DE102022204291A1 - Method for operating a steer-by-wire steering system and steer-by-wire steering system - Google Patents

Abstract

The invention relates to a method for operating a steer-by-wire steering system (1), wherein the steer-by-wire steering system (1) has a steering wheel actuator (3) and a steering actuator (2), which are coupled to one another in terms of signaling, wherein the steering actuator (2) is controlled for setting a target steering variable (20) derived from at least one steering wheel angle (10) detected on a steering wheel (50) on at least one steerable wheel (51) using first control parameters (6), wherein the steering wheel actuator (3) for adjusting a feedback torque (11) on the steering wheel (50) derived from at least one detected actual steering variable (21) of the at least one steerable wheel (51) is controlled using second control parameters (7), wherein in At least one selected driving situation when controlling the steering wheel actuator (3) changed second control parameters (7x) are used or are controlled without feedback. The invention further relates to a steer-by-wire steering system (1).

Description

The invention relates to a method for operating a steer-by-wire steering system and a steer-by-wire steering system.

Steer-by-wire (SbW) steering systems, which can be used in large series in the automotive sector in the future, have no mechanical connection between a steering wheel and a steering gear. An electric machine is used to provide the driver with realistic hand torque (“force feedback”). This regulates a defined hand torque on the steering wheel. The hand torque is usually determined from various factors, such as the vehicle speed, the steering wheel angle and many other variables.

An actuator system of the steer-by-wire steering system, which converts the steering wheel movements into steering movements, usually includes a steering actuator (road wheel actuator, RWA), which implements a target steering angle specified for the steerable wheels by moving a rack, and a steering wheel actuator (force feedback actuator, FFA), which generates a hand torque as feedback on the steering wheel. The controllers in the FFA and RWA are in a synchronous state, resulting in precise steering behavior and an authentic steering feel.

From the DE 10 2019 108 166 A1 a control unit for controlling a steering system of a vehicle is known. The steering system includes a steering means that can be actuated by a driver of the vehicle to adjust a steering center angle, and a steering actuator that is configured to adjust a wheel angle of a wheel of the vehicle for steering the vehicle depending on steering means data with respect to the steering center angle. The control unit is set up to detect that the driver of the vehicle has caused a reversal of the steering direction of the steering means. Furthermore, the control unit is set up, in response to this, to cause the steering actuator to cause a reversal of the steering direction of the wheel, even if, in advance of the reversal of the steering direction of the steering means, there is an offset between a target wheel angle, which is due to The steering center angle caused by the driver corresponds to the actual wheel angle set by the steering actuator.

The invention is based on the object of improving a method for operating a steer-by-wire steering system and a steer-by-wire steering system, in particular with regard to comfort and functionality.

The object is achieved according to the invention by a method with the features of patent claim 1 and a steer-by-wire steering system with the features of patent claim 10. Advantageous embodiments of the invention result from the subclaims.

In particular, a method for operating a steer-by-wire steering system is provided, wherein the steer-by-wire steering has a steering wheel actuator and a steering actuator, which are coupled to one another in terms of signaling, the steering actuator for adjusting one of at least one A target steering variable derived from a steering wheel detected steering wheel angle is controlled on at least one steerable wheel using first control parameters, wherein the steering wheel actuator is controlled to adjust a feedback torque on the steering wheel derived at least from a detected actual steering variable of the at least one steerable wheel using second control parameters is, wherein in at least one selected driving situation changed second control parameters are used when controlling the steering wheel actuator or are controlled without feedback.

Furthermore, in particular, a steer-by-wire steering system is created, comprising a steering actuator, set up for adjusting a target steering variable derived at least from a steering wheel angle detected on a steering wheel, on at least one steerable wheel, a steering wheel actuator, set up for adjusting one of at least one detected Actual steering variable of the feedback torque derived from at least one steerable wheel on the steering wheel, a steering actuator module, set up to control the steering actuator using first control parameters, a steering wheel actuator module, set up to control the steering wheel actuator using second control parameters, the steering wheel actuator module being set up to do so, in to use changed second control parameters in at least one selected driving situation when controlling the steering wheel actuator or to control them without feedback.

The method and the steer-by-wire steering system make it possible to partially or completely decouple the control of the steering wheel actuator from the actual steering variable. In particular, the changed second control parameters can ensure that strong changes in the actual steering variable, which are caused, for example, by vibrations of the wheel on an uneven road surface, have only a dampened effect or no effect at all on a feedback torque generated on the steering wheel. This can increase comfort for a driver so that the driver only experiences vibrations to a reduced extent or not noticeable at all on the steering wheel. This is achieved by using changed second control parameters in at least one selected driving situation when controlling the steering wheel actuator or by controlling it without feedback. This allows the controls of the steering wheel actuator and the steering actuator to be decoupled from one another. In particular, the actuators can be operated using asynchronous controls.

An advantage of the method and the steer-by-wire steering system is that in selected driving situations in which, for example, uneven road surfaces (potholes, cobblestones, level crossings, etc.) lead to a high rack speed and/or force amplitude, can be designed to be more comfortable, since a Decoupling the position and force control between the steering wheel actuator and the steering actuator leads to a reduced feedback torque on the steering wheel. The driver therefore receives reduced or no feedback in the form of a feedback or hand torque on the steering wheel, which increases comfort. For example, it can be provided to detect uneven road surfaces using a sensor system set up for this purpose (e.g. cameras, acceleration sensors, etc.) and an evaluation of recorded sensor data from the sensor system set up for this purpose. For example, known pattern recognition methods and/or machine learning methods can be used here.

Separate modified second control parameters can also be provided for different selected driving situations.

The steer-by-wire steering system basically works as follows: an actual steering wheel angle is detected on a steering wheel using a suitable sensor system. Based on at least the recorded actual steering wheel angle, a target steering variable is determined for at least one steerable wheel. The target steering variable can be, for example, a target rack position or a target steering lift rod position or a target steering angle. Based on the determined target steering size and a recorded actual steering size (e.g. actual rack position or an actual steering lift rod position or an actual steering angle), a steering size difference (e.g. rack position difference or steering lift rod difference or steering angle difference) is determined. The determined steering variable difference is supplied to the control in the steering actuator module as an input value (in particular as a control deviation). The steering actuator module uses a controller and the first control parameters to determine a phase current for the steering actuator, which in particular leads to a displacement force on a rack, which leads to a reduction in the steering size difference (in particular the rack position difference or the steering lift rod difference or the steering angle difference). In the opposite direction, a target steering wheel angle is determined from at least the detected actual steering wheel size and a steering wheel angle difference between the determined target steering wheel angle and the detected actual steering wheel angle is determined. This specific steering wheel angle difference is supplied to the control in the steering wheel actuator module as an input value (in particular as a control deviation) for the control with the second control parameters, the steering wheel angle difference being determined by generating a (feedback) torque (which can also be referred to as a feedback torque or hand torque). Steering wheel is removed using the steering wheel actuator.

The first control parameters and the second control parameters each include, in particular, at least one control parameter. Several control parameters can also be included. A control parameter is in particular a parameter that influences the control behavior of the control system. A change in the control parameters includes in particular a change in at least one control parameter.

The control of the steering wheel actuator receives, for example, the steering wheel angle difference between the actual steering wheel angle and the target steering wheel angle as an input value (in particular as a control deviation). Based on this, the control determines a feedback torque that the steering wheel actuator should implement on the steering wheel. A second control parameter can, for example, be a prefactor that indicates to what extent the steering wheel angle difference is converted into a feedback torque or how quickly the steering wheel angle difference is reduced. In the changed second control parameters, for example, to implement damping, a changed, in particular reduced, prefactor can reduce the specific feedback torque. In the case of complete decoupling, in particular no feedback torque at all is generated on the steering wheel or a steering wheel angle difference caused by a movement of the at least one steerable wheel (normally) at least no longer leads to any feedback torque on the steering wheel.

Parts of the steer-by-wire steering system, in particular the steering wheel actuator module and the steering actuator module, can be designed individually or collectively as a combination of hardware and software, for example as program code that is executed on a microcontroller or microprocessor. However, it can also be provided that parts are installed individually or combined as an application-specific integrated circuit (ASIC) and / or field programmable gate field (FPGA) are formed.

In one embodiment it is provided that changed first control parameters are used in the control of the steering actuator in at least one selected further driving situation or that the steering actuator is controlled independently of the steering wheel angle. This also makes it possible to decouple the steering actuator, i.e. in the opposite direction. A change in a steering wheel angle is then only converted to a lesser extent into a steering movement of the at least one steerable wheel. For this purpose, for example, a certain steering size difference (in particular rack position difference or steering lift rod difference or steering angle difference) can be reduced with a lower rack speed. This achieves damping. As a first control parameter, for example, a prefactor in front of the rack speed can be reduced (changed). Separate modified first control parameters can also be provided for different selected additional driving situations.

In one embodiment it is provided that a selected driving situation is determined when a rate of change of the detected actual steering variable is greater than or equal to a predetermined maximum value. This makes it particularly easy to detect large force effects on the at least one steerable wheel and the rack. Such forces can be caused, for example, by uneven road surfaces. The specified maximum value is specified, for example, as a measure of length per second or as degrees per second (e.g. max. 2°, 3° or 5° per second, etc.). The rate of change of the recorded actual steering variable is then continuously determined and compared with the specified maximum value. If the specified maximum value is reached or exceeded, the selected driving situation is recognized and the second control parameters are changed. In particular, for example, a prefactor is adjusted such that a feedback torque is reduced compared to the use of the (unchanged) second control parameters. Several different selected driving situations can also be provided, each of which is linked to associated second control parameters. In one embodiment it is provided that a selected further driving situation is determined when a vehicle speed is less than a predetermined speed threshold. This means that in driving situations in which the vehicle is not moved at all or only moves very slowly, for example when parking/out of parking spaces and maneuvering, it can be achieved that changed first control parameters are used to control the steering actuator. In particular, the first control parameters can be changed in such a way that a steering variable difference between a target steering variable and an actual steering variable is reduced more slowly, for example by limiting a rack speed and / or changing time constants of the control (e.g. time constants that reduce the reduction the steering size difference can be enlarged). Limiting the rack speed results in lower forces on the steering actuator, a pinion, and the rack. This can reduce wear and increase service life. Particularly in large and heavy vehicles, such as an off-road vehicle or a sport utility vehicle (SUV), forces of several kN can occur on the rack when the vehicle is at a standstill at high rack speeds. The specified speed threshold can be, for example, a few kilometers per hour (e.g. 3 or 5 km/h etc.).

In one embodiment it is provided that a selected driving situation and/or a selected further driving situation is determined when uneven road surfaces are detected. In this way, driving comfort for the driver can be increased in particular, since feedback moments on the steering wheel caused by uneven road surfaces can be reduced or dampened or completely prevented. To detect unevenness in the road, a road can be detected, for example, by means of at least one camera and/or acceleration sensors can be used, with the unevenness in the road being recognized, for example, by means of pattern recognition methods and/or machine learning methods known per se.

In one embodiment it is provided that a transition between control parameters and changed control parameters and/or a transition between a control with second control parameters and a feedback-free control and/or a transition between a control with first control parameters and a steering wheel angle-independent control takes place step by step. This allows the transitions to be designed in such a way that they are not noticeable to a driver. For this purpose, the control parameters can, for example, be linearly converted into the changed control parameters. The transition between the control with the second control parameters and the feedback-free control and / or the transition between the control with the first control parameters and the steering wheel angle-independent control can also take place in that the target steering wheel angle determined from the actual steering variable or the target steering variable determined from the actual steering wheel angle is gradually less taken into account in the respective control. A transition can take place in particular in a linear form. In principle, other forms are also possible (gradual, progressive, degressive, etc.).

In one embodiment it is provided that control with predetermined control parameters takes place during and/or upon termination of the feedback-free control and/or the steering wheel angle-independent control. As a result, the control can also be carried out in a predetermined manner without taking into account the target steering wheel angle determined from the actual steering wheel angle or the target steering variable determined from the actual steering wheel angle. When terminating, the respective regulations must be synchronized with each other again. This is done using the specified control parameters. For example, it can be provided to use fixed control parameters for this, for example control parameters that were determined based on empirical tests and/or based on simulations.

In one embodiment it is provided that control parameters used in the past are saved, with control taking into account the stored control parameters taking place during and/or upon termination of the feedback-free control and/or the steering wheel angle-independent control. This allows the last used (not changed) control parameters to be used during and/or when ending the feedback-free control and/or the steering wheel angle-independent control. In particular, this enables a return to the control parameters that were used before the respective controls were decoupled. In this way, steering behavior and feedback of the steer-by-wire steering system in particular can be kept constant. For example, the stored control parameters of the controls can be trained for the last N control steps (with N > 1). This can be done, for example, with the help of artificial intelligence methods, for example with the help of neural networks. In addition, current vehicle parameters can also be taken into account when determining the control parameters, for example a vehicle speed and/or a steering angle. Alternatively, it can also be provided that the control parameters are determined only based on the last control step (N = 1). In one embodiment it is provided that the functionality of the steering wheel actuator is checked during the feedback-free control of the steering wheel actuator and/or that the functionality of the steering actuator is checked during the steering wheel angle-independent control of the steering actuator. This allows a diagnosis of the functionality of the steering actuator and the steering wheel actuator to be carried out while they are decoupled.

• 1a) Diagnose im Lenkaktuator (vom Fahrer am Lenkrad nicht wahrnehmbar):
  • Hierbei wird für den Lenkradaktuator eine entkoppelte Regelung (weiter oben beschrieben) aktiviert, während der Lenkaktuator einen Diagnosezyklus durchläuft. Durch die Entkopplung bleibt die Durchführung des Diagnosezyklus unbemerkt für den Fahrer.
• 1 b) Diagnose im Lenkaktuator (für den Fahrer am Lenkrad wahrnehmbar):
  • Hierbei wird dieselbe Diagnose wie im Beispiel 1a) ausgeführt, es erfolgt jedoch keine Entkopplung. Die ggf. auftretenden Lenkradbewegungen sind für den Fahrer wahrnehmbar.
  • Dies kann bei einer Diagnose von Sensoren und Aktoren im Lenkaktuator notwendig sein.
  • Durch eine Handerkennung kann der Fahrer bewusst davon abgehalten werden, während des Diagnosezyklus in das Lenkrad einzugreifen, sodass die Diagnose ungestört durchgeführt werden kann.
• 2) Diagnose im Lenkradaktuator:
  • Hierbei wird für den Lenkradaktuator ein Diagnosezyklus durchlaufen. Durch die Entkopplung bleibt die Durchführung des Diagnosezyklus für den Lenkaktuator folgenlos. Durch eine
  • Handerkennung kann eine Situation erkannt werden, in welcher der Fahrer die Hände nicht am Lenkrad hat und in welcher die Diagnose dann durchlaufen wird.

The availability of all sensors and actuators in the steering system is an essential component for a safe overall system. Due to the exclusively signaling connection, additional position sensors are required to record the actual steering wheel angle and the actual steering size. For example, through an external signal (camera-based, V2X information, GPS coordinates, etc.) and/or an internal signal (previous parking situation / traffic light situation / vehicle start detected), the steering system receives information about an upcoming diagnostic cycle. This is important, among other things, when starting the vehicle, since position synchronization between the steering wheel and the at least one steerable wheel when stationary may have been changed by a previous control of infotainment applications or in the workshop (lift). By decoupling the position and force control when starting the vehicle or during a phase of standstill during operation, it is possible to run through separate, i.e. independent, diagnostic cycles and/or a common diagnostic cycle on the steering actuator side and on the steering wheel actuator side, which checks the sensors and actuators for functionality and mechanical smoothness/stiffness. This increases the safety of the steering system through increased diagnostic coverage. The diagnostic cycle can be carried out in different ways, which are described below as examples:

• 1a) Diagnosis in the steering actuator (not noticeable by the driver on the steering wheel):
  • Here, a decoupled control system (described above) is activated for the steering wheel actuator while the steering actuator goes through a diagnostic cycle. Due to the decoupling, the execution of the diagnostic cycle remains unnoticed by the driver.
• 1 b) Diagnosis in the steering actuator (perceivable by the driver on the steering wheel):
  • The same diagnosis is carried out as in example 1a), but there is no decoupling. Any steering wheel movements that may occur are noticeable to the driver.
  • This may be necessary when diagnosing sensors and actuators in the steering actuator.
  • Hand recognition can consciously prevent the driver from touching the steering wheel during the diagnostic cycle, so that the diagnosis can be carried out undisturbed.
• 2) Diagnostics in the steering wheel actuator:
  • A diagnostic cycle is run through for the steering wheel actuator. Due to the decoupling, the execution of the diagnostic cycle for the steering actuator has no consequences. By a
  • Hand detection can be used to detect a situation in which the driver does not have his hands on the steering wheel and in which the diagnosis is then carried out.

• - mechanische Leichtgängigkeit: Erkennung von Defekten (bspw. Riemenabriss/Sprung etc.),
• - mechanische / elektrische Schwergängigkeit: Erkennung von Verschmutzungen und/oder Blockierungen, oder elektrischer Motor der Aktuatoren erzeugt nicht ausreichend Kraft um Schwergängigkeit zu überwinden,
• - Diagnosefunktion für Leistungselektronik / Motor: über Erfassen / Auswerten des Phasenstroms (Batteriestroms) können Defekte erkannt werden,
• - Diagnosefunktion Winkelsensorik: Motorbewegung und Vergleich der Winkel (verschiedene Messprinzipien können hierbei Common-Cause Fehler (CCF) reduzieren.

Carrying out diagnostic cycles can include the following points:

• - mechanical ease of movement: detection of defects (e.g. belt break/crack etc.),
• - mechanical / electrical sluggishness: detection of contamination and/or blockages, or the electric motor of the actuators does not generate sufficient force to overcome sluggishness,
• - Diagnostic function for power electronics / motor: defects can be detected by detecting / evaluating the phase current (battery current),
• - Diagnostic function angle sensors: motor movement and comparison of the angles (different measuring principles can reduce common cause errors (CCF).

By carrying out the diagnostic cycles, latent errors in mechanical or electronic components in the subsystems (steering wheel actuator, steering actuator) can be detected, thereby increasing the reliability of emergency operation in the event of a redundancy failure. Particularly for potential CCF of mechanical components, it is possible to detect wear-related damage in a timely manner through regular diagnostic cycles and to ensure that the vehicle is in a safe state for the driver. The possibility of decoupling the actuators in the steer-by-wire steering system described enables a robust design of the detection mechanisms, since wear-related damage usually becomes noticeable when high performance requirements are required. In particular, when there is decoupling, the actuators can also be operated in operating ranges that cannot be implemented with a coupling (e.g. extreme values, etc.).

Further features for the design of the steer-by-wire steering system result from the description of embodiments of the method. The advantages of the steer-by-wire steering system are the same as in the embodiments of the method.

• 1 eine schematische Darstellung einer Ausführungsform des Steer-by-Wire-Lenksystems;
• 2 ein schematisches Ablaufdiagramm einer Ausführungsform des Verfahrens zum Betreiben eines Steer-by-Wire-Lenksystems;

The invention is explained in more detail below using preferred exemplary embodiments with reference to the figures. Show here:

• 1 a schematic representation of an embodiment of the steer-by-wire steering system;
• 2 a schematic flow diagram of an embodiment of the method for operating a steer-by-wire steering system;

The 1 shows a schematic representation of an embodiment of the steer-by-wire steering system 1. The steer-by-wire steering system 1 includes a steering actuator 2, a steering wheel actuator 3, a steering actuator module 4 and a steering wheel actuator module 5. The steering actuator module 4 and the steering wheel actuator module 5 are connected to each other in terms of signaling. The steer-by-wire steering system 1 is designed in particular to carry out the method described in this disclosure.

The steering actuator 2 is set up to adjust a target steering variable 20 derived at least from a steering wheel angle 10 detected on a steering wheel 50 on at least one steerable wheel 51. The target steering variable 20 can be, for example, a target rack position or a target steering lift rod position or a target steering angle. The steering wheel angle 10 is detected using a steering wheel angle sensor (not shown). The steering wheel angle sensor can also be part of the steering wheel actuator. The steering actuator 2 in particular includes an electrical machine that can change a rack position via a pinion and thereby sets the target steering size 20.

The steering wheel actuator 3 is set up to adjust a feedback torque 11 on the steering wheel 50 that is derived at least from a detected actual steering variable 21 of the at least one steerable wheel 51. The actual steering variable 21 can be, for example, an actual rack position or an actual steering lift rod position or an actual steering angle. The steering wheel actuator 3 in particular includes an electric machine that can apply a torque to the steering wheel 50, whereby a target steering wheel angle 12 derived from at least the actual steering variable 21 can be set. The actual steering variable 21 is detected using a suitable steering variable sensor (not shown), which can also be part of the steering actuator 2.

The steering actuator module 4 is set up to control the steering actuator 2 using first control parameters 6. This can be, for example, a PID controller. The input variable of the PID controller is then in particular the specific target steering variable 20.

The steering wheel actuator module 5 is set up to control the steering wheel actuator 3 using second control parameters 7. This can be, for example, a PID controller. The input variable of the PID controller is then in particular the steering size difference, in particular a rack position difference or steering lift rod difference or steering angle difference.

In normal operation, the controls of the steering actuator module 4 and the steering wheel actuator module 5 work in particular completely synchronously, that is, a movement on the steering wheel 50 leads to a change in the actual steering variable 21 and a movement of the wheels 51 or a change in the actual steering variable 21 leads to a feedback torque 11 and a change in the steering wheel angle on the steering wheel 50. Here, the first and second control parameters 6, 7 are selected in particular such that a steering feel is designed like that of an electromechanical steering system.

The steering wheel actuator module 5 is set up to use changed second control parameters 7x or to regulate them without feedback in at least one selected driving situation when controlling the steering wheel actuator 3. In this way, in particular, a coupling between the steering wheel 50 and the wheels 51 can be dampened or completely eliminated. As part of the change, for example, the feedback torque 11 can be reduced using a prefactor suitable for this purpose. For this purpose, the steering wheel actuator module 5 receives, for example, a control signal 15 that causes the change from the second control parameters 7 to the changed second control parameters 7x. The control signal 15 can be generated and provided, for example, by a vehicle control 52 of a vehicle in which the steer-by-wire steering system 1 is installed.

In particular, it can be provided that different changed second control parameters 7x are provided or used for different selected driving situations.

It can be provided that in at least one selected further driving situation changed first control parameters 6x are used in the control of the steering actuator 2 or that the steering actuator 2 is controlled independently of the steering wheel angle 10. As part of the change, for example, a speed at which a control deviation is reduced can be reduced, for example by specifying a changed maximum rack speed. For this purpose, the steering actuator module 4 also receives, for example, the control signal 15 (or another control signal provided for this purpose) that causes the change from the first control parameters 6 to the changed first control parameters 6x.

In particular, it can be provided that different changed first control parameters 6x are provided or used for different selected further driving situations.

It can be provided that a selected driving situation is determined when a rate of change of the detected actual steering variable 21 is greater than or equal to a predetermined maximum value. For this purpose, a rate of change is determined from a time profile of the detected actual steering variable 21, for example by means of the steering actuator module 4, and compared with a predetermined threshold value. When the predetermined threshold value is reached or exceeded, the selected driving situation is determined and subsequently the second control parameters 7 are changed to the changed second control parameters 7x. For this purpose, the steering actuator module 4 communicates with the steering wheel actuator module 5.

It can be provided that a selected further driving situation is determined when a vehicle speed is less than a predetermined speed threshold. For this purpose, the steering wheel module 4 queries the vehicle speed 16, for example from the vehicle controller 52, and compares the queried vehicle speed 16 with the predetermined speed threshold value. If the queried vehicle speed 16 falls below the predetermined speed threshold, a selected further driving situation is determined and the steering actuator module 4 changes the first control parameters 6 into the changed first control parameters 6x. It can also be provided here that different further first control parameters 6x are provided or used for different selected further driving situations.

It can be provided that a selected driving situation and/or a selected further driving situation is determined when uneven road surfaces are detected. For this purpose, a road can be recorded, for example, using a camera (not shown) and uneven road surfaces can be recognized in captured camera images. This is done in particular using a camera on the vehicle. In principle, the steer-by-wire steering system 1 can also have one or more cameras for this purpose. The detection of uneven road surfaces can be carried out using the vehicle control 52 or another device (not shown) of the vehicle. If bumps in the road are detected, the vehicle control 52 then transmits the corresponding information corresponding control signal 15 to the steering actuator module 4 and/or the steering wheel actuator module 5.

It can be provided that a transition between the control parameters 6, 7 and the changed control parameters 6x, 7x and/or a transition between a control with second control parameters 7, 7x and a feedback-free control and/or a transition between a control with first control parameters 6, 6x and a steering wheel angle-independent control step by step. For example, such a transition can take place by linearly blending/transferring the control parameters 6, 6x, 7, 7x or with the help of another (mathematical) transition rule.

It can be provided that control with predetermined control parameters 8, 9 takes place during and/or at the end of the feedback-free control and/or the steering wheel angle-independent control. Predetermined control parameters 8, 9 can, for example, correspond to the last control parameters 6, 7 before decoupling.

It can be provided that control parameters 6, 7 used in the past are stored, with control taking into account the stored control parameters 6, 7 taking place during and/or upon termination of the feedback-free control and/or the steering wheel angle-independent control. For this purpose, the actuator modules 4, 5 have, for example, memories (not shown) in which the last used control parameters 6, 7 are stored and can be called up again if necessary and in particular used as predetermined control parameters 8, 9.

It can be provided that the functionality of the steering wheel actuator 3 is checked during the feedback-free control of the steering wheel actuator 5 and/or that the functionality of the steering actuator 2 is checked during the steering wheel angle-independent control of the steering actuator 2. In this way, for example, after starting the vehicle before starting the journey, the functionality of the steering wheel actuator 3 and/or the steering actuator 4 can be checked, as has already been described above in the general description.

The 2 shows a schematic flowchart of an embodiment of the method for operating a steer-by-wire steering system. The steer-by-wire steering system is designed in particular according to one of the embodiments described above. As part of the method, measure 100 and measure 200 in the steering actuator module are carried out in parallel to one another in the steering wheel actuator module. Measure 100 includes measures 101 to 104. Measure 200 includes measures 201 to 204.

In measure 101, the steering wheel actuator is regulated using second control parameters to adjust a feedback torque on the steering wheel derived at least from a detected actual steering variable of the at least one steerable wheel.

Measure 102 checks whether a selected driving situation exists or not. Such a selected driving situation can exist, for example, when bumps in the road are detected and a control signal from a vehicle control or other device is subsequently received by the steering wheel actuator module. If there is no selected situation, proceed to action 101.

If, on the other hand, there is a selected driving situation, the process continues with measure 103. In measure 103, the second control parameters are changed and the control takes place with the changed second control parameters. It can be provided here that the change takes place taking into account the respective selected driving situation, so that different changed second control parameters are used for the different selected driving situations. Alternatively, it can be provided that regulation takes place without feedback.

Measure 104 checks whether the selected driving situation still exists or not. If the selected driving situation still exists, the process continues with measure 103. If, on the other hand, the selected driving situation has ended, measure 101 is continued, that is, control is again carried out using the original second control parameters.

Measures 201 to 204 are carried out in an analogous manner, with the measures relating to selected further driving situations and first control parameters as well as alternatively a steering wheel angle-independent control.

Further embodiments of the method have already been described above with reference to the steer-by-wire steering system.

Reference symbol list

1

Steer-by-wire steering system

2

Steering actuator

3

Steering wheel actuator

4

Steering actuator module

5

Steering wheel actuator module

6

first control parameters

6x

changed first control parameters

7

second control parameter

7x

changed second control parameters

8th

specified control parameters

9

specified control parameters

10

(Actual) steering wheel angle

11

feedback moment

12

Target steering wheel angle

15

Control signal

16

Vehicle speed

20

Target steering size

21

Actual steering size

50

steering wheel

51

wheel

52

Vehicle control

100-104

Measures of the procedure

200-204

Measures of the procedure

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The 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

• DE 102019108166 A1 [0004]

Claims (10)

Method for operating a steer-by-wire steering system (1), the steer-by-wire steering system (1) having a steering wheel actuator (3) and a steering actuator (2), which are coupled to one another in terms of signals, wherein the steering actuator (2) is controlled for setting a target steering variable (20) derived from at least one steering wheel angle (10) detected on a steering wheel (50) on at least one steerable wheel (51) using first control parameters (6), wherein the steering wheel actuator (3) is controlled for setting a feedback torque (11) on the steering wheel (50) derived from at least one detected actual steering variable (21) of the at least one steerable wheel (51) using second control parameters (7), wherein in at least one selected driving situation, changed second control parameters (7x) are used when controlling the steering wheel actuator (3) or are controlled without feedback. Procedure according to Claim 1 , characterized in that in at least one selected further driving situation changed first control parameters (6x) are used in the control of the steering actuator (2) or the steering actuator (2) is controlled independently of the steering wheel angle (10). Procedure according to Claim 1 or 2 , characterized in that a selected driving situation is determined when a rate of change of the detected actual steering variable (21) is greater than or equal to a predetermined maximum value. Procedure according to one of the Claims 2 or 3 , characterized in that a selected further driving situation is determined when a vehicle speed is less than a predetermined speed threshold. Method according to one of the preceding claims, characterized in that a selected driving situation and/or a selected further driving situation is determined when uneven road surfaces are detected. Method according to one of the preceding claims, characterized in that a transition between control parameters (6,7) and changed control parameters (6x,7x) and/or a transition between a control with second control parameters (7.7x) and a feedback-free control and/ or a transition between a control with first control parameters (6.6x) and a steering wheel angle-independent control takes place gradually. Method according to one of the preceding claims, characterized in that control with predetermined control parameters (6,7) takes place during and/or at the end of the feedback-free control and/or the steering wheel angle-independent control. Method according to one of the preceding claims, characterized in that control parameters (6,7) used in the past are stored, with control taking into account the stored control parameters ( 6.7). Method according to one of the preceding claims, characterized in that the functionality of the steering wheel actuator (3) is checked during the feedback-free control of the steering wheel actuator (3) and/or that the functionality of the steering actuator (2) is checked during the steering wheel angle-independent control of the steering actuator (2 ) is checked. Steer-by-wire steering system (1), comprising: a steering actuator (2), set up to adjust a target steering variable (20) derived from at least one steering wheel angle (10) detected on a steering wheel (50) on at least one steerable wheel (51), a steering wheel actuator (3), set up to adjust a feedback torque (11) on the steering wheel (50) derived from at least one detected actual steering variable (21) of the at least one steerable wheel (51), a steering actuator module (4), set up to control the steering actuator (2) using first control parameters (6), a steering wheel actuator module (5), set up to control the steering wheel actuator (3) using second control parameters (7), wherein the steering wheel actuator module (5) is set up to use changed second control parameters (7x) in at least one selected driving situation when controlling the steering wheel actuator (3) or to control them without feedback.

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