DE102022119973A1 - Method for operating a motor vehicle, in particular a passenger car, and motor vehicles - Google Patents

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

Description

The invention relates to a method for operating a motor vehicle, in particular a passenger car. The invention further relates to a motor vehicle, in particular a passenger car.

So-called steer-by-wire steering systems for motor vehicles are known from the general state of the art, with the respective steer-by-wire steering also being referred to as a steer-by-wire system. Such steer-by-wire steering is to be understood as a steering system, i.e. a steering system, in which a steering handle, which is usually designed as a steering wheel and can be operated by a person, is not mechanically connected to steerable vehicle wheels in such a way that the steering handle can be actuated via a mechanical Coupling between the steering handle and the vehicle wheels is transmitted in order to steer the vehicle wheels, but 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 devices to an electromechanical actuator, for example, which drives the vehicle wheels and thereby directs. This means that the actuation and the resulting movement of the steering handle is a steering command, in particular from the person mentioned, whereby this steering command is not transmitted mechanically to the steerable vehicle wheels, but is detected by a sensor device and sent exclusively to the actuator via one or more control devices is transmitted, which then executes the steering command, in that the actuator drives the steerable vehicle wheels and thus steers. With such steer-by-wire steering, there is no mechanical connection between the steering handle and the steerable vehicle wheels. Steering the steerable vehicle wheels means that by steering the steerable vehicle wheels, changes in direction of travel, cornering and lane changes of the respective motor vehicle can be effected.

The object of the present invention is to create a method and a motor vehicle so that particularly safe operation can be achieved.

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

A first aspect of the invention relates to a method for operating a motor vehicle, which is also simply referred to as a vehicle and is preferably designed as a passenger car. In particular, the method is carried out during a journey of the motor vehicle, which is driven along a floor while driving. 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 sequentially 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, the vehicle wheels also being referred to as wheels. The vehicle wheels of the motor vehicle are ground contact elements via which the motor vehicle can be supported or supported downwards on the aforementioned ground in the vertical direction of the motor vehicle. If the motor vehicle is driven along the ground while the motor vehicle is supported on the ground in the vertical direction of the vehicle downwards via 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 sides of the motor vehicle that are opposite one another in the vehicle transverse direction of the motor vehicle. The vehicle wheels of the front axle are front wheels, so the front axle has the front wheels. In addition, the front axle has a front axle steering, which is designed as a steer-by-wire steering system, i.e. as a steer-by-wire system. As is well known from the general state of the art, steer-by-wire steering is to be understood as steering in which an actuation, for example in the interior of the motor vehicle, is effected by a person such as the driver of the motor vehicle arranged and in particular designed as a steering wheel steering handle is detected by means of a sensor device which provides an electrical actuation signal characterizing the detected actuation. The detected operation 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 therefore operated, whereby the actuator drives the front wheels and thereby steers them, and therefore pivots them, whereby the motor vehicle is steered. The actuation of the handlebar is understood to mean, in particular, 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 by the actuator driving the front wheels depending on the steering command and thereby steering. With steer-by-wire steering, for example, there is no mechanical connection between the steering handle and the front wheels the operation of the steering handle can be transferred to the front wheels in order to thereby steer the front wheels. The front axle steering has an electric motor for actively steering the front wheels. The electric motor is therefore the aforementioned actuator, by means of which the front wheels can be actively driven and thereby steered in order to steer the front wheels and thus the motor vehicle as a whole.

The vehicle wheels of the rear axle are also called the rear wheels, so the rear axle has the rear wheels. The rear axle also has rear axle steering. This means that the front wheels are steerable wheels which can be steered by means of the electric motor in order to be able to effect cornering, changes of direction and lane changes of the motor vehicle. The rear wheels are also steerable wheels, which can be steered to change the direction of travel, change lanes and corner corners of the vehicle. It is conceivable that the rear axle is also designed as steer-by-wire steering.

The rear axle also has a torque vectoring device, which is also referred to 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, a distribution of a drive torque that can be provided by a drive device of the motor vehicle to the rear wheels, also known as torque distribution or torque distribution, can be adjusted, that is to say actively varied, by means of the torque vectoring device. In other words, the torque vectoring device can be used to actively distribute the drive torque to the individual rear wheels. This is to be understood in particular as meaning that the torque vectoring device can distribute the drive torque to the rear wheels in such a way that, for example, a first torque resulting from the drive torque with a first value is applied to a first of the rear wheels and to a second one A second torque resulting from the drive torque with a second value acts on the rear wheels. It is particularly conceivable that the first value and the second value 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 by means of the drive torque, which, as described, is actively distributed to the rear wheels by means of the torque vectoring device, that is, can be divided. The torque vectoring device thus 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 that is different from the first value. 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.

The drive device is therefore 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 electrical 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 most preferably is 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).

If, in the method, a malfunction of the front axle steering is determined by means of an electrical computing device, which can have at least or exactly one control device or several control devices, in particular that are connected to one another in terms of signaling technology, a phase short circuit of the electric motor is specifically caused by the electronic computing device. The malfunction of the front axle steering is determined by means of the electronic computing device, for example in that at least one, in particular electrical, measurement signal meets 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, in particular a rotational or pivoting position, of the component, the position being detected, for example, by means of the detection device. For example, if the position of the component differs from one If the target position is reached, the criterion is met and the malfunction is then determined.

In the method, if the malfunction is determined using the electrical computing device, the rear axle steering and the torque vectoring device are specifically controlled by the electronic computing device in order to thereby steer the motor vehicle in a targeted manner. By controlling the rear axle steering, for example, the rear wheels are pivoted and thus steered, whereby the motor vehicle is steered. By controlling the torque vectoring device, the drive torque is, for example, specifically distributed to the rear wheels, that is, divided so that the motor vehicle is steered, in particular that the rear wheels are steered. For example, by controlling the torque vectoring device using the torque vectoring device, the drive torque is specifically distributed 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, for example, a torque acting in particular around the vertical direction of the motor vehicle, also referred to as a yaw moment, can be caused, which causes a steering movement of the motor vehicle, and therefore the motor vehicle is specifically steered in a desired direction, in particular the direction of travel can be. 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, in order to continue to enable lateral guidance of the motor vehicle, that is, despite the malfunction.

As a result, for example, in the event of a malfunction, in particular if the front axle steering fails, a so-called emergency driving state can be realized, in which, despite the malfunction, the motor vehicle can, for example, be steered in a targeted manner in such a way that the motor vehicle can still go to a desired location, such as the driver's home, despite the malfunction or the driver can be driven to a workshop, or that the motor vehicle can be steered to the edge of a road or carriageway, in particular onto a shoulder or hard shoulder, despite the malfunction.

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.

The front axle steering has, for example, a steering gear, via which the front wheels can be driven by the electric motor and thereby steered. In particular, the steering gear can have a rack that can be displaced, for example, at least in the transverse direction of the vehicle. Furthermore, the steering gear can, for example, have a gear, also known as a pinion, which meshes with the rack and therefore engages in the rack. For example, the electric motor can drive the gear and thereby rotate it, thereby displacing the rack and subsequently steering the front wheels. In the method according to the invention, the phase short circuit of the electric motor is used as blocking or damping in order to be able to steer the motor vehicle in a targeted manner by controlling the rear axle steering and by controlling the torque vectoring device. In other words, the electric motor is or acts as a blocking or damping device as a result of causing the phase short circuit of the electric motor, in particular through self-locking and/or friction, so that, for example, undesirable pivoting movements of the front wheels and/or undesirable resetting of the front wheels can be avoided . As a result, despite the malfunction of the front axle steering, the motor vehicle can be steered advantageously and in particular in a targeted manner using 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 the front axle steering malfunctions, in particular a failure, occurs. In particular, due to the phase short circuit, the electric motor has a blocking or damping effect on the rack, in order, for example, to counteract an undesirable resetting of the front wheels or to avoid such an undesirable resetting.

• - Nutzen von Synergien der Hinterachslenkung und der Torque-Vectoring-Einrichtung, um eine redundante Lenkfunktion für die Steer-by-Wire-Lenkung zu realisieren. Dabei werden die Hinterachslenkung und die Torque-Vectoring-Einrichtung als weitere Aktoren verwendet, um durch Aktoreingriffe, mithin durch das Ansteuern der weiteren Aktoren ein um die Fahrzeughochrichtung wirkendes Giermoment zu erzeugen und somit den Kraftwagen zu lenken.
• - Durch den Phasenkurzschluss des Elektromotors kann der Elektromotor als Dämpfungseinheit, insbesondere in dem oder auf das Lenkgetriebe, wirken, um dadurch beispielsweise.

The method can, for example, be allocated in a steer-by-wire steering control unit or in another intelligent control unit. This is possible in particular because the method is only required or carried out when the malfunction is detected, in particular if the steer-by-wire steering has failed. In particular, at least the following advantages can be realized by the invention:

• - Using synergies of the rear axle steering and the torque vectoring device to realize a redundant steering function for steer-by-wire steering. The rear axle steering and the torque vectoring device are used as further actuators in order to create a yaw moment acting around the vehicle's vertical direction through actuator interventions, i.e. by controlling the further actuators to generate and thus steer the motor vehicle.
• - 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, for example.

In order to be able to steer the motor vehicle precisely despite the malfunction of the front axle steering and thus achieve particularly safe operation, it is provided in one embodiment of the invention that the steering angle of the front wheels is kept constant, in particular in a targeted manner, by specifically causing the phase short circuit. As a result, by controlling the rear axle steering, i.e. by steering the rear wheels, the vehicle can be steered precisely despite the malfunction, so that particularly safe operation can be achieved.

In a further, particularly advantageous embodiment of the invention, it is provided that the steering angle of the front wheels is adjusted, in particular in a targeted manner, by the targeted effect of the phase short circuit and, for example, is then kept constant. This is to be understood in particular as meaning that, for example, by specifically causing the phase short circuit, the steering angle of the front wheels is set, in particular specifically, from a first value to a second value that is different from the first value and is thus changed and preferably then kept constant at the second value becomes. This makes it possible, for example, to set a defined state, in particular a defined position, of the front wheels, so that the rear wheels can then be steered in a targeted manner by controlling the rear axle steering in such a way that the motor vehicle can be steered in a targeted and therefore safe and precise manner.

A further embodiment is characterized in that by activating the torque vectoring device, braking of at least or exactly one of the rear wheels is specifically brought about by means of the torque vectoring device. This can, for example, cause a particularly large yaw moment acting around the vertical direction of the vehicle, whereby the motor vehicle can be steered precisely and strongly. This ensures a particularly high level of security.

Finally, it has proven to be particularly advantageous if, by activating the torque vectoring device, a driving, i.e. 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 to be understood in particular as meaning that the at least or exactly one rear wheel initially rotates in a direction of rotation and is accelerated by activating the torque vectoring device, so that a 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 controlling them using the torque vectoring device and to drive another of the rear wheels by controlling them using the torque vectoring device, that is to say to accelerate positively, whereby the motor vehicle can be steered particularly strongly can.

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 refinements of the first aspect of the invention are to be viewed as advantages and advantageous refinements of the second aspect of the invention and vice versa.

Further advantages, features and details of the invention result from the following description of a preferred exemplary embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and/or shown alone in the single figure can be used not only in the combination specified in each case, but also in other combinations or on their own, without the frame of the invention.

The drawing shows a schematic representation of a motor vehicle in the only figure.

The only figure shows a schematic representation of a motor vehicle 10 designed as a passenger car and also referred to as a vehicle, which, for example, has a steering handle designed in particular as a steering wheel in its interior, also referred to as a passenger cell or passenger compartment. The steering handle can be operated and thus moved by a person staying in the interior, such as the driver of the motor vehicle, in order to thereby steer the motor vehicle 10, for example, and thus cause a steering movement of the motor vehicle 10. This will be 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, the vehicle is illustrated longitudinally 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, the vehicle wheels 16 of the front axle being front wheels and the vehicle wheels 18 of the rear axle being rear wheels. The vehicle wheels 16 and 18 are ground contact elements via which the motor vehicle 10, which is also referred to as a motor vehicle, can be supported or supported downwards on a ground in the vertical direction of the vehicle. The vehicle 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 sides of the motor vehicle 10 that are opposite one another in the transverse direction of the vehicle. The vehicle transverse direction is illustrated by a double arrow 22.

The front axle includes a front axle steering 24, shown particularly schematically in the figure, which is designed as steer-by-wire steering. This means in particular the following: If the steering handle is actuated and thereby moved by a person in the interior, the movement of the steering handle is detected by means of a sensor device. The sensor device provides an electrical sensor signal, with an actuator of the front axle steering 24 designed as an electric motor 26 being controlled and thereby operated depending on 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.

In this way, for example, lane changes, changes in direction of travel and cornering of the motor vehicle 10 can be effected. There is no mechanical connection between the steering handle and the vehicle wheels 16, via 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 24 includes a steering gear 28, shown particularly schematically in the figure, which has, for example, a rack. It can be seen that the electric motor 26 can drive and thereby steer the vehicle wheels 16 via the steering gear 28 and thus via the rack.

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 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 to be 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 between the vehicle wheels 18, in particular in such a way that the drive torque is distributed differently between the vehicle wheels 18, so that, for example, the drive torque acts on a first of the vehicle wheels 18. first torque and a second torque acting on the second vehicle wheel 18 and different from the first torque results. The first torque and the second torque differ from each other, for example, in terms of their values, that is, in terms of magnitude, and/or the first torque and the second torque differ from one another, for example, in terms of their respective direction of action.

An electronic computing device 36 is also shown particularly schematically in the figure, which is, for example, a component of the motor vehicle 10. The electronic computing device 36 can comprise at least or exactly one control device or several control devices. In other words, the electronic computing device 36 can be formed by at least or exactly one control device or by several control devices, in particular connected to one another.

If a malfunction of the front axle steering 24 is determined using the electronic computing device 36 in the method, a phase short circuit of the electric motor 26 is specifically caused by the electronic computing device 36. In addition, if the malfunction is determined by means of the electronic computing device 36, the rear axle steering 32 and the torque vectoring device 34 are specifically controlled by the electronic computing device 36 in order to thereby steer the motor vehicle 10 in a targeted manner.

The malfunction is determined, for example, when it is determined that the steering angle of the front wheels can no longer be measured, and therefore detected, by means of a detection device. The detection device is intended, 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. For example, if the measuring device now sets the measurement signal is not (no longer) ready, although the measuring device should, should or should provide the measuring signal, the malfunction is concluded. Furthermore, it is conceivable, for example, that if the measurement signal deviates from a target signal, the malfunction is concluded and the malfunction is therefore determined. The malfunction therefore includes, in particular, that the measuring device no longer detects the steering angle of the front wheels. For example, the malfunction is determined when at least one specifiable or predetermined criterion is met. The criterion is fulfilled, for example, if the measuring device does not provide the measurement signal. Alternatively or additionally, the criterion is fulfilled, for example, if the measurement signal deviates from the specified target signal.

By controlling the torque vectoring device 34 and the rear axle steering 32, a redundant steering function can be implemented, in particular at the overall vehicle level, so that particularly safe operation of the motor vehicle 10 can be guaranteed.

Reference symbol list

10

motor vehicle

12

Vehicle axle

14

Vehicle axle

15

Double arrow

16

vehicle wheel

18

vehicle wheel

20

Double arrow

22

Double arrow

24

Front axle steering

26

Electric motor

28

Steering gear

30

Drive device

32

Rear axle steering

34

Torque vectoring facility

36

electronic computing device

Claims (6)

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 steer-by-wire steering, 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 (32) and a torque vectoring device (34), by means of which a distribution of a drive device (30) of the motor vehicle (10) drive torque that can be provided to the rear wheels (18) can be actively adjusted; - if a malfunction of the front axle steering (24) is determined using an electronic computing device (36): o a phase short circuit of the electric motor (26) is specifically caused by means of the electronic computing device (36); o the rear axle steering (32) and the torque vectoring device (34) are controlled in a targeted manner by means of the electronic computing device (36) in order to thereby steer the motor vehicle (10) in a targeted manner. Procedure 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. Procedure according to Claim 1 or 2 , characterized in that the steering angle of the front wheels (16) is adjusted by specifically causing the phase short circuit. 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 specifically 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), at least or exactly one of the rear wheels (18) is specifically driven 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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