Steering Reaction Force Control for Smooth Wheel Return
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Solution Overview
Problem
Conventional steer-by-wire systems experience abrupt steering force changes during quick turns or when encountering bumpy road surfaces, hindering quick steering wheel responses and making it difficult for drivers to maneuver effectively.
Innovation Solution
A steering control device with a reaction force device and controller that adjusts the steering reaction force based on the road surface reaction force, increasing the force during turns and decreasing it during returns, using a gain that varies according to the steering state to prevent excessive shock and ensure smooth wheel return.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the steering reaction force is increased to transmit road surface conditions to the driver, then the driver can sense road conditions better, but the steering wheel response becomes sluggish during quick turns
Solution Approach 1:
The steering reaction force control is made dynamic by detecting steering wheel angular velocity and adjusting the reaction force accordingly. When angular velocity exceeds a threshold (quick turn detected), the reaction force is reduced to enable fast response. When angular velocity is within normal range, full reaction force is applied to transmit road surface conditions. This dynamic adjustment resolves the contradiction between road sensing and quick response.
Solution Approach 2:
The control system changes the parameter of steering reaction force based on the detected steering state. By monitoring steering angular velocity and adjusting the reaction force parameter in real-time, the system adapts to different operating conditions, providing high road surface feedback during normal steering and reduced feedback during quick maneuvers.
2Measurement precision
If the steering reaction force is increased to track kickback from road surface, then road surface information is transmitted to the driver, but abrupt steering force changes occur on bumpy roads
Solution Approach 1:
The system dynamically adjusts reaction force based on steering angular velocity. During quick steering movements (which occur when navigating bumps), the high angular velocity triggers reduction of reaction force, preventing shock transmission. During steady-state steering, full reaction force is maintained for accurate road surface feedback.
Solution Approach 2:
The control system detects steering angular velocity in advance and preemptively adjusts the reaction force before abrupt shocks can occur. When quick turn is detected, the reaction force is reduced beforehand, preventing the harmful effect of shock transmission to the driver.
3Measurement precision
If the steering reaction force is maintained at high level during return steering, then road surface conditions are continuously monitored, but the steering wheel return is hindered
Solution Approach 1:
The reaction force control is dynamically adjusted based on steering angular velocity direction. When the steering wheel is returned quickly (high negative angular velocity), the reaction force is reduced to facilitate smooth return. When steering is performed slowly in either direction, full reaction force is applied to maintain road surface monitoring capability.
Data Source
AI summary
A vehicle steering control device is provided that suppresses changes in the steering force accompanying the shock transmitted from the road surface during the steering wheel return operation. The vehicle steering device is a steer-by-wire steering device where a steering wheel receiving the steering input which is transmitted electronically to the steering unit which turns steered road wheels of the vehicle. The steering reaction force correction (Gf×F) corresponding to road surface reaction force F is applied to the steering wheel. The device includes a turn/return sensor that senses turn/return of the steering wheel, and during return of steering wheel, road surface reaction force feedback gain Gf is made smaller than the initial turning.