SE539830C2

SE539830C2 - Method and system for setting a vehicle in motion

Info

Publication number: SE539830C2
Application number: SE1650491A
Authority: SE
Inventors: Udd Jonas; Kjell Anders
Original assignee: Scania Cv Ab
Priority date: 2016-04-12
Filing date: 2016-04-12
Publication date: 2017-12-12
Also published as: DE102017002929B4; DE102017002929A1; SE1650491A1

Description

METHOD AND SYSTEM FOR SETTING A VEHICLE IN MOTION Technical field The present invention relates to a method for setting a vehicle in motion from a standstill comprising controlling a backlash of a powertrain included in the vehicle according to the preamble to claim 1. The present invention also relates to a system arranged for setting a vehicle in motion from a standstill comprising controlling a backlash of a powertrain included in the vehicle according to the preamble to patent claim 14. The present invention also relates to a computer program and a computer program product, that implement the method according to the invention.

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

Vehicles, such as for example cars, buses and trucks are driven forward by an engine torque produced by an engine in the vehicle. This engine torque is provided to the driving wheels of the vehicle through a powertrain/driveline/ drivetrain in the vehicle. The powertrain includes a number of components, such as e.g. a clutch, a gearbox/transmission device, shafts, and a differential. The powertrain may also include other components, and is described more in detail below.

One or more of the components included in the powertrain may comprise a play/backlash, i.e. are coupled with a play/backlash. For example, different parts of a component, such as meshing gear wheels included e.g. in the gearbox and/or the differential, may have a play/backlash between them. In other words, the cogs/teeth of two interacting gear wheels of at least one powertrain component may at some time instances be out of contact with each other, such that no torque is transferred from the engine to the driving wheels, which is denoted play/backlash in this document. The play in the powertrain may cause oscillations in torque and/or revolutions, so called powertrain oscillations, in the vehicle when the vehicle, for example, starts moving once a torque has been requested from the engine. If the play/backlash is big/considerable, a difference AM between a rotational speed coShaft of an input shaft of a gearbox and a rotational speedOwheei of a driving wheel of the vehicle will have time to also grow big/considerable before the play/backlash can be wound up by a torque applied to/on the input shaft when the vehicle starts moving. If the difference AM is big/considerable when the play/backlash is gone/eliminated, the difference AM results in big/considerable powertrain oscillations. Powertrain oscillations may cause vehicle speed variations, which make the vehicle rock longitudinally. These rocking movements in the vehicle are very disruptive for the driver of the vehicle.

Therefore, in some prior art solutions, various strategies have been used in connection with the request of engine torque in order to reduce these powertrain oscillations. Such strategies may utilise limiting torque ramps when the engine torque is requested. These torque ramps have then been chosen in a way that the requested engine torque is limited, such that the play/backlash is eliminated/wound up, and the powertrain oscillations are reduced. For example, the torque ramp should, according to some prior art solutions, initially be limited to being relatively flat in order not to apply too much energy into the powertrain per time unit of time, which would then result in powertrain oscillations.

Brief description of the invention As described above, allowing the driver and/or, for example, a cruise control to freely request a torque would for prior art solutions often result in considerable and disruptive powertrain oscillations. Therefore, limiting torque ramps, including a first relatively flat ramp followed by a second steeper ramp, are often used in prior art systems. The use of limiting torque ramps obviously slows down the torque build-up, since this is the very purpose of the limiting ramps, which also slows down drive-off with the vehicle, i.e. slows down setting the vehicle in motion from a standstill. Thus, the use of limiting torque ramps according to prior art solutions results in a delayed/prolonged powertrain torque build-up, which may be perceived by the driver as the vehicle being week and/or slow.

In order to reduce the delay in the drive-offs, the clutch plates, i.e. the frictional surfaces cooperating in the clutch, should be placed as closely together as possible without transferring any torque when the clutch is open, since clutch plates positioned further apart cause additional delay when closing the clutch. However, the position and control of the clutch plates, i.e. of the frictional surfaces cooperating in the clutch, are normally neither very exact nor very reliable. There is therefore a risk that the vehicle is set in unwanted motion if the inexact control of the clutch plates positions the clutch plates too closely to each other, such that an unexpectedly high torque is transferred by the clutch when the clutch should have been open. In other words, there is, for prior art solutions aiming to speed up drive-offs, a risk that the clutch plates for an open clutch are positioned so close to each other that the vehicle starts moving.

It is therefore one objective of the present invention to provide a method and a system for setting a vehicle in motion from a standstill comprising controlling a backlash of a powertrain included in the vehicle that at least partly solve these problems.

According to an aspect of the present invention, this objective is achieved through the above-mentioned method according to the characterising portion of claim 1. The method includes: - controlling, when the vehicle is standing still, a clutch included in the powertrain to a slipping position CsiiP, in which slipping position CsiiPthe clutch transfers a backlash torque Tbackiashbeing less than a torque Tciosedbeing transferred in a closed position Cciosedfor the clutch, the backlash torque Tbackiashhaving a controlled value for eliminating the backlash; - applying, when the backlash has been eliminated, a braking torque Tbrake on a shaft of a gearbox included in the powertrain, thereby continuing to keep the backlash eliminated; - opening the clutch to an open position Copenfor the clutch; and - setting the vehicle in motion, based on at least one indication, using a start gear Gstart, the backlash still being eliminated until the vehicle is set in motion.

According to the present invention, a substantially even and non-oscillating torque profile, or at least a torque profile having oscillations with significantly lower amplitudes than for prior art solutions, is provided. The present invention does not result in oscillations that have a negative impact on the comfort in the vehicle. When the present invention is used, powertrain oscillations may be reduced in number and/or size for drive-offs, where previously known control methods would have resulted in problematic rocking of the vehicle. A driver desires a soft and comfortable driving experience, and when such a comfortable driving experience is achieved, this gives a sense of the motor vehicle being a refined and well developed product.

When the present invention is utilised, the backlash is eliminated already when the vehicle is standing still, i.e. before drive-off, and is kept eliminated until, and during, drive-off by the braking torque Tbrakebeing applied on the gearbox input shaft. Therefore, little or even no attention has to be paid to a potential backlash when the vehicle drives off, since the backlash has already been eliminated during the standstill. Thus, the time periods when the vehicle is standing still and being braked anyway, such ase.g.time periods a bus is standing still at bus stops or time periods a vehicle is standing still at traffic lights, can here be used for eliminating the backlash. Since the backlash is then eliminated when the vehicle is later driving off after the standstill, the clutch can then be closed much faster than if the backlash would still be present in the powertrain. Therefore, the torque limitations/restrictions having been used at drive-offs in prior art solutions can here be omitted.

Also, since the braking torque Tbrakeis applied on the gearbox shaft during the standstill in order to apply a well-defined and well controlled torque TsiiP_freeon the powertrain, the problems of inexactness and unreliability of the clutch regarding the position and control of the clutch plates are mitigated. When the braking torque Tbrakeis applied on the gearbox shaft, i.e. when the controllable torque TsiiP_free is applied on the powertrain, the torque TsiiP_free can easily be controlled to a value for which the vehicle does not start moving. Thus, the risk for the vehicle being set in unwanted motion due to inexact and unreliable control of the clutch plates is eliminated. As a result of this, the clutch plates can also in a secure way be positioned closer to each other for an open clutch when the present invention is utilised than was possible for prior art solutions. To have the clutch plates positioned closer to each other for the open clutch facilitates faster closing of the clutch, and thus also faster drive-offs for the vehicle, whereby the driver perceives the vehicle as powerful.

Thus, the application of the braking torque Tbrakeon the gearbox input shaft eliminates the risk for unwanted movement of the vehicle, since only the well-defined torque TsiiP_free then is kept on the powertrain by an input shaft brake arrangement when the present invention is used. Thus, a positive and backlash free torque is provided by the present invention, which results in quick drive-offs being free of powertrain oscillations.

Further, to be able to eliminate the backlash/play in a controlled manner also reduces the wear on components in the powertrain, such as e.g. the wear on cog wheels.

Also, the present invention can be implemented without the need of additional hardware components in the vehicle. Thus, the present invention does neither add to the hardware cost nor to the hardware complexity for the vehicle.

According to an embodiment of the present invention, the applying of the braking torque Tbrakeis performed by activating at least one shaft brake arrangement acting on the shaft of the gearbox included in the powertrain.

According to an embodiment of the present invention, a free of backlash clutch position CsiiP_free for the clutch is determined when the backlash has been eliminated by the backlash torque Tbackiash• According to an embodiment of the present invention, the setting the vehicle in motion includes: - controlling the clutch to the free of backlash position Cslip_free} - deactivating the at least one shaft brake arrangement providing the braking torque Tbrake on the shaft; and - controlling the clutch from the free of backlash position CsiiP_free towards the closed position Cciosed.

According to an embodiment of the present invention, an input shaft braking torque Tbrake_inPut corresponding to the braking torque Tbrakeapplied on the shaft is equal to or greater than a torque TsiiP_free the clutch transfers at the free of backlash clutch position C slip_free• According to an embodiment of the present invention, a determination of if the vehicle is in a standstill is performed based on one or more signals in the group of: - a number of shaft revolutions signal provided by a sensor at an output shaft of the gearbox; - an acceleration signal provided by an accelerometer in the vehicle; - a number of wheel revolutions signal provided by a sensor at a wheel in the vehicle; - a brake pedal signal provided by a brake system in the vehicle; and - a positioning signal.

According to an embodiment of the present invention, an input shaft braking torque Tbrake_inPut corresponding to the braking torque Tbrakeapplied on the shaft is controlled to be high enough for keeping the backlash eliminated.

According to an embodiment of the present invention, the controllable value of the backlash torque Tbackiashis within a range of 10-50 Nm, or within a range of 15-25 Nm, or approximately 20Nm.

According to an embodiment of the present invention, the determining if the backlash has been eliminated includes at least one in the groupof:- analysing an increase of an engine torque Tengineduring the controlling of the clutch; - analysing a length of a time period during which the backlash torque Tbackiashhas been applied by the clutch; and - analysing a difference AM between a rotational speed oShaft of an input shaft of the gearbox and a rotational speed oWheei of a driving wheel of the vehicle.

According to an embodiment of the present invention, a ramping up of a powertrain torque Tp0wertrain is performed after the setting in motion of the vehicle, the backlash still being kept eliminated during the rampingup.

According to an embodiment of the present invention, the controlling of the clutch to the slipping position CsiiPand setting the vehicle in motion are separated in time by a standstill time period tstandstm, wherein tstandstm > 0 s.

According to an aspect of the present invention, the objective is achieved through the above-mentioned system according to the characterising portion of claim14.The system includes: - a clutch control unit, arranged for controlling, when the vehicle is standing still, a clutch included in the powertrain to a slipping position CsiiP, in which slipping position CsiiPthe clutch transfers a backlash torque Tbackiashbeing less than a torque Tciosedbeing transferred in a closed position Cciosedfor the clutch, the backlash torque Tbackiashhaving a controlled value for eliminating the backlash; - a brake control unit, arranged for applying, when the backlash has been eliminated, a braking torque Tbrake on an shaft of a gearbox included in the powertrain, thereby continuing to keep the backlash eliminated; - the clutch control unit, arranged for opening the clutch to an open position Copenfor the clutch; and - a vehicle movement control unit, arranged for setting the vehicle in motion, based on at least one indication, using a start gear Gstart, the backlash still being eliminated until the vehicle is set in motion.

According to an embodiment of the present invention, the system further includes: - a determination unit, arranged for determining a free of backlash clutch position CsiiP_free for the clutch when the backlash has been eliminated by the backlash torque Tbackiash," - the clutch control unit, arranged for controlling the clutch to the free of backlash position CsiiP_free; - the brake control unit, arranged for deactivating the at least one shaft brake arrangement providing the braking torque Tbrake on the shaft; and - the clutch control unit, arranged for controlling the clutch from the free of backlash position CsiiP_free towards the closed position Cciosed.

According to an embodiment of the present invention, the brake control unit is arranged for applying the braking torque Tbrakeby activating at least one shaft brake arrangement acting on the shaft of the gearbox included in the powertrain.

According to an embodiment of the present invention, an input shaft braking torque Tbrake_inPut corresponding to the braking torque Tbrakeapplied on the shaft is equal to or greater than a torque TsiiP_free the clutch transfers at the free of backlash clutch position C slip_free• According to an embodiment of the present invention, a standstill determination unit is arranged for determining if the vehicle is in a standstill based on one or more signals in the group of: - a number of shaft revolutions signal provided by a sensor at an output shaft of the gearbox; - an acceleration signal provided by an accelerometer in the vehicle; - a number of wheel revolutions signal provided by a sensor at a wheel in the vehicle; - a brake pedal signal provided by a brake system in the vehicle; and - a positioning signal.

According to an embodiment of the present invention, the brake control unit is arranged for controlling an input shaft braking torque Tbrake_inPut corresponding to the braking torque Tbrakeapplied on the shaft to be high enough for keeping the backlash eliminated.

According to an embodiment of the present invention, the controllable value of the backlash torque Tbackiashis within a range of 10-50 Nm, or within a range of 15-25 Nm, or approximately 20 Nm.

According to an embodiment of the present invention, the determination unit is arranged for determining if the backlash has been eliminated by use of at least one in the group of: - analysing an increase of an engine torque Tengineduring the controlling of the clutch; - analysing a length of a time period during which the backlash torque Tbackiashhas been applied by the clutch; and - analysing a difference AM between a rotational speedQshaft of an input shaft of the gearbox and a rotational speed oWheei of a driving wheel of the vehicle.

According to an embodiment of the present invention, a torque requesting unit is arranged for requesting a ramping up of a powertrain torque Tp0wertrainafter the setting in motion of the vehicle, the backlash still being kept eliminated during the ramping up.

According to an aspect of the present invention, the above mentioned computer program and computer program product are arranged for implementing the method described herein.

According to an aspect of the present invention, a vehicle including a system as described herein and arranged for controlling a backlash of a powertrain included in the vehicle in connection with a start from a standstill is presented.

Brief list of figures 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 shows an example vehicle, in which the present invention may be implemented, Figures 2a-b show flow charts for methods according to various embodiments of the present the invention, Figures 3a-c schematically illustrate a play in the powertrain. Figures 4a-c show an illustration of a non-limiting start from standstill, used for explaining various embodiments of the present invention, Figures 5a-c show an illustration of a start from standstill according to a prior art solution, Figure 6 shows a control device, in which a method according to the present invention may be implemented, Figure 7 schematically shows an input shaft brake arrangement according to an embodiment.

Description of preferred embodiments Figure 1 schematically shows a heavy example vehicle 100, such as a truck, a bus or similar, which will be used to explain the present invention. The present invention is, however, not limited to use in heavy goods vehicles as the one shown in figure 1, but may also be used in lighter vehicles such as passenger cars. The vehicle 100, shown schematically in Figure 1, comprises a pair of driving wheels 110, 111. The vehicle furthermore comprises a powertrain 130 with an engine 101, which may be, for example, a combustion engine, an electrical motor or a combination of these, a so called hybrid drive. The engine 101 may, for example, in a customary fashion, via an output shaft 102 of the engine 101, be connected with a gearbox 103, via a clutch 106 and an input shaft 109 connected to the gearbox 103. A propeller shaft 107, connected to an output shaft of the gearbox 103, drives the driving wheels 110, 111 via a central gear 108, such as e.g. a customary differential, and drive shafts 104, 105 connected with the central gear 108.

A control unit 120 is in figure 1 schematically illustrated as receiving signals and/or providing control signals from and/or to the engine 101, the clutch 106 and/or the gearbox 103. As described below, the control unit 120 may according to some embodiments of the present invention comprise a clutch control unit 121, a determination unit 122, a brake control unit 123, a vehicle movement control unit 124, and other herein mentioned control units. These units are described in more detail below.

Figure 2a shows a flow chart for a method for setting a vehicle 100 in motion from a standstill comprising controlling a backlash of a powertrain included in the vehicle, according to an embodiment of the present invention.

In a first step 210, the clutch 106 included in the powertrain 130 is controlled to a slipping position Csiip when the vehicle 100 is standing still. As state above, the clutch 106 is here controlled to transfer a backlash torque Tbackiashhaving a controlled value for eliminating the backlash. The backlash torque Tbackiashis less than a torque Tciosedbeing transferred in a closed position Cciosedfor the clutch 106, and is obviously higher than a torque Topen(essentially equal to 0 Nm) being transferred in an open position Copenfor the clutch 106.

In a third step 230, a braking torque Tbrakeis applied on a shaft, such as an input shaft 109, of a gearbox 103 included in the powertrain 130 when the backlash has been eliminated by the backlash torque Tbackiash. By this applied braking torque Tbrake, the backlash is kept eliminated, i.e. no backlash is created again, since the shaft is held in a backlash free position by the braking torque Tbrake.

In a fourth step 240, the clutch 103 is opened to an open position Copen. Thus, the clutch is opened to a clutch position for which essentially no torque is transferred by the clutch. The method, and thus also the vehicle 100, then waits, i.e. does not perform any further actions for a period of time; topen > 0 s; until it receives an indication that the vehicle should be set in motion. This waiting period topencan have essentially any length, i.e. can be rather short or rather long, depending e.g. on the driving situation for the vehicle. For example, the waiting period may occur in connection with a stop at a traffic light, a traffic jam or a bus stop.

In a fifth step 250, the vehicle 100 is set in motion 250, based on at least one indication, such as an indication from a driver and/or from a cruise control system. Thus, the driver may e.g. by usage of a gas and/or a brake input means, such as one or more pedals, provide an indication which can be interpreted as an indication of that the vehicle should be set in motion. Also, such an indication may be provided by some kind of driver assisting arrangement, such as a cruise control system. The vehicle is then, based on this indication, set in motion by usage of a start gear Gstart in the gearbox. According to the present invention, the backlash is still kept eliminated until the vehicle is set in motion. In other words, the braking torque Tbrakeis still applied until the vehicle 100 starts to move.

Thus, according to the present invention, backlash in the powertrain is eliminated by controlling the clutch 106 to transfer a backlash torque Tbackiashhaving a value suitable for eliminating backlash. Once the backlash has been eliminated, a braking torque Tbrakeis applied on a shaft, such as an input shaft 109 of the gearbox, whereby the powertrain is forced to stay free of backlash by the applied braking torque Tbrake. The braking torque Tbrakeis thus applied to/on the shaft during a standstill tstandstm of the vehicle, including also when the clutch is open topen, until it is time for the vehicle to be set in motion. When a start indication is provided, bye.g. adriver or a cruise control system, a start gear Gstart is used in the gearbox and the vehicle is set in motion. The braking torque Tbrakeis applied on a shaft until the vehicle starts moving, whereby no backlash is present in the powertrain at drive-off.

By the use of the present invention, an efficient and reliable elimination of potential backlash/play in the powertrain is achieved. Also, the risk for unwanted movement of the vehicle when the clutch should be open is eliminated. Therefore, also quick and reliable starts from standstill, also called drive-offs, are achieved. Thus, a quick and safe start from a standstill, without driveline oscillations, can be provided by the present invention. This is possible since the backlash has been eliminated already during the standstill, whereby backlash related limitations on the torque build-up can be omitted, and since the clutch plates can be positioned close to each other for the open clutch, which makes closing of the clutch faster.

As described above, play/backlash in the powertrain may, for example, arise when two cogs in the powertrain, such as for example the cogs in two cogwheels in the gearbox, do not engage/mesh with each other.

The position of the cogwheels in relation to each other during and outside of the play is schematically illustrated in figures 3a-c. The cogs of the cogwheels make contact in a first shaft position, during rotation in a first direction, as illustrated in Figure 3a, in a position corresponding to a maximum backward turn. The cogs in the cogwheels also make contact in a third shaft position, during rotation in a second direction, as illustrated in Figure 3c, in a position corresponding to a maximum forward turn. Therefore, the cogs are engaged/meshed in both these positions (illustrated in figures 3a and 3c respectively), which also means that the play is rotated backwards and forwards respectively. The play in the powertrain is made up of the rotation angle when the cogs are not engaged/meshed with each other, that is to say the angle range between the first and third shaft positions, corresponding to a second position/angle within the play, illustrated in Figure 3b. Thus, no torque is transmitted during the play, since the cogs do not engage with each other in this second gear/position. It should be noted that figures 3a-c illustrate, in a schematic and simplified manner, a play between only two cogwheels, and that a powertrain may comprise connections between more than two cogwheels, as described above. However, figures 3a-c may be used to explain, in principle, the occurrence of a play.

A backlash/play may thus, for example, occur at a transition between dragging the engine and an acceleration/torque request when engaging the clutch, e.g. in connection with a drive-off/start from a standstill. Since an efficient elimination/winding up of such a play may be provided by the use of the present invention, a rapid torque build-up may be obtained at drive-offs.

Figure 2b shows a flow chart for a method for setting a vehicle 100 in motion from a standstill comprising controlling a backlash of a powertrain included in the vehicle, according to an embodiment of the present invention.

In a first step 210, corresponding to step 210 described above, the clutch 106 included in the powertrain 130 is controlled to a slipping position CsiiPwhen the vehicle 100 is standing still, whereby the clutch 106 is here controlled to transfer a backlash torque Tbackiashhaving a controlled value for eliminating the backlash.

In a second step 220, a free of backlash clutch position Csiip_free is determined for the clutch 106 when the backlash has been eliminated by the backlash torque Tbackiash. This determination can be made in various ways, as is described below.

In a third step 230, corresponding to step 230 described above, a braking torque Tbrakeis applied on a shaft of a gearbox 103 when the backlash has been eliminated by the backlash torque Tbackiash, whereby the backlash is kept eliminated by the braking torque Tbrake.

In a fourth step 240, corresponding to step 240 described above, the clutch 103 is opened to an open position Copen.

In a fifth step 250, the vehicle 100 is set in motion 250, based on at least one indication, such as an indication from a driver and/or from a cruise control system, as described above. According to an embodiment of the present invention, setting the vehicle in motion includes controlling 251 the clutch 106 to the free of backlash position CsiiP_free, which was determined in the second step 220 when the backlash had been eliminated. Then, the at least one shaft brake arrangement 701 is deactivated 252 when the clutch again reaches the free of backlash position CsiiP_free, after which the braking torque Tbrakeis no longer applied on the shaft 109. Thereafter, the clutch 106 is controlled 253 to move from its free of backlash position C slip_free towards a closed position Cciosed, and the drive-off of the vehicle is achieved.

Thus, according to the embodiment, the backlash is eliminated and the clutch position for which there is no more backlash is determined and stored. The braking torque Tbrakeis applied to the shaft and the clutch is then opened. When the vehicle is set in motion, the clutch is gradually closed until the free of backlash position CsiiP_free is reached for the clutch. When the free of backlash position CsiiP_free is reached, the braking torque Tbrakeis deactivated, and the clutch is further closed until it reaches its closed position Cciosedand the vehicle starts moving.

According to an embodiment of the present invention, the braking torque Tbrakeis applied 230 by activating at least one shaft brake arrangement 701 acting on a shaft 109 of the gearbox 103 included in the powertrain 130. Essentially any kind of brake arrangement 701 which directly or indirectly acts on a shaft included in the gearbox, such as e.g. on a shaft 109 connected to the clutch 106, can be utilised for providing this braking Torque Tbrake. The shaft brake arrangement 701 is configured to be able to provide a higher/greater maximal braking torque Tbrake_max, e.g. 200 Nm as a non-limiting example, than the braking torque Tbrake, e.g. 100 Nm as a non-limiting example, which according to an embodiment of the present invention is applied on the shaft in order to keep the powertrain 130 free of backlash.

One non-limiting example of such a shaft brake arrangement 701 is schematically illustrated in figure 7. A shaft brake arrangement can be arranged in a number of ways, as long as a braking torque Tbrakeis applied to at least one shaft included in the gearbox 103. The braking torque Tbrakecan, according to various embodiments, be applied to the input shaft 109, to the main/transmission shaft 705 and/or to another shaft being connected to the input shaft via at least one gear wheel meshing, such as a lay shaft 702. Figure 7 schematically illustrates one non-limiting example of a gearbox 103 including an input shaft 109, a lay shaft 702, and a main/transmission shaft 705 being journaled to the input shaft 109 in bearings 706. Also, a lay shaft brake 701, configured to apply a braking torque to a lay shaft 702, is schematically illustrated. The lay shaft 702 is here braked by the lay shaft brake 701, and the braking force Tbrakeis then provided to the input shaft 109 of the gearbox 103 via one or more gear wheel meshes 703, 704. The shaft brake arrangement may be constructed in a number of ways, and is not limited to the schematic illustration of figure7.For instance, an input shaft brake arrangement may be arranged for braking the input shaft 109 with a braking force Tbrakeand/or a main shaft brake arrangement may be arranged for braking the main shaft 705 with a braking force corresponding to the input shaft braking force Tbrake.

As described in this document, the shaft brake arrangement, such as an input shaft brake arrangement, a lay shaft brake arrangement and/or a main shaft brake arrangement, may be controlled by a brake control unit 124 included in a control unit 120. The control unit 120 may also include a gearbox control unit 125.

An input shaft braking torque Tbrake_inPut, according to an embodiment being equal to the braking torque Tbrakeapplied on the input shaft 109, is according to an embodiment, equal to or greater than a torque TsiiP_free which the clutch 106 transfers at the free of backlash clutch position CsiiP_free, which was determined when the backlash/play had been eliminated by the backlash torque Tbackiash, as described above. Correspondingly, an input shaft braking torque Tbrake_input corresponding, possibly including gear ratios, to a braking torque Tbrakewhich is applied on the lay shaft 702 and/or on the main shaft 705, is also, with the possible gear ratios taken into consideration, equal to or greater than the torque Tslip_free• The input shaft braking torque Tbrake_inPut corresponding to the braking torque Tbrakebeing applied on the shaft, i.e. on the input shaft 109, on the lay shaft 702 and/or the main shaft 705, is according to an embodiment controlled to be high enough for keeping the backlash eliminated, i.e. to keep the backlash eliminated when the shaft, i.e. one of more of the input, main and lay shafts, are standing still.

Also, the backlash torque Tbackiash, and therefore also the torque TsiiP_free being transferred by the clutch at the free of backlash clutch position CsiiP_free, should be controlled to be low enough for not setting the vehicle 100 in motion. Hereby, it may be ensured that the vehicle does not perform an unwanted drive-off. Thus, the backlash torque Tbackiashbeing applied when the shaft brake arrangement 701 is activated winds up the powertrain in order to eliminate the backlash. When the shaft brake arrangement 701 is activated, the powertrain 130 will stay in this wound-up state, and the backlash torque TsiiP_free is maintained and still applied on the powertrain, but now by the shaft brake arrangement 701 instead. Thus, since the backlash torque Tbackiashis controlled to be low enough for not setting the vehicle 100 in motion, an unwanted drive-off can be prevented.

The shaft brake arrangement 701 thus holds/maintains the torque TsiiP_free on the shaft 701 by the braking torque Tbrakeapplied on the shaft. The torque TsiiP_free will thus act as a driving torque on the drive wheels, and could possibly cause an unwanted drive-off if the torque would be too high. However, according to an embodiment of the present invention, the torque TsiiP_free being transferred by the clutch at the free of backlash clutch position CsiiP_free, should be controlled/restricted to be low enough for keeping the vehicle 100 at standstill.

Thus, a quick and safe start from a standstill, without driveline oscillations, can be provided by the present invention, since the backlash has been eliminated already during the standstill and since the clutch plates can be positioned close to each other for the open clutch without risking unwanted drive-offs.

As is illustrated in Figure 1, the different parts of the powertrain 130 have different rotational inertias, comprising a rotational inertiaJe forthe engine 101, a rotational inertiaJgfor the gearbox 103, a rotational inertiaJcfor the clutch 106, a rotational inertiaJpfor the propeller shaft 107 and rotational inertiasJafor each drive shaft 104, 105. Generally speaking, all rotating bodies have a rotational inertia /, which depends on the mass of the body and the distance of the mass from the rotational centre. For reasons of clarity, in Figure 1, only the above mentioned rotational inertias have been added, and their significance for the present invention may be described hereafter. A person skilled in the art does, however, realise that more rotational inertias may occur in a powertrain than those listed here.

Generally, the torqueTand the changecoof the rotational speed for the rotating shafts/parts are related to each other and to a rotational inertia / according toT = Jco.For the powertrain, or at least for parts of the powertrain, the rotational inertia / is known or can be calculated. Thus, a valuecofor the change in rotational speed is dependent at least on a rotational inertia / of one or more parts of the clutch 106 and the gearbox 103. One non-limiting example value for the inertia / for the rotating parts of the clutch 106 and the gearbox 103 can be e.g. 0.5 kg<*>m<2>. According to an embodiment of the present invention, the controllable value of the backlash torque Tbackiashsuitable for eliminating the backlash/play may be empirically determined and may have a value exceeding at least the frictional torques of the gearbox and the drive shafts 104, 105, for example within a range of 10-50 Nm, or within a range of 15-25 Nm, or approximately 20 Nm for the input shaft 109.

By usage of such a controllable value for the backlash torque Tbackiash, a quick and safe start from a standstill can be provided by the present invention, without risking unwanted drive-offs.

As described above, the elimination of the backlash is performed during a standstill of the vehicle 100. This can also be expressed as the above described first method step of controlling 210 the clutch 106 to the slipping position CsiiPand the above described fifth method step 250 of setting the vehicle in motion are separated in time by a standstill time period t standstill f wherein tstandstm > 0 s. Thus, the backlash elimination is, according to the present invention, eliminated when the vehicle is standing still, whereby the backlash elimination does not affect the driving performance of the vehicle. For many vehicles, e.g. buses and also other vehicles, standstills e.g. at bus stops and/or traffic lights are a natural part of the use of the vehicles. To be able to drive off after such stops with a powertrain free from backlash/play is a great advantage.

To be able to know if the method according to the present invention may be activated, it is according to an embodiment of the present invention, determined if the vehicle is at a standstill. This standstill determination can be made in a couple of ways. The standstill determination may for example be performed based on if an output shaft 107 from the gearbox rotates or not,e.g.based on a number of shaft revolutions signal provided by a sensor arranged at the output shaft 107. The standstill determination may also be made based on a determined acceleration of the vehicle, for example based on an acceleration signal provided by an accelerometer in the vehicle 100. The standstill determination may also be made based on a determined rotation or non-rotation of one or more wheels in the vehicle, for example based on a number of wheel revolutions signal provided by a sensor at a wheel in the vehicle 100. The standstill determination may also be made based on a determined of if brakes, such ase.g.service/foot brakes, are activated in the vehicle,e.g.based on a brake pedal signal provided by a brake system in the vehicle 100. The standstill determination may also be made based on a geographical movement of the vehicle, e.g. based on GPS-signals (Global Positioning System signals) utilised in a GPS device in the vehicle.

The signals used for the above described methods for determining that the vehicle is standing still are normally already available in the vehicle. These embodiments can thus be implemented without adding to the hardware complexity of the vehicle 100.

The second method step 220, including a determination of if the backlash has been eliminated can be made in a number of ways. According to an embodiment, the elimination of the backlash can be determined by an analysis of an increase of an engine torque Tenginewhen the clutch 106 is controlled to the slipping position CsiiPin the first method step 210. Thus, the engine torque Tenginecan be analysed during the control of the clutch 106 in the first step 210. If the engine torque Tengineincreases when the clutch is slightly closed to the slipping position Csiip, and if the increase of the engine torque Tengineis correlated to the closing of the clutch to the slipping position Csiip, it can be determined that the backlashed is eliminated.

According to an embodiment, the elimination of the backlash can be determined by an analysis of a length of a time period during which the backlash torque Tbackiashhas been applied by the clutch 106. If the backlash torque Tbackiashhas been applied for a time period tbackiashbeing longer than a predetermined Value tbacklash_predet; tbackiash> tbacklash_predet , ' where the predetermined value tbackiash_Predet may be e.g. 0.5 s, the backlash is determined to have been eliminated in the powertrain.

According to an embodiment, the elimination of the backlash can be determined by an analysis of a difference AM between a rotational speedQshaft of an input shaft 109 of the gearbox and a rotational speedQwneei of a driving wheel 110, 111 of the vehicle 100. If there is essentially no difference between these rotational speeds after a small difference has been created when the clutch is controlled in the first step 210; if AM = Oshaft - Owheei = 0; it can be determined that the backlash has been eliminated in the powertrain.

The above described methods for determining that the backlash has been eliminated can be made based on information and/or signals normally already being available in the vehicle, and can thus be implemented without adding to the hardware complexity for the vehicle 100. Figures 4a-c and 5a-c show an example of a drive-off situation when the present invention is used (figure 4a-c) and when a prior art solution is used (figure 5a-c). Figure 4a shows the clutch position, i.e. the positions for the clutch plates of the clutch 106. In this document, the closed clutch position Cciosedmay be defined as the clutch being closed and no longer slipping, which also means that the rotational speeds for the clutch's input 102 and output 109 shafts are substantially equal. This may also be expressed as the clutch at this clutch position Cciosedis able to transfer a higher torque than an actual/momentary torque that should be transferred to the input shaft 109 and/or to the driving wheels at a time instant. When the clutch 106 is in the slipping clutch position CsiiP, the clutch transfers a backlash torque Tbackiash, i.e. a slipping torque, which has a permitted and suitable value to wind up the play of the powertrain and/or to prepare the powertrain for the future torque increase/ramp. This may also be expressed as the powertrain is being wound up when the clutch 106 is in the slipping clutch position Csiip. As is illustrated in figure 4a, the slipping clutch position CsiiPincludes a range of clutch plate positions, where the clutch plates move closer and closer together until the clutch is completely closed in the closed end position Cciosed.

Also, the open position Copenfor the clutch includes a range of clutch plate positions for which essentially no torque should be transferred by the clutch. Thus, the clutch plates are moved further and further away from each other the more the clutch is opened, until an open end position Copen_endis reached.

Control/Activation of the clutch 106 is usually carried out by the use of one or more actuators. These actuators may for example be hydraulic, pneumatic and/or electrically driven/activated/controlled. Thus, the clutch positions and/or clutch plate positions discussed in this document also correspond to positions for such clutch actuators. Figure 4b shows the activation/deactivation of an indication, such as a signal indicating is a gas pedal is pressed and/or a signal provided by a cruise control system. Figure 4c shows activation/deactivation of a shaft brake arrangement. Figures 4a-c show a non-limiting example situation where the vehicle is at a standstill until it is set in motion at a drive-off time instant 407. It should be noted that one non-limiting example of the drive-off time instant 407, and of the clutch movement in connection with the drive-off time instant 407, is only schematically illustrated in figure 4a. As is clear for a skilled person, the actual time instant when the vehicle is set in motion depends on a number of parameters, such as for example road conditions, wind conditions and/or a slope/inclination of the road.

First, the vehicle is standing still, and the clutch 106 is in a totally open position Copen_end401. Then, the clutch 106 is gradually closed 402, i.e. the clutch plates are moved closer to each other, until the clutch 106 is in a slipping position CsuP. The clutch 106 is hereby controlled 210 to transfer a backlash torque Tbackiashhaving a controlled value for eliminating the backlash.

Then, in a free of backlash time instant 403, it is determined 220 that the backlash has been eliminated by the applied backlash torque Tbackiash. A free of backlash clutch position Csiip_free, i.e. the positions the clutch plates have when the backlash has been eliminated, is hereby determined and stored.

When the backlash has been eliminated, i.e. when the free of backlash clutch position CsiiP_free has been determined, the shaft brake arrangement is activated in an activation time instant 421. Hereby, the braking torque Tbrakeis applied on a shaft of a gearbox 103, such as an input shaft 109. Hereby, the backlash can be kept eliminated by the braking torque Tbrake, and the clutch 106 can be controlled to be gradually opened 404 again. According to an embodiment of the present invention, the clutch 106 can now be opened to an open position, more in detail to an intermediate open position Copen_int405, which is a more closed position than the open end position Copen_end, and does not have to return to the open end position Copen_end. This can also be described as there is a clutch closing position difference Cp0s_diffbetween the open end position C open_end 401 and the intermediate open position CoPen_int405; CPos_diff > 0. As described above, the torque TsiiP_freebeing transferred by the clutch at the free of backlash clutch position CsiiP_free, and thus also being locked and provided to the powertrain and driving wheels when the shaft brake is activated, is low enough for keeping the vehicle 100 standing still, i.e. for the vehicle not to move.

Then, at least one indication, such as an indication from a driver and/or from a cruise control system is activated/provided in an indication time instant 411.

When this indication is provided, the clutch 106 is controlled to be gradually closed 406 from the intermediate open position Copen_int. When the clutch 106 again reaches the free of backlash position CsiiP_free, which was determined in the second step 220 when the backlash had been eliminated, the at least one shaft brake arrangement 701 is deactivated in the deactivation time instant 422. Thereafter, the clutch 106 may be controlled to move from its free of backlash position CsiiP_free towards the closed position Cciosed, if the driver and/or cruise control system requests a higher torque. In a drive-off time instant 407, the vehicle is set in motion using the start gear Cstart of the gearbox.

When the method for setting the vehicle in motion according to the present invention is utilised, there is a time interval tinvbetween the indication time instant 411 and the drive-off time instant 407, which is rather short when compared to corresponding time intervals for prior art solutions, as is described below.

After the vehicle is set in motion, a ramping up of a powertrain torque Tp0wertrain is performed. According to an embodiment of the present invention, the ramping up of the powertrain torque Tp0wertrainis controlled such that backlash is still kept eliminated during the ramping up of the powertrain torque Tp0wertrain. This is achieved by a control of the motor 101 and the clutch 106 such that a powertrain torque is generated which constantly forces the backlash/play to stay eliminated/wound up.

Thus, according to the embodiment, the backlash is eliminated 403 during the standstill. The braking torque Tbrakeis applied 421 to the shaft in order to force the backlash to remain eliminated. The clutch position CsiiP_free for which there is no backlash anymore is determined and stored 403. The clutch is then controlled to be open Copen_int405 until an indication is provided/activated 411. After the indication is provided/activated 411, the clutch is controlled to be gradually closed 406. When the free of backlash position CsiiP_free is reached, the braking arrangement is deactivated 422 when the free of backlash clutch position CsiiP_free is reached, and the clutch is further controlled 407 towards its closed position Cciosedwhen the vehicle starts moving. Figures 5a-c show figures for a prior art solution for the same example situation as the one shown for the present invention in figures 4a-c. Figure 5a shows the clutch position, i.e. the positions for the clutch plates of the clutch 106. Figure 5b shows the activation/deactivation of an indication, such as a signal indicating is a gas pedal is pressed and/or a signal provided by a cruise control system. Figure 5c shows activation/deactivation of a shaft brake arrangement.

First, the vehicle is standing still, and the clutch 106 is in a totally open position Copen_end501. Then, when the indication is activated in an indication time instant 511, the clutch 106 is gradually closed, i.e. the clutch plates are moved closer to each other, initially more steep 502 and then less steep 503, until the clutch 106 is in a closed position Cciosed, and the vehicle is set in motion in a drive-off time instant 507. As is shown in figure 5c, no activation of a shaft brake arrangement is utilised for prior art solutions. Some vehicles do also not even have such a shaft brake arrangement implemented in the vehicle.

When the method for setting the vehicle in motion according to the prior art solution is utilised, there is a time interval tPrior_art between the indication time instant 511 and the drive-off time instant 507, which is much longer than the corresponding time interval tinvfor the present invention, as is described above. One reason for this is that the clutch starts closing from the open end position Copen_endwhen the indication is activated for the prior art solutions, whereas the clutch starts closing from the intermediate open position Copen_intwhen the indication is activated for the present invention. Also, for the present invention, the powertrain is guaranteed to be free of backlash when the indication is activated, which reduces the necessity of backlash related restrictions for the torque to be requested at drive-off. For the prior art solution, the torque build-up must be restricted such that the backlash is eliminated in a controlled way after the drive-off indication 511, whereas the backlash is eliminated already during the standstill, i.e. already before the drive-off indication, when the present invention is used.

In other words, the method according to the present invention offers much faster drive-offs of the vehicle, which will be perceived by the driver as the vehicle having a fast torque response and being powerful.

According to an aspect of the present invention, a system for setting a vehicle in motion from a standstill comprising controlling a backlash of a powertrain 130 included in a vehicle 100 is presented.

With reference to figures 1 and 7, the system includes a clutch control unit 121, which is arranged for controlling 210 a clutch 106 included in the powertrain 130 to a slipping position Csiip when the vehicle 100 is standing still. As described above, the clutch 106 transfers a backlash torque Tbackiashbeing less than a torque Tciosedtransferred in a closed position Cciosedfor the clutch 106 in the slipping position Csiip. The backlash torque Tbackiashhas a controlled value being suitable for eliminating the play/backlash.

The system further includes a brake control unit 123, which is arranged for applying 230 a braking torque Tbrake on a shaft 109 of a gearbox 103 included in the powertrain 130, when the backlash has been eliminated. Hereby, the backlash is forced to continue to be eliminated, i.e. the powertrain is still maintained to stay free of backlash.

The system also includes the clutch control unit 121, being arranged for opening 240 the clutch 106 to an open position Copen• The system further includes a vehicle movement control unit 124, which is arranged for setting the vehicle in motion 250, based on at least one indication, using a start gear Gstart. The backlash is here still eliminated until, and during, the vehicle is set in motion 250.

According to an embodiment, the system further includes a determination unit 122, being arranged for determining 220 a free of backlash clutch position CsiiP_free for the clutch 106 when the backlash has been eliminated by application of the backlash torque Tbackiash. Also, the system includes the clutch control unit 121, which is arranged for controlling 251 the clutch 106 to the free of backlash position CsiiP_free. The system further includes the brake control unit 123, which is arranged for deactivating 252 the at least one shaft brake arrangement 701 providing the braking torque Tbrake on the shaft 109 when the clutch again reaches the free of backlash position Csiip_free. Also, the system includes the clutch control unit 121, being arranged for controlling 253 the clutch 106 from the free of backlash position CsiiP_free towards the closed position Cciosed.

The system according to the present invention may be arranged for performing all of the above, in the claims, and in the herein described embodiments method steps. The system is hereby provided with the above described advantages for each respective embodiment. The present invention is also related to a vehicle 100, such as a truck, a bus or a passenger car, including the herein described system for controlling a backlash of a powertrain.

The person skilled in the art will appreciate that a method for controlling a backlash of a powertrain according to the present invention can 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, 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 6 shows in schematic representation a control unit 600. The control unit 600 comprises a computing unit 601, 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 601 is connected to a memory unit 602 arranged in the control unit 600, which memory unit provides the computing unit 601 with, for example, the stored program code and/or the stored data which the computing unit 601 requires to be able to perform computations. The computing unit 601 is also arranged to store partial or final results of computations in the memory unit 602 .

In addition, the control unit 600 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, 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), 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 figures 1, 6 and 7, which is well known to the person skilled in the art within this technical field.

In the shown embodiment, the present invention is implemented in the control unit 120. The invention can 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, 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 at least one control unit 120 is in figure 1 illustrated as including separately illustrated units 121, 122, 123, 124, 125. These units 121, 122, 123, 124, 125 can, however, be logically separated by physically implemented in the same unit, or can be both logically and physically arranged together. These units 121, 122, 123, 124, 125 can for example 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 units are active and/or are utilized for performing its method step, respectively.

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

1. Method for setting a vehicle in motion from a standstill comprising controlling a backlash of a powertrain (130) included in said vehicle (100); characterized by: - controlling (210), when said vehicle (100) is standing still, a clutch (106) included in said powertrain (130) to a slipping position Cs iiP , in which slipping position Cs iiP said clutch (106) transfers a backlash torque Tback iash being less than a torque Tc iosed being transferred in a closed position Cc iosed for said clutch (106), said backlash torque Tback iash having a controlled value for eliminating said backlash; - applying (230), when said backlash has been eliminated, a braking torque Tbrake on a shaft (109, 702, 705) of a gearbox (103) included in said powertrain (130), thereby continuing to keep said backlash eliminated; - opening (240) said clutch (106) to an open position Co pen for said clutch (106); and - setting said vehicle (100) in motion (250), based on at least one indication that the vehicle should be set in motion, using a start gear Gs tart, said backlash still being eliminated until said vehicle is set in motion (250).

2. Method as claimed in claim 1, wherein said applying (230) of said braking torque Tbrake is performed by activating at least one shaft brake arrangement (701) acting on said shaft (109, 702, 705) of said gearbox (103) included in said powertrain (130).

3. Method as claimed in any one of claims 1-2, wherein a free of backlash clutch position Cs iiP _free for said clutch (106) is determined (220) when said backlash has been eliminated by said backlash torque Tback iash .

4. Method as claimed in claim 3, wherein said setting said vehicle (100) in motion (250) includes: - controlling (251) said clutch (106) to said free of backlash position C slip_free/ - deactivating (252) said at least one shaft brake arrangement (701) providing said braking torque Tbrake on said shaft (109, 702, 705) when the clutch reaches said free of backlash position C slip_free} and - controlling (253) said clutch (106) from said free of backlash position Cs iiP _free towards said closed position Cc iosed .

5. Method as claimed in any one of claims 3-4, wherein an input shaft braking torque Tbrake _input corresponding to said braking torque Tbrake applied on said shaft (109, 702, 705) is equal to or greater than a torque Ts iiP _free said clutch (106) transfers at said free of backlash clutch position Cs iiP _free.

6. Method as claimed in any one of claims 1-5, wherein a determination of if said vehicle is at a standstill is performed based on one or more signals in the group of: - a number of shaft revolutions signal provided by a sensor at an output shaft (107) of said gearbox (103); - an acceleration signal provided by an accelerometer in said vehicle (100); - a number of wheel revolutions signal provided by a sensor at a wheel in said vehicle (100); - a brake pedal signal provided by a brake system in said vehicle (100); and - a positioning signal.

7. Method as claimed in any one of claims 1-6, wherein an input shaft braking torque Tbrake _input corresponding to said braking torque Tbrake applied on said shaft (109, 702, 705) is controlled to be high enough for keeping said backlash eliminated.

8. Method as claimed in any one of claims 1-7, wherein said controllable value of said backlash torque Tback iash is within a range of 10-50 Nm, or within a range of 15-25 Nm, or approximately 20 Nm.

9. Method as claimed in any one of claims 1-8, wherein said determining (220) if said backlash has been eliminated includes at least one in the group of: - analysing an increase of an engine torque Ten gine during said controlling (210) of said clutch (106); - analysing a length of a time period during which said backlash torque Tback iash has been applied by said clutch (106); and - analysing a difference AM between a rotational speed oShaft of an input shaft (109) of said gearbox (103) and a rotational speedOwhee i of a driving wheel (110, 111) of said vehicle (100).

10. Method as claimed in any one of claims 1-9, wherein a ramping up of a powertrain torque Tp0wer train is performed after said setting in motion (250) of said vehicle, said backlash still being kept eliminated during said ramping up.

11. Method as claimed in any one of claims 1-10, wherein said controlling (210) of said clutch (106) to said slipping position Csii p and setting said vehicle in motion (250) are separated in time by a standstill time period ts tand stm, wherein tstandstm > 0 S .

12. Computer program, characterized in code means, which when run in a computer causes the computer to execute the method according to any of the claims 1-11.

13. Computer program product including a computer readable medium and a computer program according to claim 12, wherein said computer program is included in the computer readable medium.

14. System arranged for setting a vehicle in motion from a standstill comprising controlling a backlash of a powertrain (130) included in a vehicle (100); characterized by: - a clutch control unit (121), arranged for controlling (210), when said vehicle (100) is standing still, a clutch (106) included in said powertrain (130) to a slipping position Cs iiP , in which slipping position CsiiP said clutch (106) transfers a backlash torque Tback iash being less than a torque Tc iosed being transferred in a closed position Cciosed for said clutch (106), said backlash torque Tback iash having a controlled value for eliminating said backlash; - a brake control unit (123), arranged for applying (230), when said backlash has been eliminated, a braking torque Tbrake on an shaft (109, 702, 705) of a gearbox (103) included in said powertrain (130), thereby continuing to keep said backlash eliminated; - said clutch control unit (121), arranged for opening (240) said clutch (106) to an open position Co pen for said clutch (106); and - a vehicle movement control unit (124), arranged for setting said vehicle in motion (250), based on at least one indication that the vehicle should be set in motion, using a start gear Gs tart, said backlash still being eliminated until said vehicle is set in motion (250) .

15. The system claimed in claim 14, further including: - a determination unit (122), arranged for determining (220) a free of backlash clutch position Cs iiP _free for said clutch (106) when said backlash has been eliminated by said backlash torque Tb ackiash} - said clutch control unit (121), arranged for controlling (251) said clutch (106) to said free of backlash position Cslip_free} - said brake control unit (123), arranged for deactivating (252) said at least one shaft brake arrangement (701) providing said braking torque Tbrake on said shaft (109, 702, 705) when the clutch reaches said free of backlash position Cslip_free/ and - said clutch control unit (121), arranged for controlling (253) said clutch (106) from said free of backlash position Csl ip_free towards Said ClOSed position Cc iosed .