DE102021209390B4 - Method for adjusting a steering angle and/or a yaw rate of a motor vehicle and motor vehicle with a control unit - Google Patents

Abstract

Method for setting a steering angle (α) and/or a yaw rate (α') of a motor vehicle (1) with the following steps: - Providing a target value (α, α') for the steering angle (α) and/or the yaw rate (α' ),- Determining multiple pressure pulses (PK) for a brake unit (3) based on the target value (α, α'),- Providing a vehicle parameter and a surface quality of a roadway (10) of the motor vehicle (1), or providing the surface quality of the Roadway (10) of the motor vehicle (1), - Detecting an actual value (β, β') for the steering angle (α) and/or the yaw rate (α'), - Braking one or more wheels (4) of the motor vehicle ( 1) based on the target value (α, α') and the multiple pressure pulses (PK), where the multiple pressure pulses (PK) depend on the target value (α, α'), the actual value (β, β`), the vehicle parameters and the surface condition of the roadway (10) are regulated and/or determined in order to bring the actual value (β, β') closer to the target value (α, α'), or the multiple pressure pulses (PK) depending on the The target value (α, α'), the actual value (β, β') and the surface quality of the roadway (10) are regulated and/or determined in order to adjust the actual value (β, β') to the target value (α, α ') to approach.

Description

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 adjusting the yaw rate. In autonomous motor vehicles, steering is often implemented using a so-called “stear-by-wire” method. In this case, the motor vehicle no longer has a steering wheel at all, but 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 for 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 sometimes be very cost-intensive.

In this context, for example, the disclosure document mentions DE 10 2014 006 614 A1 a pneumatic braking device for motor vehicles and a method for operating a pneumatic braking system. An electronic control unit determines default values for the target braking pressures of the wheel brakes, taking into account a brake signal generator. Each wheel brake module includes at least one ventilation valve and one vent valve, electrically actuable activation means for activating the ventilation valve and/or the vent valve, and control logic with means for generating an actuating signal for the activation means corresponding to the default value for the target brake pressure.

The WO 2017/ 021 401 A1 describes a method for autonomously steering a vehicle. The DE 10 2014 200 608 B4 discloses a method that supports steering of the wheels if the power steering fails.

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

The invention is based on the knowledge that in a fully automated motor vehicle the so-called stear-by-wire steering system replaces conventional steering with a steering wheel. An autonomous motor vehicle can be accepted from a level 4 according to the SAE J3016 definition. 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, creating more space for further activities. By folding and retracting the steering wheel, new interior concepts can be created, for example seats can be rotated and additional tables can be folded out.

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

In an autonomous motor vehicle, the stear-by-wire system enables adjustment of a steering angle and/or a yaw rate of the motor vehicle. In a conventional, manually operated motor vehicle, a driver is involved in these functions. By operating the steering wheel, he can adjust the steering angle and/or the yaw rate of the motor vehicle. A conventional motor vehicle can also have a stear-by-wire system as part of an ESC or ESP assistance function. However, what both motor vehicles have in common is that the main steering or the stear-by-wire system could fail, making maneuvering 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 independently take over the stear-by-wire system, i.e. steering and setting the yaw rate.

Due to safety aspects, the operation of the motor vehicle is often only permitted if there is another additional steering system or steering device as a reserve in addition to a currently existing and operated steering system or steering method.

Autonomous motor vehicles therefore preferably have several steering devices or steering systems, which can be structured hierarchically. Operating the motor vehicle is preferably only possible if the last level of this hierarchy has not yet been reached, i.e. at least one further steering device is available as a reserve beyond the current steering. Additional However, redundancies often lead to additional components and thus to increased complexity and increased costs in vehicle production.

A first aspect of the invention therefore proposes a method for adjusting 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 an adaptation of an already existing control unit.

A target steering angle and/or yaw rate may be provided. Separate target values can also be provided for the steering angle and the yaw rate. Providing the target value can be done manually or automatically. For example, turning a steering wheel can provide a target value manually. A control unit or computing unit can determine the target value for the steering angle and/or the yaw rate based on sensor information and/or external information such as cloud data. In this case, providing the target value means determining the target value by the control unit or computing unit.

Multiple pressure pulses can be determined for a braking unit based on the target value or values. Determining the pressure pulses can be implemented by a control unit or regulating unit. The pressure pulses can in particular be designed as rectangular 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 help of the brake unit. With the help of the multiple pressure pulses, at least one wheel of the motor vehicle can be “braked”. “Braking” preferably means briefly braking the wheel in accordance with the pressure pulse or the multiple pressure pulses. Due to the multiple pressure pulses, a change in the steering angle and/or the yaw rate of the motor vehicle can result.

In a further step, a vehicle parameter and a surface condition of a roadway of the motor vehicle, or the surface condition, are provided. This information can be provided using appropriate sensor technology and/or using external information. For example, a camera can determine the surface condition of the road in conjunction with a corresponding image evaluation. Using digitally stored route data such as a digital friction 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, in particular 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 using 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 made 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 braked based on the target value and the multiple pressure pulses. A pressure pulse can be viewed as a short-term increase and decrease in pressure or vice versa. A pressure pulse can be designed similarly to a delta distribution. The pressure pulse is preferably rectangular or approximately rectangular. The multiple pressure pulses are regulated and/or determined depending on the target value, the actual value, the surface condition of the road and, alternatively, additionally depending on the vehicle parameter, in order to bring the actual value closer to the target value.

In particular, after determining an initial set of pressure pulses, a control loop for determining further additional pressure pulses can follow. With the help of such a control loop, a difference between the target value and the actual value can be reduced. In most cases it is not necessary to adjust a difference between the actual value and the target value to exactly 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, using the control loop or regulation the vehicle parameters and/or the surface condition of the road surface are taken into account as a disturbance variable for the steering angle and/or the yaw rate. These disturbances can cause a deviation between the 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 control and/or determination of the multiple pressure pulses can be carried out iteratively. This means that after several pressure pulses have been determined, a difference between the target value and the actual value is recorded and, based on this difference, several new pressure pulses are determined. This determination can be continued until the actual value is sufficiently close to the target value. With this regulation, the vehicle parameters and/or the surface condition of the road can also be taken into account.

This procedure is preferably used as emergency steering. In particular, the motor vehicle can be brought to a safe standstill using the multiple pressure pulses. Ideally, the motor vehicle is not only brought to a standstill, but also brought to a standstill in a safe place. For example, in a motor vehicle on a highway, 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 the nearest workshop. In this situation, with the help of the method described and the following embodiments, the motor vehicle can still be safely steered from a lane on the highway towards the hard shoulder and brought to a standstill there. Preferably, existing components are used so that an additional emergency steering system can be provided without additional components. In this way, traffic safety can be easily increased.

An additional or alternative embodiment enables the surface condition of the motor vehicle's road surface to be determined using a camera. Additionally or alternatively, the surface quality can be provided by a friction map stored on an external storage unit. The external storage device can be viewed as cloud data storage. Digital route data as well as information regarding the surface condition of the road along a route of the motor vehicle can be stored on this cloud data storage. The multiple pressure pulses can be adjusted accordingly if the surface texture changes, as this can be detected using the camera. For example, a change in 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 indicate a change in the surface condition of the road. For example, a transition from a tarred road to a road with gravel, snow, ice or rain can induce a corresponding change in the camera images. This change can be detected, for example, using optical flow or other image analysis. The image evaluation can be carried out using a neural network that is trained to recognize surface properties. The multiple pressure pulses can be re-determined or calculated as a result of the changed surface properties. In this way, an impending new surface texture can be taken into account when calculating the multiple pressure pulses, which ideally enables the actual value to be aligned more quickly with the target value. In this case, readjustment can be carried out by increasing the pulse widths and/or pulse heights of the several pressure pulses. Additionally or alternatively, a pulse interval between the multiple pressure pulses can be reduced or expanded. Alternatively, the different surface properties can be accessed using the friction map. This means that the steering angle or yaw rate can be determined, controlled and/or adjusted more precisely and quickly.

Additionally or alternatively, a speed sensor can be used to record a speed as a vehicle parameter and a wheel slip derived from this can be taken into account when regulating. Preferably, two associated speeds can be recorded for each two wheels on an axle. Wheel slip can be determined based on these two speeds. As a result, spinning of the wheels can be detected in good time and the multiple pressure pulses can be adjusted so that the motor vehicle can be safely guided at least to a standstill.

Additionally or alternatively, moisture can be detected in an area around the wheels using a microphone and/or an ultrasonic sensor. The surface condition of the road can preferably be derived based on the detected moisture. For example, the ultrasonic sensor or the microphone can be arranged in the area of a wheel arch. With the help of the ultrasonic sensor or the microphone, the characteristic acoustics of a wet road can be detected. This means that the microphone or the ultrasonic sensor can be damp, icy or stony “Hear” the road. Depending on the detected background noise or sound wave characteristics, conclusions can be drawn about the surface condition of the road. This provides another way to easily determine the surface condition of the road.

Additionally or alternatively, a volume of the surface condition of the road can be recorded. The surface quality of the road can be determined based on the volume. For example, the level of moisture can be used to determine the level of adhesion of the road as a surface quality. Instead of the volume, a sound wave characteristic or noise characteristic can additionally or alternatively be detected. The surface condition of the road can be determined using the noise characteristics or sound wave characteristics. The surface condition of the road can include friction of the road to the tire of the vehicle, adhesion of the tire to the road and a wheel contact area of the tire to the road. In conjunction with the weight of the motor vehicle, conclusions can be drawn about the tire contact area. In addition to the surface quality, the tire contact area can also be determined. These parameters can also be taken into account when regulating the multiple pressure pulses.

Determining the tire contact area based on the vehicle weight and/or the surface quality based on the volume can be done analogously in all other embodiments. This allows the steering angle and/or the yaw rate of the motor vehicle to 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. Several pressure pulses can preferably be regulated depending on the type of tire and the tire temperature. Steering the motor vehicle can depend in particular on the type of tire and the tire temperature. For example, winter tires generally have a longer stopping distance in summer. Different tire temperatures can also influence braking or stopping distances. These parameters can also influence the steering behavior of the motor vehicle. The type of tire can be specified, for example, using manual input. In this way, the type of tire can be communicated to the control unit. The tire temperature can be measured using a corresponding temperature sensor. These additional vehicle parameters can also be used to regulate the multiple pressure pulses. The motor vehicle can still be guided safely, at least temporarily, despite the failure of a higher-level steering system.

Additionally or alternatively, a speed, an acceleration and/or a jerk can be measured as the vehicle parameters using a motion sensor of the motor vehicle. The pressure pulses can preferably be regulated depending on these vehicle parameters in order to adjust the steering angle and/or the yaw rate. The parameters in this embodiment can be taken into account in the control in addition to the vehicle parameters and the surface condition. The speed, acceleration and/or jerk can be measured using an inertial sensor, acceleration sensor or speed sensor. The jerk is in particular a derivative of the acceleration or a third derivative of the position with respect to time. The acceleration is preferably a change in speed over time. In addition, the vehicle weight can be recorded and measured as another parameter. This allows the control of the multiple pressure pulses to 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 can exclude these certain target values for the steering angle or yaw rate. In particular, the target value can also be determined depending on object detection around the motor vehicle. The target value is preferably set so 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 corresponds to emergency 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, steered and transferred to a safe final state. Permanent braking of individual wheels on a rear 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 done using multiple pressure pulses be avoided. With the help of braking using the multiple pressure pulses, the motor vehicle can be steered safely in the area of low lateral accelerations. 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 on the braked wheel or wheels. A speed of the motor vehicle can also be recorded. Depending on the braking torque and the speed, a stopping distance of the motor vehicle can be determined. The braking torque can be a momentary braking torque, i.e. it can be variable over time. In particular, several braking torques can be recorded over time. The same can apply to the speed of the motor vehicle. Based on these braking torques and speed values of the motor vehicle, a stopping distance of the motor vehicle can be determined or calculated. This makes it possible to predict 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 the lane on which the motor vehicle is to be brought to a safe stop. In many cases this is the right side of a street. On a country road this can be a parking bay or a shoulder. On a motorway, the target lane can be a shoulder or hard shoulder. The target value can preferably be specified depending on the lane and the target lane. In addition, in this context, the speed of the motor vehicle can 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 location. This makes it possible to steer the motor vehicle from the lane to a safe target lane and bring it to a standstill there. With the help 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 stop 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 a visual 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. This means that other autonomously driving vehicles can be informed about a malfunction or emergency situation in the motor vehicle. Other autonomous vehicles can adapt their driving style accordingly to enable the vehicle to steer and brake safely. In particular, an alternative corridor can be created for the motor vehicle, which can be used for steering and braking. By appropriately braking the other vehicles, the motor vehicle is much more successful in determining a trajectory from the lane to the target lane and using the multiple pressure pulses to maneuver the vehicle there accordingly.

Additionally or alternatively, the provision of the target value for the steering angle and/or the yaw rate as well as the regulation of the pressure pulses can take place 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 depending on detected objects around the motor vehicle. The target value is preferably determined or adjusted in such a way that collisions are avoided. This allows a suitable target value for the steering angle and/or the yaw rate to be determined or specified for regulating the multiple pressure pulses. The target value is preferably determined or defined in advance. To do this, a camera can be used to detect an object in a radius around the motor vehicle. 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 during control. Controlling the yaw rate and/or the steering angle can be carried out more smoothly or more comfortably.

Additionally or alternatively, the pressure pulses can be determined by a control unit, with information regarding the surface quality of the road being stored on the control unit. The multiple pressure pulses can additionally be determined and/or regulated depending on this information regarding the surface quality. This allows the control unit to be preconditioned using the information about the surface condition of the road. A surface condition of a road on a route of the motor vehicle can be taken into account by a sensor before the surface condition of the road is detected. In this way, the multiple pressure pulses can 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 use the vehicle's own sensors and collect sensor data to determine the surface condition of the road. Using 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 in particular designed to determine a plurality of pressure pulses for the brake unit based on a provided target value for a steering angle and/or a yaw rate. The control unit can determine or provide a vehicle parameter and a surface condition of a roadway of the motor vehicle, or determine or provide the surface condition of the roadway of the motor vehicle. The control unit can detect 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 surface condition of the road and alternatively additionally the vehicle parameter Bring the actual value closer to the target value.

The features, examples and advantages mentioned in connection with the process apply mutatis mutandis and analogously to the motor vehicle and vice versa. The vehicle parameter can be recorded or measured using appropriate sensors of the motor vehicle. Inertial sensors, motion sensors, microphones, ultrasonic sensors, cameras and other sensors can be used for this purpose. 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 their 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 accordingly 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 that is designed 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 designed as a cloud unit. The motor vehicle may include a computer program [product] that includes instructions that cause each embodiment of the method to be carried out. The computer program product may 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 the features of the described embodiments.

• 1 eine schematische Seitendarstellung eines Kraftfahrzeugs mit einer Regeleinheit zum einstellen eines Lenkwinkels und/oder einer Gierrate;
• 2 eine schematische Draufsicht auf das Kraftfahrzeug mit einer vor dem Kraftfahrzeug liegenden Fahrbahn sowie unterschiedlichen Fahrspuren;
• 3 eine beispielhafte Darstellung verschiedener Komponenten des Verfahrens zum Einstellen des Lenkwinkels und/oder der Gierrate sowie des Kraftfahrzeugs;
• 4 eine beispielhafte Darstellung für einen Regelkreis zum Einstellen des Lenkwinkels und/oder der Gierrate des Kraftfahrzeugs;
• 5 eine schematische Darstellung mehrerer verschiedener Druckimpulse zum Bremsen eines oder mehrerer Räder des Kraftfahrzeugs, um den Lenkwinkel und/oder die Gierrate einzustellen; und
• 6 ein schematisches Ablaufdiagramm für ein mögliches Verfahren.

This shows:

• 1 a schematic side view of a motor vehicle with a control unit for adjusting a steering angle and/or a yaw rate;
• 2 a schematic top view of the motor vehicle with a road ahead of the motor vehicle and different lanes;
• 3 an exemplary representation of various components of the method for adjusting the steering angle and/or the yaw rate and of the motor vehicle;
• 4 an exemplary representation of a control loop for adjusting the steering angle and/or the yaw rate of the motor vehicle;
• 5 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 a schematic flow diagram for a possible procedure.

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 that can be viewed independently of one another, which also develop the invention independently of one another and are therefore to be viewed 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 that have already been described.

In the figures, functionally identical elements are each provided with the same reference numerals.

In 1 For example, a motor vehicle 1 is shown. The motor vehicle 1 can be designed 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 control several brake units 3 of the motor vehicle 1 in order to brake one or more wheels 4 of the motor vehicle 1.

The control unit 2 can preferably generate control signals to the brake units 3 for the rear wheels 4 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 retrieve information from various components. For example, information or data can be transmitted and/or provided to the control unit 2 using an inertial sensor 5, an external storage unit 6, a sensor 7 of the motor vehicle 1 and/or a central computing unit 9 of the motor vehicle 1. The vehicle's own sensors 7 can be designed, for example, as ultrasonic sensors, microphone, camera, radar sensor, laser scanner and/or lidar sensor. 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 location.

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

In the case of autonomously driving motor vehicles, the motor vehicle 1 usually no longer has a steering wheel 8. Manually operated motor vehicles 1 are usually steered or controlled with a steering wheel 8. In a fully autonomous motor vehicle 1, 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 completely retracted. Stear-by-wire can thus be enabled during a fully automated journey, such as in a Level 4 motor vehicle 1 in accordance with SAE J3016. A driver becomes a pure passenger during a fully automated journey of the motor vehicle 1. This can create more space 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, using rotating seats and additional 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, accidental touching of the steering wheel 8 would not lead to an unwanted vehicle reaction. In fully autonomous motor vehicles 1 according to Level 5, such as robot taxis, there is no longer a driver, so in this case a steering-by-wire system is present.

Stear-by-wire can also be advantageous in conventional, manually operated motor vehicles 1 without automatic driving functions. Various stabilization functions can be used, such as crosswind stabilization or trailer stabilization in conjunction with the Len 8 can be carried out. 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. This means, in particular, that for short periods of time steering is carried out exclusively by the stear-by-wire system in order to safely survive critical traffic situations.

A stear-by-wire system can provide additional comfort. When getting in and out, the steering wheel 8 can be folded away, which can make getting out easier. When parking the motor vehicle 1, a slight movement of the steering wheel 8 may be sufficient to set a required large steering angle α. This can be done, for example, by electronically adjusting the gear ratio between the steering angle α and the steering wheel angle. In addition, stear-by-wire allows you to personalize the steering behavior. Haptic feedback to the driver can be softer or harder, sporty or comfortable, direct or dampened. This setting can, for example, be transferred from an old vehicle to the new one when purchasing a new motor vehicle.

With 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 applies preferably 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 that influences the lateral dynamics (usually mainly the steering) should meet certain safety and availability requirements. Depending on the vehicle manufacturer, a different safety philosophy may be implemented.

In most cases, a high level of security is desired or even required. In order to meet these safety requirements, the stear-by-wire system 8 or steering system must, according to current standards, be designed to be at least single-redundant. This can happen, for example, through double windings in the motor, double control devices as well as double electrical power supplies and double data communication.

In the case of simple redundancy, the motor vehicle 1 is stopped after a short time, particularly after a fault in the stear-by-wire system 8, since a further fault would result in a motor vehicle 1 that cannot be steered. Although it is statistically unlikely that two steering systems would 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 safety strategy is pursued which provides that when the motor vehicle 1 is operated, at least one further fallback level must always be available for adjusting the steering angle α and/or the yaw rate α'. If the last fallback level with respect to the steering 8 is reached, it is preferably provided to bring the motor vehicle 1 to a safe standstill. It is therefore provided in particular that the motor vehicle 1 is only operated in regular operation when the final redundancy has not yet been reached with regard to 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 brought to a safe standstill at a suitable location.

In 2 A top view of the motor vehicle 1 is shown as an example. Two different steering angles α and β as well as yaw rates α' and β' are shown. α and α' represent the target value for the steering angle, while β 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. In front of the motor vehicle 1, a roadway 10 with different lanes FS and ZF is shown. 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. The current lane FS is shown in broken and dotted areas. This is intended to indicate different road conditions. These different road conditions can be detected by the sensor 7 and/or transmitted by the external storage unit 6 as a digital friction value map to the control unit 2 or the vehicle computer 9. In the example of 2 The information for steering is collected by the central vehicle computer 9 and transmitted to the control unit 2. The control unit 2 can control a brake unit 3 in order to briefly brake the rear right wheel 4. This brief braking causes the motor vehicle 1 to be 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 β` of the yaw rate α'. The actual values β, β' are preferably set as part of a control loop in order to bring them closer to the target values α, α'. This control loop can implement a control regarding the steering angle α and/or the yaw rate α'.

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 the roadway 10.

In 3 Some components for such a control loop are shown as examples. The control unit 2 preferably forms the center of the control loop. The target value for the steering angle α or the yaw rate α 'can be specified by the steering wheel 8 or the stear-by-wire system 8. The control unit 2 can calculate or determine several pressure pulses PK for the brake unit 3 based on the target value α, α '. The brake unit 3 can generate braking torque pulses or clamping force pulses using brake calipers or brake shoes. The pressure pulses are preferably designed as short-term rectangular pulses. They can last a few milliseconds and have a pressure level between 1 bar and 100 bar. Due to this temporary short-term braking (braking), the motor vehicle 1 is preferably not fully braked, but rather 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 the motor vehicle 1 is in a safe place and is to be brought to a standstill there. Beforehand, 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 hard shoulder or emergency lane on a motorway. In the case of a country road, the target lane ZF can be an area next to the road.

The control unit 2 can take different information into account to calculate or determine the multiple pressure pulses PK. For example, sensors 7 of the motor vehicle 1 can provide local coefficient of friction information. This local coefficient of friction information can be, for example, road conditions or road conditions that lie 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. Using one or more inertial sensors 5, the actual value β for the steering angle or the actual value β` for the yaw rate can be measured. 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, after each iterative step, a difference between the target value α and the actual value β can be determined. Determining the further pressure pulses PK can depend in particular on this difference.

In 4 A control loop or a control system is shown as an example. The control circuit is used in particular to adjust the steering angle α and/or the yaw rate α' of the motor vehicle 1. The steering angle α or the yaw rate α' are preferably set using several pressure pulses PK. The calculation or determination of these multiple pressure pulses PK is preferably carried out using a control system which the control unit 2 can implement.

Basically, it should be noted that this method represents an additional, but usually final, redundancy with regard to a steering system or a stear-by-wire system 8. The method for adjusting the steering angle α or the yaw rate α' is generally preferably not intended for control operation. However, this can be used to create an additional redundancy or fallback level with regard to the steering 8. Preferably, existing components of the motor vehicle 1 are used, which can easily enable additional redundancy when steering.

First, the steering angle α or the yaw rate α 'is specified using the steering wheel 8 or the stear-by-wire system 8. The target value α or α' is the basis for determining the multiple pressure pulses PK by the control unit 2. In a first step, this calculation can be carried out exclusively on the basis of the target value α or α', especially if there is no information regarding the actual value for the steering angle β or the yaw rate β`. If information regarding the actual values is already available, the control unit 2 can preferably take into account a difference Δα, Δα 'between the target value and the actual value when calculating the multiple pressure pulses PK. A control deviation can be calculated from the difference Δα, Δα' between the target value and the actual value with regard to the steering angle α or the yaw rate α'. 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 several pressure pulses PK to the brake unit 3 as control signals. These multiple pressure pulses PK in particular 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 due to the multiple pressure pulses PK.

In addition, these new actual values β, β` can be influenced by various disturbance variables. These disturbance variables can result, for example, from changing coefficients of friction between the wheels 4 and the road 10. The control unit 2 can preferably take into account the surface condition of the road 10 in advance when determining the multiple pressure pulses PK. This means that the control unit 2 can be suitably preconditioned. For this purpose, the control unit 2 can access data from the vehicle's own sensors 7 and/or from the external storage unit 6 in order to determine the surface condition. 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 α, α'. 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 or transverse jerk when calculating or determining the multiple pressure pulses PK. This in 4 The control method shown can be carried out iteratively. This means in particular that multiple new pressure pulses PK can be calculated for each iterative step. The braking of the rear wheel 4 can thus be continuously adjusted.

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, we will again refer to the 2 referred. In this example, the motor vehicle 1 is to be transferred from the current lane FS to the target lane ZF. Motor vehicle 1 is to be brought to a standstill in the target lane ZF. The target value for the steering angle α or the target value for the yaw rate α 'is adapted to the presence of the other vehicle 1. In particular, these target values are selected so 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 1' can, for example, reduce its speed in order to enable the motor vehicle 1 to safely change the lane to the target lane ZF. The other vehicle 1' 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 framework of the stopping distance AW. If the motor vehicle 1 has arrived in the target lane ZF, the multiple pressure pulses PK can be converted into full braking. 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 storage unit 6 can take the vehicle parameters and the surface condition of the road 10 into account when calculating the multiple pressure pulses PK. For example, the camera 7 can recognize that the current lane FS is wet or has gravel. The dashed area of the FS lane is intended to represent a wet road surface, while the dotted area is intended to represent gravel. These different surface properties usually lead to a deviation between the target value and the actual value for the steering angle α or the yaw rate α'. On the one hand, the method can provide for this difference to be recorded using the inertial sensor 5 and/or to record the vehicle parameters and surface condition 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 location on the roadway 10. In any case, a difference that occurs between the target value and the actual value for the steering angle α or the yaw rate α' is preferably taken into account when calculating or determining the multiple pressure pulses PK.

In 5 Different pressure pulses PK are shown as examples. The x-axis is designed as time t. The y-axis represents a pressure P. In 5 Three different types of modulation for braking are shown as examples. In the left area of 5 The pressure pulses PK can be different with regard to a pulse length bt. A change in the several pressure pulses PK is indicated by the dashed lines. For example, the pulse length bt can be converted into a modified pulse length bt'. In the middle area of the 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 brake pressure changes. That's how they can Pressure pulses are transferred from a current pulse height to a modified pulse height ba'. In the right area of the 5 a change in a pulse interval bd is indicated for the multiple pressure pulses PK. A current pulse spacing bd can be converted into a modified pulse spacing bd'. Adjusting or regulating 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 in terms of their pulse length, their pulse height and the pulse spacing. The pulse lengths bt, bt' preferably have a time extension of 10 milliseconds to 1,000 milliseconds. The pulse heights ba, ba` can reach values between 1 bar and 100 bar. A pulse height 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. This additional redundancy can be achieved by providing additional technology, i.e. additional components, but this is usually associated with higher costs. By braking the rear wheel 4 using the multiple pressure pulses with a correspondingly adjusted pulse length, pulse height and pulse distance, the steering angle α and/or the yaw moment α' can be adjusted 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 α' tends to be. A sequence of multiple pressure pulses PK can set a constant steering angle α over a longer period of time. With the help of a targeted modulation of the pulse length bt, pulse distance ba and/or pulse height bd, the steering angle α or the yaw rate α' can be set accordingly to the target value.

In the 5 The different types of modulation shown in terms of pulse length, pulse height and pulse spacing can be combined with one another. This allows the actual value for the steering angle β and the actual value for the yaw rate β` to be increased or decreased in order to bring the actual value closer to the target value. With the help of this control, the motor vehicle 1 can be kept within a lane even if the steering system 8 fails. This advantageously prevents the front wheel from twisting. If there is a reduced coefficient of friction, which cannot be adjusted, for example due to gravel, rain, snow, ice or other gravel, the control unit 2 can carry out readjustment by adjusting the several pressure pulses PK, as in 5 is shown, enable. In the 4 The control shown as an example 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.

In 6 A further possible control method for adjusting the steering angle α and/or the yaw rate α' of the motor vehicle 1 is shown as an example. First, in a first step S1, the target value for the steering angle α and/or the yaw rate α' can be provided. This provision can take place in the form of recording a traffic situation or based on manual input. In a second step S2, several 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 the motor vehicle 1. In a fourth step S4, an actual value β, β' for the steering angle and/or the yaw rate is preferably detected, for example by means of the sensors 7. In a fifth step S5, the rear wheel 4 of the motor vehicle 1 can be determined based on the target value α, α' and the multiple pressure pulses PK are braked. The multiple pressure pulses PK are preferably regulated and/or determined in the fifth step S5 depending on the target value α, α', the actual value β, β', the vehicle parameter and/or the surface quality of the roadway 10. This serves to approximate the actual value β, β` to the target value α, α'.

Overall, the embodiments and examples mentioned show how the motor vehicle 1 can still be maneuvered safely, at least up to a standstill, even in the event of a complete failure of the steering system 8 or the stear-by-wire system 8, using the multiple pressure pulses PK. 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 particularly because an additional fallback level can be created with regard to the steering.

Reference symbol list

1

vehicle, motor vehicle

2

Controller, control unit

3

Brake unit

4

Wheel, rear wheel

5

Inertial sensor

6

external storage unit

7

Onboard sensor, camera, ultrasonic sensor

8th

Steering wheel, stear-by-wire system

9

central vehicle computer

10

roadway

AW

stopping distance

FS

current lane

ZF

Target lane

α

Steering angle, target value for steering angle

α'

Yaw rate, target value for yaw rate

β

Actual value for steering angle

β'

Actual value for yaw rate

Δα

Difference steering angle

Δα'

Yaw rate difference

PK

pressure pulses

S1

first step

S2

second step

S3

Third step

S4

fourth step

S5

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 (15)

Method for adjusting a steering angle (α) and/or a yaw rate (α') of a motor vehicle (1) with the following steps: - Providing a target value (α, α') for the steering angle (α) and/or the yaw rate (α'), - Determining multiple pressure pulses (PK) for a brake unit (3) based on the target value (α, α'), - Providing a vehicle parameter and a surface quality of a roadway (10) of the motor vehicle (1), or providing the surface quality of the roadway (10) of the motor vehicle (1), - Detecting an actual value (β, β') for the steering angle (α) and/or the yaw rate (α'), - Braking one or more wheels (4) of the motor vehicle (1) based on the target value (α, α') and the multiple pressure pulses (PK), the multiple pressure pulses (PK) depending on the target value (α, α') , the actual value (β, β`), the vehicle parameter and the surface quality of the road (10) are regulated and/or determined in order to bring the actual value (β, β') closer to the target value (α, α'), or wherein the multiple pressure pulses (PK) are regulated and/or determined depending on the target value (α, α'), the actual value (β, β') and the surface quality of the roadway (10) in order to obtain the actual value (β, β') to approach the target value (α, α'). Procedure 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 card stored on an external storage unit (6). Method according to one of the preceding claims, wherein a speed is detected as a vehicle parameter by means of a speed sensor (7) and a wheel slip derived therefrom is taken into account when regulating. Method according to one of the preceding claims, wherein moisture is detected in an area around the wheels by means of a microphone (7) and/or an ultrasonic sensor (7) and the surface quality of the road is derived based on the detected moisture. Method according to one of the preceding claims, wherein a volume is recorded and the surface quality of the road (10) is determined based on the volume. Method according to one of the preceding claims, wherein a type of tire of the wheels (4) and a tire temperature are recorded as vehicle parameters and the plurality of pressure pulses (PK) are additionally regulated depending on the type of tire and the tire temperature. Method according to one of the preceding claims, wherein a speed, acceleration and/or jerk is recorded as the vehicle pa by means of a motion sensor (5) of the motor vehicle rameters are measured, and the pressure pulses (PK) for adjusting the steering angle (α) and / or the yaw rate (α ') are additionally regulated depending on these vehicle parameters. Method according to one of the preceding claims, wherein the target value (α, α') is determined based on the vehicle parameter and/or the surface condition. Method according to one of the preceding claims, wherein the pressure pulses (PK) have a duration of 10 to 1000 milliseconds and a pressure level between 10 to 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 depending on 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 (α, α ') 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 (1') or road users are informed of a malfunction of the motor vehicle (1) by a warning signal. Procedure according to Claim 12 , wherein the target value (α, α') is provided for the steering angle (α) and/or the yaw rate (α') and the pressure pulses (PK) are regulated based on the presence of the other vehicles (1') or road users. Method according to one of the preceding claims, wherein the pressure pulses (PK) are determined by a control unit (2), information relating to the surface quality of the road (10) is stored on the control unit (2) and the plurality of pressure pulses (PK) are additionally dependent on This information regarding the surface quality can be determined and/or regulated. 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 (α, α') for a steering angle (α) and/or yaw rate (α'), - to provide or determine a vehicle parameter and a surface condition of a roadway (10) of the motor vehicle (1), or to provide or determine the surface condition of the roadway (10) of the motor vehicle (1), an actual value (β, β') for to record the steering angle (α) and/or the yaw rate (α'), and - to brake the at least one wheel (4) of the motor vehicle (1) based on the target value (α, α') and the multiple pressure pulses (PK), the multiple pressure pulses (PK) depending on the target value (α, α' ), the actual value (β, β'), the vehicle parameter and the surface quality of the roadway (10) can be regulated and/or determined in order to bring the actual value (β, β') closer to the target value (α, α'). , or wherein the multiple pressure pulses (PK) are regulated and/or determined depending on the target value (α, α'), the actual value (β, β') and the surface quality of the roadway (10) in order to achieve the actual Value (β, β') to approach the target value (α, α').

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