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DE-102024132704-A1 - Method for operating a steer-by-wire steering system for a motor vehicle, assembly and motor vehicle

DE102024132704A1DE 102024132704 A1DE102024132704 A1DE 102024132704A1DE-102024132704-A1

Abstract

The disclosure generally relates to a method (60) for operating a steer-by-wire steering system (14) for a motor vehicle (10) according to a calibration mode, an assembly (12), and a motor vehicle (10). The steer-by-wire steering system (14) comprises at least a 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) is actuated by the control device (42) with a control signal such that, or a steering wheel rotation of the steering wheel (24) is utilized, the steering wheel (24) is rotated by the steering wheel actuator (32) at a predetermined constant speed. The steering wheel sensor (36) detects the rotation angle of the steering wheel (24) during rotation of the steering wheel (24) at a predetermined constant speed. The control device (42) estimates or determines the motor torque of an electric motor (34) of the steering wheel actuator (32) during rotation of the steering wheel (24) at the predetermined constant speed, depending on the detected rotation angle.

Inventors

  • Oliver Nehls
  • Alexander Ein Waldt
  • Sergio Codonesu
  • Brian Branham

Assignees

  • FORD GLOBAL TECHNOLOGIES, LLC

Dates

Publication Date
20260513
Application Date
20241108

Claims (12)

  1. Method (60) for operating a steer-by-wire steering system (14) for a motor vehicle (10) according to a calibration mode, wherein the steer-by-wire steering system (14) comprises at least a 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), wherein the method (60) for the steer-by-wire steering system (14) operated in calibration mode comprises at least the following steps: - Applying an actuation signal to the steering wheel actuator (32) by the control device (42) such that the steering wheel actuator (32) is rotated by the steering wheel actuator (32) at a predetermined constant speed, or exploiting a steering wheel rotation of the steering wheel (24) such that the steering wheel (24) is rotated by the steering wheel actuator (32) at a predetermined constant speed, - Detecting a rotation angle of the steering wheel (24) during the Rotation of the steering wheel (24) at the specified constant speed by the steering wheel sensor (36), and - Determining or estimating a motor torque of an electric motor (34) of the steering wheel actuator (32) during the rotation of the steering wheel (24) at the specified constant speed depending on the detected rotation angle by the control device (42).
  2. Procedure (60) according to Claim 1 , characterized in that when determining the motor torque, a detected torque in a steering column (26) is taken into account by the control device (42), wherein the steering wheel (24) is coupled to the steering column (26).
  3. Procedure (60) according to Claim 1 or 2 , characterized in that when estimating the motor torque, a detected amplitude of an actuator current received by the steering wheel actuator (32) is taken into account by the control device (42).
  4. Method (60) according to one of the preceding claims, characterized in that the steering wheel (24) is repeatedly rotated at the same and/or different predetermined constant rotational speeds in accordance with different control signals, that the angle of rotation is recorded during the rotation of the steering wheel (24), and that the motor torque of the electric motor (34) is determined or estimated in each instance.
  5. Method (60) according to one of the preceding claims, characterized in that the calibration mode of the steer-by-wire steering system (14) is carried out during a manufacturing phase, an assembly phase, a maintenance phase, a functional testing phase, a start-up adjustment phase, an automatic parking or exiting maneuver phase, an entry or exit phase, an absence phase or a standstill phase of the motor vehicle (10).
  6. Procedure (60) according to Claim 5 , characterized in that the calibration mode of the steer-by-wire steering system (14) is carried out repeatedly during corresponding phases of the motor vehicle (10) at predetermined time intervals, in driving distances, in functional sequences or depending on external conditions.
  7. Method (60) according to one of the preceding claims, characterized in that the control device (42) estimates a disturbance torque (30) acting on the rotation of the steering wheel (24) depending on the detected angle of rotation, based on the determined or estimated motor torque of the electric motor (34).
  8. Procedure (60) according to Claim 7 , characterized in that the control device (42) uses a disturbance observer, an estimation algorithm, a Kalman filter or a torque equilibrium equation to estimate the disturbance torque (30).
  9. Procedure (60) according to Claim 7 or 8 , characterized in that the control device (42) takes into account the estimated disturbance torque (30) during a control for torque feedback to the driver during a normal operating mode of the steer-by-wire steering system (14) and compensates it on the basis of a determined compensation torque.
  10. Procedure (60) according to Claim 9 , characterized in that the control device (42) during the normal operating mode of the steer-by-wire steering system (14) corrects an actual motor torque of the electric motor (34) of the steering wheel actuator (32) with the determined compensation torque in order to estimate the driver torque applied by the driver to the steering wheel (24), or outputs the determined compensation torque for other components of the motor vehicle (10).
  11. Assembly (12) for operating a steer-by-wire steering system (14) for a motor vehicle (10) according to a calibration mode, wherein the steer-by-wire steering system (14) comprises at least a 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), wherein the control device (42) is for the The steer-by-wire steering system (14) operating in calibration mode is configured to: - supply the steering wheel actuator (32) with a control signal or utilize a steering wheel rotation of the steering wheel (24) such that the steering wheel (24) is rotated by the steering wheel actuator (32) at a predetermined constant speed, wherein the steering wheel sensor (36) is configured to: - detect a rotation angle of the steering wheel (24) during the rotation of the steering wheel (24) at the predetermined constant speed, and wherein the control device (42) is further configured to: - estimate or determine a motor torque of an electric motor (34) of the steering wheel actuator (32) during the rotation of the steering wheel (24) at the predetermined constant speed, depending on the detected rotation angle.
  12. motor vehicle (10) with an assembly (12) according Claim 11 or with an assembly (12) which is prepared according to a method (60) according to one of the Claims 1 until 10 is operational.

Description

The disclosure generally relates to a method for operating a steer-by-wire steering system for a motor vehicle according to a calibration mode, an assembly and a motor vehicle. Steer-by-wire steering systems (hereinafter referred to as SBW steering systems) are a steering technology in which the direct mechanical connection between the steering wheel and the vehicle wheel is eliminated and replaced by two actuators: a steering wheel actuator with feedback, which generates a feedback torque for the driver at the steering wheel, and a road wheel actuator, which controls at least one, but typically several, steerable vehicle wheels into the desired position. For lateral vehicle control, torque feedback to the driver at the steering wheel is crucial for making appropriate steering inputs. However, the center of mass of a steering wheel does not typically coincide with its axis of rotation. The axis of rotation is defined by the axis of extension of the steering column, to which the steering wheel is coupled. This results in a disturbance force based on the mass distribution of the steering wheel, which introduces an unwanted torque at the steering wheel. The amplitude of this disturbance torque is not constant but varies depending on the steering wheel angle. An additional variation arises from the fact that the actual mass distribution, and thus the torque variation, depends on the shape, design, and materials of the steering wheel. For example, a traditional "round" steering wheel has a different mass distribution than a yoke-shaped steering wheel. The number and size of the spokes also influence the mass distribution. Even within a single vehicle model, differences in mass distribution exist, for example, due to different trim levels with varying switch configurations, such as paddle shifters, different airbag designs, or modifications driven by the target market. Therefore, precisely balancing the mass for a specific steering wheel in a specific configuration is a complex and costly process. Furthermore, unwanted torque fluctuations can also occur due to other factors, such as friction variations in the steering wheel actuation unit, i.e., in the bearings or a corresponding gearbox. These friction variations can also fluctuate over the service life of the steering wheel unit or be caused by other factors, such as uneven loads from the vehicle user, manufacturing tolerances, or differing coefficients of thermal expansion, which become noticeable in the case of temperature fluctuations. As a result, the exact mass distribution generally varies from unit to unit and even for each individual steering wheel over its service life. This disturbance leads to several disadvantages, such as reduced comfort due to an inconsistent steering feel that can cause driver error, increased effort required for vehicle calibration, and driver misinterpretation through "hands-on" detection. The latter, in turn, can lead to the erroneous deactivation of driver assistance and/or automated driving functions. In this context, the EP 1 623 911 A1 a method to compensate for external disturbances, such as crosswinds, that affect the movement of the steering wheel. US 11,668,615 B2 Disclosing a method for detecting disturbances in a steering system, in which a parameter of the steering system is recorded and modeled using a state-space model. A Kalman filter is used to estimate at least one disturbance that leads to unintended steering inputs. However, only disturbances acting on the road wheel actuator and its coupling to a steerable vehicle wheel are considered here. WO 2023/153973 A1 reveals another steering system of the same type, in which a feedback force is applied to a steering wheel to provide torque feedback to the driver. The aforementioned approaches therefore do not address internal influences that arise, for example, from uneven mass distribution, changing frictional torques, or diverging coefficients of thermal expansion. As a result, the precision of the torque feedback at the steering wheel for the driver, and thus driver comfort, is reduced. There is therefore a need to eliminate or at least reduce the disadvantages of known methods and components for operating an SBW steering system. In particular, there is a need to reduce the effort required for vehicle calibration with regard to the steering wheel of an SBW steering system in a motor vehicle compared to previous approaches, and to enable more precise torque feedback than before. The problem is solved by the subject matter of the independent patent claims. Advantageous Embodiments are specified in the dependent claims and the subsequent description, each of which, individually or in (sub-)combination, can represent aspects of the disclosure. Some features are explained with regard to methods, others with regard to assemblies. However, the corresponding aspects are interchangeable. According to one aspect, some embodiments of the disclosure relate to a method for ope