages mentioned above for the methods and their embodiments. lO According to a third aspect of the invention, the aforementioned and further objectives are achieved through a vehicle comprising the control arrangement of the second aspect. The vehicle may for example be a bus, a truck, or a car.

According to a fourth aspect, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to the first aspect.

According to a fifth aspect, the invention relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to the first aspect.

The above-mentioned features and embodiments of the method, the control arrangement, the vehicle, the computer program, and the computer-readable medium, respectively, may be combined in various possible ways providing further advantageous embodiments.

Further advantageous embodiments of the method, the control arrangement, the vehicle, the computer program, and the computer-readable medium according to the present invention and further advantages with the embodiments of the present invention emerge from the detailed description of embodiments.

Brief description of the drawinqs 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: Figure1 shows a schematic view illustrating an exemplary vehicle in which embodiments of the present invention may be implemented; Figure 2a shows a flow chart of a method for controliing an electrical machine of a vehicle, according to an embodiment of the invention; lO Figure 2b a vehicle, according to further embodiments of the invention; shows a flow chart of a method for controlling an electrical machine of Figure 3 illustrates the principle of one embodiment of the invention in one driving situation; Figure 4 illustrates the principle of one further embodiment of the invention in one driving situation; Figure 5 illustrates the principle of one further embodiment of the invention in one driving situation; Figure 6 shows a control arrangement, in which a method according to any one of the herein described embodiments may be implemented.

Detailed description On conventional vehicles, including electric vehicles, speed reduction by using a brake power, e.g. by manual use of a brake pedal, or by automatically applying one or more brake systems, usually represents an energy loss. ln existing solutions, in electric vehicles on road sections where the vehicle is not accelerated by gravity forces an energy efficient speed reduction may be achieved by not providing any tractive power from the vehicle's electrical machine. The forces opposing the movement ofthe vehicle e.g. friction forces and air resistance decelerate the vehicle until a required speed is achieved.

However, it has been realized that further energy optimizations may be achieved when decreasing the speed of the vehicle. lt is thus an objective of the present invention to provide a method and a control arrangement for controlling an electrical machine of a vehicle such that these problems are at least partly solved. lO lO Now turning to Figure 1, which schematically illustrates a vehicle 100 and its powertrain, that will be used to explain the herein presented embodiments. The vehicle 100 may e.g., be a car, a bus, or a truck. The powertrain of the vehicle 100 illustrated in Figure 1 comprises at least one electric machine 101 configured for providing power to the drive wheels 111, 112 of the vehicle 100. ln the shown embodiment, the vehicle 100 comprises two drive wheels 111, 112 but it should be understood that the vehicle 100 may be arranged with one of more drive wheels. The at least one electric machine 101 may, as depicted in Figure 1, be connected to a gearbox 102 via an input shaft 104. The vehicle 100 may comprise a propeller shaft 105 from the gearbox 102 which drives the drive wheels 111, 112 via a central gear 103, for example a conventional differential, and two drive shafts 106, 107 of the vehicle 100. lt should be understood that the vehicle 100 may be arranged in any known way, for example without a gearbox 102 or conventional differential without limiting the scope of the invention.

The at least one electric machine 101 may be arranged essentially anywhere, as long as torque power is provided to one or more of the drive wheels 111, 112, for example adjacent to one or more of the wheels, or in any other conventional way as is understood by a skilled person. The at least one electric machine 101 may be provided with electrical power from a battery system (not depicted).

The vehicle 100 may be a pure electric vehicle having no internal combustion engine and instead only including the one or more electric machines 101 for driving the drive wheels 111, 112. However, the vehicle 100 may also be a so-called hybrid vehicle and also include an internal combustion engine (not depicted), which may in a conventional manner be connected to the gearbox 102 via a clutch (not depicted).

The electric machine 101 as well as various components of the vehicle's drive line may be controlled by a vehicle control system via a control arrangement 120. The control arrangement 120 may be distributed on several control units configured to control various parts of the vehicle 100. The control arrangement 120 may e.g. include an applying unit 121 arranged for performing the method steps of the disclosed invention as is explained further on. The control arrangement 120 and/or another lO ll control arrangements may further be configured for controlling any other units/devices/entities of the vehicle 100. However, in Figure 1, only the units/devices/entities of the vehicle useful for understanding the present invention are illustrated. The control arrangement 120 will be described in further detail in Figure 6.

The vehicle 100 may further comprise a positioning system/unit 140. The positioning unit 140 may be based on a satellite navigation system such as the Navigation Signal Timing and Ranging (Navstar), Global Positioning System, GPS, Differential GPS, DGPS, Galeo, GLONASS, or the like. Thus, the positioning unit 140 may comprise a GPS receiver.

The vehicle 100 may further include at least one communication device 150 arranged for communication with at least one entity 160 external to the vehicle 100, such as at least one communication entity of another vehicle. Correspondingly, the at least one communication device 150 may be a vehicle-to-vehicle, V2V, communication device, a vehicle-to-infrastructure, V2|, communication device, a vehicle-to-everything, V2X, communication device, and/or a wireless communication device such that communication between the vehicle and the at least one external entity 160 is achieved/provided.

The vehicle 100 may be equipped with means for automatic speed control. Automatic speed control may be achieved by automatically controlling the electrical machine 101, e.g. by means of a control arrangement, to provide a propelling power such that a desired speed is obtained. ln one example, such automatic control of the electrical machine 101 may be obtained by a cruise control function being configured to maintain a target set speed when the vehicle is driving on the level sections of the road. The cruise control function may be of a kind that uses additional information when controlling the speed of the vehicle. For example, the cruise control can make use of a "Look Ahead" function e.g., active prediction function. A "Look Ahead" cruise control (LACC) function consists of a cruise control function that uses knowledge concerning the upcoming section of road, i.e., knowledge about the topography of the road in front of the vehicle, in order to adapt lO 12 the vehicle velocity based on variations in the road along which the vehicle is travelling. ln another example, the speed of the vehicle 100 may be controlled in the vehicle's driveline control system executing the logic of method 200 and altering the manual driver control of the accelerator pedal.

The proposed invention will now be described with reference to a method 200 as disclosed in a flowchart in Figure 2a. Thus, ln Figure 2a, a method 200 performed by a control arrangernent for controllllïg an electrical machine 101 of a vehicle, such as the vehicle 100, is disclosed. The electrical machine 101 according to the method 200 may be configured to apply a propelling power for propelling the vehicle 100. The method 200 is performed when a speed of the vehicle is being reduced from an initial speed vant to a target speed vt. As previously explained, the initial speed vina may be the actual speed which the vehicle is maintaining when the method of the invention is executed. The target speed may a desired speed, lower that the initial speed. ln step 230 in Figure 2a, a propelling power is applied by means of the electrical machine 101 prior to the speed ofthe vehicle 100 reaching the target speed vt, wherein the speed of the vehicle is reduced while the propelling power is applied.

The present invention may be employed on substantially all types of vehicles comprising an electrical machine configured to apply a propelling powerfor propelling the vehicle, such as hybrid vehicles and electric vehicles. The method 200 being performed by a control arrangement may be understood as the speed of the vehicle 100 being controlled automatically by a control arrangement, such as the control arrangement 120, adjustlng the power of the electrical machine 101 such that a required vehicle speed is obtained.

The invention may be applied in substantially all driving situations when the vehicle 100 is driving with an initial speed vin: and where the speed of the vehicle is to be reduced to a target speed vt on a section of road where the vehicle is not accelerated lO 13 by means of gravity. Example of such section of the road is an uphill section of the road or a section of the road which is generally level.

Figure 3 illustrates the vehicle 100 in a driving situation where the method 200 and further embodiments of the invention may be applied. The vehieie 100 ie driving threugh e route vxfhere the altitude of the route is shown at the top of the figure. Figure 3 also shows a plot of the vehicle's speed, denoted as "SpeecV in the middle section of the figure as well as a power applied by the electrical meehšiwe 101 ef the vehieie te achieve the speed Eliuetreted ih the figure. The pewer is illustrated in e plet denoted ae "Pevverf at the bettem ef Figure 3.

The driving situation illustrated in Figure 3 is described in terms of points in time such as T0, T1, T2, etc., but a person skilled in the art will appreciate that these points in time correspond to respective positions along the travel route of the vehicle. ln Figure 3, the route comprises a level section between the time instance T0 and the time instance T1, a downhill section between the time instance T1 and the time instance T3 and again a level section between the time instance T3 and the time instance T6.

As may be seen in the example illustrated in Figure 3, the speed of the vehicle 100 varies between a speed maintained on the level sections of the route, here denoted as the target speed vi, and a higher speed being maintained in the downhill section of the route, here denoted as the initial speed vin: because this is the speed from which the speed reduction according to the method 200 of the invention will commence.

As previously explained, the speed of the vehicle may be controlled automatically by controlling the vehicle's electrical machine 101 to provide a propelling power or a brake power required to achieve a desired speed. According to previously known methods, the speed of the vehicle 100 may, in one example, be automatically controlled by cruise control configured to achieve a predetermined speed. Cruise control is often conducted in vehicles by two interacting systems, a cruise control function which demands a propelling power from the vehicle's traction unit and a lO 14 downhill speed control which prevents the vehicle from developing excessive speed, particularly when driving downhill. Thus, before entering the downhill road section, the speed of the vehicle may be controlled by means of a cruise control function to maintain the target speed vi. The target speed may correspond to a set speed of the cruise control function. The target speed vi may be maintained by controlling the electrical machine 101 of the vehicle to provide a propelling power P1. A person skilled in the art will realise that automatic speed control may be performed by means of different types of cruise controls e.g., Adaptive Cruise Control, ACC, Cruise Control Active Prediction, CCAP, all included in the scope of the invention. Automatic speed control may lead to increased use of the energy-saving functionality according to the invention when the speed of the vehicle is being reduced.

At the time instance T1 the vehicle enters a downhill section of the road where the speed of the vehicle may be controlled by a downhill control system to allow the vehicle to accelerate, e.g. under the influence of gravity, to the initial speed viiii and then maintain the initial speed viiii. The initial speed viiii may correspond to a braking speed of the downhill control system. Generally, the braking speed of the downhill control system may be based on the set speed of the cruise control function and correspond to the set speed plus an offset speed. Thus, the initial speed viiii in Figure 3 is higher than the target speed vi. At the time instance T1, a propelling power is no longer applied, and the speed of the vehicle increases due to gravity forces. At the time instance T2 the speed of the vehicle reaches the initial speed viiii which is then maintained in the downhill section of the road by applying a brake power PB, e.g. by the electrical machine 101 operating in generator mode. ln one embodiment the vehicle speed may be controlled by means of a cruise control being set to maintain the target speed, while the vehicle speed is being reduced from an initial speed to a target speed. Thus at time instance T3, the speed of the vehicle 100 is an overspeed in relation to the target speed vi and a speed decrease needs to be carried out. ln previously known solutions, a speed decrease, illustrated in Figure 3 by the dashed plots of "Speed" and "Power" between the time instance T3 and T4, may be performed lO by terminating the application of brake power PB, at the time instance T3 at the end of the downhill. Since the vehicle is no longer accelerated by the downhill gravity forces the speed of the vehicle 100 starts to decrease. When the target speed has been reached at the time instance T4 a propelling power P1 is applied so that the target speed vi may be maintained on the following section of the road.

According to the invention, the speed decrease is instead performed by applying a propelling power by means of the electrical machine 101 prior to the speed of the vehicle 100 reaching the target speed vi, wherein the speed of the vehicle is reduced while the propelling power is applied. The speed decrease according to the invention is illustrated in Figure 3 by the solid plots of "Speed" and "Power" between the time instance T3 and T5. ln other words, the invention controls how the speed decrease from the initial speed viiii to the target speed vi is achieved to result in an increased energy efficiency by increasing the efficiency of the electric engine components and batteries compared to previously known methods. The invention applies a propelling power during the speed decrease, which means that the deceleration from the initial speed viiii to the target speed vi will take place over a longer time than in previously known methods where the speed decrease is achieved by not providing any tractive power to the vehicle 100 or by applying a brake power.

As previously explained, during the speed reduction, the peak power being utilised in the reduction of the speed of the vehicle from the initial speed viiii to the target speed vi is lower compared to the power required to maintain the target speed vi once the target speed is reached. A high peak power is not efficient in electrical machines. This is because the power provided by an electrical machine is proportional to the current l, while the heat losses are proportional to the square of the current.

The heat losses in an electrical machine are given by the relation: Pheat = I2*R, Where Piieai is a power of thermal energy due to electrical losses I is an electrical current, and lO 16 R is an electrical resistance.

Thus, the invention applies the principles of efficient utilisation ofan electrical machine in a vehicle in such a way that heat losses and energy waste are reduced. This is obtained by utilising the electrical machine for a longer period oftime, but in a manner where the peak power, may be reduced during this period of time to thereby reduce heat and energy losses. ln addition to the method step 230 described with reference to Figure 2a, the method according to the invention may, in embodiments, comprise further optional steps. Embodiments of the invention will now be explained more in detail with reference to Figure 2b. Figure 2b discloses a flowchart of the method 200 comprising the method step 230 disclosed in Figure 2a as well as further optional method steps.

As previously described, the method 200 of the invention is performed when the speed of the vehicle 100 is being reduced from an initial speed vin: to a target speed vi. Thus, in step 210 of method 200 in Figure 2b, it may be determined whether a speed of the vehicle 100 is being reduced from an initial speed vin: to a target speed viand the speed reduction needs to be controlled according to the invention.

As discussed above with reference to Figure 3, in an embodiment, the initial speed vin: may be an overspeed in relation to the target speed vi, where the overspeed may result from the vehicle being accelerated by the downhill section between the time instance T1 and the time instance T3 in Figure 3. Thus, determining whether the speed of the vehicle 100 is being reduced from an initial speed vin: to a target speed vi may comprise determining whether the vehicle 100 is in overspeed. ln an embodiment, as will be explained further with reference to Figure 4 and Figure 5, the initial speed vin: may, instead, be a current target speed of the vehicle 100 and the speed reduction may result from the current target speed of the vehicle 100 being reduced. Thus, determining whether the speed of the vehicle 100 is being reduced from an initial speed vin: to a target speed vi may comprise determining whether the current target speed of the vehicle 100 is or will soon be reduced. lO 17 Determining whether the vehicle 100 is in overspeed, and/or if the current target speed of the vehicle 100 is or will soon be reduced, may be performed in the control system of the vehicle 100 by comparing the current speed of the vehicle, corresponding to the initial speed viiii with the target speed vi. The current speed of the vehicle as well as the target speed vi may be available in the vehicle's control system according to conventional methods. The target speed vi may, for example, be set by the driver of the vehicle or automatically according to conventional methods, based e.g., on legal speed limits along the route of the vehicle 100, the curvature of the section of the road in front of the vehicle and/or on map data. ln one example, such an automatic setting of the target speed may be done by speed sign recognition in the vehicle. lf the current speed of the vehicle 100 is determined to exceed the target speed vi at a given position, a speed reduction needs to be controlled. lf it is determined that a speed reduction from the initial speed viiii to the target speed vi needs to be controlled, i.e., 'Yes' in step 210, the method 200 continues to step 220, and if no speed reduction is required, i.e., 'No' in step 210, the method 200 returns back to step 210 or is ended. ln step 220, the propelling power Pa to be applied by the electrical machine 101 during the reduction of the vehicle speed from the initial speed viiii to the target speed vi, is determined. The propelling power may be determined prior to applying the propelling power by the electrical machine, wherein the applying of the propelling power comprises applying by the electrical machine 101 the determined propelling power. ln an embodiment, the propelling power Pa applied by means of the electrical machine 101 when reducing the speed of the vehicle from the initial speed viiii to the target speed vi may be lower compared to a propelling power Pi that would have been applied to maintain the target speed vi. By applying a propelling power Pa during the speed reduction from the initial speed viiii to the target speed vi according to the invention, the duration of the speed reduction is increased compared to if the speed decrease was performed according to previously known solutions. Consequently, the lO 18 peak power applied during the speed decrease is reduced compared to if the speed decrease was performed according to previously known methods.

As may be seen in Figure 3, the prope||ing power required to maintain the target speed vi of the vehicle 100 is illustrated as the prope||ing power P1 applied between the time instances T0 and T1 and the time instances T5 and T6. As previously explained, the speed decrease from the initial speed viiii to the target speed vi performed according to previously known methods, is completed at the time instance T4. Consequently, from time instance T4 the target speed vi needs to be maintained by applying the prope||ing power P1 in previously known methods. However, by applying the prope||ing power Pa during the speed reduction according to the invention, the speed decrease is not completed until at the time instance T5. Thus, the peak power P1 required to maintain the target speed vidoes not need to be applied until the speed reduction has been performed i.e., at a later time instance compared to previously known methods. Consequently, the peak power during the speed reduction controlled according to the invention is decreased.

An advantage of the invention is thus that the applied peak power level is reduced during the speed decrease leading to increased efficiency of the electric engine components and batteries due to reduced use of high power.

The prope||ing power Pa to be applied during the speed reduction from the initial speed viiii to the target speed vi may be determined in various ways. ln one example, the prope||ing power may be determined based on the power P1 required to maintain the target speed vi of the vehicle after the vehicle's speed has been reduced from the initial speed viiii to the target speed vi. The prope||ing power to be applied by the electrical machine 101 during the reduction of the vehicle speed from the initial speed viiii to the target speed vi, may be determined as a portion of the power required to maintain the target speed vi of the vehicle 100 taking into consideration parameters like required speed decreased duration and required position to reach the target speed vi. lO 19 The power required to maintain the target speed vi may be determined according to conventional methods, e.g., based on topography information of the section of the road where the power may be applied, the road inc|ination and a weight of the vehicle 100. For example, by using Newton's laws of motion the required power needed to maintain a target speed vi of the vehicle 100 may be estimated for a situation when the vehicle 100 is driving on said section of the road.

The vehicle internal parameters like weight of the vehicle 100 and the current gear ratio is in general available and may be obtained from the vehicle's control system via one or more communication buses linking the control arrangement 150 with various components and controllers located on the vehicle. ln another example, the propelling power may be determined by simulating several different strategies in terms of applying a propelling power when the speed of the vehicle is being reduced and applying one or more limitations. ln an embodiment, the propelling power may at least partly be based on information related to the section of the road in which the speed is reduced. ln an embodiment the information related to the section of the road in which the speed is reduced may comprise knowledge of prevailing topography such as the inc|ination of the section of the road and/or a traffic situation within said section of the road. ln one example, the propelling power may be based on a required speed of the vehicle during the speed decrease which may need to be adapted to road and traffic conditions in front of the vehicle. For example, the speed of the vehicle during the speed decrease may need to be adapted in such a way that there will be no risk of running into, or coming too close to, other vehicles in front of the vehicle 100. ln similar way, the speed of the vehicle during the speed decrease may need to be adapted to prevailing road conditions such as curvature the road in such a way that a safe speed is obtained. The propelling power may, in another example, be determined based on an algorithm analysing how much energy that needs to be reduced during the reduction of the vehicle speed from the initial speed vini to the target speed vi taking lO into consideration the gradient of the road where the speed reduction is performed, and vehicle related parameters like vehicle weight. Thus, a larger propelling power may be required if the speed decrease is performed on an uphill section of the road compared to a level section.

Many vehicles today are provided with systems, which may provide such information. Generally, information about road inclination and prevailing traffic situation may be provided by means of one or more sensors which may be included in the vehicle 100 such as one or more camera, one or more radar equipment and/or a positioning system/unit, such as GPS.

Moreover, such information may be provided by at least one second vehicle, e.g., by V2V communication, and/or by an infrastructure entity, e.g., by V2l communication, be obtained based on radar information, on camera information, on positioning information stored previously in the vehicle 100 and, on information obtained from traffic systems related to the section of the road. For example, information associated with a position of the vehicle 100 may be provided by the positioning system in the vehicle 100. Map associated information e.g., from digital maps may, for example include topology information of an electronic map. Typically, positioning information may be used for positioning the vehicle 100 on the correct location of a digital map, whereby e.g., inclination of a section of the road in front of the vehicle may be determined. ln an embodiment, the duration of the speed reduction from the initial speed viiii to the target speed vi when the propelling power is applied by means of the electrical machine 101 may be controlled to amount to at least a first period of time. The first period of time D1 may correspond to the time period when a propelling power is applied by means of the electrical machine 101 during the time the speed reduction from the initial speed viiii to the target speed vi is ongoing. Thus, as illustrated in Figure 3, the first period of time D1 extends from the time instance T3, when a propelling power Pa is first applied during the speed reduction from the initial speed viiii to the target speed vi, to the time instance T5 when the speed decrease has been performed. lO 21 Note that in Figure 3, the propelling power Pa is applied during the total period of time when the speed of the vehicle 100 is reduced from the initial speed vin: to the target speed vi, and thus, the first period of time D1 corresponds to the total time the speed reduction is ongoing. However, as previously explained, the speed reduction may be performed also in situations when it is not favourable, or even possible, to apply the propelling power during the entire duration of speed reduction from the initial speed vini to the target speed vi. ln a non-limiting example, when a vehicle driving with a speed of 80km/h performs a speed decrease to 65km/h when approaching a road section with a speed limit of 70km/h, the speed reduction from 80km/h to 70km/h may be favourable to perform without any applied propelling power to achieve a fast speed reduction and avoid speeding. However, the speed reduction from 70km/h to 65km/h may be performed while a propelling power is applied. ln that example, the first period of time would correspond to the time it takes to perform the speed reduction from 70km/h to 65km/h. ln some situations, the applied propelling power may need to change dynamically when the speed of the vehicle is reduced due to e.g., traffic conditions or road characteristics within the travelled section of the road. ln a non-limiting example, a comfortable, constant deceleration in a vehicle performing a speed decrease on a road section with a gradually increasing inclination may be achieved by gradually increasing the propelling power applied during the speed decrease. Hereby, the speed of the vehicle, and the applying of the propelling power, may be controlled dynamically in a flexible and reliable way. Thus, in some situations the propelling power may be applied during a part of the total period of the speed reduction of the vehicle, corresponding to the first period of time D1. ln one example, the propelling power may be applied during at least a substantial part of the period of time when the reduction in speed is ongoing. ln a non-limiting example, the propelling power may be applied during at least half of the period of time during which the reduction in speed is ongoing. ln an example the first period of time D1 may be a time period corresponding to at least 2 seconds, preferably between 5 - 20 seconds. lO 22 ln one example, the required propelling power may be determined further based on the position when the speed reduction is to be applied, the position when the speed reduction is to be completed etc. and selecting a strategy that meets the one or more limitations. ln an embodiment, the determining of the propelling power of the electrical machine may at least partly be based on the first period oftime D1 during which the propelling power is applied.

Thus, in one example, the invention may determine the propelling power to a power required to be applied during the first period of time D1. The propelling power may here be determined to serve as a basis for reducing the speed of the vehicle 100 from the initial speed viiii to the target speed vi.

The first period of time D1 may be determined in various ways. ln one example, the first period of time may be determined in such a way that one or more limitations are met. For example, the first period of time may be selected based on a preferred speed deceleration extending from the initial speed viiii at the time instance the propelling power may be applied. Furthermore, the first period of time may be based on further parameters that are to be optimized e.g., energy efficiency, acceptability to the driver of the vehicle, acceptability to other road users and/or driver comfort. ln an embodiment the first period of time may be determined at least partly based on a speed difference between the initial speed viiii and the target speed vi. lt may, for example, be preferable, from a driver comfort point of view, to achieve a smooth speed transition between the initial speed viiii and the target speed vi and thus to keep a low deceleration rate from initial speed viiii. When the speed difference between the initial speed viiii and the target speed vi is small a shorter time for decelerating the vehicle may be needed compared to when the speed difference between the initial speed viiii and the target speed vi is larger. ln another example, the first period of time may be selected such that energy efficiency is optimised rather than driver comfort. lO 23 ln an embodiment, the first period of time D1 may further be determined based on a total period of time during which the reduction in speed of the vehicle from the initial speed viiii to the target speed vi is ongoing. The period of time during which the reduction in speed is ongoing may in one example be preconfigured in the vehicle 100 and be based on legal requirements related to speed limitations and/or drivability aspects. For example, if the speed reduction is performed when the vehicle's speed exceeds legal speed requirements, the period of time during which the reduction in speed is ongoing may be limited by a threshold time period during which overspeeding may be allowed. ln one example, such threshold time period may be based on timing requirements related to overspeed warning systems in the vehicle. Heavy vehicles are, for example, often equipped with tachographs continuously logging the speed of the vehicle. lf the vehicle exceeds a permitted speed an infringement will be logged in the tachograph. ln several countries in the world, the driver of the vehicle can be fined based on the logged infringements. However, in many vehicles the driver will be warned if there is a risk of an infringement being logged. For example, the driver may be warned if the speed of the vehicle has been exceeded for 45 seconds. ln that example the threshold time period during which overspeeding is allowed may be set to 45 seconds. ln a further example, the driver of a vehicle driving at a speed exceeding the legal speed limit by more than +3%+1kmh must be warned if a propelling power has been applied during more than 6 seconds. lf the speed reduction is performed when the vehicle's speed is within legal speed requirements, the period of time during which the reduction in speed is ongoing may be based on aspects like drivability, acceptance to driver, driver comfort to mention a few.

The determining of the first period of time D1 may further be based on a position where the target speed vi is to be reached. lt may, for example, be desirable to reach the target speed vi at a certain position. For example, it might be favourable to reach the target speed before reaching an approaching downhill section to avoid entering the downhill section at a too high speed. ln similar fashion, the desired position to reach the target speed may be determined based on curvature of the road and/or lO 24 speed limitation ahead of the vehicle. ln one example, the required position may be determined according to conventional methods based on information related to the road section in front of the vehicle, such as topology of the road in front of the vehicle determined from map data or by using e.g., radar or camera means in the vehicle or in any other known way. ln step 230 of method 200 in Figure 2b, the propelling power, determined in step 220 may be applied by means of the electrical machine 101. As previously explained, the propelling power may be applied prior to the speed of the vehicle 100 reaching the target speed vi.

Thus, the invention controls when and how the electrical machine 101 of the vehicle 100 is to apply the propelling power Pa such that an energy efficient speed reduction from an initial speed vin: to a target speed vi is achieved. The time instance when the propelling power Pa is applied may be determined according to conventional methods based on one or more of: the size of the propelling power Pa, the duration of the first period of time D1 and the total duration of the speed decrease. ln one example, the propelling power Pa may be applied at the time instance when it is determined that the vehicle is in overspeed. Thus, in the example illustrated in Figure 3, the propelling power may be applied when the vehicle has reached the end of the downhill section of the road, i.e., at the time instance T3. The time instance when the end of the downhill has been reached may be obtained in various ways. lt may be determined on the basis of map data, e.g. from digital maps including e.g. topographical information, in combination with positioning information, e.g. GPS information. The positioning information may be used to determine the location of the vehicle relative to the map data so that the section of the road information may be extracted from the map data. ln another example, the time instance may be obtained from the cruise control function when overspeed have been determined i.e. at time instance T3 in Figure 3. ln another example, when it has been determined that the propelling power is not to be applied during the whole duration of the speed reduction, i.e. as previously lO described when the first period of time D1 is shorter than the total duration of the speed reduction, the propelling power may be applied when the speed reduction is ongoing. ln yet another example, as will be explained further with reference to Figure 5, the propelling power may be applied prior to the time instance where the target speed vi starts to apply such that the speed reduction may at least partly have been carried out at the time instance the target speed vi starts to apply.

While the propelling power Pa is applied in step 230 of the method 200, the speed of the vehicle 100 is reduced. ln step 240 of method 200 in Figure 2b, it may be determined if the target speed vi has been reached. As long as the speed decrease is ongoing, i.e., when the target speed has not been reached, i.e., 'No' in step 240, the method 200 returns back to step 230 where the propelling power is applied. lf it is determined that the target speed vi has been reached, i.e., 'Yes' in step 240, the method 200 continues to step 250. ln step 250 of method 200 in Figure 2b, a propelling power required to maintain the target speed vi may be applied according to previously known methods and the method 200 returns back to the previously described step 210, or otherwise is ended.

As previously explained, with reference to step 210 of Figure 200, the speed reduction from the initial speed viiii to the target speed vi may, in an embodiments, result from the current target speed of the vehicle 100 being reduced. The current target speed of the vehicle 100, may hence be the initial speed viiii , which is then reduced to the target speed vi. ln one example, such reduction of the current target speed may be effectuated as soon as the current target speed is reduced. That would be the case, for example, when the vehicle speed is automatically controlled by means of a cruise control maintaining a lO 26 set speed and, at a time instance the driver of the vehicle 100 manually reduces the set speed. Such driving scenario is illustrated in Figure 4. The vehicle route comprises here a gertereiiy teve! seetieri betweeh the time iristenee TE) and the tirne instance Tri. As iri the exerrieie iiiustreted in Figure 3, the vehicies eieetrieet rrieehirte 1431 rriey he eentretied by a cruise control function being configured to maintain a set speed which in Figure 4 is denoted as the initial speed viiii. The initiei speed »fint in Figure 4 is achieved by eentreiiirtg the eiectrieei rheehihe ef the vehieie 1612) te previde a erepeiiing eeirifeir P2, The initiei speed viiii rney here eerrespehd te e ertiise eeritrei set speed ter the tirst seetiert ef the read. At the tirne instenee T1 the ettrrent target speed, i.e., the ihitiei speed trim, is reduced te e speed eerrespendiitg te the target speed vi. The reduced target speed vi rriey here eppiy es seen es the reduetieh et the ctirrent target speed hes beeh reeueeted, ter exemeie hy the driver et the tfehieie riienuaiiy redueing the set speed et the cruise centret.

The reduetierw ef the current target speed ntey tz-e deterrniried in the vehieie iri step 2163 et the rnetheci Edt), virhereetter e speed decrease rney' be pertermed aeeerding te steps 22% - Bet? et the iriethed ZÜÜ es erevieusiy described tryith reterehee te Figure 21:-.

As illustrated in Figure 4, in previously known solutions, a speed decrease, illustrated by the dashed plots of "Speed" and "Power" between the time instance T1 and T3, are performed by turning off the applied propelling power P2 at the time instance T1 causing the vehicle to lose speed. When the target speed vi has been reached at the time instance T2 a propelling power Pi is applied so that the target speed vi may be maintained on the following section of the road.

According to the invention, the speed decrease is instead performed while simultaneously applying a propelling power Pa by means of the electrical machine 101 prior to the speed of the vehicle 100 reaching the target speed vi, wherein the speed of the vehicle is reduced while the propelling power is applied. The speed decrease according to the invention is illustrated in Figure 4 by the solid plots of "Speed" and "Power" between the time instance T1 and T3. Thus, the peak power applied during the speed reduction according to the method of the invention, i.e., the propelling power Pa is lower that the peak power that would have been applied if the speed lO 27 reduction was performed according to previously known methods, i.e., propelling power Pi applied between the time instance T2 and T3 to maintain the target speed vi. ln another example, the reduction of the current target speed may take effect at a location, in front of the vehicle 100 as is illustrated in the driving scenario in Figure 5. Here, in similar fashion as in Figure 4, the vehicle route comprises a generaiiy ievei eeetien bettfveen the time instance "iii anti the time irietanee Til, in tiie driving eeenarie in Figure 5, the current target speed et the vehieie, eerrespeitding te the initiai speed viiii, ie reduced at tne tirne instance TB te a target speed iii. Hexwever, the irnpending target speed decrease may be determined in the vehicle prior to the new target speed comes into force, i.e., prior to the time instance T3 which makes it possible to have carried out the speed reduction at least partly at the time instance the target speed vi starts to apply.

As previously explained, the reduction of the current target speed may be determined in the vehicle in step 210 of the method 200, whereafter a speed decrease may be performed according to steps 220 - 250 of the method 200 as previously described with reference to Figure 2b. ln Figure 5, the speed decrease from the initial speed viiii to the target speed vi is performed prior to the time instance T3 where the target speed vi is to be applied. As previously described, the speed reduction may thus at least partly have been carried out at the time instance T3 the target speed vi starts to apply to reduce the risk of speeding. Since the duration ofthe speed reduction according to the invention is longer compared to the duration of the speed reduction if the speed reduction would have been performed according to previously known methods, the speed reduction may start at time instance T1 i.e., earlier than time instance T2 where the speed decrease according to previously known methods would have commenced to timely conclude the speed decrease, according to Figure 5. As may be seen in Figure 5, the peak power applied during the speed reduction according to the method of the invention, i.e., the propelling power Pa is lower that the peak power that would have been applied if the speed reduction was performed according to previously known methods, i.e., lO 28 propelling power P2 applied between the time instance T1 and T2 to maintain the initial speed vant. lt should be noted that the method steps 210 - 250 illustrated in Figure 2b and described herein do not necessarily have to be executed in the order illustrated in Figure 2b. The steps may essentially be executed in any suitable order, as long as the physical requirements and the information needed to execute each method step is available when the step is executed.

According to an aspect of the invention, a control arrangement 120 for controiiing an electrical machine 101 of a vehicle 100, the electrical machine 101 being configured to apply a propelling power for propelling the vehicle 100. The control arrangement comprises means 121 for, when a speed of the vehicle is being reduced from an initial speed vin: to a target speed vi, applying 230 a propelling power by means of the electrical machine 101 prior to the speed of the vehicle reaching the target speed vi, wherein the speed of the vehicle is reduced while the propelling power is applied.

The control arrangement 120, e.g. a device or a control device, according to the invention may be arranged for performing all of the above, in the claims, and in the herein described embodiments method steps. The control arrangement 120 is hereby provided with the above-described advantages for each respective embodiment.

The invention is also related to a vehicle 100 including the control arrangement 120.

Now turning to Figure 6 which illustrates the control arrangement 600/120, which may correspond to or may include the above-mentioned control unit 121 i.e. the control unit performing the method step of the disclosed invention. The control arrangement 600/120 comprises a computing unit 601, which can be constituted by essentially any suitable type of processor or microcomputer, e.g. 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 601 is connected to a memory unit 602 arranged in the control arrangement 600/120, which memory unit provides the computing unit 601 with, e.g., the stored program code and/or the stored data which the computing unit 601 requires to be able to perform computations. lO 29 The computing unit 601 is also arranged to store partial or final results of computations in the memory unit 602. ln addition, the control arrangement 600/120 is provided with devices 611, 612, 613, 614 for receiving and transmitting input and output signals. These input and output signals can contain waveforms, impulses, or other attributes which, by the devices 611, 613 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 601. These signals are then made available to the computing unit 601. The devices 612, 614 for the transmission of output signals are arranged to convert signals received from the computing unit 601 in order to create output signals by, e.g., modulating the signals, which can be transmitted to other parts of and/or systems in the vehicle 100.

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), or some other bus 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 601 and that the above- stated memory can be constituted by the memory unit 602.

Control systems in modern vehicles commonly comprise communication bus systems consisting of one or more communication buses for linking a number of electronic control units (ECU's), or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units and the responsibility for a specific function can be divided amongst more than one control unit. Vehicles of the shown type thus often comprise significantly more control units than are shown in Figure 1 and Figure 6, which is well known to the person skilled in the art within this technical field. ln a shown embodiment, the invention may be implemented by the above-mentioned control unit 121. The invention can also, however, be implemented wholly or partially lO in one or more other control units already in the vehicle 100, or in some control unit dedicated to the invention.

Here and in this document, units are often described as being arranged for performing steps of the method according to the invention. This also includes that the units are designed to and/or configured to perform these method steps.

The control unit 121 is in Figure 1 illustrated as a separate unit. This units may, however, be logically separated but physically implemented in the same unit or can be both logically and physically arranged together. The unit may e.g. correspond to groups of instructions, which can be in the form of programming code, that are input into, and are utilized by a processor/computing unit 601 when the unit is active and/or is utilized for performing its method step.

The person skilled in the art will appreciate that the herein described embodiments for controlling an engine 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 603 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, e.g.: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit, etc.

The invention is not limited to the above-described embodiments. lnstead, the invention relates to, and encompasses all different embodiments being included within the scope of the independent claims.

Claims

1. A method (200), performed by a control arrangerrient, for controiling an electrical machine (101) of a vehicle (100), the electrical machine (101) being configured to apply a propelling power for propelling the vehicle (100), the method comprising, when a speed of the vehicle is being reduced from an initial speed (viiii) to a target speed (vi): applying (230) a propelling power by means of the electrical machine (101) prior to the speed of the vehicle reaching the target speed (vi), wherein the speed of the vehicle is reduced while the propelling power is applied.

2. The method (200) according to claim 1, wherein the propelling power applied by means of the electrical machine (101) when reducing the speed of the vehicle from the initial speed (viiii) to the target speed (vi) is lower compared to a propelling power that would have been applied to maintain the target speed (vi).

3. The method (200) according to any one of the claims 1-2, wherein a duration of the speed reduction from the initial speed (viiii) to the target speed (vi) when the propelling power is applied by means of the electrical machine (101) is controlled to amount to at least a first period of time (D1 ).

4. The method (200) according to claim 3, further comprising: determining the first period of time (D1) at least partly based on a speed difference between the initial speed (viiii) and the target speed (vi).

5. The method (200) according claim 4, wherein the determining of the first period of time (D1) is further based on a total period oftime during which the reduction in speed of the vehicle from the initial speed (viiii) to the target speed (vi) is ongoing.

6. The method (200) according to any one of the claims 1-5, wherein: the vehicle speed is controlled by means of a cruise control function being set to maintain the target speed (vi), while the vehicle speed is being reduced from an initial speed (viiii) to a target speed (vi). lO

7. The method (200) according to any one of the claims 1-6, further comprising; applying (230) the propelling power when the vehicle speed is reduced from the initial speed (vini), the initial speed (vini) being an overspeed in relation to the target speed (vi), the overspeed resulting from the vehicle being accelerated by a downhill section of road.

8. The method (200) according to any one of the claims 1-6, further comprising; applying (230) the propelling power when the vehicle speed is reduced from the initial speed (vini), the initial speed (vini) being a current target speed of the vehicle (100), the speed reduction resulting from the current target speed of the vehicle being decreased.

9. The method (200) according to any of the claims 1-8, further comprising; determining (220) a propelling power to be applied by the electrical machine (101) during the reduction of the vehicle speed from the initial speed vini to the target speed vi, prior to applying (230) the propelling power by the electrical machine wherein the applying (230) of the propelling power comprises applying by the electrical machine (101) the determined propelling power.

10. The method (200) according to claim 9, wherein the determining (220) of the propelling power is at least partly based on information related to the section of the road in which the speed is reduced.

11. The method (200) according to claim 9, wherein the information related to the section of the road in which the speed is reduced comprises at least one of: - an inclination of said section of the road, - a traffic situation within said section of the road.

12. The method (200) according to any one of the claims 9-11, wherein the determining (220) of the power level of the electrical machine is at least partly based on the first period of time (D1) during which the propelling power is to be applied. lO

13. A control arrangement (120) for controliing an electrical machine (101 ) ofa vehicle (100), the electrical machine (101) being configured to apply a propelling power for propelling the vehicle (100), the control arrangement being configured to, when a speed of the vehicle is being reduced from an initial speed (vill) to a target speed (vi): apply (230) a propelling power by means of the electrical machine (101) prior to the speed of the vehicle reaching the target speed (vi), wherein the speed of the vehicle is reduced while the propelling power is applied.

14. A vehicle (100) comprising a control arrangement (120) according to claim

15. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method (200) according to any one of the claims 1 to

16. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method (200) according to any one of the claims 1 to 12.