Patent Description:
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.

In the gearbox/transmission, different gear ratios between an input shaft and an output shaft of the gearbox can be provided. Thus, the gearbox may change the gear ratio being provided by performing a gear shifting operation, e.g. including shifting a coupling sleeve between one or more of the gear wheels interacting in the gearbox, in order to provide a desired gear ratio for the gearbox.

A conventional gear shifting operation can be described as including four phases. The first phase of the gear shifting operation includes down-ramping of a powertrain torque Tpowertrain to <NUM>, such that the gear initially used, which is often also called the current gear, can be disengaged after the first phase.

In the second phase of the gear shifting operation, the current gear is disengaged, i.e. a gear coupling sleeve is moved out of position, such that it does not anymore couple the gear wheel of the current gear to a main/transmission shaft in the gearbox. Then, the gearbox is synchronised with a target gear, i.e. the gear which should be used after the gear shifting operation is synchronised with a rotational target ωe_target speed of the main/transmission shaft. Then, the target gear is coupled/engaged/meshed with the main/transmission shaft in the gearbox, i.e. the gear coupling sleeve is moved/changed in to a new target gear position Gtarget, such that the target gear wheel is coupled/engaged/meshed with the main/transmission shaft in the gearbox in the new target gear position. In other words, a new target gear ratio between an input shaft and an output shaft of the gearbox is provided by shifting one or more gear coupling sleeves in the gearbox, such that a target gear position Gtarget for the gearbox is achieved. After the shifting, the target gear wheel is coupled/engaged/meshed with the main/transmission shaft in the gearbox, and the target gear ratio is provided by the gearbox.

In the third phase of the gear shifting operation, a play/backlash of the powertrain is eliminated/wound up. 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 Δω between a rotational speed ωshaft of an input shaft of a gearbox and a rotational speed ωwheel 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 on the input shaft. If the difference Δω is big/considerable when the play/backlash is gone/eliminated, the difference Δω 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, strategies have been used at the request of engine torque in order to reduce these powertrain oscillations. Such strategies utilise limiting torque ramps when the engine torque is requested. These torque ramps have 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, which would then result in powertrain oscillations.

In the fourth phase of the gear shifting operation, the engine torque is ramped up to the torque requested by the driver and/or driving assisting devices, such as vehicle speed/cruise control systems. In the fourth phase, the torque ramps used are usually steeper/less flat than in the third phase.

<CIT> discloses a method for reducing backlash in a vehicle.

As described above, allowing the driver and/or, for example, a cruise control to freely request a torque would 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 first relatively flat torque ramp is then usually manually calibrated and does not provide any comfort feedback information, i.e. no feedback information related to powertrain oscillations is provided. Thus, it is in prior art systems not known by the control system if the used torque ramp causes oscillations or not.

In order to eliminate/wind up the play/backlash of the power train in a safe and reliable way, a small engine torque having a very precise value need to be provided for the prior art solutions. Such a high accuracy value for the small engine torque is today very hard, and often impossible, to provide. Probably, an additional high precision engine torque sensor would have to be implemented in the vehicle in order be able to provide a sufficiently accurate small engine torque value. Such an additional sensor is expensive to implement in the vehicle, especially since it has to be a high precision sensor. Also, to add another sensor adds to the hardware complexity of the vehicle.

It is therefore one objective of the present invention, to provide a method and a system for controlling a backlash of a powertrain that at least partly solve these problems.

This objective is achieved through a method according to claim <NUM>. The objective is also achieved through a system according to claim <NUM>, a computer program according to claim <NUM>, and a computer program product according to claim <NUM>.

The invention will be illustrated in more detail below, along with the enclosed drawings, where similar references are used for similar parts, and where:.

<FIG> schematically shows a heavy example vehicle <NUM>, 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 <FIG>, but may also be used in lighter vehicles such as passenger cars. The vehicle <NUM>, shown schematically in <FIG>, comprises a pair of driving wheels <NUM>, <NUM>. The vehicle furthermore comprises a powertrain <NUM> with an engine <NUM>, which may be, for example, a combustion engine, an electrical motor or a combination of these, a so called hybrid drive. The engine <NUM> may, for example, in a customary fashion, via an output shaft <NUM> of the engine <NUM>, be connected with a gearbox <NUM>, via a clutch <NUM> and an input shaft <NUM> connected to the gearbox <NUM>. An output shaft <NUM> from the gearbox <NUM>, also known as a propeller shaft, drives the driving wheels <NUM>, <NUM> via a final gear <NUM>, such as e.g. a customary differential, and drive shafts <NUM>, <NUM> connected with said final gear <NUM>.

A control unit <NUM> is in <FIG> schematically illustrated as receiving signals and/or providing control signals from and/or to the engine <NUM>, the clutch <NUM> and/or the gearbox <NUM>. As described below, the control unit <NUM> may comprise a clutch control unit <NUM>, an analysis unit <NUM>, and a determination unit <NUM>. According to some embodiments of the present invention, the control device <NUM> may also comprise a gearbox control unit <NUM>, a brake control unit <NUM> and/or a verification unit <NUM>. These units are described in more detail below.

<FIG> shows a flow chart for a method for controlling a backlash of a powertrain included in a vehicle <NUM> in connection with a gear shifting operation, according to an embodiment of the present invention.

In a third step <NUM>, a clutch <NUM> included in the powertrain <NUM> is controlled in connection with a first gear shifting operation. As is described below, a first step <NUM> and/or a second step <NUM> may precede the third step <NUM> according to some embodiments.

The clutch <NUM> is in the third step <NUM> controlled to a slipping position Cslip, in which slipping position Cslip the clutch <NUM> transfers a slipping torque Tslip being less than a torque Tclosed being transferred in a closed position Cclosed for the clutch <NUM>. Thus, in the slipping position Cslip, the clutch <NUM>, i.e. a clutch actuator controlling the position of the clutch, is in a position between a closed position Cclosed and an open position Copen, whereby the slipping torque Tslip is lower than a closed torque Tclosed and higher than an open torque Topen being transferred by the clutch <NUM> in the closed position Cclosed and in the open position Copen, respectively; Topen<Tslip<Tclosed.

In a fourth step <NUM>, a change ω̇ of a rotational speed ω for an input shaft <NUM> of the gearbox <NUM> included in the powertrain <NUM> is analysed. This analysis will be described more in detail below.

In a fifth step <NUM>, a position Cdet for the clutch <NUM> is determined, such that the change ω̇ of the rotational speed has a value ω̇det corresponding to a backlash torque Tbacklash for that position Cdet. The backlash torque Tbacklash has here a predetermined value being suitable for eliminating the backlash in the powertrain, as will be described below.

In a seventh step <NUM>, the determined clutch position Cdet is utilised for controlling the clutch <NUM> in connection with a second subsequent gear shifting operation. As is described below, a sixth step <NUM> may precede the seventh step in some embodiments.

Thus, according to the present invention, the position Cdet for the clutch <NUM>, which in connection with a first gear shifting operation has been determined to be suitable for eliminating the powertrain backlash/play, is utilised <NUM> in a second subsequent gear shifting operation for eliminating the powertrain backlash/play. Hereby, the powertrain oscillations and/or the component wear may be reduced considerably in connection with the second subsequent gear shifting operation. The reduction in powertrain oscillations increases the driver comfort in the vehicle.

By the use of the present invention, a more efficient and reliable elimination of potential backlash/play in the powertrain is achieved. Therefore, also quick and reliable gear changing operations are achieved. 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, fail to 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 the <FIG>. The cogs of the cogwheels make contact in a first shaft position, during rotation in a first direction, as illustrated in <FIG>, 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 <FIG>, in a position corresponding to a maximum forward turn. Therefore, the cogs are engaged/meshed in both these positions (illustrated in <FIG> 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 within the play, illustrated in <FIG>. 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 <FIG> 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, <FIG> 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, or during a shift operation. 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.

<FIG> shows a flow chart illustrating different embodiments of the present invention including a number of steps being performed in connection with a gear shifting operation, that will hereafter be described. <FIG> schematically illustrates a non-limiting example of a first and a second gear shifting operations, that are here used for explaining the principles of the embodiments descried in this document.

In <FIG>, the third <NUM>, the fourth <NUM>, the fifth <NUM> and the seventh <NUM> steps correspond to the steps described above in connection with <FIG>. These steps are only briefly described here, and reference is made to <FIG>. In addition to these previously described steps, a number of further steps are described in connection with <FIG> and exemplified by the non-limiting first gear shifting operation illustrated in <FIG>.

As is illustrated in <FIG>, the clutch <NUM> is in a first gear shifting operation controlled <NUM> to be opened <NUM>, i.e. is controlled to an open position Copen, after which the gearbox <NUM> is shifted <NUM> into a neutral gear Gneutral. After the gearbox <NUM> is shifted into a neutral gear Gneutral, the target value ωe_target <NUM> for a rotational speed ωe of the engine <NUM> (solid line in <FIG>) is reduced from a higher value <NUM> to a lower value <NUM>. The target value ωe_target <NUM> for the rotational speed ωe of the engine <NUM> can be calculated based on the rotational speed of the wheels ωdrive_wheel and the total target gear ratio gpowertrain_target for the powertrain/driveline from the input shaft <NUM> to the drive wheels <NUM>, <NUM>.

When the target value ωe_target <NUM> is reduced to its lower value <NUM>, the rotational speed ω <NUM> for the input shaft <NUM> of the gearbox <NUM> (<NUM>; dashed line in <FIG>) is also reduced. The dashed line for the rotational speed ω <NUM> for the input shaft <NUM> in <FIG> represents the rotational speed ω in connection with the first gear shifting operation. According to an embodiment of the present invention, an input shaft brake arrangement providing a braking torque directly or indirectly on the input shaft <NUM> is activated <NUM> in order to brake the rotational speed to a value ωlow being lower than the target value ωe_target <NUM>.

The input shaft brake arrangement can be arranged in a number of ways, as long as a braking torque is applied to the input shaft <NUM>. The braking torque can according to different embodiments be applied directly to the input shaft <NUM> and/or to another shaft <NUM> being connected to the input shaft via at least one gear wheel meshing. <FIG> schematically illustrates one example of a gearbox <NUM> including an input shaft <NUM>, and a main/transmission shaft <NUM> being journaled to the input shaft <NUM> in bearings <NUM>. Also, a lay shaft brake <NUM>, configured to apply a braking torque to a lay shaft <NUM>, is schematically illustrated. The lay shaft <NUM> is here braked by the lay shaft brake <NUM>, and the braking force is then provided to the input shaft <NUM> of the gearbox <NUM> via one or more gear wheel meshes <NUM>, <NUM>. The input shaft brake arrangement may be constructed in a number of ways, and is not limited to the schematic illustration of <FIG>. As described in this document, the input shaft brake arrangement may be controlled by a brake control unit <NUM> included in a control unit <NUM>. The control unit <NUM> may also include a gearbox control unit <NUM>.

This is also illustrated in a first step <NUM> and a second step <NUM> in <FIG>. Thus, in the first step <NUM>, the gearbox <NUM> is shifted into a neutral gear position. Also, in the second step <NUM>, the input shaft <NUM> of the gearbox <NUM> is braked to a rotational speed <NUM> having a value ωlow being lower than the target value ωe_target for the rotational speed of the engine <NUM>. Thus, the rotational speed value ω <NUM> of the input shaft <NUM> for the first gear shifting operation (dashed line) is braked passed the target value ωe_target <NUM> until the input shaft braking arrangement is deactivated <NUM> when the rotational speed value ω <NUM> is lower than the target value ωe_target <NUM>.

As described above, the clutch <NUM> is then controlled <NUM> in a third step <NUM> to the slipping position Cslip from the open position Copen. In this document, the positions for the clutch <NUM>, such as the open position Copen, the closed position Cclosed, the slipping position Cslip and the determined position Cdet, each corresponds to a position Cact of a clutch actuator controlling a degree of opening for said clutch <NUM>. Thus, the position of the clutch/actuator determines the torque being transferred by the clutch <NUM>.

The deactivation of the input shaft braking arrangement in combination with the use of the slipping position Cslip of the clutch <NUM> causes the rotational speed ω <NUM> for the input shaft <NUM> to increase again after its lowest value <NUM>. Thus, the rotational speed ω <NUM> for the input shaft <NUM> increases such that a change ω̇ of the rotational speed ω <NUM> is provided. This change ω̇ of the rotational speed is then in a fourth step <NUM> analysed during an analysis time period Tanalysis. This analysis will be described more in detail below.

The analysis of the change ω̇ of the rotational speed can then in a fifth step <NUM>, be used for determining a position Cdet for the clutch <NUM> for which the acceleration/change/derivative ω̇ of the rotational speed has a value ω̇det corresponding to a backlash torque Tbacklash for that position Cdet. The position Cdet can here be determined such that the backlash torque Tbacklash corresponding to the value ω̇det has a predetermined value being suitable for eliminating the backlash in the powertrain.

As is illustrated in <FIG>, the different parts of the powertrain have different rotational inertias, comprising a rotational inertia Je for the engine <NUM>, a rotational inertia Jg for the gearbox <NUM>, a rotational inertia Jc for the clutch <NUM>, a rotational inertia Jp for the propeller shaft <NUM> and rotational inertias Jd for each drive shaft <NUM>, <NUM>. Generally speaking, all rotating bodies have a rotational inertia J, which depends on the mass of the body and the distance of the mass from the rotational centre. For reasons of clarity, in <FIG>, only the above mentioned rotational inertias have been added, and their significance for the present invention will be described hereafter. A person skilled in the art does, however, realise that more moments of inertia may occur in a powertrain than those listed here.

Generally, the torque T and the change ω̇ of the rotational speed are related to each other and to a rotational inertia J according to T = Jω̇. For the powertrain, or at least for parts of the powertrain, the rotational inertia J is known or can be calculated.

The determined value ω̇det for the change in rotational speed is dependent at least on a rotational inertia J of one or more parts of the clutch <NUM> and the gearbox <NUM>. One non-limiting example value for the inertia J for the rotating parts of the clutch <NUM> and the gearbox <NUM> can be e.g. <NUM>*m<NUM>. According to an embodiment of the present invention, the predetermined value of the backlash torque Tbacklash suitable 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 <NUM>, <NUM>, for example within a range of <NUM>-<NUM>, or within a range of <NUM>-<NUM>, or approximately <NUM>.

Thus, the value ω̇det for the acceleration/change/derivative ω̇ of the rotational speed corresponding to the backlash torque Tbacklash value being useable for eliminating the backlash/play is calculated. Then, the clutch <NUM> is controlled to be gradually more and more closed from its open position Copen <NUM> (solid line for the first shifting operation in <FIG>). During the analysis time period Tanalysis, the clutch is gradually closed until the wanted value ω̇det for the acceleration/change/derivative ω̇ results <NUM> from the control of the clutch. As described above, when the acceleration/change/derivative ω̇ has this wanted value ω̇det <NUM>, the backlash torque Tbacklash is provided to the powertrain, which eliminates/winds up the backlash/play. In the fifth step <NUM>, the position Cdet for the clutch <NUM> which results in the wanted value ωdet, and thus also in the backlash torque Tbacklash, is determined based on the actual position of the clutch <NUM> when the wanted value ω̇det is provided.

The rotational speed ω <NUM> of the input shaft <NUM> then continues to increase, such that it reaches <NUM> the target value ωe_target <NUM> for the rotational speed of the engine <NUM> again. The gearbox <NUM> is changed into a target gear position Gtarget <NUM> (solid line for the first gear shifting operation in <FIG>) when the rotational speed ω for the input shaft <NUM> is essentially equal <NUM>, e.g. within an interval of ±<NUM> rpm, with the target value ωe_target for the rotational speed of the engine <NUM>.

When the rotational speed ω <NUM> of the input shaft <NUM> has increased above the target value ωe_target <NUM>/<NUM> for the rotational speed of the engine <NUM>, the backlash/play is eliminated <NUM> and the rotational speed ω is reduced to the target value ωe_target <NUM>/<NUM> again <NUM>.

In a sixth step <NUM> of the method, the elimination of the backlash is verified based on an analysis of a difference Δ between the rotational speed ω <NUM> for the input shaft <NUM> and a converted rotational wheel speed ωwheel. The converted rotational wheel speed ωwheel can here be calculated based on a rotational speed of at least one driving wheel <NUM>, <NUM> in the vehicle <NUM> and on a total gearing ratio between the input shaft <NUM> of the gearbox <NUM> and the at least one driving wheel <NUM>, <NUM>, e.g. including at least the gearing ratio of the gearbox and the differential <NUM>.

According to an embodiment of the present invention, the backlash torque Tbacklash is controlled such that the difference Δ is less than a predetermined value Δpredet; Δ<Δpredet; during the elimination of the backlash. Here, a constant and/or predetermined value for the backlash torque Tbacklash can be requested/provided during the backlash elimination process, which results in a value for the difference Δ. The difference Δ is then analysed in order to determine if the backlash/play has been eliminated or not. Alternatively, the value for the backlash torque Tbacklash is adapted in order to achieve the predetermined value Δpredet for the difference Δ. For the embodiments mentioned herein, the predetermined value Δpredet can be e.g. <NUM> rotations per minute; i.e. Δpredet =<NUM> rpm and Δ < <NUM> rpm. Hereby, a controlled elimination of the backlash/play is achieved.

As described above, the first to sixth steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are performed in connection with the first gear shifting operation. By these steps, the position Cdet for the clutch <NUM> being suitable for eliminating the backlash in the powertrain can be determined in connection with the first gear shifting operation.

In a seventh step <NUM>, the determined clutch position Cdet is utilised for controlling the clutch <NUM> in connection with a second subsequent gear shifting operation. Thus, the clutch position Cdet having been determined in connection with the first gear shifting operation can then be used later in connection with a second gear shifting operation, as is illustrated with the dot-dashed line <NUM> in <FIG>.

The dot-dashed line <NUM> for the rotational speed ω for the input shaft <NUM> in <FIG> illustrates the rotational speed ω <NUM> for the second subsequent gear shifting operation. Also, the dot-dashed line <NUM> for the gears in <FIG> illustrates the gearing in connection with the subsequent second gear shifting operation. As is clearly illustrated in <FIG>, the target gear Gtarget can be engaged already <NUM> when the rotational speed ω for the input shaft <NUM> has a value being essentially equal to the target value ωe_target <NUM>/<NUM> for the rotational speed of the engine <NUM>. Also, the rotational speed ω <NUM> for the second subsequent gear shifting operation can be directly increased <NUM> when the the rotational speed ω for the input shaft has a value being essentially equal to the target value ωe_target <NUM>/<NUM>, e.g. within an interval of ±<NUM> rpm around the target value ωe_target <NUM>/<NUM>.

Thus, a quick and safe gear shifting operation, without driveline oscillations can be provided by the present invention, after the above described steps in connection with the first gear shifting operation have been performed. In other words, the first gear shifting operation will according to the present invention, take a little more time than a standard gear shifting operation, but after that, quick and comfortable gear shifting operations are provided according to the present invention. The first gear shifting operation can for example be performed in a driving situation in which there is plenty of time to perform the gear shifting operation, and to determine the clutch position Cdet to be used in one or more upcoming gear shifting operations after the first gear shifting operation.

The clutch <NUM> is, according to an embodiment, controlled 270a to be in the determined clutch position Cdet when the gearbox <NUM> is changed into the target gear position Gtarget in connection with the second subsequent gear shifting operation, as is illustrated by the dot-dashed line <NUM> in <FIG>. Thus, the determined clutch position Cdet is here used when the gear wheels and/or shafts in the gearbox <NUM> corresponding to the target gear position Gtarget engage with each other.

According to an embodiment, the clutch <NUM> is controlled 270b to be in the determined clutch position Cdet after the gearbox <NUM> has been changed into a target gear position Gtarget in connection with the second subsequent gear shifting operation, e.g. at least initially during up-ramping of a powertrain torque Tpowertrain after the second gear changing operation.

According to an embodiment, the clutch <NUM> is controlled 270a to be in the determined clutch position Cdet when the gearbox <NUM> is changed into the target gear position Gtarget, and is also kept in this position thereafter, e.g. during the up-ramping.

In this document, the closed clutch position Cclosed may be defined as the clutch being closed and no longer slipping, which also means that the rotational speeds for the clutch's input <NUM> and output <NUM> shafts are substantially equal. This may also be expressed as the clutch at this clutch position Cclosed is able to transfer a higher torque than an actual/momentary torque that is transferred to the input shaft <NUM> and/or to the driving wheels at a time instant.

When the clutch <NUM> is in the slipping clutch position Cslip, the clutch can according to an embodiment transmit a slip 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 wound up when the clutch <NUM> is in the slipping clutch position Cslip.

Control/Activation of the clutch is usually carried out with the use of one or more actuators. These actuators may for example be hydraulic, pneumatic and/or electrically driven/activated/controlled.

According to an aspect of the present invention, a system for controlling a backlash of a powertrain <NUM> included in a vehicle <NUM> in connection with a gear shifting operation is presented.

With reference to <FIG> and <FIG>, the system includes a clutch control unit <NUM>, arranged for controlling <NUM>, in connection with a first gear shifting operation, a clutch <NUM> included in the powertrain <NUM> to a slipping position Cslip, in which slipping position Cslip the clutch <NUM> transfers a slipping torque Tslip being less than a torque Tclosed being transferred in a closed position Cclosed for the clutch.

The system also includes an analysis unit <NUM>, arranged for analysing <NUM> a change ω̇ of a rotational speed ω for an input shaft <NUM> of a gearbox <NUM> included in the powertrain <NUM>.

The system also includes a determination unit <NUM>, arranged for determining <NUM> a position Cdet for the clutch <NUM>, for which position Cdet the change ω̇ of the rotational speed has a value ω̇det corresponding to a backlash torque Tbacklash, the backlash torque Tbacklash having a predetermined value suitable for eliminating the backlash.

The clutch control unit <NUM> is further arranged for utilising <NUM> the determined clutch position Cdet for controlling the clutch <NUM> in connection with a second subsequent gear shifting operation.

The system according to the present invention can 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 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 <NUM> 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. Said 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..

<FIG> shows in schematic representation a control unit <NUM>. The control unit <NUM> comprises a computing unit <NUM>, 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 <NUM> is connected to a memory unit <NUM> arranged in the control unit <NUM>, which memory unit provides the computing unit <NUM> with, for example, the stored program code and/or the stored data which the computing unit <NUM> requires to be able to perform computations. The computing unit <NUM> is also arranged to store partial or final results of computations in the memory unit <NUM>.

In addition, the control unit <NUM> is provided with devices <NUM>, <NUM>, <NUM>, <NUM> for receiving and transmitting input and output signals. These input and output signals can contain waveforms, impulses, or other attributes which, by the devices <NUM>, <NUM> 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 <NUM>. These signals are then made available to the computing unit <NUM>. The devices <NUM>, <NUM> for the transmission of output signals are arranged to convert signals received from the computing unit <NUM> 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 <NUM> and that the above- stated memory can be constituted by the memory unit <NUM>.

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 <FIG>, <FIG>, 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 <NUM>. 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 <NUM> is in <FIG> illustrated as including separately illustrated units <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. These units <NUM>, <NUM>, <NUM>, <NUM>, <NUM> can, however, be logically separated by physically implemented in the same unit, or can be both logically and physically arranged together. These units <NUM>, <NUM>, <NUM>, <NUM>, <NUM> 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 <NUM> when the units are active and/or are utilized for performing its method step, respectively.

Claim 1:
Method for controlling a backlash of a powertrain (<NUM>) included in a vehicle (<NUM>) in connection with a gear shifting operation; said method comprising the steps of:
- controlling (<NUM>), in connection with a first gear shifting operation, a clutch (<NUM>) included in said powertrain (<NUM>) to a slipping position Cslip, in which slipping position Cslip said clutch (<NUM>) transfers a slipping torque Tslip being less than a torque Tclosed being transferred in a closed position Cclosed for said clutch (<NUM>);
- analysing (<NUM>) a change ω̇ of a rotational speed ω for an input shaft (<NUM>) of a gearbox (<NUM>) included in said powertrain (<NUM>);
- determining (<NUM>) a position Cdet for said clutch (<NUM>), for which position Cdet said change ω̇ of said rotational speed ω has a value ω̇det corresponding to a backlash torque Tbacklash, and
- utilising (<NUM>) said determined clutch position Cdet for controlling said clutch (<NUM>) in connection with a second subsequent gear shifting operation, characterized in that said gearbox (<NUM>) is changed into said target gear position Gtarget when said rotational speed ω for an input shaft (<NUM>) is essentially equal to a target value ωe_target for a rotational speed of an engine (<NUM>) included in said powertrain (<NUM>).