Method and device for determining the steering angle specification for the steering of a vehicle

Abstract

A device for determining a steering angle target for a motor vehicle is described. The device is configured to determine trajectory data relating to the desired trajectory for the motor vehicle and, based on this trajectory data, to determine a permissible range of values ​​for the steering angle target. The device is further configured to limit the steering angle target to this permissible range.

Description

[0001] The invention relates to a method and a corresponding device designed to effect safe and reliable automated steering of a vehicle.

[0002] A vehicle may have a driving function that is designed to automatically steer the vehicle laterally and, if necessary, longitudinally. The driving function may be designed according to SAE Level 3 or higher.

[0003] This document addresses the technical challenge of achieving a particularly safe and reliable automated lateral guidance system for a vehicle.

[0004] The problem is solved by each of the independent claims. Advantageous embodiments are described, inter alia, in the dependent claims. It should be noted that additional features of a claim dependent on an independent claim, without the features of the independent claim itself or only in combination with a subset of the features of the independent claim, can constitute a separate invention independent of the combination of all features of the independent claim, which can be made the subject of an independent claim, a divisional application, or a subsequent application. This applies equally to technical teachings described in the description, which can constitute an invention independent of the features of the independent claims.

[0005] According to one aspect, a device for determining a steering angle target for the steering of a motor vehicle is described. The steering angle target can be transmitted as a setpoint for the steering angle to a steering control unit. The control unit can be configured, for example by means of a controller, to actuate the (electrical) steering actuator depending on the steering angle target in order to produce an actual steering angle value that corresponds as closely as possible to the steering angle target.

[0006] As part of a driving function for automated lateral guidance of the vehicle, current steering angle specifications can be repeatedly determined at a sequence of successive time points and transferred to the steering control unit.

[0007] The device can be configured to determine trajectory data relating to the desired trajectory for the motor vehicle. The device can be configured (e.g., based on sensor data from one or more of the vehicle's environmental sensors and / or based on a digital map of the road network traveled by the vehicle) to determine the upcoming course of the roadway traveled by the motor vehicle. The trajectory data, in particular the desired trajectory, can be determined based on the upcoming course of the roadway, especially to ensure that the vehicle follows the upcoming course of the roadway.

[0008] The device is further configured to determine a permissible range of steering angle input values ​​for the vehicle's steering based on the trajectory data. In particular, the device can be configured (based on the trajectory data) to determine a permissible minimum and a permissible maximum steering angle input value as limits to the permissible range. The permissible minimum value can, for example, be between 5% and 30% below the permissible maximum value.

[0009] Alternatively or additionally, the permissible range of values, in particular the permissible minimum value and / or the permissible maximum value, may depend on one or more of the following parameters: • The expected time for manual (steering) intervention by the vehicle's driver (especially for a driving function trained to SAE Level 2 or lower); the expected time can be determined based on sensor data relating to the driver (where the sensor data relates, for example, to the driver's attention to the driving task); the permissible range of values ​​can be reduced as the expected time increases and / or increased as the expected time decreases; • The expected time for activating a (multiple) redundant fallback level of the driving function (especially for a driving function designed according to SAE Level 3 or higher); the expected time may depend on the design of the driving function (and may be predefined); the permissible range of values ​​may be reduced with increasing expected time and / or increased with decreasing expected time; and / or • The dynamics with which the (diverse) redundant fallback level can intervene (in the steering) to prevent an unacceptably large deviation from the intended trajectory (e.g., to leave the currently driven lane, for example, by more than a predefined distance threshold (e.g., 10 cm) to the lane marking); the dynamics may depend on the design of the driving function (and may be predefined); the permissible value range can be increased with increasing dynamics and / or decreased with decreasing dynamics.

[0010] The device can therefore be set up to determine the permissible value range in a particularly precise manner, based on • the time required to activate a redundant fallback level of the driving function; • the expected time required for a driver of the motor vehicle to manually take over lateral control; and / or • the dynamics of the redundant fallback level with regard to the automated lateral guidance of the motor vehicle.

[0011] The trajectory data, in particular the target trajectory, can specify the target curvature of the vehicle's path. The device can be configured to determine the permissible value range based on the target curvature of the vehicle's path. Based on the target curvature of the vehicle's path, a curvature-based steering angle can be determined (which, for example, ensures that the vehicle's path has the target curvature). The permissible value range of the steering angle setting can be determined such that the curvature-based steering angle lies, particularly in its midpoint, within the permissible value range.

[0012] As previously explained, a current steering angle setting can be repeatedly determined at each point in time within a sequence. Furthermore, a current permissible value range for the respective steering angle setting can be repeatedly determined at each point in time within the same sequence.

[0013] The device is further configured to limit the steering angle setting to the permissible range. In particular, the device can be configured to use the permissible minimum or maximum value as the steering angle setting if the vehicle's trajectory tracking controller determines a steering angle setting outside the permissible range for tracking the target trajectory.

[0014] The device may also be configured to control the steering of the motor vehicle depending on the, possibly limited, steering angle specification in order to operate a driving function with automated lateral guidance of the motor vehicle.

[0015] By taking into account the upcoming course of the road and / or the desired trajectory to be driven, a particularly safe, comfortable and reliable determination, especially limitation, of the steering angle specification can be achieved.

[0016] The device can be configured to determine a current steering angle target for each sequence of successive time points, based on the trajectory data and the trajectory tracking controller, and to determine a current permissible value range based on the trajectory data. The device can also be configured to check whether the current steering angle target is within the current permissible value range. Furthermore, the device can be configured to limit the current steering angle target to a value from the current permissible value range, in particular to the permissible minimum or maximum value of the current permissible value range, if the current steering angle target is not within the current permissible value range. This ensures safe and comfortable automated lateral control of the vehicle at all times.

[0017] The device can be configured to detect when the current steering angle input is repeatedly outside the permissible range for a specific period of time. In response to this detection, the automated lateral control function can be downgraded (e.g., to a reduced level of automation). This downgrading of the driving function can (especially if the driving function is designed according to SAE Level 2 or lower) include prompting the driver to take over lateral control. Furthermore, after the driver has taken over lateral control, the downgrading of the driving function can include deactivating the automated lateral control. This allows for particularly safe automated lateral control of the vehicle.

[0018] As previously explained, the driving function can have a (multiple) redundant fallback level (especially if the driving function is designed according to SAE Level 3 or higher). In normal operation, the driving function can be operated based on sensor data from one or more environmental sensors and / or using one or more lateral control actuators of the vehicle. The redundant fallback level can utilize one or more environmental sensors and / or one or more lateral control actuators of the vehicle that are not used for automated lateral control of the vehicle in the normal operation of the driving function. For example, the redundant fallback level can use a lidar sensor and / or an inertial measurement unit that is not used in the normal operation of the vehicle.

[0019] The device can be configured to detect when the current steering angle setting is outside the permissible range for a specific period of time. Furthermore, the device can be configured to activate the (multiple) redundant fallback level of the driving function for automated lateral control of the vehicle in response to this detection. Automated lateral control can then be achieved using this (multiple) redundant fallback level of the driving function. This allows for particularly safe automated lateral control of the vehicle.

[0020] The target trajectory can specify target values ​​for one or more state variables of the motor vehicle, where the one or more state variables include, for example, • the lateral offset of the motor vehicle within the lane being traveled by the motor vehicle; • the curvature of the road traveled by the motor vehicle; and / or • the heading angle of the vehicle.

[0021] The target trajectory can specify target values ​​for one or more vehicle parameters for a specific (time) planning horizon. This planning horizon can, for example, encompass 6 seconds or more of driving time.

[0022] The device can be configured, within the framework of the trajectory tracking controller, to determine actual values ​​for one or more state variables and to compare these actual values ​​with the corresponding setpoint values ​​for the one or more state variables in order to determine a control error. The steering angle target can then be determined in a particularly robust and precise manner, especially using a control unit, based on the control error.

[0023] According to another aspect, a (road) motor vehicle (in particular a passenger car or a truck or a bus or a motorcycle) is described that includes the device described in this document.

[0024] According to one aspect, a procedure for determining a steering angle target for the steering of a motor vehicle is described. The procedure includes determining trajectory data relating to the desired trajectory for the motor vehicle, as well as determining, based on the trajectory data, a permissible range of values ​​for the steering angle target. The procedure further includes ensuring that the steering angle target is limited to the permissible range of values.

[0025] It should be noted that the aspects described in connection with the device, in particular the claims described in connection with the device, are also applicable to the method as corresponding process features.

[0026] Another aspect described is a software (SW) program. The SW program can be configured to run on a processor (e.g., on a vehicle's control unit) and thereby execute the procedure described in this document.

[0027] Another aspect describes a storage medium. This storage medium can include a software program configured to run on a processor and thereby execute the procedure described in this document.

[0028] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspect of the methods, devices, and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways. Features listed in parentheses are to be understood as optional features.

[0029] The invention will now be described in more detail using exemplary embodiments. Fig. 1. Exemplary components of a vehicle; Fig. 2a an example of a road layout; Fig. 2b an exemplary time course of the steering angle or the steering angle specification; Fig. 2c an exemplary trajectory tracking controller; and Fig. 3 A flowchart of an exemplary procedure for limiting the steering angle specification for the steering of a vehicle.

[0030] As stated at the outset, this document deals with increasing the safety and / or reliability of the automated lateral guidance of a vehicle 100. In this context, it shows Fig. 1 An exemplary vehicle 100 with one or more environmental sensors 102, each configured to acquire sensor data (also referred to as environmental data) relating to the environment of the vehicle 100. Examples of environmental sensors 102 are a camera, a radar sensor, a lidar sensor, an ultrasonic sensor, etc.

[0031] A (control) device 101 of the vehicle 100 can be configured to evaluate environmental data, e.g., to detect one or more objects (e.g., other vehicles) in the vicinity of the vehicle 100. The device 101 can further be configured to effect automated longitudinal and / or lateral control of the vehicle 100 based on the environmental data, in particular based on the one or more detected objects. For this purpose, one or more longitudinal and / or lateral control actuators 103 (e.g., a drive motor, a braking device, and / or a steering device) of the vehicle 100 can be controlled.

[0032] The vehicle 100 may further comprise one or more vehicle sensors 105 which are configured to acquire sensor data relating to the state of the vehicle 100, e.g., relating to the vehicle speed, steering angle, and / or acceleration of the vehicle 100. The sensor data from the one or more vehicle sensors 105 may be taken into account during the automated longitudinal and / or lateral control of the vehicle 100.

[0033] Fig. Figure 2a shows an exemplary driving situation in which vehicle 100 is traveling on a roadway 200 which has a specific ahead profile. The ahead profile of the roadway can be determined, for example, based on sensor data from one or more environmental sensors 102 and / or based on roadway data relating to roadway 200 from a digital map of the road network traveled by vehicle 100.

[0034] The device 101 of the vehicle 100 can be configured (based on the sensor data of one or more environmental sensors 102 and / or on the road surface data) to determine a target trajectory 210 for the vehicle 100 for travel along the road surface 200, i.e., along the road's course. The target trajectory 210 can be determined for a specific, forward-looking (time-based and / or distance-based) planning horizon. The planning horizon can be, for example, 50 meters or more, or 2 seconds or more.

[0035] The device 101 can further be configured to operate one or more actuators 103 of the vehicle 100 depending on the determined target trajectory 210, in order to cause the vehicle 100 to follow the target trajectory 210. For this purpose, a trajectory tracking controller 250 can be used, as exemplified in Fig. 2c is shown.

[0036] The target trajectory 210 can specify target values ​​for one or more state variables of the vehicle 100 as a function of time or distance. Examples of state variables relating to the lateral guidance of the vehicle 100 are: • the lateral offset of the vehicle 100 (within the roadway 200); • the vehicle's heading angle 100° (within the lane 200°); and / or • the curvature of the vehicle's path 100.

[0037] An actual value 263 of one or more state variables can be determined (based on the sensor data from one or more environmental sensors 102 and / or one or more vehicle sensors 105). Based on this, a control error 261 can be determined by comparison with the target trajectory 210 (in the reference unit 251). The control error 261 can depend on the deviation of the actual value from the target value of one or more state variables.

[0038] The trajectory tracking controller 250 typically includes a control unit 252, which is configured to determine a manipulated variable 262 based on the control error 261. The manipulated variable 262 can, for example, be a target steering angle for the vehicle 100. The manipulated variable 262 can be transmitted as a setpoint to an actuator 103, in particular to the steering system of the vehicle 100. The actuator 103 is then prompted to implement the manipulated variable 262 (e.g., using a controller), for instance, to produce an actual steering angle that corresponds to the steering angle target. As a result, an updated actual value 263 is generated, which affects one or more state variables of the vehicle 100.

[0039] Similarly, for a sequence of successive time points, an updated control variable 262 can be determined as a target value for the lateral guidance actuator 103, in particular an updated steering angle value for the steering, in order to effect automated lateral guidance of the vehicle 100.

[0040] The device 101 can be configured to limit the target value 262 determined within the framework of the trajectory tracking control to the actuator 103. In particular, a permissible value range for the target value 262, for example for the steering angle target, can be determined. The permissible value range is typically limited by a permissible minimum value and a permissible maximum value.

[0041] If a setpoint 262 is determined (by the control unit 252) that lies outside the permissible range, the setpoint 262 can be limited to the permissible minimum value (if the setpoint 262 is smaller than the permissible minimum value) or to the permissible maximum value (if the setpoint 262 is larger than the permissible maximum value). This ensures functionally safe operation of the trajectory tracking control.

[0042] The device 101 can be configured to determine the permissible range of values ​​of the target specification 262 for the steering angle on the basis of the target trajectory 210, in particular on the basis of the target value of the curvature of the vehicle's travel path 100.

[0043] Fig. Figure 2b shows an example of the steering angle 220 as a function of the distance traveled or time 230 (starting from a current position or time 231). Based on the target value of the vehicle's path curvature (at the current position or time 231), it can be determined how the steering angle 225 must be changed for the subsequent journey along the target trajectory 210. This expected change in the steering angle 225 can be taken into account when determining the permissible value range 223. In the example shown, for instance, a permissible minimum value 221 can be chosen that is further removed from the steering angle 220 curve than the permissible maximum value 222 (in order to account for the expected change in the steering angle 225).

[0044] A sliding limiter is thus described for limiting the target value 262 for the steering angle 225, in which information regarding the upcoming lane profile of the traveled lane is taken into account within the limiter, while still providing sufficient scope for steering angle control. In this way, functionally safe operation of the steering system can be achieved even with relatively low steering dynamics.

[0045] By taking into account the information about the upcoming track alignment, a relatively narrow limiter (with a relatively small or narrow permissible value range 223) can be used, since typically only a relatively small, short-term disturbance compensation needs to be allowed and not all possible track alignments within the operating range of the driving function need to be taken into account.

[0046] Based on the sensor data from one or more environmental sensors 102 and / or based on the road data from a digital map, a lane model of the currently traveled lane can be determined. Based on this, a target trajectory 210 can be determined, which specifies, for example, a target value for the curvature of the vehicle's path 100 (for the current time).

[0047] The target value of the curvature can be directly fed into and / or considered in a limiter at the output of the target steering angle calculation (i.e., the target value 262). Based on information about the vehicle's own motion 100 (e.g., based on sensor data from one or more vehicle sensors 105), the target value of the curvature can be converted into a corridor (i.e., a permissible value range 223) within which the target steering angle 262 may lie. The target steering angle 262 can then be limited to the values ​​221 and 222 specified by the corridor 223.

[0048] If the determined corridor 223 is continuously exceeded by the target value 262 for a specific minimum duration, a switch to a (multiple) redundant fallback level of the driving function (e.g., the SAE Level 3 / 4 / 5 driving function) can be triggered. The duration for activating this (multiple) redundant fallback level and / or the dynamics of the fallback level can be used to define the permissible value range 223.

[0049] Fig.Figure 3 shows a flowchart of a (possibly computer-implemented) procedure 300 for determining a steering angle target 262 for the steering of a motor vehicle 100. The procedure 300 can be executed by a control device 101 of the vehicle 100. The procedure 300 can be executed repeatedly at a sequence of successive time points in order to repeatedly determine a current steering angle target 262 and, based on this, to effect automated lateral control of the motor vehicle 100.

[0050] Procedure 300 comprises determining 301 trajectory data with respect to the target trajectory 210 to be driven by the motor vehicle 100. The trajectory data can be based on the course of the roadway 200 traveled by the motor vehicle 100. The trajectory data can, for example, specify (at the current time) the target value of the curvature of the route to be driven by the motor vehicle 100. The trajectory data, in particular the target trajectory 210, can be updated repeatedly for the individual time points.

[0051] Procedure 300 further comprises determining 302 a permissible value range 223 of the steering angle specification 262 for the steering of the motor vehicle 100 based on the trajectory data. Based on the target value for the curvature of the route to be traveled, specified by the trajectory data, a curvature-based steering angle for the vehicle 100 can be determined. The permissible value range 223 can be determined such that the curvature-based steering angle lies, in particular at its midpoint, within the permissible value range 223.

[0052] Alternatively or additionally, the permissible value range 223 can be determined such that, when using a steering angle setting 262 that lies within the permissible value range 223, leaving the currently driven lane can be avoided even if it is necessary to switch to a (multiple) redundant fallback level of the driving function. When defining the value range 223, the time until the fallback level is activated and / or the possibility or ability of the fallback level to dynamically steer the vehicle 100 back to the center of the currently driven lane can be taken into account.

[0053] Furthermore, the procedure 300 includes the effect 303 that the steering angle input 262 is limited to the permissible value range 223. In particular, it can be ensured that (at no point in time) the steering angle input 262 to the steering system lies outside the (currently determined) permissible value range 223. This allows for particularly comfortable, safe, and reliable automated lateral control of the vehicle 100.

[0054] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the figures are intended only to illustrate the principle of the proposed methods, devices, and systems by way of example.

Claims

[1] Device (101) for determining a steering angle specification (262) for the steering of a motor vehicle (100); wherein the device (101) is configured, to determine trajectory data relating to a target trajectory (210) to be driven for the motor vehicle (100); to determine a permissible range of values ​​(223) for the steering angle specification (262) for the steering of the motor vehicle (100) based on the trajectory data; and to ensure that the steering angle specification (262) is limited to the permissible range of values ​​(223). [2] Device (101) according to claim 1, wherein the trajectory data include a target curvature of a motor vehicle's travel path (100); and the device (101) is set up to determine the permissible range of values ​​(223) on the basis of the target curvature of the travel path of the motor vehicle (100). [3] Device (101) according to claim 2, wherein the device (101) is configured, to determine a curvature-based steering angle based on the target curvature of the motor vehicle's travel path (100); and to determine the permissible range of values ​​(223) of the steering angle specification (262) such that the curvature-based steering angle lies in the middle within the permissible range of values ​​(223). [4] Device (101) according to one of the preceding claims, wherein the device (101) is configured, to determine the prior course of a roadway (200) traveled on by the motor vehicle (100); and to determine the target trajectory (210) based on the preceding course of the roadway (200). [5] Device (101) according to one of the preceding claims, wherein the device (101) is configured, to determine a permissible minimum value (221) and a permissible maximum value (222) of the steering angle specification (262) as limits of the permissible value range (223); and to use the permissible minimum value (221) or the permissible maximum value (222) as the steering angle specification (262) if a steering angle specification (262) is determined by a trajectory tracking controller (250) of the motor vehicle (100) for tracking the target trajectory (210) which is outside the permissible range of values ​​(223). [6] Device (101) according to one of the preceding claims, wherein the device (101) is configured for a sequence of successive time points, to determine a current steering angle specification (262) based on the trajectory data and using a trajectory tracking controller (250); to determine a current permissible range of values ​​(223) based on the trajectory data; to check whether the current steering angle setting (262) is within the current permissible range (223) or not; and to limit the current steering angle setting (262) to a value from the current permissible range of values ​​(223) if the current steering angle setting (262) is not within the current permissible range of values ​​(223). [7] Device (101) according to claim 6, wherein the device (101) is configured to limit the current steering angle setting (262) to a permissible minimum value (221) or a permissible maximum value (222) of the current permissible value range (223). [8] Device (101) according to claim 6, wherein the device (101) is configured, to recognize that the current steering angle setting (262) is not within the current permissible range (223) for a certain period of time; and in response to the detection, to cause the driving function to be downgraded to automated lateral control of the motor vehicle (100); wherein the downgrading of the driving function includes a request to a driver of the motor vehicle (100) to take over the lateral control of the motor vehicle (100). [9] Device (101) according to one of claims 6 to 7, wherein the device (101) is configured, to recognize that the current steering angle setting (262) is not within the current permissible range (223) for a certain period of time; and in response to the detection, to cause a redundant fallback level of the driving function for automated lateral control of the motor vehicle (100) to be activated; wherein the redundant fallback level uses one or more environmental sensors (102) and / or one or more lateral control actuators (103) of the motor vehicle (100) that are not used in normal operation of the driving function for automated lateral control of the motor vehicle (100). [10] Device (101) according to one of the preceding claims, wherein the device (101) is configured to determine the permissible range of values ​​(223) based on a time period for activating a redundant fallback level of the driving function; an expected time period for a manual takeover of lateral control by a driver of the motor vehicle (100); and / or a dynamics of the redundant fallback level with regard to the automated lateral guidance of the motor vehicle (100). [11] Device (101) according to one of the preceding claims, wherein the target trajectory (210) specifies target values ​​for one or more state variables of the motor vehicle (100); which include one or more state variables, at least one of which a lateral offset of the motor vehicle (100) within a lane travelled by the motor vehicle (100); a curve in a route traveled by the motor vehicle (100); and / or a heading angle of the motor vehicle (100); and the device (101) is set up within the framework of a trajectory tracking controller (250), To determine actual values ​​(263) for one or more state variables; to compare the actual values ​​(263) with the corresponding target values ​​for the one or more state variables in order to determine a control error (261); and to determine the steering angle specification (262) using a control unit (252) based on the control error (261). [12] Device (101) according to one of the preceding claims, wherein the device (101) is configured to control the steering of the motor vehicle (100) depending on the, possibly limited, steering angle specification (262) in order to operate a driving function with automated lateral control of the motor vehicle (100). [13] Method (300) for determining a steering angle specification (262) for the steering of a motor vehicle (100); wherein the method (300) comprises, Determining (301) trajectory data with respect to a target trajectory (210) to be driven for the motor vehicle (100); Determine (302), based on the trajectory data, a permissible range of values ​​(223) for the steering angle specification (262) for the steering of the motor vehicle (100); and Cause (303) that the steering angle specification (262) is limited to the permissible range of values ​​(223).

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