Method of operating a motor vehicle, in particular a passenger motor vehicle, and motor vehicles

Abstract

The invention relates to a method for operating a motor vehicle (10), in which the motor vehicle (10) has a front axle (12) with front wheels (16) and a front axle steering system (24) designed as a steer-by-wire steering system, which has an electric motor (26) for actively steering the front wheels (16). The motor vehicle (10) also comprises a rear axle (14) with rear wheels (18), a rear axle steering system (32) and a torque vectoring device (34), by means of which drive torque which can be provided by a drive device (30) of the motor vehicle (10) and is distributed to the rear wheels (18) can be actively adjusted. If a malfunction of the front axle steering (24) is detected by means of an electronic computing device (36), a phase short-circuit of the electric motor (26) is specifically effected by means of the electronic computing device (36).

Description

[0001] Method for operating a motor vehicle, in particular a passenger car, and motor vehicles

[0002] The invention relates to a method for operating a motor vehicle, in particular a passenger car. Furthermore, the invention relates to a motor vehicle, in particular a passenger car.

[0003] So-called steer-by-wire steering systems for motor vehicles are known from the general state of the art, whereby the respective steer-by-wire steering is also referred to as a steer-by-wire system. Such a steer-by-wire steering system is to be understood as a steering system, i.e. a steering system in which a steering handle, usually designed as a steering wheel and operated by a person, is not mechanically connected to steerable vehicle wheels in such a way that an actuation of the steering handle is transmitted via a mechanical coupling between the steering handle and the vehicle wheels in order to steer the vehicle wheels. Instead, an actuation and thus a movement of the steering handle is detected by means of a sensor device and transmitted exclusively electrically via one or more control units to, for example, an electromechanical actuator that drives the vehicle wheels and thus steers them.This means that the actuation and resulting movement of the steering handle constitutes a steering command, particularly from the person named. This steering command is not transmitted mechanically to the steerable vehicle wheels, but is instead detected by a sensor device and transmitted exclusively via one or more control units to the actuator, which then executes the steering command by driving the steerable vehicle wheels and thus steering them. Thus, with such a steer-by-wire steering system, there is no mechanical connection between the steering handle and the steerable vehicle wheels. Steering the steerable vehicle wheels means that the vehicle can change direction, corner, and change lanes by steering the steerable vehicle wheels.

[0004] The object of the present invention is to provide a method and a motor vehicle so that particularly safe operation can be realized.

[0005] This object is achieved by a method having the features of patent claim 1 and by a motor vehicle having the features of patent claim 6. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0006] A first aspect of the invention relates to a method for operating a motor vehicle, also referred to simply as a vehicle and preferably designed as a passenger car. In particular, the method is carried out while the motor vehicle is traveling along a ground. In the method, the motor vehicle has at least or exactly two vehicle axles, also referred to simply as axles, which are arranged one behind the other and thus consecutively in the longitudinal direction of the motor vehicle, namely at least or exactly one front axle and at least or exactly one rear axle. The respective vehicle axle has at least or exactly two vehicle wheels, wherein the vehicle wheels are also referred to as wheels. The vehicle wheels of the motor vehicle are ground contact elements by means of which the motor vehicle can be or is supported downwards on the aforementioned ground in the vertical direction of the motor vehicle.If the motor vehicle is driven along the ground while supported vertically and downwards by the ground contact elements, the vehicle wheels roll, in particular directly, on the ground. The respective vehicle wheels of the respective vehicle axle are arranged on opposite sides of the vehicle in the transverse direction of the vehicle. The vehicle wheels of the front axle are front wheels, so the front axle has the front wheels. Furthermore, the front axle has a front-axle steering system, which is designed as a steer-by-wire steering system.As is well known from the general state of the art, steer-by-wire steering is a steering system in which an actuation by a person, such as the driver of the motor vehicle, of a steering handle, for example, arranged in the interior of the motor vehicle and designed in particular as a steering wheel, is detected by a sensor device that provides an electrical actuation signal characterizing the detected actuation. The detected actuation of the steering handle is or describes a steering command. Depending on the signal, an actuator, designed for example as an electrical actuator or electromechanical actuator, is controlled, and thus operated, whereby the actuator drives the front wheels and thus steers, and thus pivots, thereby steering the motor vehicle. Actuation of the steering handle is understood in particular to mean a movement of the steering handle caused by the person.With steer-by-wire steering, the steering command is transmitted exclusively electrically to the actuator, which executes the steering command to steer the front wheels. The actuator drives the front wheels depending on the steering command and thus steers them. With steer-by-wire steering, there is therefore no mechanical connection between the steering handle and the front wheels, for example, through which the actuation of the steering handle could be transmitted to the front wheels and thus steer the front wheels. The front-axle steering system has an electric motor for actively steering the front wheels. The electric motor is thus the aforementioned actuator, by means of which the front wheels can be actively driven and thus steered to steer the front wheels and thus the vehicle as a whole.

[0007] The vehicle wheels of the rear axle are also referred to as rear wheels, so the rear axle has the rear wheels. The rear axle also features rear-axle steering. This means that the front wheels are steerable wheels, which can be steered by the electric motor to enable the vehicle to corner, change direction, and change lanes. The rear wheels are also steerable wheels, which can be steered to enable the vehicle to change direction, change lanes, and corner. It is conceivable that the rear axle also features a steer-by-wire steering system.

[0008] The rear axle also features a torque vectoring device, also known as a torque vectoring unit or torque distribution unit or torque distribution device. As is already well known from the general state of the art, the torque vectoring device can be used to adjust, i.e., actively vary, the distribution of a drive torque provided by a drive device of the motor vehicle to the rear wheels. In other words, the torque vectoring device can be used to actively distribute the drive torque to the individual rear wheels.This means, in particular, that the torque vectoring device can distribute the drive torque to the rear wheels, i.e., divide it up, in such a way that, for example, a first torque resulting from the drive torque with a first value acts on a first of the rear wheels, and a second torque resulting from the drive torque with a second value acts on a second of the rear wheels. In this case, it is particularly conceivable for the first value and the second value to differ from one another, in particular while the first torque acts on the first rear wheel and the second torque acts on the second rear wheel. In particular, the drive device can drive the rear wheels via the torque vectoring device using the drive torque, which, as described, can be actively distributed, i.e., divided, between the rear wheels by means of the torque vectoring device.Thus, the torque vectoring device makes it possible, in particular, to distribute the drive torque differently to the rear wheels, such that the first torque has the first value and, at the same time, the second torque has the second value different from the first value.

[0009] In particular, it is conceivable that the torque vectoring device is designed to selectively distribute the drive torque to the rear wheels in such a way that the first torque and the second torque are in the same direction or in opposite directions, so that, for example, one of the rear wheels is driven while, for example, another of the rear wheels is braked.

[0010] The drive device is thus designed to provide the drive torque and thereby drive the rear wheels and thus the motor vehicle as a whole. In particular, the drive device can drive the rear wheels via the torque vectoring device. For example, the drive device comprises at least one electric machine by means of which the rear wheels and thus the motor vehicle can be driven, in particular purely electrically. The electric machine is preferably designed as a high-voltage component whose electrical voltage, in particular electrical operating or nominal voltage, is preferably greater than 50 volts, in particular greater than 60 volts, and very preferably amounts to several hundred volts. Alternatively or additionally, the drive device can have an internal combustion engine by means of which the rear wheels and thus the motor vehicle can be driven.The motor vehicle can therefore be designed as a hybrid vehicle or as an electric vehicle, in particular as a battery electric vehicle (BEV).

[0011] If, in the method, a malfunction of the front-axle steering is detected by means of an electronic computing device, which may have at least one or exactly one control unit or several control units, in particular those that are interconnected by signaling, a phase short circuit of the electric motor is deliberately caused by the electronic computing device. The malfunction of the front-axle steering is determined by means of the electronic computing device, for example, by at least one, in particular electrical, measurement signal fulfilling at least one predetermined criterion. The measurement signal is provided, for example, by a detection device. The measurement signal characterizes, for example, a state of at least one component of the motor vehicle.In particular, the measurement signal characterizes, for example, a position, especially a rotational or pivoting position, of the component, with the position being detected, for example, by the detection device. If, for example, the position of the component deviates from a target position, the criterion is met, and the malfunction is then determined.

[0012] In the method, if the malfunction is determined by the electronic computing device, the rear-axle steering and the torque vectoring device are specifically controlled by the electronic computing device in order to steer the motor vehicle in a targeted manner. By controlling the rear-axle steering, for example, the rear wheels are pivoted and thus steered, thereby steering the motor vehicle. By controlling the torque vectoring device, the drive torque is distributed, for example, specifically to the rear wheels by means of the torque vectoring device, i.e., divided so that the motor vehicle is steered, in particular the rear wheels.For example, by controlling the torque vectoring device by means of the torque vectoring device, the drive torque is distributed specifically to the rear wheels in such a way that the first torque has the first value and, at the same time, the second torque has the second value that is different from the first value. By specifically controlling the torque vectoring device, a torque can be caused, for example, which acts in particular about the vertical direction of the motor vehicle and is also referred to as a yaw moment, which causes a steering movement of the motor vehicle, and thus the motor vehicle can be steered in a desired direction, in particular the direction of travel. The method according to the invention thus enables a redundant steering function at the overall vehicle level, so that the motor vehicle remains steerable or can be steered if the malfunction occurs.In particular, the method according to the invention enables a fallback level in the event of a malfunction, in particular in the event of a failure of the front-axle steering, to continue to enable lateral guidance of the motor vehicle, i.e., despite the malfunction. This makes it possible, for example, to implement a so-called emergency driving state in the event of a malfunction, in particular in the event of a failure of the front-axle steering, in which, despite the malfunction, the motor vehicle can be steered in a targeted manner, for example, such that the motor vehicle can still be driven to a desired location, such as the driver's home or a workshop, despite the malfunction, or that the motor vehicle can be steered to the edge of the road or carriageway, in particular onto a hard shoulder or emergency lane, despite the malfunction.

[0013] The phase short circuit of the electric motor is switched on or caused, for example, by software, i.e. by an algorithm also known as a software algorithm.

[0014] The front-axle steering system has, for example, a steering gear via which the front wheels can be driven by the electric motor and thus steered. In particular, the steering gear can have a rack that can be moved, for example, at least in the transverse direction of the vehicle. Furthermore, the steering gear can have, for example, a gear, also referred to as a pinion, which meshes with the rack and thus engages the rack. For example, the electric motor can drive the gear and thereby rotate it in order to move the rack and subsequently steer the front wheels. In the method according to the invention, the phase short circuit of the electric motor is used as a blocking or damping device in order to subsequently be able to steer the motor vehicle in a targeted manner by controlling the rear-axle steering system and by controlling the torque vectoring device.In other words, as a result of causing the phase short circuit of the electric motor, the electric motor is or acts as a blocking or damping device, in particular through self-locking and / or friction, so that, for example, undesired pivoting movements of the front wheels and / or undesired reversing of the front wheels can be avoided. As a result, despite the malfunction of the front-axle steering, the vehicle can be advantageously and specifically steered by means of the rear-axle steering using the torque vectoring device. The targeted control of the rear-axle steering and the torque vectoring device is used as a redundant steering function if a malfunction, in particular a failure, of the front-axle steering occurs.In particular, due to the phase short circuit, the electric motor acts in a blocking or damping manner on the steering rack, for example, to counteract or prevent an undesired return of the front wheels. The method can be allocated, for example, in a control unit of the steer-by-wire steering system or in another intelligent control unit. This is particularly possible because the method is only required or executed when the malfunction is detected, especially when the steer-by-wire steering system has failed. In particular, the invention can realize at least the following advantages:

[0015] Utilizing synergies between the rear-axle steering and the torque vectoring system to implement a redundant steering function for the steer-by-wire steering system. The rear-axle steering and the torque vectoring system are used as additional actuators to generate a yaw moment acting around the vehicle's vertical direction through actuator interventions, thus controlling the additional actuators, and thus steer the vehicle.

[0016] Due to the phase short circuit of the electric motor, the electric motor can act as a damping unit, in particular in or on the steering gear, in order to, for example,

[0017] In order to be able to steer the motor vehicle precisely despite the malfunction of the front-axle steering system and thus ensure particularly safe operation, one embodiment of the invention provides for the steering angle of the front wheels to be kept constant, particularly in a targeted manner, by deliberately inducing the phase short circuit. This allows the motor vehicle to be steered precisely despite the malfunction by controlling the rear-axle steering system, thus by steering the rear wheels, thus ensuring particularly safe operation.

[0018] In a further, particularly advantageous embodiment of the invention, it is provided that the steering angle of the front wheels is set, in particular in a targeted manner, by deliberately causing the phase short circuit and, for example, is then kept constant. This is to be understood in particular as meaning that, for example, the steering angle of the front wheels is set, in particular in a targeted manner, from a first value to a second value different from the first value and is thus changed and is preferably then kept constant at the second value. In this way, for example, a defined state, in particular a defined position, of the front wheels can be set, so that subsequently, by controlling the rear axle steering, the rear wheels can be steered in a targeted manner such that the motor vehicle can be steered in a targeted manner and thus safely and precisely.A further embodiment is characterized by the fact that, by controlling the torque vectoring device, braking of at least one of the rear wheels is specifically effected by the torque vectoring device. This can, for example, create a particularly large yaw moment acting around the vehicle's vertical direction, allowing the vehicle to be steered precisely and powerfully. This ensures a particularly high level of safety.

[0019] Finally, it has proven particularly advantageous if, by controlling the torque vectoring device, a drive, thus a positive acceleration, of at least or exactly one of the rear wheels is specifically effected by means of the torque vectoring device. Driving the at least or exactly one rear wheel is understood in particular to mean that the at least or exactly one rear wheel initially rotates in one direction of rotation and is accelerated by controlling the torque vectoring device, so that the rotational speed at which the at least or exactly one rear wheel rotates in the same direction of rotation is increased.In particular, it is conceivable to brake a first of the rear wheels by means of the torque vectoring device by controlling it and to drive another of the rear wheels by means of the torque vectoring device by controlling it, i.e. to accelerate positively, whereby the motor vehicle can be steered particularly strongly.

[0020] A second aspect of the invention relates to a motor vehicle, preferably designed as a passenger car, which is also simply referred to as a vehicle and is designed to carry out a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

[0021] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the single figure, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. The drawing shows a schematic representation of a motor vehicle in the single figure.

[0022] The single figure shows a schematic representation of a motor vehicle 10 designed as a passenger car and also referred to as a vehicle, which has, for example, in its interior, also referred to as the passenger cell or passenger compartment, a steering handle designed in particular as a steering wheel. The steering handle can be actuated and thus moved by a person located in the interior, such as the driver of the motor vehicle, in order to steer the motor vehicle 10, for example, and thus to cause a steering movement of the motor vehicle 10. This is explained in more detail below. A method for operating the motor vehicle 10 is also described below with reference to the single figure. The motor vehicle 10 has exactly two vehicle axles 12 and 14 arranged one behind the other in the longitudinal direction of the motor vehicle 10, wherein the vehicle longitudinal direction is illustrated by a double arrow 15.The vehicle axle 12 is a front axle, and the vehicle axle 14 is a rear axle. The respective vehicle axle 12, 14 has exactly two vehicle wheels 16, 18, wherein the vehicle wheels 16 of the front axle are front wheels and the vehicle wheels 18 of the rear axle are rear wheels. The vehicle wheels 16 and 18 are ground contact elements by means of which the motor vehicle 10, which is also referred to as a motor vehicle, can be or is supported downwards on a ground in the vehicle's vertical direction. The vehicle's vertical direction is illustrated in the figure by a double arrow 20 and runs perpendicular to the image plane of the figure. It can be seen that the respective vehicle wheels 16, 18 of the respective vehicle axle 12, 14 are arranged on opposite sides of the motor vehicle 10 in the vehicle's transverse direction. The vehicle's transverse direction is illustrated by a double arrow 22.

[0023] The front axle comprises a front-axle steering system 24, shown particularly schematically in the figure, which is designed as a steer-by-wire steering system. This particularly means the following: If the steering handle is actuated and thereby moved by a person located in the interior, the movement of the steering handle is detected by a sensor device. The sensor device provides an electrical sensor signal, whereby an actuator of the front-axle steering system 24, designed as an electric motor 26, is controlled and operated as a function of the sensor signal. As a result, the electric motor 26 drives the vehicle wheels 16 (front wheels), whereby the vehicle wheels 16 and thus the motor vehicle 10 are steered. This can, for example, cause lane changes, changes in direction of travel, and cornering of the motor vehicle 10.There is no mechanical connection between the steering handle and the vehicle wheels 16 through which the movement of the steering handle can be transmitted to the vehicle wheels 16 and thus converted into a respective steering movement of the vehicle wheels 16. The front-axle steering system 24 comprises a steering gear 28, shown particularly schematically in the figure, which, for example, has a rack. It can be seen that the electric motor 26 can drive and thus steer the vehicle wheels 16 via the steering gear 28 and thus via the rack.

[0024] The motor vehicle 10 has a drive device 30, shown particularly schematically in the figure, which can provide a drive torque for driving the vehicle wheels 18 and thus the motor vehicle 10 as a whole. The vehicle axle 14 (rear axle) has a rear-axle steering system 32, by means of which the rear wheels (vehicle wheels 18) can be steered. The rear axle also has a torque vectoring device 34, wherein, for example, the drive device 30 can drive the vehicle wheels 18 via the torque vectoring device 34. By means of the torque vectoring device 34, a distribution of the drive torque provided or capable of being provided by the drive device 30 to the wheels can be actively adjusted.In other words, the torque vectoring device 34 can distribute or divide the drive torque specifically among the vehicle wheels 18, in particular such that the drive torque is distributed differently among the vehicle wheels 18, so that, for example, the drive torque results in a first torque acting on a first of the vehicle wheels 18 and a second torque acting on the second vehicle wheel 18 and different from the first torque. The first torque and the second torque differ from one another, for example, in terms of their values, i.e., in terms of their magnitude, and / or the first torque and the second torque differ from one another, for example, in terms of their respective directions of action.

[0025] The figure also shows, particularly schematically, an electronic computing device 36 which, for example, is a component of the motor vehicle 10. The electronic computing device 36 can comprise at least or exactly one control unit or a plurality of control units. In other words, the electronic computing device 36 can be formed by at least or exactly one control unit or by a plurality of control units, in particular control units that are connected to one another. If a malfunction of the front-axle steering system 24 is determined by means of the electronic computing device 36 during the method, a phase short circuit of the electric motor 26 is deliberately brought about by means of the electronic computing device 36. Furthermore, if the malfunction is determined by means of the electronic computing device 36, the rear-axle steering system 32 and the torque vectoring device 34 are deliberately controlled by means of the electronic computing device 36 in order to thereby steer the motor vehicle 10 in a targeted manner.

[0026] The malfunction is identified, for example, if it is determined that the steering angle of the front wheels can no longer be measured, and thus detected, by a detection device. The detection device is provided, for example, to measure the steering angle of the front wheels and to provide a measurement signal which characterizes the steering angle of the front wheels measured by the detection device. If, for example, the measuring device no longer provides the measurement signal, although the measuring device is intended, should or must provide the measurement signal, a conclusion is drawn that there is a malfunction. Furthermore, it is conceivable, for example, that if the measurement signal deviates from a target signal, a conclusion is drawn that there is a malfunction, and the malfunction is therefore identified. The malfunction therefore includes, in particular, that the measuring device no longer detects the steering angle of the front wheels.For example, a malfunction is detected if at least one predeterminable or specified criterion is met. This criterion is met, for example, if the measuring device does not provide the measurement signal. Alternatively or additionally, this criterion is met, for example, if the measurement signal deviates from the specified target signal.

[0027] By controlling the torque vectoring device 34 and the rear-axle steering 32, a redundant steering function can be realized, particularly at the overall vehicle level, so that particularly safe operation of the motor vehicle 10 can be ensured.

[0028] 10 motor vehicles

[0029] 12 vehicle axles

[0030] 14 vehicle axle

[0031] 15 Double arrow

[0032] 16 vehicle wheel

[0033] 18 vehicle wheel

[0034] 20 double arrow

[0035] 22 Double arrow

[0036] 24 Front axle steering

[0037] 26 electric motor

[0038] 28 steering gear

[0039] 30 Drive device

[0040] 32 Rear-axle steering

[0041] 34 Torque vectoring device

[0042] 36 electronic computing device

Claims

Patent claims Method for operating a motor vehicle (10), in which: - the motor vehicle (10) has a front axle (12) with front wheels (16) and a front axle steering system (24) designed as a steer-by-wire steering system, which has an electric motor (26) for actively steering the front wheels (16); - the motor vehicle (10) has a rear axle (14) with rear wheels (18), a rear axle steering system (32) and a torque vectoring device (34) by means of which a distribution of a drive torque that can be provided by a drive device (30) of the motor vehicle (10) to the rear wheels (18) can be actively adjusted; - if a malfunction of the front-axle steering (24) is determined by means of an electronic computing device (36): o a phase short circuit of the electric motor (26) is deliberately caused by means of the electronic computing device (36); o the rear-axle steering (32) and the torque vectoring device (34) are deliberately controlled by means of the electronic computing device (36), in order to steer the motor vehicle (10) in a targeted manner. Method according to claim 1, characterized in that the steering angle of the front wheels (16) is kept constant by deliberately causing the phase short circuit. Method according to claim 1 or 2, characterized in that by deliberately causing the phase short circuit, the steering angle of the front wheels (16) is adjusted. Method according to one of the preceding claims, characterized in that by controlling the torque vectoring device (34), braking of at least or exactly one of the rear wheels (18) is deliberately effected by means of the torque vectoring device (34). Method according to one of the preceding claims, characterized in that by controlling the torque vectoring device (34), driving of at least or exactly one of the rear wheels (18) is deliberately effected by means of the torque vectoring device (34). Motor vehicle (10) which is designed to carry out a method according to one of the preceding claims. characterized in that

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