Methods for operating a motor vehicle, as well as motor vehicles with a steering unit

Abstract

Method for operating a motor vehicle (10) with a steering unit (12) which is configured to specify a steering angle of a pair of wheels (14) on the basis of a steering signal and to provide an angle signal characterizing an actual steering angle of the pair of wheels (14), wherein, in the event of a failure to receive the angle signal at a control unit (16) which is configured to provide the steering signal, the actual steering angle is estimated on the basis of at least one sensor signal provided by a vehicle-internal sensor unit (18) characterizing a movement of the motor vehicle (10), and on the basis of this estimate, at least one actuator unit (20) external to the steering unit is positioned such that a target trajectory (22) and / or a safety operation of the motor vehicle (10) is specified on the basis of the steering signal.

Description

[0001] The invention relates to a method for operating a motor vehicle with a steering unit according to patent claim 1. Furthermore, the invention relates to a motor vehicle with a steering unit according to patent claim 10.

[0002] A motor vehicle, such as a passenger car, has a steering unit that serves to steer and thus control the vehicle. The steering unit is often designed so that actuating a gear moves a rack, which can be used to adjust the steering angle of the wheels, particularly the front axle of the vehicle.

[0003] Nowadays it can happen that the steering wheel is no longer mechanically connected to the gear, for example, to specify the steering angle. For example, a steering servo can be controlled purely by an electrical signal, which is provided by the steering wheel and / or a driver assistance system. To receive feedback on the steering position, a sensor is usually provided which reports the steering angle position back, for example to the driver assistance system. The servo of the steering unit forms a steering actuator, for example, which in the case of the steering rack can output a rack position signal, or a sensor unit can be provided to output the signal. It can be provided that, for example, the sensor fails and the signal is not returned.

[0004] DE 10 2017 223 295 A1 discloses a method for operating a motor vehicle, with which, after an initial accident involving the motor vehicle in which the brakes and / or the steering of the front wheels of the motor vehicle were impaired and / or the motor vehicle was involved in a collision, a subsequent accident involving the motor vehicle is to be prevented by activating a rear-wheel steering system.

[0005] The object of the present invention is to provide a method for operating a motor vehicle and a motor vehicle by means of which it is possible to compensate for the failure or absence of an angle signal from a steering unit to a control unit in such a way that the motor vehicle can be advantageously guided or moved in a safe mode.

[0006] This object is achieved according to the invention by the subject matter of the independent patent claims. Advantageous embodiments and further developments of the invention are specified in the dependent patent claims as well as in the description and the drawings.

[0007] A first aspect of the invention relates to a method for operating a motor vehicle with a steering unit which is designed to predetermine a steering angle of a pair of wheels, in particular one mounted on the front axle, on the basis of a steering signal or as a function of a steering signal and to provide an angle signal characterising an actual steering angle of the pair of wheels, for example by means of a sensor device.

[0008] In order that the motor vehicle, which is designed in particular as a passenger car or truck, can be operated advantageously, in the method according to the invention, if the angle signal is not received at a control unit which is designed to provide the steering signal, the actual steering angle is estimated on the basis of at least one sensor signal provided by a sensor unit which characterizes a movement of the motor vehicle, and on the basis of this estimation of the actual steering angle, at least one actuator unit is set or adjusted in such a way that a desired trajectory predetermined on the basis of the steering signal and / or a safety operation of the motor vehicle is predetermined or controlled.

[0009] The control unit comprises, for example, an electronic processing unit and can be configured to provide driver assistance or a driver assistance system. Furthermore, the control unit can be configured to convert the movement of a steering wheel into the steering signal. The steering signal thus specifies a target steering angle, which, for example, depending on the vehicle speed, also specifies a target trajectory along which the vehicle should move based on a driver request or a specification from the driver assistance system.

[0010] The sensor unit that provides the sensor signal characterizing the movement of the motor vehicle can be, for example, an acceleration sensor, so that, for example, a yaw rate of the vehicle can be provided as the at least one sensor signal. The sensor unit can further comprise, for example, a gyroscope and / or a tachometer or the like, so that, for example, the movement of the motor vehicle can be estimated via the sensor signal or based on the sensor signal, for example by odometry. Based on this estimation or the determination of the movement based on the sensor signal, in particular by the control unit, the actual steering angle can be estimated. If the actual steering angle is known, a difference and thus a deviation from the target trajectory can be estimated based on the target angle specified by the steering signal.

[0011] Depending on the difference, the method activates at least one actuator unit. This actuator unit can be, for example, a braking system of the motor vehicle, which can, in particular, brake individual tires of the motor vehicle. Thus, by actuating the actuator unit, the difference between the actual and desired trajectory can be reduced, so that the method, in particular, attempts to achieve the desired trajectory without having to resort to the steering unit. If the difference is too large, or in particular if the difference exceeds a threshold, the safety mode of the motor vehicle can be specified or initiated, which can, for example, involve deceleration or emergency braking.

[0012] In other words, it is processed whether an angle signal, which in particular comprises a sensor signal status of the steering unit, is transmitted by the sensor unit or received at the receiving location, the control unit. If this is not the case, vehicle-specific sensors are used, which correspond in particular to actuators or the at least one actuator unit or multiple actuator units of the motor vehicle, to estimate the missing angle signal. Based on this estimate, the available actuators or actuators are used to maintain a reference trajectory or the target trajectory of the motor vehicle, for example, through rear-wheel steering and / or asymmetric braking.

[0013] This means that the failure of a sensor unit in the steering unit is compensated for by reading sensor signals from other actuators and using them to determine the trajectory or the target steering angle. This results in the advantage that the motor vehicle can be kept at least partially on track or can continue to travel along its target trajectory by positioning or operating at least one actuator unit in such a way that the target trajectory can be influenced, which can compensate for the failure to provide a new steering signal. This also results in the advantage that the motor vehicle can be operated particularly safely by avoiding deviations from the target trajectory or, if the deviation becomes too great, initiating safety mode.

[0014] In an advantageous embodiment of the invention, the at least one sensor signal characterizing the movement of the motor vehicle comprises a yaw rate and / or a slip angle and / or a wheel speed and / or a rear wheel handlebar position. In other words, the actual steering angle can be estimated based on the yaw rate, the slip angle, the wheel speed, or the rear wheel handlebar position. Yaw describes a rotational movement of the motor vehicle and its vertical axis, from which the steering angle can be derived. The slip angle describes an angle between a velocity vector of the motor vehicle and an intersection line between the wheel center plane and the road plane. The slip angle can be used, for example, to determine lateral guidance forces and / or a restoring moment, from which the actual steering angle can be estimated.Based on the position of the rear wheel steering rod, the steering angle of the rear wheels is known, especially if the pair of wheels of the steering unit is mounted on the front axle, allowing the actual steering angle of the vehicle to be estimated. The sensor signal examples mentioned, which are by no means exhaustive, offer the advantage that the steering angle can be estimated particularly simply and / or precisely, allowing the vehicle to be operated particularly advantageously.

[0015] In a further advantageous embodiment of the invention, the angle signal describes a position of a coupling rod, for example a rack, of the steering unit and / or the pair of wheels is arranged on a front axle of the motor vehicle. In other words, the steering unit is designed such that the steering angle of the pair of wheels is specified by moving a coupling rod or a rack, for example by means of a servo unit of the steering unit, so that the angle signal can be determined or specified by the position of the coupling rod or the rack. Additionally or alternatively, the pair of wheels that specifies the steering angle or which is to be set by the steering signal is the pair of wheels on the front axle of the motor vehicle, so that the steering unit is in particular a conventional steering unit.This offers the advantage that the method can be performed with a conventional steering unit, eliminating the need to install a special steering unit on the motor vehicle. This also offers the advantage that the method can be performed particularly cost-effectively.

[0016] A rack is a coupling rod that has a toothed section with teeth.

[0017] An embodiment of the method is advantageous in which the actuator unit or at least one actuator unit comprises a braking device and / or a rear-wheel steering device and / or a spoiler element and / or drive train, whereby the setting of the actuator unit describes a particularly asymmetric braking of at least one front wheel and / or one rear wheel, a steering angle of a rear pair of wheels or the rear-wheel steering and / or the retraction and / or extension of a spoiler element and / or the deceleration or acceleration of at least one front wheel and / or rear wheel. In other words, at least one wheel of the motor vehicle, a front wheel and / or a rear wheel, is braked by a braking device or a drive train in the form of an engine brake, so that an influence on the actual trajectory of the motor vehicle can be exerted by a particularly asymmetric braking of the individual wheels.In addition or as an alternative to the steering device that steers the pair of wheels on the front axle, a rear-wheel steering device is provided, which specifies a steering angle on the pair of wheels on the rear axle, whereby the actual trajectory can also be influenced. Furthermore, it is conceivable that at least one extendable spoiler element, such as a wing element, can also be moved asymmetrically, in particular, or that different spoiler elements are provided for a left and / or right side of the vehicle, so that the actual trajectory can also be influenced by specifically moving the spoiler elements. This has the advantage that the target trajectory can be achieved in a particularly advantageous manner.

[0018] In a further advantageous embodiment of the invention, the safety mode comprises decelerating the entire motor vehicle, in particular to a standstill. In other words, the safety mode initiates a particularly uniform deceleration and thus braking of the motor vehicle, which is intended to bring the motor vehicle to a stop in a controlled manner. For example, the safety mode can be provided by an emergency braking assistance system. This offers the advantage that the motor vehicle can be operated particularly safely.

[0019] In a further advantageous embodiment of the invention, a driving situation of the motor vehicle is detected by means of an environmental sensor, and the positioning of the actuator unit is adapted depending on the detected driving situation. In other words, the motor vehicle has an environmental sensor, such as a camera, which in particular is a panoramic camera or has two camera units, so that the surroundings of the motor vehicle can be detected and the driving situation can be determined or evaluated, for example using computer vision. In this case, the sensor signals of the at least one sensor unit can be used to determine or detect the driving situation, in addition to the data from the environmental sensor, such as a camera image. The positioning of the actuator unit can then be adapted depending on the driving situation.For example, if the vehicle is on a multi-lane road with good visibility and is not occupied by other vehicles or road users, an attempt can be made to achieve the desired trajectory as accurately as possible by adjusting the actuator unit, even if the difference from the actual trajectory is significant. If the road is narrow, for example, and / or there are many other road users on the road, safety mode can be initiated instead. This has the advantage of allowing the vehicle to be operated particularly safely.

[0020] In an advantageous embodiment of the method for operating the motor vehicle, an adapted steering signal is specified before the actuator unit is set, and the estimation of the actual steering angle is then repeated. In other words, after the angle signal fails or is absent, a check is carried out to determine whether the steering unit responds to a correction or confirmation of the steering angle, after an initial estimation of the actual steering angle has already been made. If it is determined that the steering unit responds to the steering signal even though the angle signal is absent, the target trajectory can be maintained by the steering unit, which also comprises an actuator, instead of the one actuator unit. This has the advantage that the target trajectory can be achieved in a particularly advantageous manner.

[0021] In a further advantageous embodiment of the method, the motor vehicle is operated in a manual operating state and / or in an autonomous operating state during the implementation of the method. In other words, the motor vehicle is manually controlled or, in particular, steered by a driver during operation. Additionally or alternatively, a driver assistance system is capable of operating the motor vehicle at least partially autonomously, so that, for example, lateral guidance of the motor vehicle is the responsibility of the driver assistance system. This results in the advantage that the presented method can be used particularly flexibly for operating the motor vehicle, since it is irrelevant for the method whether the motor vehicle is operated manually or autonomously.

[0022] In a further advantageous embodiment of the method, the safety mode is specified based on a difference value between an actual trajectory or the actual trajectory and the desired trajectory. In other words, the actual trajectory achievable by setting the actuator unit, which can be estimated based on the at least one sensor signal, and the actually desired desired trajectory, which should be maintained, for example, due to a traffic situation, are compared, and a difference or the difference value is determined based on the comparison. If the latter assumes a particular, specific, predeterminable value or exceeds this value, the implementation of the safety mode is initiated. Thus, if the actual trajectory deviates significantly from the desired trajectory, emergency braking of the motor vehicle can be initiated, for example.This has the advantage that the vehicle can be operated particularly safely.

[0023] A second aspect of the invention relates to a motor vehicle. The motor vehicle according to the second aspect of the invention comprises a steering unit configured to specify a steering angle of a wheel pair based on a steering signal and to provide an angle signal characterizing an actual steering angle of the wheel pair. Furthermore, the motor vehicle comprises a control unit configured to provide the steering signal or to specify a target steering angle, a sensor unit configured to provide a sensor signal characterizing a movement of the motor vehicle, and an actuator unit configured to specify the movement of the motor vehicle.

[0024] The motor vehicle according to the invention is designed to estimate the actual steering angle based on the at least one sensor signal if the angle signal is not received at the control unit and to position the actuator unit based on this estimate in such a way that a desired trajectory, which is predetermined in particular based on the steering signal, and / or a safety operation of the motor vehicle can be predetermined.

[0025] Advantageous embodiments and further developments as well as advantages of the first aspect of the invention are to be regarded as advantageous embodiments and further developments as well as advantages of the second aspect of the invention and vice versa.

[0026] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combinations, but also in other combinations or on their own, without departing from the scope of the invention.

[0027] It shows: Fig. 1 is a schematic plan view of a motor vehicle with a steering unit; and Fig. 2 a schematic flow diagram of a method for operating the motor vehicle according to Fig. 1.

[0028] Fig. 1 shows a schematic plan view of a motor vehicle 10 with a steering unit 12, which is designed to specify a steering angle of a wheel pair 14 based on a steering signal output, for example, by a control unit 16, i.e., the steering angle of the wheel pair 14 is set, in particular, as the actual steering angle. The steering unit 12 is further designed to provide or output an angle signal that characterizes the actual steering angle of the wheel pair 14. The motor vehicle 10 further comprises the control unit 16, which is designed to provide the steering signal that specifies or is intended to specify a target steering angle. Furthermore, the motor vehicle 10 comprises a sensor unit 18, by means of which a sensor signal characterizing a movement of the motor vehicle 10 can be provided.

[0029] In order for the motor vehicle 10 to be able to compensate for a lack of the angle signal at the control unit 16, for example due to a defect in a sensor of the steering unit 12, the motor vehicle 10 is designed to estimate the actual steering angle on the basis of the at least one sensor signal of the sensor unit 18 in the event of a lack of reception of the angle signal at the control unit 16 and to set the at least one actuator unit 20 on the basis of this estimate in such a way that a desired trajectory 22 and / or a safety operation of the motor vehicle 10, which is predetermined on the basis of the steering signal or in principle, can be predetermined or controlled.

[0030] Thus, based on the Fig. 1 shown motor vehicle which in Fig.2 using a flowchart. This method serves to operate the motor vehicle 10, which comprises the steering unit 12, which is designed to specify a steering angle of the wheel pair 14 based on a steering signal and to provide the angle signal characterizing the actual steering angle of the wheel pair 14. In the method, if the angle signal is not received at the control unit 16, which is designed to provide the steering signal, the actual steering angle is estimated based on at least one sensor signal provided by the sensor unit 18 and characterizing a movement of the motor vehicle. Based on this estimate, the at least one actuator unit 20 is set such that a target trajectory 22 specified based on the steering signal or the specified target trajectory and / or a safety operation of the motor vehicle 10 is specified or set.

[0031] The flowchart shows the three steps S1, S2, and S3. In step S1, it is checked whether the angle signal is being received at the control unit 16. If it is not received, the actual steering angle is estimated in step S2 based on the at least one sensor signal characterizing the movement of the motor vehicle 10. Subsequently, in step S3, based on the estimate, the at least one actuator unit 20 is set such that the motor vehicle 10 is moved or controlled such that the predetermined target trajectory 22 is reached or, if this cannot be reached, the safety mode is specified or initiated.

[0032] It may be advantageous if, as an intermediate step of the presented method, an adapted steering signal is specified by the control unit 16 before setting the actuator unit in step 3 and the estimation is then repeated, so that it can be checked whether the steering unit 12 reacts to the steering signal despite the absence of the angle signal, so that the steering unit 12 can be used to achieve the desired trajectory 22.

[0033] It is equally advantageous if the sensor signal characterizing the movement of the motor vehicle 10 includes a yaw rate and / or a slip angle and / or a wheel speed and / or a rear wheel handlebar position. Thus, the at least one sensor unit 18 can be configured, for example, as an acceleration sensor and / or gyroscope, as a tachometer, as a steering angle sensor, or the like. The yaw rate describes, for example, a yaw 28 of the motor vehicle 10, represented by an arrow, which describes a rotation of the motor vehicle 10 about its vertical axis, from which, for example, the actual steering angle can be derived. The actual steering angle can also be determined from the wheel speed, in particular an individual wheel speed for each wheel 30 of both the front wheel pair 14 and the rear wheel pair 32.

[0034] An actuator unit 20 that can advantageously influence the movement of the motor vehicle 10 or a trajectory of the motor vehicle 10 is, for example, a braking device 24 and / or a rear-wheel steering device 26 and / or a spoiler element and / or a drive train. Thus, by adjusting the at least one actuator unit 20, the movement of the motor vehicle 10 can be influenced such that the motor vehicle 10 can be moved along the desired trajectory 22.

[0035] In order to influence the movement of the motor vehicle 10 and thus its actual trajectory in order to achieve the desired trajectory 22, the setting of the actuator unit can in particular be an asymmetric braking or acceleration of the individual wheels 30 of the motor vehicle 10, which is represented by the arrows 34, wherein the length of the arrows represents the strength of a respective deceleration and thus of the respective braking of the respective wheel 30.

[0036] For an advantageous embodiment of the steering unit 12, the steering angle is specified by means of a coupling rod 36 designed as a rack, whereby the angle signal thus describes a position of the rack. The pair of wheels 14 is advantageously arranged on a front axle 38 of the motor vehicle 10, so that the steering unit 12 is designed as a conventional front-axle steering system of the motor vehicle 10.

[0037] The safety mode can, in particular, comprise deceleration down to a standstill of the motor vehicle 10 and can be carried out, for example, by an emergency braking assistant, which comprises the at least one electronic processing unit with the control unit 16. In addition, an environmental sensor 40 can be provided, by which, in particular, for example, in combination with the sensor signal of the at least one sensor unit 18, a driving situation of the motor vehicle 10 can be estimated and, depending on the detected driving situation, a setting of the at least one actuator unit 20 can be adapted, or a distinction can be made between the setting of the actuator unit 20 and the specification of the safety mode.It has also proven advantageous if a difference value between the actual trajectory and the target trajectory 22 is determined and, based on the size of the difference value, a decision is made as to whether the at least one actuator unit 20 is set and / or the safety mode is activated.

[0038] The motor vehicle 10 can be operated both in a manual operating state in which a driver controls the motor vehicle 10 and / or in an at least partially autonomous operating state in which the motor vehicle 10 is controlled by a driver assistance system, so that the method is also suitable for manual as well as autonomous operation of the motor vehicle 10.

[0039] The motor vehicle 10 and the method can ensure that the motor vehicle 10, which is particularly designed as a passenger car, does not become uncontrollable if the position of the steering actuator, which represents, for example, a servo of the steering unit 12, is unknown. Thus, information from at least one sensor unit 18 is collected in the form of at least one sensor signal, and an actual steering angle is determined based on this information. Countermeasures can be taken by adjusting the at least one actuator or actuator unit 20 or by performing the safety mode to ensure the controllability and / or stability of the motor vehicle 10. List of reference symbols 10 motor vehicle 12 Steering unit 14 pairs of wheels 16 Control unit 18 Sensor unit 20 Actuator unit 22 Target trajectory 24 Braking device 26 Rear wheel steering device 28 Yaw 30 wheels 32 rear pair of wheels 34 Arrow 36 coupling rod 38 front axle 40 Environmental sensor S1 first step S2 second step S3 third step QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 223 295 A1

[0004]

Claims

[1] Method for operating a motor vehicle (10) with a steering unit (12) which is designed to predetermine a steering angle of a pair of wheels (14) on the basis of a steering signal and to provide an angle signal characterising an actual steering angle of the pair of wheels (14), wherein, in the event of a failure to receive the angle signal at a control unit (16) which is designed to provide the steering signal, the actual steering angle is estimated on the basis of at least one sensor signal provided by a sensor unit (18) which characterises a movement of the motor vehicle (10), and based on this estimation, at least one actuator unit (20) is positioned such that a desired trajectory (22) and / or a safety operation of the motor vehicle (10) predetermined on the basis of the steering signal is predetermined. [2] Method according to claim 1, characterized bythat the at least one sensor signal comprises a yaw rate and / or a slip angle and / or a wheel speed and / or a rear wheel handlebar position. [3] Method according to claim 1 or 2, characterized by that the angle signal describes a position of a coupling rod (36) of the steering unit (12) and / or the pair of wheels is arranged on a front axle (38) of the motor vehicle (10). [4] Method according to one of the preceding claims, characterized by that the at least one actuator unit (20) comprises a braking device (24) and / or a rear wheel steering device (26) and / or a spoiler element and / or drive train and the setting of the actuator unit describes a braking and / or acceleration of at least one front wheel and / or rear wheel, a steering angle of a rear pair of wheels (32) and / or the retraction and extension of the spoiler element. [5] Method according to one of the preceding claims, characterized bythat the safety operation includes slowing down the entire motor vehicle (10). [6] Method according to one of the preceding claims, characterized by that a driving situation of the motor vehicle (10) is detected by means of an environmental sensor and the setting of the at least one actuator unit (20) is adapted depending on the detected driving situation. [7] Method according to one of the preceding claims, characterized by that an adapted steering signal is specified before setting the at least one actuator unit (20) and then the estimation is repeated. [8] Method according to one of the preceding claims, characterized by that the motor vehicle (10) is operated in a manual operating state and / or in an autonomous operating state. [9] Method according to one of the preceding claims, characterized bythat the safety operation is specified based on a difference value between an actual trajectory and the target trajectory (22). [10] Motor vehicle (10) with a steering unit (12) which is designed to predetermine a steering angle of a wheel pair (14) on the basis of a steering signal and to provide an angle signal characterising an actual steering angle of the wheel pair (14), with a control unit (16) which is designed to provide the steering signal, with a sensor unit (18) by which a sensor signal characterising a movement of the motor vehicle (10) can be provided, and with at least one actuator unit (20) by which the movement of the motor vehicle (10) can be predetermined, wherein the motor vehicle (10) is designed to estimate the actual steering angle on the basis of the at least one sensor signal in the event of failure to receive the angle signal at the control unit (16) and to set the at least one actuator unit (20) on the basis of this estimate in such a way thatthat a desired trajectory (22) and / or a safety operation of the motor vehicle (10) can be specified based on the steering signal.

Images