Torque distribution system

Abstract

The invention relates to a method for operating a torque distribution system for drive wheels (6a, 6b, 8a, 8b) of a vehicle (2), wherein an actual yaw moment is provided for the vehicle (2) by the torque distribution system, wherein in the event of a fault in the torque distribution system, depending on a type and / or level of the actual yaw moment for the torque distribution system, a first shutdown strategy for the torque distribution system - first an active short circuit, then a freewheel or as a second shutdown strategy for the torque distribution system - first the freewheel and then the active short circuit are carried out.

Description

[0001] The invention relates to a method for operating a torque distribution system and a torque distribution system.

[0002] The document DE 10 2021 208 442 A1 describes a method for controlling the operation of an electrical machine of a motor vehicle.

[0003] An electric axle drive for a road vehicle is known from the publication US 2015 / 0 065 283 A1.

[0004] The document DE 10 2013 016 960 A1 describes the shutdown of an inverter unit.

[0005] The publication DE 10 2013 100 598 A1 describes a method for controlling a drive device of an electric vehicle with electric motors for driving the electric vehicle. This method involves monitoring the driving stability of the electric vehicle on the vehicle using a control unit of the electric vehicle, comparing the monitored driving stability with a target value for the driving stability of the electric vehicle, and changing at least one operating parameter of at least one electric motor if the monitored driving stability deviates from the target value.

[0006] The document DE 10 2015 203 782 A1 describes a method for safely operating a motor vehicle with a motor vehicle control system which comprises a propulsion control unit which controls first components, wherein the propulsion control unit, when it receives a warning in a yaw rate warning signal, controls the first components in such a way that a total yaw moment generated by the first components as a whole is not greater than a total yaw moment limit value.

[0007] Against this background, the task was to operate a torque distribution system for a vehicle in a suitable manner.

[0008] This object is achieved by a method and a torque distribution system having the features of the independent patent claims. Embodiments of the method and the torque distribution system are evident from the dependent patent claims and the description.

[0009] The invention relates to a method for operating a torque distribution system for drive wheels of a drive axle of a vehicle, e.g., a motor vehicle. The torque distribution system or torque vectoring system has an electric machine that is or will be assigned to the drive wheels of the drive axle of the vehicle, wherein an actual yaw moment is provided by the one electric machine for the drive axle or its drive wheels. Furthermore, in the event of a fault in the torque distribution system, depending on the type and / or magnitude of the actual yaw moment for the torque distribution system, an active short circuit, followed by freewheeling, is usually carried out by a control unit as a first shutdown strategy for the torque distribution system.Alternatively, depending on the type and / or magnitude of the actual yaw moment, the second shutdown strategy for the torque distribution system, in contrast to the first shutdown strategy, is to first execute freewheeling and then active short circuit. Furthermore, a check is performed, for example, by the control unit, to determine whether the torque distribution system was in an agile mode or system state or in a stabilizing mode or system state before the fault occurred. The first shutdown strategy is implemented if the torque distribution system was in an agile mode, or the second shutdown strategy is implemented if the torque distribution system was in a stabilizing mode.

[0010] The torque distribution system comprises a superposition gear and an electric motor, for example, as an electric machine. The torque distribution system can rotate the drive wheels of the drive axle relative to each other. The electric machine is located between the two drive wheels of the drive axle and acts on the drive wheels. Due to the design of the superposition gear, the speed of the electric machine corresponds to the difference between the speeds of the two drive wheels. The electric machine can rotate the two drive wheels relative to each other, thus creating a differential.

[0011] Typically, a target yaw moment is specified for the vehicle, wherein one of the two switch-off strategies is carried out depending on a vectorial and / or absolute deviation of the actual yaw moment from the target yaw moment, wherein the first switch-off strategy is carried out when the actual yaw moment is vectorially and / or in terms of absolute value greater than the target yaw moment or equal to the target yaw moment, or alternatively wherein the second switch-off strategy is carried out when the actual yaw moment is vectorially and / or in terms of absolute value smaller than the target yaw moment.

[0012] In one embodiment, the driving dynamics of the vehicle that arise when the vehicle travels around a bend are taken into account, with the driving dynamics resulting in understeering or oversteering of the vehicle. In a first variant, the first switch-off strategy is implemented if the actual yaw moment is a yaw moment turning into the bend, which results when the vehicle understeers when traveling around a bend. Accordingly, in the first variant, the second switch-off strategy is implemented if the actual yaw moment is a yaw moment turning out of the bend, which results when the vehicle oversteers when traveling around a bend. In a second variant, the first switch-off strategy is implemented if the actual yaw moment is a yaw moment turning out of the bend, which results when the vehicle oversteers when traveling around a bend.Accordingly, in the second variant, the first switch-off strategy is implemented if the actual yaw moment is a cornering yaw moment that results when the vehicle understeers when driving through a curve.

[0013] Whether a particular shutdown strategy creates an outward or inward yaw moment depends on the speeds of the two drive wheels and whether a right-hand or left-hand bend is being negotiated. Regardless of the direction of rotation, the selected shutdown strategy can be used to set the magnitude and temporal progression of the resulting or generated yaw moment as the target yaw moment. When selecting the respective shutdown strategy, the design takes into account whether the resulting or resulting yaw moment or target yaw moment has a positive or negative effect on the desired driving behavior of the vehicle. If the resulting yaw moment has a positive effect on driving behavior, the shutdown strategy with the higher resulting yaw moment is selected.If, however, the resulting yaw moment negatively impacts driving behavior, the shutdown strategy with the lower yaw moment is selected. This maximizes benefits and minimizes damage.

[0014] In one embodiment, the method provides that, based on a driving state of the vehicle and / or a driver's input, the desired yaw moment is determined, typically by the control unit, which desired yaw moment is favorable and / or compatible for the vehicle and / or which of the two shutdown strategies can be used to achieve this desired yaw moment based on the actual yaw moment and / or taking into account a vectorial and / or absolute deviation of the actual yaw moment from the desired yaw moment or a difference between the actual yaw moment and the desired yaw moment. For example, the magnitude of the actual yaw moment turning into a curve or the actual yaw moment turning out of a curve is taken into account.Taking into account the expected behavior of the vehicle based on a respective shutdown strategy and / or the magnitude of the resulting and / or to be achieved target yaw moment, the more favorable of the two shutdown strategies is selected depending on the error.

[0015] Both shutdown strategies comprise an active short circuit and a freewheeling mode as two stabilization measures in different temporal sequences. In some configurations, it is possible that after one of the two shutdown strategies has been executed, a switch is subsequently made between the short circuit and the freewheeling mode due to the fault.

[0016] The decision regarding which shutdown strategy to implement is usually made automatically by the control unit, depending on at least one parameter or a value of the at least one parameter, usually detected by sensors, before and / or upon the occurrence of the fault. Several parameters are provided, among which the at least one parameter or its value is taken into account.

[0017] In this case, a drive torque of the electric machine or of an electric actuator of the torque distribution system is taken into account as a parameter, in particular before the fault or its occurrence. A speed as a parameter of the electric machine is determined by or through a speed sensor of the electric machine and / or by or through a wheel speed sensor of the drive axle of the vehicle on which the torque distribution system is arranged and / or installed. In this case, a check is carried out to determine whether a difference between the speeds of usually two drive wheels per drive axle is equal to a speed of the electric machine or deviates from it. In order to ensure the most accurate calculation possible, at least one additional parameter, for example a twisting of a drive shaft and / or transmission shaft of the vehicle, is taken into account in addition to values ​​of the speeds of the drive wheels determined by the wheel speed sensor.

[0018] A further parameter to be taken into account is the direction of rotation of the electric machine, which is determined by or with a speed sensor of the electric machine and the wheel speed sensor on the drive axle on which the torque distribution system is installed. In addition, an effective direction of the electric machine along or parallel to the drive axle is taken into account, which results from a torque and / or the speed of the drive wheels on the drive axle, usually from a difference in the speeds and / or the torques of two drive wheels on the respective drive axle. In one embodiment, during torque distribution operation, the torque of the faster rotating drive wheel of the drive axle is increased, while a difference in the speed of the drive wheels is reduced. During limited-slip differential operation, the torque of the slower rotating drive wheel of the drive axle is increased.

[0019] At least one further parameter to be taken into account is / are a yaw rate, a lateral acceleration or a longitudinal acceleration of the vehicle. With regard to the vehicle's driving dynamics, sensors are used, e.g. based on yaw rates and / or lateral accelerations of the vehicle and / or based on the speeds of the drive wheels, to determine whether the vehicle is understeering or oversteering. A further parameter that can be measured as a parameter is the vehicle speed or estimated by the control unit based on parameters for the driving state and / or on models, e.g. using a Kalman filter. An additional parameter is wheel slip, which is determined from the speeds of the drive wheels at and / or taking into account the measured or estimated speed. Further parameters are the vehicle's steering angle and the braking torque of a brake, e.g. a friction brake, of the vehicle.In addition, a drive torque, usually a level of the drive torque, or a recuperation or deceleration torque, usually a level of the same, are parameters that can be taken into account.

[0020] If the vehicle's yaw rate is higher than a yaw rate desired by the driver, which is set by the driver using a steering angle, the shutdown strategy is selected which applies the greatest possible yaw moment that opposes the yaw rate, stabilizing the vehicle and assisting the driver. The first shutdown strategy is implemented, which initially comprises the active short circuit followed by freewheeling, as this leads to a higher opposing yaw moment if an outside drive wheel is expected to rotate faster than an inside drive wheel. If, on the other hand, the inside drive wheel is expected to rotate faster than the outside drive wheel in this situation, the second shutdown strategy is selected, which first carries out freewheeling and then the active short circuit, generating a lower incoming yaw moment.In addition, it is taken into account which of the two shutdown strategies places less strain on the vehicle's components.

[0021] Furthermore, for a respective selectable or selected shutdown strategy, a duration of the active short circuit and a duration of the freewheeling are set as a respective stabilization measure depending on at least one parameter, namely the magnitude of a torque distribution (torque vectoring moment) between the vehicle's drive wheels, the vehicle's speed, the vehicle's lateral acceleration, the rotational speeds of the drive wheels, the vehicle's yaw rate, the temperature of the electric motor of the torque distribution system, and / or the power electronics of the torque distribution system. The yaw rate can also be referred to as yaw velocity, which corresponds to an angular velocity that results when the vehicle rotates around its vertical axis, usually due to different rotational speeds of the drive wheels of a drive axle.

[0022] The duration of the active short circuit and freewheeling in a respective shutdown strategy is selected depending on a change in the difference in speeds between the left and right drive wheels and / or the speed of the electric motor of the torque distribution system, since the torque depends on at least one of these speeds. If switching between the shutdown strategies occurs at a suitable time, at least one additional yaw moment can be generated briefly by means of a dynamic effect, whereby a shaping of the torque can be achieved through cleverly timed switching.

[0023] The torque distribution system according to the invention is designed for drive wheels and / or drive axles of a vehicle. The torque distribution system typically has an electric machine or an electric actuator, which is assigned to drive wheels of a drive axle of the vehicle and is designed to provide an actual yaw moment for the vehicle by mechanically applying force to the drive wheels on the drive axle. In the event of a fault in the torque distribution system, e.g., a fault in the electric machine, the electric machine is designed, depending on the type and / or magnitude of the actual yaw moment for the torque distribution system, to first perform an active short circuit and then a freewheel as a first shutdown strategy.Alternatively, in the event of a torque distribution system failure, the torque distribution system, usually the electric machine, is designed to first perform freewheeling and then active short-circuiting as a second shutdown strategy for the torque distribution system.

[0024] Typically, the torque distribution system has a control unit, e.g. a computer, which is designed to monitor operation of the torque distribution system, to detect, recognize and / or detect the occurrence of an error and, in the event of a correspondingly detected, recognized and / or detected error of the torque distribution system, to automatically control the electric machine of the torque distribution system depending on a type and / or magnitude of the actual yaw moment for the torque distribution system and to automatically cause the electric machine to carry out or should carry out either the first or alternatively the second shutdown strategy.

[0025] Furthermore, it is possible for the torque distribution system and / or the vehicle to have at least one sensor which is designed to detect at least one parameter of the vehicle and / or the torque distribution system and to transmit a respective, usually currently detected value of the at least one parameter to the control unit, which, on the basis of the respective value of the at least one parameter, usually of several parameters, automatically detects whether or not there is an error in the torque distribution system and, in the event of a detected error, automatically decides which of the two possible shutdown strategies is to be selected and implemented, taking into account the respective value of the at least one parameter detected by a sensor and a correspondingly detected type of error.

[0026] The control unit provides a sequence control for the electric machine or for the electric actuator, with which the behavior of the torque distribution system is controlled in the event of a fault, whereby the control unit automatically and actively determines the respective shutdown strategy to be carried out and thus the temporal sequence of the two stabilization measures and also a duration of the respective stabilization measures taking into account the at least one parameter.

[0027] Both shutdown strategies feature a chronological sequence of the two stabilization measures, i.e., the active short circuit and the freewheeling. In the event of a fault in which the vehicle generally requires short-term stabilization, but a safe driving state is to be achieved in the long term, the combination of both stabilization measures is selected in chronological order and usually dependent on additional information about the driving state derived from the values ​​of the sensor-detected parameters. Overall, this provides the vehicle with greater driving stability and robustness against fault conditions or errors.

[0028] In one embodiment, in the case of the first shutdown strategy, when the usually electromechanical torque distribution system is shut down due to a fault, the active short circuit is first adopted and / or provided, followed by freewheeling. This first shutdown strategy introduces a stabilising yaw moment into the vehicle via the active short circuit immediately after the fault occurs, with the torque distribution system then changing to a thermally stable state. In the case of the second shutdown strategy, the freewheel is first adopted and / or provided, followed by the active short circuit.Idle and only through the subsequent active short circuit is the stabilizing yaw moment introduced into the vehicle, whereby the torque distribution system also subsequently changes to a thermally stable state.

[0029] In this case, it is provided in one embodiment that the two stabilization measures, i.e. their sequence or order, are linked to the at least one parameter in the respective shutdown strategy and thus to a corresponding driving state variable of the vehicle and / or to a corresponding system state variable of the torque distribution system. A decision as to whether the active short circuit is adopted before freewheeling or vice versa and how long the respective stabilization measure can be applied and / or carried out can also be made automatically depending on the state of the torque distribution system before the fault, taking into account whether the torque distribution system was or was in use in an agility-enhancing or stabilizing manner before the fault. When used in an agility-enhancing manner before the fault, the first shutdown strategy and thus initially the short circuit is carried out as a stabilization measure after a fault.Conversely, with pre-fault stabilization, the second shutdown strategy, and thus freewheeling, is implemented after a fault as a stabilization measure. Furthermore, the respective duration of the active short circuit and freewheeling can be adjusted depending on the respective value of at least one parameter, usually depending on several parameters simultaneously.

[0030] If the vehicle is stabilized after the fault by an active short circuit, the torque distribution system becomes more fault-tolerant, providing higher agile torque distributions, since in the event of the fault a stabilizing yaw moment is reliably, reproducibly and, due to physical reasons, usually always imposed on the torque distribution system for the vehicle by a magnetic field of the electrical machine, e.g. an electric motor.

[0031] The method can be implemented independently of the configuration of the torque distribution system's electric motor and its power density, i.e., for both high and low power densities. With each of the two possible shutdown strategies, different torques can be provided for both drive wheels located on the same drive axle, since the torque distribution system is not completely deactivated in the event of a fault.

[0032] If the electric motor is switched to freewheeling, for example, in a single-wheel drive system, each drive wheel has no drive torque or braking torque beyond mechanical friction losses. If the electric motor is switched to active short circuiting, a drag torque is provided to or applied to both drive wheels, which depends on the speed of the vehicle and / or the electric motor. It can be provided that the freewheeling and thus a resulting torque-free state can last longer than the active short circuit.

[0033] The torque distribution system can maintain the torque-free state for longer than the active short circuit, as the active short circuit can place thermal stress on the torque distribution system. The torque-free state frees the drive wheels from longitudinal forces, thus offering a high lateral force potential. The active short circuit applies a locking torque that stabilizes the vehicle's lateral dynamic behavior.

[0034] The two stabilization measures that are carried out one after the other cause different braking torques for the drive wheels of the same drive axle of the vehicle, depending on the speed of the electric motor, which leads to a differential torque between the two drive wheels of the drive axle on which the torque distribution system is installed. This differential torque on the drive axle imparts a yaw moment to the vehicle. Depending on the direction of action, i.e. which drive wheel of the drive axle is subjected to a positive moment and which to a negative moment, usually torque, this can be stabilizing, whereby the vehicle's yaw movement is slowed down and / or dampened to correct the error, or agile, whereby the vehicle's yaw movement is accelerated to correct the error. The yaw movement is a rotation of the vehicle around its vertical axis, which is intended, for example, for cornering.

[0035] In a further embodiment, a respective switch-off strategy is selected depending on a request from a driver of the vehicle, for example depending on the target yaw moment and / or a steering direction of the vehicle which is specified by the driver when steering the vehicle, as well as depending on the driving state, i.e. depending on where, for example in which direction, the vehicle is traveling, with knowledge of the sensor-determined behavior of the electric machine, wherein a level of the braking torque to be expected due to a respective switch-off strategy is determined, usually predicted, and one of the two switch-off strategies is selected on the basis of this.This takes into account that the freewheeling of the electrical machine, which can be separated and / or disconnected from an electrical power supply for a time interval, can result in a feedback voltage that can damage the vehicle's electrical system. This can be avoided by adjusting the freewheeling duration, regardless of the selected shutdown strategy.

[0036] The respective switch-off strategy to be implemented is selected depending, among other things, on whether the resulting yaw moment supports the driver's request, which, depending on the current driving state of the vehicle, e.g. when driving through a curve, can mean that the vehicle is steered in the direction desired by the driver or against this direction due to the resulting yaw moment.

[0037] If the vehicle is already at least following a steering command as a driver request, in some embodiments follows it too closely, causing the vehicle to oversteer, or follows the steering command too quickly, causing the vehicle to dynamically oversteer and / or skid, the second switch-off strategy can be selected automatically, wherein a yaw movement is dampened and a yaw moment is provided by the torque distribution system that is oriented or set against the steering direction desired by the driver, whereby the vehicle is easier for the driver to control due to the reduction in yaw rate. To select one of the two possible switch-off strategies, a target yaw behavior, e.g. the target yaw moment, is compared with an actual yaw behavior, e.g. the actual yaw moment, of the vehicle, e.g. with a single-track model of the vehicle.The direction in which the resulting yaw moment will act due to the selected deactivation strategy can be derived from the difference in the speeds of the left and right drive wheels on the drive axle where the torque distribution system is installed. In a refinement, the magnitude of the braking torque and thus the yaw moment can be stored in functional software and / or a map depending on this difference in speeds.

[0038] Since the braking torque is changed via the difference in speeds, and the braking torque also changes, e.g. reduces, the difference in speeds, it is intended that the selected switch-off strategy can be carried out several times in succession and that it can be switched between the stabilization measures. When selecting the switch-off strategy and / or sequence of stabilization measures, the current driving state or a current driving situation of the vehicle is taken into account, which is determined and / or recognized depending on the values ​​of the parameters recorded by sensors, e.g. longitudinal acceleration, lateral acceleration, yaw rate and / or steering angle. Based on the current driving situation, an automatic decision is made as to whether a higher or lower yaw moment is required for the vehicle, whereby one of the two switch-off strategies is selected.

[0039] The selection is made depending on the state of the torque distribution system and / or the vehicle or its driving state, whereby a combination of both states is usually taken into account. In one embodiment, the state of the torque distribution system can be dependent on at least one parameter of the electric machine of the torque distribution system, whereby the at least one parameter is a voltage applied to the electric machine and / or a current flowing through it. Furthermore, at least one parameter of a battery as an electrical energy store for the electric machine and / or at least one further component of the torque distribution system, e.g. an inverter, can be taken into account in the selection. In this case, the braking torque of the vehicle can also be stabilized despite the fault in the electric machine. The electric machine is connected to the battery via terminals.These terminals are opened to perform the active short circuit.

[0040] In one embodiment, a shutdown strategy can be selected due to the error, which can lead to damage to an electrical energy supply, for example a high-voltage supply, but which is the only alternative due to the current driving state, since the state more favorable for an electrical drive system of the vehicle is unfavorable from the point of view of driving stability of the vehicle, wherein when selecting the shutdown strategy, driver safety is preferred and / or taken into account over damage to the drive system of the vehicle.

[0041] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0042] The invention is illustrated schematically in the drawing using embodiments and is described schematically and in detail with reference to the drawing. Fig. 1 shows a schematic representation of an example of a vehicle having a first embodiment of the torque distribution system according to the invention for carrying out a first embodiment of the method according to the invention. Fig. 2 shows a flow chart for a second embodiment of the method according to the invention, which is carried out with a second embodiment of the torque distribution system according to the invention.

[0043] The Fig. 1 schematically illustrated vehicle 2 has a front drive axle 4a with two front drive wheels 6a, 6b arranged thereon and a rear drive axle 4b with two rear drive wheels 8a, 8b arranged thereon.

[0044] The first embodiment of the torque distribution system according to the invention for this vehicle 2 has an electric machine 10 which is assigned to drive wheels 6a, 6b of the front drive axle 4a, at least one sensor 12 and a control unit 14 for controlling the first embodiment of the method according to the invention.

[0045] The electric machine 10 is designed to distribute torque between the two drive wheels 6a, 6b on and / or along the front drive axles 4a, 4b. In this case, the electric machine 10 provides an actual yaw moment for the front drive axle 4a, 4b. In one embodiment, the torque distribution system with the electric machine 10 can alternatively be assigned to the rear drive axle 4b. It is also possible for each of the two drive axles 4a, 4b to be assigned an embodiment of the torque distribution system.

[0046] In the method, the at least one sensor 12 monitors a state, in this case the system state, of the electric machine 10 and thus also of the torque distribution system based on at least one parameter of the machine 10, and a state, in this case the driving state, of the vehicle 2 based on at least one parameter of the vehicle 2. Values ​​of the at least one parameter, usually of several parameters, are transmitted from the at least one sensor 12 to the control unit 14, where they are evaluated.

[0047] If an error is determined and / or detected by the control unit 14 for the torque distribution system, the electric machine 10 is controlled by the control unit 14 and causes the electric machine 10 to first carry out an active short circuit, then a freewheeling operation, as a first switch-off strategy for the torque distribution system, depending on a type and / or magnitude of the actual yaw moment which results or results according to the detected values ​​of the at least one parameter, or as an alternative second switch-off strategy for the torque distribution system, in the reverse order, first the freewheeling operation and then the active short circuit, wherein the electric machine 10 is disconnected from an energy storage device, for example a battery, of the vehicle 2 in order to carry out the active short circuit.

[0048] In the second embodiment of the method according to the invention for operating the second embodiment of the torque distribution system according to the invention, as can be seen from the flow chart from Fig. 2, in a first step S1, an operation of the torque distribution system for a vehicle designed as a motor vehicle is automatically monitored and a state of the vehicle is checked for any presence of a fault.

[0049] In the first step S1, a fault in the torque distribution system is detected. In a second step S2, a control unit automatically evaluates, taking into account first parameters P1, namely a speed, a drive torque, a current and / or a voltage of an electric machine in the torque distribution system, and taking into account speeds of drive wheels on the vehicle's drive axles, which shutdown strategy A1 or A2 can be implemented for the electric machine and / or adopted by the electric machine to rectify the fault. According to the first shutdown strategy A1, an active short circuit is first implemented for the electric machine and then freewheeling, or conversely, according to the second shutdown strategy A2, freewheeling is first implemented and then the active short circuit is carried out for the electric machine.

[0050] The control unit then automatically determines and / or predicts the respective expected and / or resulting braking torque for a respective shutdown strategy A1, A2 to correct the detected fault. Taking this and second parameters P2 into account, namely a steering angle of the vehicle, speeds of the drive wheels, and a yaw rate, longitudinal acceleration, and lateral acceleration of the vehicle, the control unit automatically evaluates in a third step S3 which shutdown strategy A1, A2 is most suitable for correcting the vehicle fault. In doing so, it takes into account whether a braking torque resulting from a respective shutdown strategy A1, A2 generates a yaw moment turning into a curve or a yaw moment turning out of a curve, depending on the current speeds of the drive wheels.This also takes into account whether the vehicle follows a set steering angle too closely or too little, i.e., whether the vehicle will turn too far or too little. The A1 or A2 deactivation strategy is selected depending on whether a higher or lower resulting yaw moment is better for the vehicle. Alternatively or additionally, the A1 or A2 deactivation strategy is selected depending on whether a resulting high or low braking torque will have a positive or negative effect on the vehicle's handling.

[0051] Regardless of which of the two shutdown strategies A1 or A2 was or has been implemented for the torque distribution system after the third step S3, the resulting braking torque of the vehicle and the fault state of the torque distribution system will change in a current driving situation of the vehicle. In addition, the state of the vehicle is continuously monitored and / or evaluated with regard to the presence of the fault. If the fault was or has been rectified as a result of the selected shutdown strategy A1 or A2, the second embodiment of the method presented here can be terminated. However, if a fault still exists despite the selected shutdown strategy A1 or A2, the method continues with the second step S2 and the same shutdown strategy A1, A2 or alternatively the other of the two shutdown strategies A1, A2 is selected again.

[0052] The method is intended to consider a plurality of parameters P1, P2, which have different values ​​in a given driving situation. In one embodiment, a characteristic map containing all parameters P1, P2 is considered. Using the characteristic map, one of the two deactivation strategies A1, A2 is selected by the control unit and implemented for the torque distribution system, taking into account a combination of the currently available values ​​of these parameters. REFERENCE SYMBOL: 2 vehicles 4a, 4b drive axle 6a, 6b drive wheel 8a, 8b 10 Machine 12 Sensor 14 Control unit S1, S2, S3 step P1, P2 parameters A1, A2 shutdown strategy

Claims

[1] Method for operating a torque distribution system for drive wheels (6a, 6b, 8a, 8b) of a vehicle (2), wherein an actual yaw moment is provided by the torque distribution system for the vehicle (2), wherein in the event of a fault in the torque distribution system, depending on a type and / or level of the actual yaw moment for the torque distribution system, a first shutdown strategy (A1) for the torque distribution system - first an active short circuit, then a freewheel or as a second shutdown strategy (A2) for the torque distribution system - first the freewheeling and then the active short circuit are carried out, whereby it is checked whether the torque distribution system was in an agile operation or in a stabilizing operation before the fault occurred, whereby the first shutdown strategy (A1) is carried out if the torque distribution system was in an agile operation, or whereby the second shutdown strategy (A2) is carried out if the torque distribution system was in stabilizing operation. [2] Method according to claim 1, in which a desired yaw moment is specified for the vehicle (2), wherein one of the two switch-off strategies (A1, A2) is carried out as a function of a deviation of the actual yaw moment from the desired yaw moment, wherein the first switch-off strategy (A1) is carried out when the actual yaw moment is greater than the desired yaw moment or equal to the desired yaw moment, or wherein the second switch-off strategy (A2) is carried out when the actual yaw moment is smaller than the desired yaw moment. [3] Method according to claim 1 or 2, which is carried out when the vehicle (2) travels through a curve. [4] Method according to one of the preceding claims, in which a decision as to which shutdown strategy (A1, A2) is carried out is made depending on at least one parameter (P1, P2), namely - depending on a drive torque of an electric machine (10) of the torque distribution system, - depending on a speed of the electric machine (10) of the torque distribution system, - depending on a direction of rotation of the electric machine (10) of the torque distribution system, - depending on an effective direction of the electric machine (10) of the torque distribution system, - depending on a yaw rate of the vehicle (2), - depending on the lateral acceleration of the vehicle (2), - depending on a longitudinal acceleration of the vehicle (2), - depending on understeering or oversteering of the vehicle (2), - depending on the speed of the vehicle (2), - depending on a wheel slip of the drive wheels (6a, 6b, 8a, 8b) of the vehicle (2), - depending on the steering angle of the vehicle (2), - depending on a level of a drive torque and / or a deceleration torque of the vehicle (2), and / or - is carried out depending on a braking torque of the vehicle (2). [5] Method according to one of the preceding claims, in which a duration of the active short circuit and a duration of the freewheeling in the respective switch-off strategy (A1, A2) is set as a function of at least one parameter (P1, P2), namely as a function of a level of torque distribution between drive wheels (6a, 6b, 8a, 8b) of the vehicle (2), as a function of a speed of the vehicle (2), as a function of a lateral acceleration of the vehicle (2), as a function of rotational speeds of the drive wheels (6a, 6b, 8a, 8b), as a function of a yaw rate of the vehicle (2), as a function of a temperature of an actuator of the torque distribution system and / or as a function of a power electronics of the torque distribution system. [6] Torque distribution system for drive wheels (6a, 6b, 8a, 8b) of a vehicle (2), wherein the torque distribution system is designed to provide an actual yaw moment for the vehicle (2), wherein the torque distribution system is designed, in the event of a fault, to act as a first shutdown strategy (A1) depending on a type and / or magnitude of the actual yaw moment - first an active short circuit, then a freewheel or as a second shutdown strategy (A2) for the torque distribution system - first carry out the freewheeling and then the active short circuit, checking whether the torque distribution system was in agile operation or in stabilizing operation before the fault occurred, the first shutdown strategy (A1) being carried out if the torque distribution system was in agile operation, or the second shutdown strategy (A2) being carried out if the torque distribution system was in stabilizing operation. [7] Torque distribution system according to claim 6, comprising a control unit (14) which is designed to monitor an operation of the torque distribution system, to detect an occurrence of a fault and, in the event of a fault in the torque distribution system, to control a machine (10) of the torque distribution system depending on a type and / or level of the actual yaw moment for the torque distribution system and to cause the machine (10) to carry out the first or the second shutdown strategy (A1, A2).

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