Steer-by-Wire Feedback Control Using Wheel Slip Frequency
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Solution Overview
Problem
Steer-by-wire steering systems lack appropriate feedback mechanisms that simulate road conditions accurately, leading to unpredictable steering feel and noise issues, especially in varying driving situations.
Innovation Solution
A method for controlling steer-by-wire systems that determines wheel slip and performs frequency analysis of front wheel speed vectors to generate a feedback signal, independent of mechanical forces, using a control unit and feedback actuator to provide realistic steering torque based on road conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If rack force is used to determine steering feedback, then steering feel is provided, but noise and unwanted deflections occur due to mechanical component forces
Solution Approach 1:
The patent extracts the harmful mechanical forces from the feedback determination process by excluding rack force measurements. Instead of using the total rack force which contains unwanted mechanical component forces, the invention uses only wheel slip and vehicle speed data to calculate steering feedback, thereby removing the source of noise and deflections while preserving the essential steering feel information.
Solution Approach 2:
The patent replaces the mechanical measurement approach (rack force sensors) with a computational model based on wheel slip and vehicle dynamics. By substituting direct mechanical force measurement with calculated forces derived from wheel slip frequency analysis, the system eliminates mechanical noise while maintaining accurate steering feedback representation.
2Ease of operation
If feedback actuator replicates reaction forces, then predictable steering feel is provided, but feedback does not accurately reflect actual road conditions
Solution Approach 1:
The patent implements a feedback mechanism where wheel slip frequency analysis continuously monitors actual road conditions and adjusts the steering feedback signal accordingly. The control unit analyzes the frequency spectrum of wheel slip signals and uses this information to generate accurate feedback forces that truly represent current road surface conditions, eliminating the disconnect between replicated forces and actual road state.
Solution Approach 2:
The patent changes the parameters used for feedback determination from rack force measurements to wheel slip characteristics and vehicle speed. By analyzing frequency components of wheel slip signals across different driving conditions, the system dynamically adjusts feedback parameters to accurately represent varying road conditions while maintaining predictable steering feel.
Data Source
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AI summary
The invention relates to a method for controlling a steer-by-wire steering system for a motor vehicle comprising: an electronically controllable steering actuator (6) which acts on the steered wheels (7); an actuation unit (60); and a feedback actuator (4) to which a driver can apply a driver's request for a steering angle via a steering input means (3) and which outputs a feedback signal to the steering input means in reaction to the driver's request and outputs a driving state of the motor vehicle; a signal transmission which transfers the driver's request to the actuation unit (60); wherein the actuation unit (60) actuates the steering actuator (6) in order to transform the driver's request into a deflection of the steered wheels (7); determining the wheel slip of at least one front wheel; frequency analysis of the time profile of the wheel slip signal of the at least one front wheel; and determining the feedback signal as a function of the result of the frequency analysis.