Method for at least partial compensation of disturbance oscillations in a steering system designed as a steer-by-wire steering system

Abstract

The invention relates to a method for at least partially compensating for disturbance oscillations (10) in a steering system (12) designed as a steer-by-wire steering system, in particular during operation of the steering system (12) in a vehicle (14), wherein the steering system (12) comprises at least one wheel steering angle controller (16) having a steering control element (18), in particular a steering rack, for changing a wheel steering angle of at least one vehicle wheel (20) and at least one detection sensor system (22) associated with the steering control element (18) for detecting status information of the steering control element (18), wherein a detection signal (24) of the detection sensor system (22) correlated with the status information is determined and supplied to a monitoring function (26) which determines a disturbance parameter (28) correlated with the disturbance oscillation (10) on the basis of the detection signal (24), wherein the disturbance parameter (28) is supplied to a compensation function (30) which determines a compensation signal (32) on the basis of the disturbance parameter (28), and wherein the compensation signal (32) is applied to a steering actuator (34) of the wheel steering angle controller (16) in order to at least partially compensate for the disturbance oscillations (10).

Description

[0001] R. 415728

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for at least partially compensating for disturbance vibrations in a steering system designed as a steer-by-wire steering system

[0006] State of the art

[0007] The invention relates to a method for at least partially compensating for disturbance vibrations in a steering system designed as a steer-by-wire system, particularly during operation of the steering system in a vehicle. The invention also relates to a computing unit for carrying out such a method and to a vehicle with such a computing unit.

[0008] Various methods for compensating for disturbance vibrations in conventional steering systems or EPS (Electric Power Steering) systems are known in the prior art. These disturbance vibrations can be caused, for example, by wheel imbalances and manifest themselves as steering wheel torsional vibrations. To reduce these vibrations, a detection signal, typically in the form of a torque signal from the steering spindle, an operating signal from a servo motor, and / or a wheel speed signal, is monitored. Based on this, an active counter-torque is determined and applied to the servo motor of the steering system to compensate for the disturbance vibrations. Such steering systems are described, for example, in DE 10 2009 028 448 A1 and DE 10 2017 211 043 B3.

[0009] Furthermore, vehicles with steer-by-wire steering systems are known, which do not require a direct mechanical connection between a steering handle and the steered vehicle wheels and in which a steering input is purely R. 415728

[0010] - 2 - is transmitted electrically. Such a steer-by-wire steering system typically comprises a control unit with a steering handle and a feedback actuator for generating steering resistance and / or a return torque on the steering handle, as well as at least one wheel steering angle adjuster, mechanically separate from the control unit, for changing the steering angle of at least one vehicle wheel. Although a mechanical connection is lacking, disturbance vibrations can still occur in this case, which can lead to chassis vibrations and possibly to vibrations at the steering handle.

[0011] In this context, for example, DE 10 2021 206 743 A1 discloses a method for at least partially compensating for disturbance vibrations in a steering system designed as a steer-by-wire system, particularly during operation of the steering system in a vehicle. This method involves determining a rack force signal and filtering it to remove disturbance vibrations. The filtered rack force signal is then transmitted to a control unit of the steering system and used to generate an active counter-torque. DE 10 2021 206 743 A1 thus aims to prevent a deterioration of the steering feel when disturbance vibrations occur. However, it does not dampen the disturbance vibrations or corresponding chassis vibrations.This can lead to an occupant perceiving chassis vibrations, even if these do not manifest as vibrations in the steering handle.

[0012] The object of the invention is, in particular, to provide a method for at least partially compensating for disturbance vibrations in a steering system designed as a steer-by-wire system, with improved vibration compensation characteristics. This object is achieved by the features of claims 1, 8, and 9, while advantageous embodiments and further developments of the invention can be found in the dependent claims. R. 415728

[0013] - 3 -

[0014] Disclosure of the invention

[0015] A method, in particular a computer-implemented method, is proposed for at least partial compensation of disturbance vibrations in a steering system designed as a steer-by-wire steering system, particularly during operation of the steering system in a vehicle, wherein the steering system comprises at least one wheel steering angle actuator with a steering actuating element, in particular a rack, for changing a wheel steering angle of at least one vehicle wheel, and at least one detection sensor associated with the steering actuating element for detecting state information of the steering actuating element, wherein a detection signal correlated with the state information is determined by the detection sensor and fed to a monitoring function, which determines a disturbance parameter correlated with the disturbance vibration based on the detection signal, and wherein the disturbance parameter is fed to a compensation function.which determines a compensation signal based on the disturbance parameter, and wherein a steering actuator of the wheel steering angle adjuster is supplied with the compensation signal to at least partially compensate for the disturbance vibrations. The present compensation functionality thus explicitly affects only the wheel steering angle adjuster, but implicitly also affects the steering feel at a steering handle of the steering system through the reduction of disturbance vibrations in the wheel steering angle adjuster. This design can, in particular, improve vibration compensation, whereby disturbance vibrations in the wheel steering angle adjuster, especially in the form of chassis vibration, can be reduced.

[0016] The steering system is designed as a steer-by-wire system in which a steering input, particularly from the driver, is advantageously transmitted purely electrically to the vehicle wheels. In this case, the steering system comprises a control unit with a steering handle and advantageously with a feedback actuator for generating steering resistance and / or a return torque on the steering handle, as well as at least one wheel steering angle actuator mechanically separate from the control unit. A "wheel steering angle actuator" is understood to mean, in particular, an actuating unit coupled to at least one vehicle wheel, which is designed to change the steering angle by altering the steering angle. R. 415728

[0017] - 4 - The steering angle actuator of at least one vehicle wheel transmits a steering input, in particular from a driver, to the vehicle wheel, thereby advantageously controlling at least one orientation of the vehicle wheel and / or influencing the vehicle's direction of travel. For this purpose, the steering angle actuator comprises at least one steering actuating element, for example in the form of a rack, and at least one steering actuator operatively connected to the steering actuating element, for example in the form of an electric motor. The steering angle actuator can be designed as a centering actuator and assigned to at least two, in particular steerable, vehicle wheels. Alternatively, the steering angle actuator can also be designed as a single-wheel actuator and assigned to exactly one, in particular steerable, vehicle wheel.The wheel steering angle adjuster can also be assigned to a vehicle axle designed as a rear axle or, advantageously, to a vehicle axle designed as a front axle of the vehicle.

[0018] Furthermore, the vehicle comprises at least one computing unit designed to perform the procedure for at least partial compensation of the disturbance vibrations. A "computing unit" is understood to mean, in particular, an electrical and / or electronic unit that has an information input, information processing, and information output. Advantageously, the computing unit also comprises at least one processor, at least one operating memory, at least one input and / or output device, at least one operating program, at least one control function, at least one calculation function, and at least one determination function. In addition, the computing unit in this case includes the monitoring function and the compensation function. In particular, the computing unit is designed to determine, especially by means of the determination function, the detection signal from the detection sensors that correlates with the state information.Furthermore, the processing unit, or more precisely the monitoring function, is designed to determine a disturbance parameter correlated with the disturbance oscillation based on the detection signal and to feed it to the compensation function. Additionally, the processing unit, or more precisely the compensation function, is designed to determine a compensation signal based on the disturbance parameter. Finally, the processing unit is designed, in particular by means of the control function, to control the steering actuator of the wheel steering angle adjuster (R. 415728).

[0019] - 5 - in particular to at least partially compensate for the disturbance vibrations with the compensation signal. Preferably, the processing unit is integrated into a control unit of the vehicle, for example a central vehicle control unit or a control unit of the steering system. Furthermore, a "disturbance vibration" is to be understood in particular as a vibration occurring in the steering system, preferably in a shimmy-critical frequency range and / or in a frequency range typical for steering wheel torsional vibrations, which is based in particular on a vehicle disturbance and is caused, for example, by an imbalance and / or disturbance in at least one brake disc ("brake judder") and / or an imbalance and / or disturbance in at least one vehicle wheel ("shimmy"). In this context, the disturbance vibrations can in particular lead to chassis vibration.In this case, the disturbance vibrations can therefore be correlated, in particular, with chassis vibration and may be caused, for example, by brake disc and / or vehicle wheel imbalance and / or vibration of the steering actuator, especially during ferry operation. Furthermore, a "disturbance parameter" is understood to mean, in particular, a parameter correlated with the disturbance vibration, which is taken into account and / or used by the compensation function when generating the compensation signal. "Provided for" is understood to mean, in particular, specifically programmed, designed, and / or equipped. The fact that an object is intended for a specific function is understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0020] Advantageously, it is proposed that the detection sensor system comprises at least one position sensor, in particular a rack and pinion position sensor, and that the status information corresponds to a position of the steering actuator, in particular a rack and pinion position. This allows, in particular, a simple and advantageous way to detect the status of the steering actuator.

[0021] Alternatively or additionally, it is proposed that the detection sensor system include at least one force sensor, in particular a rack and pinion force sensor, R. 415728

[0022] - 6 - and the status information corresponds to a force acting on the steering actuator, in particular a rack force. In particular, individual signals from the position sensor and the force sensor can also be combined and / or fused in this context. This allows, in particular, an alternative way to acquire status information about the steering actuator, or it can advantageously acquire additional information about the state of the steering actuator.

[0023] Furthermore, it is proposed that the steering system comprise at least one position controller, which is designed to supply the steering actuator with a control signal to set the position of the steering element. A "position controller" is understood to be, in particular, an electrical and / or electronic unit designed to provide control functionality for the operation of the steering actuator. Advantageously, the position controller is integrated into a control unit of the vehicle, for example, a central vehicle control unit or a control unit of the steering system. Preferably, the steering actuator is supplied with the compensation signal independently of the steering actuator being supplied with the control signal, and particularly preferably in parallel with the steering actuator being supplied with the control signal, so that the compensation functionality and the control functionality are preferably independent of each other.In this context, it is also possible to implement the compensation functionality as a subcomponent in the position controller. This can achieve a particularly advantageous compensation effect, since the disturbance oscillations, due to their relatively high frequency, are difficult for a corresponding position controller or its control algorithm to compensate for.

[0024] The method for at least partially compensating the disturbance vibrations and the vehicle are not to be limited to the application and embodiment described above. In particular, the method for at least partially compensating the disturbance vibrations and the vehicle may, to fulfill a function described herein, have a different number of individual elements, components, and units than specified herein. R. 415728

[0025] - 7 -

[0026] Drawings

[0027] Further advantages become apparent from the following description of the drawings. The drawings illustrate an embodiment of the invention.

[0028] They show:

[0029] Fig. 1 shows a simplified representation of a vehicle with a steering system designed as a steer-by-wire system.

[0030] Fig. 2 shows a schematic representation of a compensation functionality and a control functionality in the steering system, and

[0031] Fig. 3 shows an exemplary flowchart with main process steps of a method for at least partial compensation of disturbance vibrations in the steering system.

[0032] Description of the exemplary embodiment

[0033] Figures 1a and 1b show a simplified representation of a vehicle 14, specifically a passenger car, with several wheels 20 and a steering system 12. The steering system 12 is operatively connected to the wheels 20 and is designed to influence the direction of travel of the vehicle 14. Furthermore, the steering system 12 is configured as a steer-by-wire system, in which a steering input is transmitted electrically to the wheels 20 in at least one operating state.

[0034] The steering system 12 has a control unit 44, which can be operated, in particular, by a driver and / or occupants. The control unit 44 comprises a steering handle 46, for example in the form of a steering wheel, and a feedback actuator 48 mechanically coupled to the steering handle 46. The feedback actuator 48 is designed to provide feedback torque and thereby generate steering resistance and / or a restoring torque on the steering handle 46. Alternatively, a steering handle could also be designed as a joystick, a steering lever, and / or a steering ball or the like. R. 415728

[0035] - 8 -

[0036] Furthermore, the steering system 12 includes a wheel steering angle actuator 16. The wheel steering angle actuator 16 is mechanically separate from the control unit 44. The wheel steering angle actuator 16 is connected to the control unit 44 purely electrically. In this case, the wheel steering angle actuator 16 is also designed as a centering actuator. The wheel steering angle actuator 16 has an operative connection with at least two of the vehicle wheels 20, in particular two front wheels, and is designed to translate the steering input into a steering movement of the vehicle wheels 20. For this purpose, the wheel steering angle actuator 16 comprises a steering actuating element 18, in particular in the form of a rack and pinion, and a steering actuator 34, in particular in the form of an electric motor, which interacts with the steering actuating element 18. In principle, a steering system could also include several wheel steering angle actuators, in particular designed as individual wheel actuators.Furthermore, a steering actuator could, for example, be designed as a linear drive and / or include several electric motors.

[0037] Furthermore, the steering system 12 includes a detection sensor 22. The detection sensor 22 is arranged in and associated with a region of the steering actuator 18. The detection sensor 22 is designed to detect the status of the steering actuator 18 and provide it as a detection signal 24 (see in particular Figure 2). In this case, the detection sensor 22 comprises at least one position sensor 36, in particular a rack and pinion position sensor, which is designed to detect the position of the steering actuator 18, in particular in the form of a rack position, as status information. Alternatively or additionally, a detection sensor for detecting the status of a steering actuator could also include at least one force sensor, in particular a rack and pinion force sensor. Furthermore, a detection sensor could also comprise several position and / or force sensors.

[0038] Furthermore, the vehicle 14 has a control unit 50. In this case, the control unit 50 is designed as a steering control unit and is therefore part of the steering system 12. The control unit 50 has an electrical connection with the operating unit 44. The control unit 50 also has an electrical connection with the wheel steering angle actuator 16, in particular the steering actuator 34, R. 415728

[0039] - 9 - Furthermore, the control unit 50 has an electrical connection to the detection sensor 22, in particular for receiving the detection signal 24. The control unit 50 is intended at least for controlling the operation of the steering system 12. In principle, however, a control unit could also be different from a steering control unit and, for example, be designed as a single, central vehicle control unit. In addition, it is conceivable to provide separate control units for a wheel steering angle actuator and for an operating unit and to connect these to each other for communication.

[0040] The control unit 50 comprises a processing unit 42. The processing unit 42 has a functional connection with the wheel steering angle actuator 16 and is connected to the steering actuator 34 via a first connection channel. The processing unit 42 comprises at least one processor (not shown), for example in the form of a microprocessor, and at least one operating memory (not shown). Furthermore, the processing unit 42 comprises at least one operating program stored in the operating memory with at least one control routine, at least one calculation routine, at least one determination routine, and at least one compensation routine. In this case, the processing unit 42 specifically comprises at least one monitoring function 26 and one compensation function 30 (see also Figure 2).

[0041] Furthermore, the control unit 50 in this case includes a position controller 38. The position controller 38 has an operative connection with the computing unit 42. In addition, the position controller 38 has an operative connection with the wheel steering angle actuator 16 and is connected to the steering actuator 34 via a second connection channel, which runs parallel to the first connection channel. The position controller 38 is designed to provide a control function, for example in the form of field-oriented control, and to supply the steering actuator 34 with a control signal 40 to set a position of the steering actuating element 18 (see also Figure 2).

[0042] During ferry operation of vehicle 14, disturbance vibrations 10, particularly in the form of chassis vibrations, can occur, especially in a critical speed range between 80 km / h and 140 km / h. These disturbance vibrations 10 are caused, for example, by an imbalance or disturbance R. 415728

[0043] - 10 - in a brake disc (“brake judder”) and / or an imbalance or disturbance in one of the vehicle wheels 20 (“shimmy”). Such disturbances 10 can manifest themselves in conventional steering systems, for example, as steering wheel rotational vibrations. In a steer-by-wire steering system, the transmission of such disturbances 10 to the steering handle 46 can, in principle, be suppressed; however, the disturbances 10 or corresponding chassis vibrations may still be perceived by an occupant, even if they do not manifest as vibrations at the steering handle 46.

[0044] To improve vibration compensation, a method for at least partially compensating disturbance vibrations 10 in the steering system 12 is described below, particularly with reference to Figure 2. The disturbance vibrations 10 are correlated with chassis vibration and can be caused, for example, by brake disc and / or vehicle wheel imbalance and / or vibration of the steering actuator 18. In this case, the processing unit 42 is specifically designed to execute the method and includes a computer program with corresponding program code. However, another processing unit, such as a central vehicle control unit, could also be used to carry out the method.

[0045] According to the invention, the detection signal 24 of the detection sensor 22, correlated with the state information, is determined and fed to the monitoring function 26. Using the monitoring function 26, a disturbance parameter 28 correlated with the disturbance oscillation 10 can be determined, at least on the basis of the detection signal 24. Furthermore, at least one operating signal 52 of the control unit 44, in particular a steering input or a target position of the steering actuator 18 correlated with the steering input, and / or at least one operating signal 54 of the steering actuator 34, in particular a current engine torque, can be taken into account when determining the disturbance parameter 28. Subsequently, the disturbance parameter 28 is fed to the compensation function 30, which determines a compensation signal 32, in this case in particular in the form of a compensation torque, on the basis of the disturbance parameter 28. Also in this context, i.e., when determining the compensation signal 32 R. 415728

[0046] - 11 - In principle, at least one operating signal 52 of the control unit 44, in particular a steering input or a target position of the steering actuator 18 correlated with the steering input, and / or at least one operating signal 54 of the steering actuator 34, in particular a current engine torque, can be taken into account. Using the compensation signal 32, the steering actuator 34 can then be controlled to compensate for the disturbance vibrations 10, in particular in the wheel steering angle adjuster 16. The compensation functionality thus explicitly affects only the wheel steering angle adjuster 16, but through the reduction of the disturbance vibrations 10 in the wheel steering angle adjuster 16, it also implicitly affects the steering feel at the steering handle 46.

[0047] Furthermore, the steering actuator 34 is supplied with the compensation signal 32 independently of the steering actuator 34 being supplied with the control signal 40. In the present case, the steering actuator 34 is advantageously supplied with the compensation signal 32 in parallel to the steering actuator 34 being supplied with the control signal 40, specifically via the two parallel connection channels, more precisely the first connection channel and the second connection channel, between the processing unit 42 and the steering actuator 34, as well as between the position controller 38 and the steering actuator 34. Alternatively or additionally, however, it could also be provided that the compensation functionality is implemented as a subcomponent in a corresponding position controller. This can achieve a particularly advantageous compensation effect, since the disturbance oscillations, due to their relatively high frequency, are difficult for the position controller 38 to absorb.can be compensated for by a corresponding control algorithm of the position controller 38.

[0048] Finally, Figure 3 shows an exemplary flowchart with main process steps of the procedure for at least partial compensation of the disturbance vibrations 10 in the steering system 12.

[0049] In process step 60, which is carried out in particular during ferry operation of the vehicle 14, a detection signal 24 correlated with the status information is determined by the detection sensor 22 and supplied to the monitoring function 26 for monitoring. R. 415728

[0050] - 12 -

[0051] In a process step 62, a disturbance parameter 28 correlated with the disturbance oscillation 10 is determined using the monitoring function 26, at least on the basis of the detection signal 24. In this context, at least one operating signal 52 of the control unit 44, such as a steering input or a target position of the steering actuator 18 correlated with the steering input, and / or at least one operating signal 54 of the steering actuator 34, in particular a current engine torque, can also be taken into account. Subsequently, the disturbance parameter 28 is fed to the compensation function 30 to compensate for the disturbance oscillations 10.

[0052] In a process step 64, a compensation signal 32 is determined using the compensation function 30 based on the disturbance parameter 28. In principle, at least one operating signal 52 of the control unit 44, such as a steering input or a target position of the steering actuator 18 correlated with the steering input, and / or at least one operating signal 54 of the steering actuator 34, in particular a current engine torque, can also be taken into account in this context.

[0053] In process step 66, the steering actuator 34 is supplied with the compensation signal 32 to compensate for the disturbance vibrations 10, particularly in the wheel steering angle adjuster 16. This allows disturbance vibrations in the wheel steering angle adjuster 16, especially in the form of chassis vibrations, to be directly reduced. At the same time, the steering feel at the steering handle 46 can also be indirectly improved.

[0054] The flowchart in Figure 3 is intended only as an example of a method for at least partially compensating the disturbance vibrations 10 in the steering system 12. In particular, individual process steps can also vary or additional process steps can be added.

Claims

R. 415728 - 13 - Claims 1. Method for at least partially compensating disturbance vibrations (10) in a steering system (12) designed as a steer-by-wire steering system, in particular during operation of the steering system (12) in a vehicle (14), wherein the steering system (12) comprises at least one wheel steering angle actuator (16) with a steering actuating element (18), in particular a rack, for changing a wheel steering angle of at least one vehicle wheel (20) and at least one detection sensor (22) associated with the steering actuating element (18) for detecting a state information of the steering actuating element (18), wherein a detection signal (24) correlated with the state information of the detection sensor (22) is determined and supplied to a monitoring function (26), which determines a disturbance parameter (28) correlated with the disturbance vibration (10) on the basis of the detection signal (24), wherein the disturbance parameter (28) is supplied to a compensation function (30) is suppliedwhich determines a compensation signal (32) based on the disturbance parameter (28), and wherein a steering actuator (34) of the wheel steering angle adjuster (16) is actuated with the compensation signal (32) to at least partially compensate the disturbance vibrations (10).

2. Method according to claim 1, characterized in that the disturbance vibrations (10) are correlated with a chassis vibration and are caused by a brake disc and / or vehicle wheel imbalance and / or a vibration of the steering actuator (18).

3. Method according to claim 1 or 2, characterized in that the detection sensor (22) comprises at least one position sensor (36), in particular a rack position sensor, and the status information corresponds to a position of the steering actuator (18), in particular a rack position. R. 415728 - 14 - 4. Method according to one of the preceding claims, characterized in that the detection sensor comprises at least one force sensor, in particular a rack force sensor, and the status information corresponds to a force acting on the steering actuator, in particular a rack force.

5. Method according to one of the preceding claims, characterized in that the steering system (12) comprises at least one position controller (38) which is provided to supply the steering actuator (34) with a control signal (40) for setting a position of the steering actuating element (18), wherein the steering actuator (34) is supplied with the compensation signal (32) independently of the steering actuator (34) being supplied with the control signal (40).

6. Method according to claim 5, characterized in that the steering actuator (34) is supplied with the compensation signal (32) in parallel with the steering actuator (34) being supplied with the control signal (40).

7. Method according to claim 5 or 6, characterized in that the compensation functionality is implemented as a subcomponent in the position controller.

8. Computing unit (42) for carrying out a method according to a preceding claim.

9. Vehicle (14) with a steering system (12) designed as a steer-by-wire steering system, comprising at least one wheel steering angle adjuster (16) with a steering actuating element (18) and with a steering actuator (34) as well as at least one detection sensor (22) assigned to the steering actuating element (18) for detecting status information of the steering actuating element (18), and with a computing unit (42) according to claim 8.

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