CN-121990037-A - Method for operating a steer-by-wire system of a motor vehicle, subassembly and motor vehicle

CN121990037ACN 121990037 ACN121990037 ACN 121990037ACN-121990037-A

Abstract

A method for operating a steer-by-wire system of a motor vehicle, a subassembly and a motor vehicle. The present invention relates generally to a method (60), a subassembly (12) and a motor vehicle (10) for operating a steer-by-wire system (14) of a motor vehicle (10) according to a calibration mode. The steer-by-wire system (14) includes at least one steering wheel (24), a steering wheel actuator (32) coupled to the steering wheel (24), a steering wheel sensor (36) coupled to the steering wheel (24), and a control device (42) coupled to the steering wheel actuator (32) and the steering wheel sensor (36). The steering wheel actuator (32) has an actuation signal applied thereto by the control device (42), or such rotation of the steering wheel (24) is utilized such that the steering wheel (24) is rotated at a predetermined constant rate by the steering wheel actuator (32). The steering wheel sensor (36) captures the rotational angle of the steering wheel (24) during rotation of the steering wheel (24) at a predetermined constant rate. During rotation of the steering wheel (24) at a predetermined constant rate, the control device (42) estimates or confirms a motor torque of an electric motor (34) of the steering wheel actuator (32) based on the captured rotation angle.

Inventors

S. Cordoneisu
O. Nels
A. Einwalt
B. Branham

Assignees

福特全球技术公司

Dates

Publication Date: 20260508
Application Date: 20251107
Priority Date: 20241108

Claims (12)

1. A method (60) for operating a steer-by-wire system (14) of a motor vehicle (10) according to a calibration mode, wherein the steer-by-wire system (14) comprises at least one steering wheel (24), a steering wheel actuator (32) coupled with the steering wheel (24), a steering wheel sensor (36) coupled with the steering wheel (24), and a control device (42) coupled with the steering wheel actuator (32) and the steering wheel sensor (36), wherein the method (60) for operating the steer-by-wire system (14) in the calibration mode comprises at least the steps of: -applying an actuation signal to the steering wheel actuator (32) by means of the control device (42), or using rotation of the steering wheel (24), such that the steering wheel (24) is rotated at a predetermined constant rate by means of the steering wheel actuator (32), -Capturing the rotation angle of the steering wheel (24) by means of the steering wheel sensor (36) during rotation of the steering wheel (24) at the predetermined constant rate, and -Confirming or estimating, by the control device (42), the motor torque of the electric motor (34) of the steering wheel actuator (32) during rotation of the steering wheel (24) at the predetermined constant rate, based on the captured rotation angle.
2. The method (60) of claim 1, wherein the control device (42) considers torque captured in a steering column (26) during validation of the motor torque, wherein the steering wheel (24) is coupled with the steering column (26).
3. The method (60) of claim 1 or 2, wherein the control device (42) considers a captured magnitude of actuator current consumed by the steering wheel actuator (32) in estimating the motor torque.
4. The method (60) according to any one of the preceding claims, wherein the steering wheel (24) is repeatedly rotated at the same and/or different predetermined constant rates according to different actuation signals, the rotation angle during rotation of the steering wheel (24) being in each case captured and the motor torque of the electric motor (34) being in each case confirmed or estimated.
5. The method (60) according to any one of the preceding claims, wherein the calibration mode of the steer-by-wire system (14) is implemented in a manufacturing phase, an installation phase, a maintenance phase, a functional test phase, a start-up adjustment phase, a robotic phase for entering or exiting a parking space, an entry phase or exit phase, a default phase or a stationary phase of the motor vehicle (10).
6. The method (60) according to claim 5, characterized in that the calibration mode of the steer-by-wire system (14) is repeatedly implemented at predetermined time intervals, at specific driving distances, in functional sequences or based on external conditions during respective phases of the motor vehicle (10).
7. The method (60) according to any one of the preceding claims, wherein the control device (42) estimates a disturbance torque (30) acting on the rotation of the steering wheel (24) based on the captured rotation angle based on a confirmed or estimated motor torque of the electric motor (34).
8. The method (60) of claim 7, wherein the control device (42) estimates the disturbance torque (30) using a disturbance observer, an estimation algorithm, a kalman filter, or a torque balance equation.
9. The method (60) according to claim 7 or 8, wherein the control device (42) considers the estimated disturbance torque (30) during control in order to provide torque feedback to the driver during a normal operation mode of the steer-by-wire system (14) and to compensate the torque feedback by means of the confirmed compensation torque.
10. The method (60) according to claim 9, wherein, in order to estimate the torque applied to the steering wheel (24) by the driver during the normal operation mode of the steer-by-wire system (14), the control device (42) corrects the actual motor torque of the electric motor (34) of the steering wheel actuator (32) with the confirmed compensation torque or outputs the confirmed compensation torque for other components of the motor vehicle (10).
11. A subassembly (12) for operating a steer-by-wire system (14) for a motor vehicle (10) according to a calibration mode, wherein the steer-by-wire system (14) comprises at least one steering wheel (24), a steering wheel actuator (32) coupled with the steering wheel (24), a steering wheel sensor (36) coupled with the steering wheel (24), and a control device (42) coupled with the steering wheel actuator (32) and the steering wheel sensor (36), wherein the control device (42) for operating the steer-by-wire system (14) in the calibration mode is configured to: Applying an actuation signal to the steering wheel actuator (32) or utilizing such rotation of the steering wheel (24) such that the steering wheel (24) is rotated at a predetermined constant rate by the steering wheel actuator (32), Wherein the steering wheel sensor (36) is configured to: capturing the rotation angle of the steering wheel (23) during rotation of the steering wheel (24) at the predetermined constant rate, And wherein the control device (42) is further configured to: -estimating or confirming a motor torque of an electric motor (34) of the steering wheel actuator (32) during rotation of the steering wheel (24) at the predetermined constant rate based on the captured rotation angle.
12. A motor vehicle (10) having a subassembly (12) according to claim 11 or a subassembly (12) operable according to the method (60) of any one of claims 1 to 10.

Description

Method for operating a steer-by-wire system of a motor vehicle, subassembly and motor vehicle Technical Field The present invention relates generally to a method, a subassembly and a motor vehicle for operating a steer-by-wire system of a motor vehicle according to a calibration mode. Background A steer-by-wire system (hereinafter SBW steering system) is a steering technique in which the direct mechanical connection between the steering wheel and the wheels is omitted, instead of two actuators, a steering wheel actuator with feedback to generate feedback torque to the driver on the steering wheel, and a wheel actuator to control at least one steerable wheel, but typically a number of steerable wheels, into a desired position. Torque feedback on the steering wheel is critical to the driver during lateral guidance of the vehicle so that they implement the appropriate steering specification/requirements. However, the center of mass of the steering wheel is generally not coincident with the rotational axis of the steering wheel. The rotation axis is defined by an extension axis of a steering column coupled to the steering wheel. This results in disturbance forces based on the mass distribution of the steering wheel, which introduce unnecessary torque on the steering wheel. The magnitude of this disturbance torque is not constant but varies with the steering wheel angle. Additional variations are created due to the fact that the actual distribution of mass and thus the variation of torque depends on the shape, design and material of the steering wheel. For example, a conventional "round" steering wheel has a different mass distribution than a yoke-shaped steering wheel. The number of spokes and their size also have an effect on the mass distribution. Even in a single vehicle model, there is a difference in mass distribution, for example, due to different equipment lines with different switch configurations, such as rocker switches, having different airbag designs, or due to changes in the target market. Thus, the exact mass balance of a particular steering wheel of a particular configuration can be costly. In addition, unwanted torque disturbances may also occur due to other effects, such as friction fluctuations in the hand wheel actuation unit (i.e., bearings or suitable gear mechanisms). Furthermore, the fluctuations in friction may fluctuate over the service life of the steering wheel unit, possibly due to other influences, such as uneven loading of the vehicle user, manufacturing tolerances, or possibly due to differences in expansion coefficients, which may become evident in the event of temperature fluctuations. Thus, even for each individual steering wheel, the exact distribution of mass will typically vary from piece to piece over the life of the steering wheel. The disturbance torque causes several drawbacks, such as a failure condition of the driver due to inconsistent steering feel, thereby affecting comfort, thus increasing the effort of vehicle calibration, and in addition, inaccurate detection by the driver with the aid of "manual detection". The latter in turn may lead to a false deactivation of the driving assistance function and/or the driving automation function. Against this background, EP 1 623 911 A1 discloses a method of compensating for external disturbing influences (e.g. crosswinds) acting on the steering wheel movement. US 11668615 B2 discloses a method for detecting disturbance variables in a steering system, wherein variables related to the steering system are captured and modeled by a state space model. At least one disturbance variable resulting in unexpected steering stimulus is estimated using a kalman filter. However, only disturbance variables acting on the wheel actuators and their coupling to the steerable wheels are considered here. WO 2023/153973 A1 discloses another universal steering system in which a feedback coupling force is applied to the steering wheel to provide torque feedback to the driver. Therefore, the above method is independent of internal influences, for example, internal influences due to mass maldistribution, friction torque variation, or expansion coefficient divergence. Thus, the accuracy in the feedback of torque on the steering wheel provided to the driver is reduced, thereby reducing the comfort of the driver. Disclosure of Invention Accordingly, there is a need to eliminate or at least reduce the drawbacks of known methods and subassemblies for operating SBW steering systems. In particular, there is a need to reduce the effort of vehicle calibration of the steering wheel of a motor vehicle SBW steering system compared to previous methods and to enable torque feedback to be more accurate than has been possible. This object is achieved by the main body of the independent claim. Advantageous configurations are specified in the dependent claims and in the following description, each of which may present aspects of the disclosure alone or in (sub) combina