WO2023025477A1

WO2023025477A1 - Method for setting a steering angle and/or a yaw rate of a motor vehicle, and motor vehicle having a control unit

Info

Publication number: WO2023025477A1
Application number: PCT/EP2022/070271
Authority: WO
Inventors: Arne Bartels; Bastian Witte
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 2021-08-26
Filing date: 2022-07-19
Publication date: 2023-03-02
Also published as: CN117858823A; DE102021209390B4; DE102021209390A1

Abstract

The invention relates to a method for setting a steering angle (α) and/or a yaw rate (α') of a motor vehicle (1). A target value (α, α') for the steering angle and/or the yaw rate is provided. A plurality of pressure pulses (PK) is determined for a brake unit (3) on the basis of the target value (α, α'). A vehicle parameter and/or a surface condition of a roadway (10) of the motor vehicle (1) is provided. An actual value (β, β') for the steering angle (α) and/or the yaw rate (α') is measured. One or more wheels (4) of the motor vehicle (1) are braked on the basis of the target value (α, α') and the plurality of pressure pulses (PK). The plurality of pressure pulses (PK) is determined in accordance with the target value (α, α'), the actual value (β, β'), the vehicle parameter and/or the surface condition of the roadway (10).

Description

Method for setting a steering angle and/or a yaw rate of a motor vehicle and motor vehicle with a control unit

The invention relates to a method for adjusting a steering angle and/or a yaw rate of a motor vehicle. The invention also relates to a motor vehicle with a control unit, brake unit and at least one wheel.

Modern motor vehicles have various, mostly redundant, systems for steering or for adjusting the yaw rate. In autonomous motor vehicles, steering is often implemented using what is known as a “stear-by-wire” method. In this case, the motor vehicle no longer has a steering wheel at all, but instead a corresponding control unit of the motor vehicle autonomously controls the motor vehicle and the associated steering. If the steering system fails, unpleasant situations can arise if the main steering system fails. For this reason, some approaches provide double redundancy or a second fallback level for a primary steering system or a stear-by-wire system. However, such an approach requires the provision of additional components and can therefore be very expensive in some cases.

In this context, for example, mentions the disclosure

DE 10 2014 006614 A1 describes a pneumatic brake device for motor vehicles and a method for operating a pneumatic brake system. An electronic control unit determines default values for target brake pressures of the wheel brakes, taking into account a brake signal generator. Each wheel brake module includes at least one ventilation valve and one ventilation valve, electrically actuable activation means for activating the ventilation valve and/or the ventilation valve, and control logic with means for generating an actuating signal for the activation means corresponding to the default value for the setpoint brake pressure.

One object of the invention can be seen as providing an additional method for operating a motor vehicle if a main steering system or a higher-level device for steering the motor vehicle should fail.

The invention is based on the finding that in a fully automated motor vehicle the so-called stear-by-wire steering system is an ordinary steering system with a steering wheel replaced. An autonomous motor vehicle can be accepted from level 4 according to the definition SAE J3016. In such fully autonomous motor vehicles, the steering wheel can be folded away or retracted. A driver can thus become a passenger during a journey and more space can be created for other activities. By folding away and retracting the steering wheel, new interior concepts can be made possible, for example, seats can be turned and additional tables can be folded out.

A mechanical decoupling between the steering wheel and steering actuator avoids unintentional incorrect operation during fully automated driving of the autonomous vehicle. In autonomous motor vehicles according to Level 5 of SAE J3016, such as robot taxis, there is often no steering wheel at all. Such vehicles no longer need a driver, so in this case a stear-by-wire system is required.

In an autonomous motor vehicle, the stear-by-wire system enables a steering angle and/or a yaw rate of the motor vehicle to be set. In a conventional, manually operated motor vehicle, a driver is involved in these functions. He can adjust the steering angle and/or the yaw rate of the motor vehicle by operating the steering wheel. A stear-by-wire system can also be present in a conventional motor vehicle as part of an ESC or ESP assistance function. What both motor vehicles have in common, however, is that the main steering or the stear-by-wire system could fail, making maneuvering of the motor vehicle more difficult or even impossible. For this reason, stear-by-wire systems can be designed with double redundancy. For example, two separate control units can be provided, both of which can take over the stear-by-wire system, ie steering and setting the yaw rate, independently of one another.

Due to safety aspects, the operation of the motor vehicle is often only permitted if, in addition to a currently available and operated steering system or steering method, another additional steering system or steering device is available as a reserve. Autonomous motor vehicles thus preferably have a plurality of steering devices or steering systems, which can be structured hierarchically. The operation of the motor vehicle is preferably only possible if the last level of this hierarchy has not yet been reached, ie at least one further steering device is available as a reserve beyond a current steering. However, additional redundancies often result to additional components and thus to increased complexity or increased costs in vehicle manufacture.

A first aspect of the invention therefore proposes a method for setting a steering angle and/or a yaw rate of a motor vehicle. This method is characterized in particular by the fact that existing components for braking the motor vehicle are also used to adjust the steering angle and/or the yaw rate of the motor vehicle. The method presented in this application preferably requires no additional components or only minor adjustments. In the best case, this method can be implemented using a corresponding control unit or by adapting an existing control unit.

A target steering angle and/or yaw rate may be provided. Likewise, separate target values can each be provided for the steering angle and the yaw rate. The target value can be provided manually or automatically. Turning a steering wheel can provide a target value manually, for example. A control unit or computing unit can use sensor information and/or external information such as cloud data to determine the target value for the steering angle and/or the yaw rate. In this case, providing the target value means determining the target value by the control unit or computing unit.

Multiple pressure pulses may be determined for a braking unit based on the target value or values. A control unit or regulating unit can implement the determination of the pressure pulses. The pressure pulses can in particular be in the form of square-wave pulses. The pressure pulses preferably relate to a hydraulic and/or pneumatic brake unit. However, they preferably do not contain any electromechanical wheel brakes. The pressure pulses lead to braking torque pulses or clamping force pulses on at least one wheel of the motor vehicle, in particular with the aid of the brake unit. The at least one wheel of the motor vehicle can be “braked” using the multiple pressure pulses. "Braking" preferably means brief braking of the wheel in accordance with the pressure pulse or the multiple pressure pulses. The multiple pressure pulses can result in a change in the steering angle and/or the yaw rate of the motor vehicle.

In a further step, a vehicle parameter and/or a surface condition of a roadway of the motor vehicle can be provided. This information can be obtained using an appropriate sensor system and/or using external information is provided. For example, a camera can determine a surface condition of the roadway in conjunction with a corresponding image evaluation. With the help of digitally stored route data such as a digital friction value map, the surface condition can be provided and transmitted by an external storage unit. The external storage unit can transmit this information to a corresponding interface of the motor vehicle or a control unit of the motor vehicle.

In a further step, an actual value for the steering angle and/or the yaw rate is recorded. In particular, an on-board sensor can be used for this purpose. A current steering angle and/or current yaw rate can be detected or measured by means of a steering angle sensor or yaw rate sensor. As a rule, this actual value deviates from the target value. Even if a first rough adjustment with regard to the steering angle and/or the yaw rate is already carried out using the multiple pressure pulses, the actual value for the steering angle can still deviate from the target value. The target value and the actual value can therefore be different.

In a further step, one or more wheels of the motor vehicle are preferably (on) braked based on the target value and the plurality of pressure pulses. A pressure pulse can be viewed as a momentary rise and fall in pressure or vice versa. A pressure pulse can be designed similar to a delta distribution. The pressure pulse is preferably rectangular or approximately rectangular. The multiple pressure pulses are preferably controlled and/or determined as a function of the target value, the actual value and the vehicle parameter and/or the surface condition of the roadway in order to bring the actual value closer to the target value.

In particular, after an initial set of pressure pulses has been determined, a control circuit for determining further additional pressure pulses can follow. Such a control circuit can be used to reduce a difference between the target value and the actual value. In most cases it is not necessary to adjust a difference between the actual value and the target value exactly to the value 0. It is usually sufficient if the actual value is brought closer to a tolerance range around the target value. The tolerance range can be, for example, 1 to 5 percent around the target value. In particular, the vehicle parameters and/or the surface condition of the roadway can be taken into account as a disturbance variable for the steering angle and/or the yaw rate with the aid of the control circuit or the regulation. These disturbances can cause a deviation between the cause actual value and the target value. By detecting a difference between the actual value and the target value, the multiple pressure pulses can be determined more precisely.

In particular, the regulation and/or determination of the plurality of pressure pulses can take place iteratively. This means that after a number of pressure pulses have been determined, a difference between the target value and the actual value is recorded and, based on this difference, a number of new pressure pulses are determined. This determination can be continued until the actual value is sufficiently close to the target value. In this regulation, the vehicle parameters and/or the surface condition of the roadway can also be taken into account.

This method is preferably used as an emergency steering. In particular, the motor vehicle can be safely brought to a standstill with the aid of the multiple pressure pulses. In the ideal case, the motor vehicle is not only brought to a standstill, but is also brought to a standstill in a safe place. For example, in a motor vehicle on a freeway, a main steering system and under unfavorable circumstances even the associated redundant steering system could fail. In this situation, the motor vehicle can no longer be operated, not even to a nearest workshop. In this situation, using the method described and the following embodiments, the motor vehicle can still be steered safely from a lane on the freeway in the direction of the hard shoulder and brought to a standstill there. Components that are already available are preferably used here, so that an additional emergency steering system can be provided without additional components. In this way, traffic safety can be increased in an uncomplicated manner.

An additional or alternative embodiment enables the surface condition of the roadway of the motor vehicle to be determined using a camera. Additionally or alternatively, the surface quality can be provided by a friction value map stored on an external storage unit. The external storage unit can be considered as cloud data storage. Digital route data and information regarding the surface condition of the roadway along a route of the motor vehicle can be stored on this cloud data memory. The multiple pressure pulses can be adjusted accordingly as the surface texture changes, as this can be seen using the camera. For example, a change in an optical flow can be detected using the camera. For this purpose, the camera can, for example, record and analyze several images of the roadway of the motor vehicle. A change in the optical flow can result in a change in the indicate the surface condition of the road. For example, a transition from a paved roadway to a roadway with gravel, snow, ice or rain can induce a corresponding change in the camera images. This change can be detected, for example, using the optical flow or another image analysis. The image evaluation can be carried out using a neural network which is trained to recognize surface properties. The multiple pressure pulses can be re-determined or recalculated as a result of the changed surface texture. In this way, an impending new surface condition can already be taken into account when calculating the multiple pressure pulses, which ideally allows the actual value to be more quickly compared to the target value. In this case, readjustment can take place by increasing the pulse widths and/or pulse heights of the multiple pressure pulses. Additionally or alternatively, a pulse spacing between the plurality of pressure pulses can be reduced or increased. Alternatively, the different surface properties can be called up using the friction value map. In this way, the steering angle or the yaw rate can be determined, controlled and/or set more precisely and quickly.

In addition or as an alternative, a speed can be detected as a vehicle parameter by means of a speed sensor, and wheel slip derived from this can be taken into account during regulation. Preferably, two associated speeds can be detected for each two wheels of an axle. A wheel slip can be determined on the basis of these two speeds. As a result, wheel spin can be detected in good time and the multiple pressure pulses can be adjusted in such a way that the motor vehicle can be safely guided at least to a standstill.

Additionally or alternatively, a microphone and/or an ultrasonic sensor can be used to detect moisture in an area around the wheels. The surface condition of the roadway can preferably be derived from the detected moisture. For example, the ultrasonic sensor or the microphone can be arranged in the area of a wheel housing. A characteristic acoustic of a wet roadway can be detected with the aid of the ultrasonic sensor or the microphone. This means that the microphone or the ultrasonic sensor can “hear” a damp, icy or stony road. Depending on the recorded background noise or sound wave characteristics, conclusions can be drawn about the surface condition of the roadway. This results in a further possibility of determining the surface condition of the roadway in a simple manner. Additionally or alternatively, a volume of the surface condition of the roadway can be recorded. The surface quality of the roadway can be determined based on the volume. For example, the level of moisture can be used to derive a degree of adhesion of the road surface as a surface condition. Instead of the volume, a sound wave characteristic or noise characteristic can additionally or alternatively be detected. With the help of the noise characteristics or sound wave characteristics, conclusions can be drawn about the surface condition of the roadway. The road surface condition may include friction of the road to the tire of the vehicle, adhesion of the tire to the road, and wheel contact patch of the tire to the road. In connection with a weight of the motor vehicle, conclusions can be drawn about the tire contact area. Thus, in addition to the surface condition, the tire contact area can also be determined. These parameters can also be taken into account when controlling the multiple pressure pulses.

The determination of the tire contact area based on the vehicle weight and/or the surface condition based on the volume can take place analogously in all other embodiments. As a result, the steering angle and/or the yaw rate of the motor vehicle can be adjusted to the target value more efficiently and quickly.

Additionally or alternatively, a tire type of the wheels and a tire temperature can be recorded as vehicle parameters. A number of pressure pulses can preferably be regulated as a function of the type of tire and the tire temperature. The steering of the motor vehicle can depend in particular on the type of tire and the tire temperature. For example, winter tires generally have a greater stopping distance in summer. Likewise, different tire temperatures can affect a braking distance or stopping distance. Likewise, these parameters can influence the steering behavior of the motor vehicle. The type of tire can be specified using manual input, for example. The type of tire can thus be communicated to the control unit. The tire temperature can be measured using an appropriate temperature sensor. These additional vehicle parameters can also be used to regulate the multiple pressure pulses. Despite the failure of a higher-level steering system, the motor vehicle can still be safely guided, at least temporarily.

Additionally or alternatively, a motion sensor of the motor vehicle can be used to measure a speed, an acceleration and/or a jerk as the vehicle parameters. The pressure pulses can preferably be dependent on these Vehicle parameters are controlled to adjust the steering angle and / or the yaw rate. The parameters in this embodiment can be considered in addition to the vehicle parameters and the surface condition when controlling. The speed, acceleration and/or jerk can be measured using an inertial sensor, acceleration sensor or speed sensor. The jerk is in particular a derivation of the acceleration or a third derivation of the location over time. The acceleration is preferably a change in speed over time. In addition, the vehicle weight can be recorded and measured as an additional parameter. As a result, the regulation of the multiple pressure pulses can be further improved.

Additionally or alternatively, the target value can be determined based on the vehicle parameter and/or the surface condition of the roadway of the motor vehicle. The target value can be determined or specified in particular by a control unit of the motor vehicle for autonomous driving. Certain constellations of vehicle parameters and surface conditions may preclude these certain target steering angle or yaw rate values. In particular, the target value can also take place as a function of an object detection around the motor vehicle. The target value is preferably set in such a way that a collision of the motor vehicle with an object is avoided.

Additionally or alternatively, the pressure pulses can have a duration of 10 to 1,000 milliseconds. The pressure level of the pressure pulses can be between 10 bar and 100 bar. 100 bar preferably correspond to full braking. The duration of the pressure pulses can be 100, 200, 300, 400, 500, 600, 700, 800, 900, 1,000 milliseconds. The pressure pulses are preferably regulated in such a way that the motor vehicle is braked safely, is steered in the process and is transferred to a safe, final end state. Permanent braking of individual wheels on a rear axle or front axle of the motor vehicle would destabilize it. For example, this can cause the motor vehicle to skid and the wheel brake can also overheat more quickly. This can be avoided by using the multiple pressure pulses. The motor vehicle can be safely steered in the range of low lateral accelerations with the aid of braking by means of the multiple pressure pulses. For this purpose, the inner wheels on the rear axle are preferably braked in accordance with the multiple pressure pulses. Additionally or alternatively, a braking torque can be detected at the braked wheel or wheels. A speed of the motor vehicle can also be detected. A stopping distance of the motor vehicle can be determined as a function of the braking torque and the speed. The braking torque can be an instantaneous braking torque, ie it can vary over time. In particular, several braking torques can be recorded over time. The same can apply to the speed of the motor vehicle. A stopping distance of the motor vehicle can be determined or calculated on the basis of these braking torques and speed values of the motor vehicle. It can thus be predicted in which area the motor vehicle will be brought to a standstill.

Additionally or alternatively, a lane of the motor vehicle and a target lane of the motor vehicle can be detected. The lane of the motor vehicle is in particular the lane on which the motor vehicle is currently located. The target lane is preferably that lane on which the motor vehicle is to be safely brought to a standstill. In many cases this is the right hand side of a street. On a country road, this can be a parking bay or a hard shoulder. On a freeway, the target lane may be a hard shoulder or hard shoulder. The target value can preferably be specified as a function of the lane and the target lane. In this context, the speed of the motor vehicle can also be taken into account when specifying the target value. In particular, the regulation of the multiple pressure pulses can be adapted to the stopping distance. This can prevent the motor vehicle from being brought to a standstill in an unsafe place.

It is thus possible to steer the motor vehicle from the lane to a safe target lane and to bring it to a standstill there. With the aid of the multiple pressure pulses, the motor vehicle can be steered from the lane to the target lane and at the same time braked accordingly so that it comes to a standstill in the target lane.

Additionally or alternatively, the presence of other vehicles or road users around the motor vehicle can be detected. The other vehicles or road users can be informed of a malfunction of the motor vehicle by a warning signal. The warning signal can be an optical or acoustic warning signal for other drivers of vehicles. Additionally or alternatively, the warning signal can be transmitted wirelessly to other control units of other vehicles. In this way, other autonomously driving vehicles can be informed about a malfunction or an emergency situation in the motor vehicle. Other autonomous vehicles can adapt their driving style accordingly to ensure safe steering and driving of the motor vehicle to allow braking. In particular, an alternative corridor can be created for the motor vehicle, which can be used for steering and braking. By braking the other vehicles accordingly, the motor vehicle is much better able to determine a trajectory from the lane to the target lane and to maneuver the motor vehicle there accordingly with the aid of the multiple pressure pulses.

Additionally or alternatively, the target value for the steering angle and/or the yaw rate and the regulation of the pressure pulses can be provided based on the presence of the other vehicles or road users. In addition, the pressure pulses can be regulated and the target value for the steering angle and/or the yaw rate can be provided as a function of detected objects around the motor vehicle. The target value is preferably determined or adjusted in such a way that collisions are avoided. As a result, a suitable target value for the steering angle and/or the yaw rate for controlling the multiple pressure pulses can be determined or specified. The target value is preferably determined or defined in advance. For this purpose, an object in a radius around the motor vehicle can be detected using a camera. For this purpose, the control unit can evaluate one or more images of the motor vehicle, which show the surroundings of the motor vehicle. This can prevent a subsequent change in the target value from causing large overshoots or undershoots when controlling. The regulation of the yaw rate and/or the steering angle can thus be carried out more fluently or more comfortably.

Additionally or alternatively, the pressure pulses can be determined by a control unit, information relating to the surface condition of the road being stored on the control unit. The multiple pressure pulses can also be determined and/or regulated as a function of this information regarding the surface condition. This allows the control unit to be preconditioned using information about the road surface conditions. A surface condition of a roadway of a route of the motor vehicle can already be taken into account by a sensor before the surface condition of the roadway is detected. In this way, the multiple pressure pulses can already be determined and adjusted more precisely in an initial phase of setting the steering angle and/or the yaw rate. In this way, accelerated regulation can take place, whereby the actual value can be adjusted to the target value more quickly. The control unit can access the vehicle's own sensors and pick up sensor data in order to determine the surface condition of the road. With the help of the friction value map from a server, the surface properties can be transmitted to the motor vehicle or the control unit. This is preferably done wirelessly. A second aspect of this invention relates to a motor vehicle. The motor vehicle preferably has a control unit, a brake unit and at least one wheel. The control unit is designed in particular to determine a number of pressure pulses for the brake unit based on a target value provided for a steering angle and/or a yaw rate. The control unit can determine or provide a vehicle parameter and/or a surface condition of a roadway of the motor vehicle. The control unit can record an actual value for the steering angle and/or the yaw rate and determine and/or control the at least one wheel of the motor vehicle based on the target value, the actual value, the vehicle parameter and/or the surface condition of the roadway in order to to bring the actual value closer to the target value.

The features, examples and advantages mentioned in connection with the method apply mutatis mutandis and analogously to the motor vehicle and vice versa. The vehicle parameter can be detected or measured using appropriate sensors in the motor vehicle. For this purpose, inertial sensors, movement sensors, microphones, ultrasonic sensors, cameras and other sensors can be used. The invention will now be explained in more detail with reference to the accompanying drawings. However, the drawings merely represent exemplary embodiments which do not limit the scope of the invention.

The features, embodiments and advantages presented in connection with the method for adjusting the steering angle and/or the yaw rate according to the first aspect of the invention apply correspondingly to the motor vehicle according to the second aspect of the invention and vice versa.

The motor vehicle preferably has the control unit. The control unit can have a processor device that is set up to carry out an embodiment of a method. For this purpose, the processor device can have at least one microprocessor, at least one microcontroller, at least one FPGA (Field Programmable Gate Array), at least one DSP (Digital Signal Processor) and/or a neural network. Furthermore, the processor device can have program code which is set up to carry out the embodiment of the method when executed by the processor device. The program code can be stored in a data memory of the processor device. The control unit can include an internal or external storage unit. The external storage unit can be in the form of a cloud unit. The motor vehicle can contain a computer program [product], that includes instructions that cause each embodiment of the method to be executed. The computer program product can be stored on a computer-readable medium.

The invention also includes developments of the method according to the invention, which have features as have already been described in connection with the developments of the motor vehicle according to the invention. For this reason, the corresponding developments of the method according to the invention are not described again here.

The invention also includes the combinations of features of the described embodiments.

It shows:

1 shows a schematic side view of a motor vehicle with a control unit for setting a steering angle and/or a yaw rate;

FIG. 2 shows a schematic plan view of the motor vehicle with a road ahead of the motor vehicle and different lanes; FIG.

3 shows an exemplary representation of various components of the method for setting the steering angle and/or the yaw rate and of the motor vehicle;

4 shows an example of a control circuit for setting the steering angle and/or the yaw rate of the motor vehicle;

5 shows a schematic representation of several different pressure pulses for braking one or more wheels of the motor vehicle in order to adjust the steering angle and/or the yaw rate; and

6 shows a schematic flowchart for a possible method.

The exemplary embodiments explained below are preferred exemplary embodiments of the invention. In the exemplary embodiments, the components described each represent individual features of the invention which are to be considered independently of one another and which also define the invention independently of one another develop further and are therefore to be regarded as part of the invention individually or in a combination other than that shown. Furthermore, the exemplary embodiments described can also be supplemented by further features of the invention already described.

Elements with the same function are each provided with the same reference symbols in the figures.

1 shows a motor vehicle 1, for example. The motor vehicle 1 can be embodied as a vehicle, motor vehicle, motor vehicle, manually operated motor vehicle or autonomously operated motor vehicle. The motor vehicle 1 has a control unit 2 or a control unit 2 . The control unit 2 can have several braking units

3 of the motor vehicle 1 control to brake one or more wheels 4 of the motor vehicle 1.

The control unit 2 can preferably send control signals to the brake units 3 for the rear wheels

4 generate and thus temporarily brake the rear wheels 4. Temporary braking can also be referred to as "braking". The control unit 2 can obtain and/or call up information from various components. For example, using an inertial sensor 5, an external storage unit 6, a sensor 7 of the motor vehicle 1 and/or a central processing unit 9 of the motor vehicle 1, information or data can be transmitted to the control unit 2 and/or made available. The on-board sensors 7 can be in the form of ultrasonic sensors, microphones, cameras, radar sensors, laser scanners and/or lidar sensors, for example. The inertial sensor 5 can be designed, for example, as an acceleration sensor, speed sensor and/or jerk sensor. The inertial sensor 5 can thus detect or measure a speed of the motor vehicle 1 , an acceleration of the motor vehicle 1 and/or a jerk of the motor vehicle 1 . The jerk is in particular a time derivative of the acceleration or a third time derivative based on the location.

The external storage unit 6 can provide a digital friction value map, for example. In particular, the friction value map provides information about roadway conditions that are ahead of the motor vehicle 1 in the direction of travel x. The friction value map can thus contain adhesion properties as well as road conditions. For example, the friction map can also take into account local weather information. The road conditions can be additionally or alternatively detected by the sensors 7 of the motor vehicle 1 or be determined. In particular, a road ahead ahead of the motor vehicle 1 can be detected with the aid of one or more cameras 7 . With the help of appropriate image processing, conclusions can be drawn about a wet road, a road with gravel, a road with rolled chippings, etc. A roadway condition or road condition can thus be determined with the aid of the camera 7 and corresponding image evaluation.

In the case of autonomously driving motor vehicles, the motor vehicle 1 generally no longer has a steering wheel 8 . Manually operated motor vehicles 1 are usually steered or controlled with a steering wheel 8 . In a motor vehicle 1 driving fully autonomously, the steering wheel 8 is designed as a stear-by-wire system 8 . In this case, the steering is preferably fully electronic. The steering wheel 8 can be deactivated or retracted completely. Stear-by-wire can thus be enabled during a fully automated journey, such as in a Level 4 motor vehicle 1 according to SAE J3016. In this case, a driver becomes a pure passenger during a fully automated journey of the motor vehicle 1 . This allows more space to be created for other activities, such as sleeping, reading the newspaper, surfing the Internet and so on. When the steering wheel 8 is retracted or folded away, new interior concepts can be made possible. This can be done, for example, with the help of rotating seats and other fold-out tables.

A mechanical decoupling between the steering wheel 8 and a steering actuator can prevent unwanted incorrect operation during fully automatic driving. Even if the steering wheel 8 were not folded away or retracted, accidentally touching the steering wheel 8 would not lead to an unwanted vehicle reaction. In the case of fully autonomous motor vehicles 1 according to Level 5, such as robot taxis, no driver is provided at all, so that a stear-by-wire system is present in this case.

Stear-by-wire can also be advantageous in conventional, manually operated motor vehicles 1 without automatic driving functions. Various stabilization functions such as crosswind stabilization or trailer stabilization can be carried out in connection with the steering 8 . In this case, a steering intervention is no longer carried out by the driver on the steering wheel 8 . In an emergency, the stear-by-wire system can override the driver's steering. In particular, this means that for a short time steering is exclusively carried out by the stear-by-wire system in order to survive critical traffic situations safely. A stear-by-wire system can allow for additional comfort. When getting in and out, the steering wheel 8 can be folded away, which can make it easier to get out. When parking the motor vehicle 1, a slight movement of the steering wheel 8 can be sufficient to set a required large steering angle a. This can be done, for example, by electronically adjusting the transmission ratio between the steering angle α and the steering wheel angle. In addition, stear-by-wire enables steering behavior to be personalized. A haptic feedback to the driver can be softer or harder, sporty or comfortable, direct or subdued. This setting can, for example, be transferred from an old to the new vehicle when buying a new motor vehicle.

In the case of stear-by-wire, in particular a mechanical connection between the steering wheel 8 and a steering gear on the axle is broken and replaced by a redundant data line. This preferably applies to fully autonomous motor vehicles 1. In conventional motor vehicles 1, stear-by-wire 8 can be added to a normal steering wheel 8. The overall system influencing the lateral dynamics (usually mainly the steering) should meet certain safety and availability requirements. Depending on the vehicle manufacturer, a different safety philosophy can be implemented.

In most cases, a high level of security is desired or even specified. In order to meet these safety requirements, the stear-by-wire system 8 or steering system must be designed with at least one redundancy according to the current state of the art. This can be done, for example, by double windings in the motor, double control devices and double electrical energy supplies and double data communication.

With a simple redundancy, the motor vehicle 1 is stopped after a short time, particularly after a fault in the stear-by-wire system 8, since another fault would result in a motor vehicle 1 that could not be steered. While it is statistically unlikely for two steering systems to fail at the same time, such a scenario is not entirely impossible. For example, if a main braking system fails, auxiliary braking is still available, which enables a maximum braking deceleration of at least 2.4 meters per second squared.

As part of this application, a security strategy is being pursued, which provides that when the motor vehicle 1 is operated, at least one further fallback level for Setting the steering angle a and / or the yaw rate a 'must be kept available. If the last fallback level with regard to the steering 8 is reached, provision is preferably made for the motor vehicle 1 to be safely brought to a standstill. Provision is therefore made in particular for the motor vehicle 1 to be operated in regular operation only when the last redundancy has not yet been reached with regard to the steering. When the last redundancy regarding the steering of the motor vehicle 1 is reached, the motor vehicle 1 is preferably steered and braked in such a way that it is safely brought to a standstill at a suitable location.

FIG. 2 shows a plan view of the motor vehicle 1 by way of example. Two different steering angles a and ß as well as yaw rates a' and ß' are shown, a and a' represent the target value for the steering angle, while ß represents an actual value for the steering angle. Likewise, α′ represents a target value for the yaw rate and β′ represents an actual value for the yaw rate. A roadway 10 with different lanes FS and ZF is shown in front of the motor vehicle 1 . FS is a current lane of motor vehicle 1 , while ZF represents a target lane for motor vehicle 1 . Another vehicle 1 is indicated in the target lane ZS. Areas of the current lane FS are shown as dashed and dotted lines. This is intended to indicate different road conditions. These different road conditions can be detected by the sensor 7 and/or transmitted from the external storage unit 6 to the control unit 2 or the vehicle computer 9 as a digital friction value map. In the example in FIG. 2 , the steering information is collected by the central vehicle computer 9 and transmitted to the control unit 2 . The control unit 2 can control a braking unit 3 in order to briefly brake the rear right wheel 4 . As a result of this brief braking, the motor vehicle 1 is rotated in the direction of the steering angle α, specifically by the amount of the actual value β. The same can apply to the actual value ß' of the yaw rate a'. The setting of the actual values ß, ß′ preferably takes place within the framework of a control circuit in order to bring them closer to the target values a, a′. This control circuit can implement a regulation with regard to the steering angle a and/or the yaw rate a'.

In all embodiments, the control unit 2 can determine a stopping distance AW and adapt the determination of the pressure pulses PK to the stopping distance AW. For example, a shortened stopping distance AW can result due to detected objects and/or changed surface properties of roadway 10 .

In Fig. 3 some components for such a control loop are shown as an example. The control unit 2 preferably forms the center of the control loop. The steering wheel 8 or the stear-by-wire system 8 can be used to set the target value for the steering angle a or the yaw rate a' be specified. The control unit 2 can use the target value a, a′ to calculate or determine a number of pressure pulses PK for the brake unit 3 . The brake unit 3 can generate braking torque pulses or clamping force pulses with the aid of brake calipers or brake shoes. The pressure pulses are preferably in the form of brief rectangular pulses. They can last a few milliseconds and have a pressure level between 1 bar and 100 bar. Due to this temporary brief braking (braking), the motor vehicle 1 is preferably not fully braked, but instead the motor vehicle 1 is steered. For example, only a single rear wheel 4 can be braked briefly. Emergency braking can be provided in particular when motor vehicle 1 is in a safe place and is to be brought to a standstill there. Before that, the motor vehicle 1 is preferably transferred from its current position, for example the lane FS, to the target lane ZF. The target lane ZF can be, for example, a breakdown lane or an emergency lane on a freeway. In the case of a country road, the target lane ZF may be an off-road area.

The control unit 2 can take different information into account for calculating or determining the plurality of pressure pulses PK. For example, sensors 7 of motor vehicle 1 can provide local friction information. This local friction value information can be road conditions or roadway conditions, for example, which are in front of the motor vehicle 1 in the direction of travel x. Such friction value information can additionally or alternatively be obtained from the external storage unit 6 . The actual value β for the steering angle or the actual value β' for the yaw rate can be measured with the aid of one or more inertial sensors 5 . These sensors 7 can each transmit their sensor signals or data to the control unit 2 . Alternatively, the central vehicle computer can collect the signals from the inertial sensors 5, on-board sensors 7, data from the external storage unit 6 and transmit this collected information to the control unit 2 in a data packet. The control unit 2 can take this collected information into account when determining the pressure pulses PK.

The calculation or determination of the pressure pulses PK can, in particular, be carried out iteratively. In particular, a difference between the target value a and the actual value ß can be determined after each iterative step. The determination of the further pressure pulses PK can depend in particular on this difference.

4 shows a control circuit or a control system by way of example. The control circuit serves in particular to set the steering angle a and/or the yaw rate a' of the motor vehicle 1. The steering angle a or the yaw rate a′ are preferably set using a plurality of pressure pulses PK. These multiple pressure pulses PK are preferably calculated or determined using a control system that the control unit 2 can implement.

In principle, it should be noted that this method represents an additional, but mostly last, redundancy with regard to a steering system or a stear-by-wire system 8 . The method for setting the steering angle a or the yaw rate a' is generally not intended for regular operation. However, an additional redundancy or fallback level with regard to the steering 8 can be created in this way. In this case, use is preferably made of already existing components of the motor vehicle 1, which can easily enable additional redundancy when steering.

First, the steering angle a or the yaw rate a' is specified using the steering wheel 8 or the stear-by-wire system 8 . The target value a or a' is the basis for the determination of the multiple pressure pulses PK by the control unit 2. In a first step, this calculation can be carried out exclusively using the target value a or a', particularly when there is still no information regarding the actual value for the steering angle ß or the yaw rate ß'. If information regarding the actual values is already available, the control unit 2 can preferably take into account a difference Aa, Aa' between the target value and the actual value when calculating the multiple pressure pulses PK. A system deviation can be calculated from the difference Aa, Aa' between the target value and the actual value with regard to the steering angle a or the yaw rate a'. Depending on the control deviation, suitable requests for pressure pulses PK can be sent to the brake unit 3 and the brake calipers of the wheels 4. The control unit 2 can thus transmit the plurality of pressure pulses PK to the brake unit 3 as control signals. In particular, these multiple pressure pulses PK cause a braking torque on the left or right wheel 4 on the rear axle of the motor vehicle 1. This leads to a new actual value for the steering angle β or a new actual value for the yaw rate β′. These actual values result in particular from the braking of the respective rear wheel 4 as a result of the multiple pressure pulses PK.

In addition, these new actual values ß, ß′ can be influenced by various disturbance variables. These disturbance variables can result, for example, from changes in the coefficients of friction between the wheels 4 and the road surface 10 . The control unit 2 can preferably already take into account a surface condition of the roadway 10 when determining the multiple pressure pulses PK. This means that the control unit 2 can be suitably preconditioned. To this end, the control unit 2 can access data from the on-board sensors 7 and/or from the external storage unit 6 in order to determine surface texture. The control unit 2 can use this surface quality in the control process to adjust the pressure pulses PK accordingly, so that the actual values β, β′ approach the target values a, a′. In addition, the control unit 2 can take into account other measured variables such as a speed of the motor vehicle 1, an acceleration and a longitudinal jerk or lateral jerk when calculating or determining the multiple pressure pulses PK. The control method shown in FIG. 4 can be carried out iteratively. This means in particular that a number of new pressure pulses PK can be calculated for each iterative step. The braking of the rear wheel 4 can thus be adjusted continuously.

In particular, the control unit 2 can also take into account the presence of other vehicles 1' when determining the multiple pressure pulses PK. In this context, reference is again made to FIG. In this example, the motor vehicle 1 is to be transferred from the current lane FS to the destination lane ZF. The motor vehicle 1 is to be brought to a standstill in the target lane ZF. The target value for the steering angle a or the target value for the yaw rate a' is adapted to the presence of the other vehicle 1. In particular, these target values are selected in such a way that a collision between the motor vehicle 1 and the other vehicle 1' is reliably avoided.

Additionally or alternatively, the motor vehicle 1 can transmit an emergency signal to the other vehicle 1'. If the other vehicle 1' is also a fully autonomously controlled vehicle, the other vehicle T can, for example, reduce its speed in order to enable the motor vehicle 1 to safely change lanes to the target lane ZF. The other vehicle T can thus provide the motor vehicle 1, which is in distress, with a safe corridor in order to come to a safe stop in the target lane ZF, preferably within the scope of the stopping distance AW. If the motor vehicle 1 has arrived at the destination lane ZF, the multiple pressure pulses PK can be converted into an emergency stop. For this purpose, the multiple pressure pulses PK can be transformed into a constant maximum pressure signal. However, this is preferably only provided when the steering has been carried out successfully and the motor vehicle 1 is to be brought to a standstill without exceeding the stopping distance AW.

In this context, the vehicle's own sensors 7 and the external memory unit 6 can take into account the vehicle parameters and the surface condition of the roadway 10 when calculating the multiple pressure pulses PK. For example, the camera 7 can recognize that the current lane FS is wet or has rolled split. The dashed area of lane FS is intended to represent a wet road surface, while the dotted area is intended to represent loose chippings. These different surface textures usually lead to a deviation between the target value and the actual value for the steering angle a or the yaw rate cf. The method can provide for detecting this difference using the inertial sensor 5 and/or the vehicle parameters and surface texture of the road 10 and to be taken into account in advance when determining the multiple pressure pulses PK. This means that a change in the surface quality of the roadway 10 can already be taken into account when the motor vehicle 1 has not yet reached the corresponding point on the roadway 10 . In any case, any difference that occurs between the target value and the actual value for the steering angle a or the yaw rate cf is preferably taken into account when calculating or determining the multiple pressure pulses PK.

In Fig. 5 different pressure pulses PK are shown as an example. The x-axis is designed as time t. The y-axis represents a pressure P. In FIG. 5, three different types of modulation for braking are shown as an example. In the left-hand area of FIG. 5, the pressure pulses PK can differ in terms of a pulse length bt. A change in the plurality of pressure pulses PK is indicated in each case on the basis of the dashed lines. For example, the pulse length bt can be converted into a modified pulse length bt'. In the middle area of FIG. 5, the multiple pressure pulses PK are adjusted with regard to a pulse height ba. A temporal extension of the pressure pulses PK remains constant, but the pressure level P for the braking pressure changes. In this way, the pressure pulses can be converted from an instantaneous pulse height to a modified pulse height ba'. A change in a pulse interval bd for the plurality of print pulses PK is indicated in the right-hand area of FIG. An instantaneous pulse spacing bd can be converted into a modified pulse spacing bd'. The adjustment or regulation of the multiple pressure pulses PK can be a combination of these three options shown. This means in particular that the multiple pressure pulses can change at the same time with regard to their pulse length, their pulse height and the pulse spacing. The pulse lengths bt, bt' preferably extend over time from 10 milliseconds to 1,000 milliseconds. The pulse heights ba, ba' can reach values between 1 bar and 100 bar. A heart rate of 100 bar preferably corresponds to emergency braking. The pulse intervals bd, bd' can also be in a range from 10 milliseconds to 1,000 milliseconds.

This method or this regulation can enable double redundancy or an additional fallback level for a stear-by-wire system 8 . Although this additional redundancy can be achieved by providing further technology, So additional components can be achieved, but this is usually associated with higher costs. The steering angle a and/or the yawing moment cf can be adjusted by braking the rear wheel 4 using the multiple pressure pulses with a correspondingly adapted pulse length, pulse height and pulse interval without destabilizing the motor vehicle 1 or overheating the brake unit 3 . The longer or higher a pressure pulse PK is, the higher the set yaw rate cf tends to be. A sequence of the multiple pressure pulses PK can set a constant steering angle a over a longer period of time. The steering angle a or the yaw rate cf can be adjusted accordingly to the target value with the aid of a targeted modulation of the pulse length bt, pulse spacing ba and/or pulse height bd.

The different types of modulation shown in FIG. 5 with regard to the pulse length, pulse height and pulse spacing can be combined with one another. As a result, the actual value for the steering angle ß and the actual value for the yaw rate ß' can be increased or decreased in order to bring the actual value closer to the target value. With the help of this regulation, the motor vehicle 1 can be kept within a lane even if the steering system 8 fails. Twisting of the front wheel is thus advantageously avoided. If there is a reduced coefficient of friction, which cannot be set due to gravel, rain, snow, ice or other loose chippings, for example, the control unit 2 can enable readjustment by adapting the multiple pressure pulses PK, as shown in FIG. The regulation shown as an example in FIG. 4 can take into account a difference between the target values and the actual values when calculating the multiple pressure pulses PK for the brake unit 3 .

Another possible control method for setting the steering angle a and/or the yaw rate cf of the motor vehicle 1 is shown as an example in FIG. 6 . First, in a first step S1, the target value for the steering angle a and/or the yaw rate cf can be provided. This provision can take the form of detecting a traffic situation or using manual input. In a second step S2, multiple vehicle parameters such as a speed of the motor vehicle 1, an acceleration, and a longitudinal jerk and/or a lateral jerk can be provided. Additionally or alternatively, information about a surface condition of the roadway 10 of the motor vehicle 1 can be provided or measured in a third step S3. Alternatively or additionally, the provision can take place using digital route data from the external storage unit 6 . This digital information can be transmitted from the external storage unit 6 to a corresponding interface of the control unit 2 or of the motor vehicle 1. in one In the fourth step S4, an actual value β, β' for the steering angle and/or the yaw rate is preferably recorded, for example by means of the sensors 7. In a fifth step S5, the rear wheel 4 of the motor vehicle 1 can be measured based on the target value a, a' and the multiple pressure pulses PK are braked. The multiple pressure pulses PK are preferably controlled and/or determined in the fifth step S5 as a function of the target value a, a′, the actual value β, β′, the vehicle parameter and/or the surface condition of the roadway 10 . This serves to approximate the actual value ß, ß' to the target value a, a'.

Overall, the specified embodiments and examples show how the motor vehicle 1 can still be safely maneuvered at least to a standstill with the aid of the multiple pressure pulses PK even if the steering system 8 or the stear-by-wire system 8 fails completely. The motor vehicle 1 is preferably steered in such a way that it is safely maneuvered to the target lane ZF and is safely stopped there. Since additional redundancy with regard to the steering can be created without installing additional components, the occurrence of breakdown situations can be noticeably reduced. This is due in particular to the fact that an additional fallback level can be created with regard to the steering.

Reference List

1 vehicle, motor vehicle

2 controllers, control unit

3 brake unit

4 wheel, rear wheel

5 inertial sensor

6 external storage unit

7 on-board sensor, camera, ultrasonic sensor

8 steering wheel, stear-by-wire system

9 central vehicle computer

10 lane

AW stopping distance

FS current lane

ZF Target lane a Steering angle, target value for steering angle a' Yaw rate, target value for yaw rate ß Actual value for steering angle ß' Actual value for yaw rate

Aa Steering angle difference

Aa' difference yaw rate

PK pressure pulses

51 first step

52 second step

53 third step

54 fourth step

55 fifth step t time, timeline

P pressure, brake pressure bt pulse length bt' modified pulse length ba pulse height ba' modified pulse height bd pulse spacing bd' modified pulse spacing

Claims

Claims Method for setting a steering angle (a) and/or a yaw rate (cf) of a motor vehicle (1) with the following steps:

Providing a target value (a, a') for the steering angle (a) and/or the yaw rate (a'), determining multiple pressure pulses (PK) for a brake unit (3) based on the target value (a, cf),

Providing a vehicle parameter and/or a surface condition of a roadway (10) of the motor vehicle (1),

Detecting an actual value (ß, ß ') for the steering angle (a) and / or the yaw rate (cf), braking one or more wheels (4) of the motor vehicle (1) based on the target value (a, cf) and the a plurality of pressure pulses (PK), the plurality of pressure pulses (PK) being regulated as a function of the target value (a, cf), the actual value (ß, ß') and the vehicle parameter and/or the surface condition of the roadway (10) and/ or determined in order to approximate the actual value (ß, ß') to the target value (a, cf). Method according to claim 1, wherein the surface condition of the roadway (10) of the motor vehicle (1) is determined by means of a camera (7) or the surface condition is provided by a friction value map stored on an external storage unit (6). Method according to one of the preceding claims, in which a speed is detected as a vehicle parameter by means of a speed sensor (7) and wheel slip derived therefrom is taken into account in the regulation. Method according to one of the preceding claims, wherein a microphone (7) and/or an ultrasonic sensor (7) is used to detect moisture in an area around the wheels and the surface quality of the roadway is derived from the detected moisture. Method according to one of the preceding claims, in which a volume is detected and the surface quality of the roadway (10) is determined on the basis of the volume. Method according to one of the preceding claims, wherein a type of tire on the wheels (4) and a tire temperature are detected as vehicle parameters and the plurality of pressure pulses (PK) are additionally regulated as a function of the type of tire and the tire temperature. Method according to one of the preceding claims, in which speed, acceleration and/or jerk are measured as the vehicle parameters by means of a movement sensor (5) of the motor vehicle, and the pressure pulses (PK) are used to adjust the steering angle (a) and/or the yaw rate (cf ) can also be regulated as a function of these vehicle parameters. Method according to one of the preceding claims, wherein the target value (a, cf) is determined based on the vehicle parameter and/or the surface condition. Method according to one of the preceding claims, in which the pressure pulses (PK) have a duration of 10 to 1000 milliseconds and a pressure level of between 10 and 100 bar. Method according to one of the preceding claims, wherein a braking torque on the braked wheel or wheels (4) and a speed of the motor vehicle (1) are detected, and a stopping distance (AW) of the motor vehicle (1) is determined as a function of the braking torque and the speed becomes. Method according to one of the preceding claims, wherein a lane (FS) of the motor vehicle (1) and a target lane (ZF) for the motor vehicle (1) are detected, the target value (a, cf) depending on the lane (FS) and target lane (ZF) is specified and the regulation of the multiple pressure pulses (PK) is adapted to the stopping distance (AW). Method according to one of the preceding claims, wherein the presence of other vehicles (1') or road users around the motor vehicle (1) is detected and the other vehicles (T) or road users are informed of a malfunction of the motor vehicle (1) by a warning signal. Method according to claim 12, wherein the provision of the target value (a, cf) for the steering angle (a) and/or the yaw rate (cf) and the regulation of the pressure pulses (PK) ba- based on the presence of other vehicles (T) or road users. Method according to one of the preceding claims, in which the pressure pulses (PK) are determined by a control unit (2), information relating to the surface quality of the roadway (10) is stored on the control unit (2) and the plurality of pressure pulses (PK) are additionally dependent on determined and/or regulated using this information regarding the surface condition. Motor vehicle (1) with a control unit (2), brake unit (3) and at least one wheel (4), the control unit (2) being designed

- to determine several pressure pulses (PK) for the brake unit (3) based on a provided target value (a, a') for a steering angle (a) and/or yaw rate (a'),

- providing or determining a vehicle parameter and/or a surface condition of a roadway (10) of the motor vehicle (1), detecting an actual value (ß, ß') for the steering angle (a) and/or the yaw rate (cf), and

- to brake the at least one wheel (4) of the motor vehicle (1) based on the target value (a, a') and the multiple pressure pulses (PK), the multiple pressure pulses (PK) depending on the target value (a, cf) , the actual value (ß, ß ') and the vehicle parameter and / or the surface condition of the roadway (10) are regulated and / or determined in order to approximate the actual value (ß, ß ') the target value (a, cf). .