Adaptive Return Torque Control for Electric Servo Steering
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Solution Overview
Problem
Existing electric servo steering systems face challenges in generating a return torque signal that is inadequate at low speeds and excessive at high speeds, leading to undesirable steering wheel movements and discomfort during driving.
Innovation Solution
A method that determines a scaling factor based on the speed of steering wheel rotation to modify the return torque signal, ensuring a more adaptive and comfortable steering experience by adjusting the return torque in response to changing vehicle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high return torque is applied at low steering angles to support natural restoring force, then the restoring movement is maintained, but the steering feel becomes rigid and the restoring movement becomes undesirably quick
Solution Approach 1:
The patent applies dynamics by making the return torque signal variable based on steering wheel rotation speed. The return torque is dynamically adjusted: higher at low rotation speeds to maintain restoring movement, and reduced at high rotation speeds to prevent rigid steering feel and excessively quick restoration. This dynamic adaptation resolves the contradiction between maintaining reliable restoring movement and ensuring comfortable steering operation.
2Device complexity
If a return torque signal is generated as a function of steering wheel position and vehicle speed only, then the system is simple to control, but the return torque is inadequate at low speeds and excessive at high speeds
Solution Approach 1:
The patent applies parameter changes by introducing steering wheel rotation speed as an additional parameter for generating the return torque signal. The control device determines rotation speed from sequential position measurements and uses this parameter to dynamically adjust the return torque magnitude. This resolves the contradiction by enhancing adaptability across different driving conditions while maintaining relatively simple control logic through straightforward parameter-based adjustment.
3Stability of the object's composition
If the return torque is increased to prevent unwanted steering wheel movements at low speeds, then steering stability is improved, but the restoring force becomes excessively high during normal operation
Solution Approach 1:
The patent resolves this contradiction through dynamic adjustment of return torque based on rotation speed. At very low rotation speeds (including stationary conditions), high return torque is applied to maintain steering wheel stability and prevent unwanted movements. When rotation speed increases during normal restoring operations, the return torque is automatically reduced to provide appropriate restoring force without being excessively high. This dynamic behavior ensures both stability and comfortable operation.
Data Source
AI summary
A method for generating a return torque signal in an electric servo steering system of a vehicle, including the steps of: determining a current steering wheel position; determining a current vehicle speed; generating a return torque signal as a function of the steering wheel position and the vehicle speed; determining a current speed of steering wheel rotation; determining a scaling factor dependent on the speed of steering wheel rotation; and multiplying the return torque signal by the scaling factor in order to obtain a modified return torque signal. Also, a servo steering system which is designed to carry out such a method.