Rear Wheel Steering Neutral Position Control
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Solution Overview
Problem
Existing vehicle steering apparatuses for four-wheel steering vehicles require complex mechanisms and increased power consumption to return rear wheels to a neutral position when stopped, and often result in rear wheels being steered away from neutral, causing aesthetic issues and potential vehicle meandering upon restart.
Innovation Solution
A vehicle steering apparatus with a rear wheel-side steering driving mechanism that includes an actuator, vehicle speed detection, stop state determination, steering direction determination, and control means to steer rear wheels to a neutral position using the actuator when the vehicle is stopped, eliminating the need for a centering spring and reducing the actuator's output requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centering spring is used to return rear wheels to neutral position when stopped, then the rear wheels can be returned to neutral position, but the rear wheel steering mechanism becomes more complex and the electric motor size increases
Solution Approach 1:
The patent removes the centering spring from the rear wheel steering mechanism and replaces it with a control system that uses the existing actuator to return the rear wheels to neutral position. This extracts the centering function from the mechanical structure and implements it through electronic control, thereby simplifying the mechanical mechanism while maintaining the neutral position return capability.
Solution Approach 2:
The patent replaces the mechanical centering spring system with an electrically-controlled actuator system. The actuator is controlled by a control unit that detects vehicle stop state and steering wheel position, then operates the actuator to return the rear wheels to neutral position. This substitutes a mechanical self-centering system with an electronically-controlled system, reducing mechanical complexity.
2Reliability
If a centering spring is used to return rear wheels to neutral position, then the rear wheels can be centered when stopped, but the electric motor must overcome the spring's elastic force during cruising, increasing power consumption
Solution Approach 1:
The patent extracts the centering function from the continuously-active spring system and implements it only when needed (when the vehicle is stopped and the steering wheel is returned to neutral). This eliminates the continuous energy consumption required to overcome spring elastic force during cruising, while maintaining the neutral position return capability when stopped.
Solution Approach 2:
The patent implements periodic or conditional action by activating the actuator only when the vehicle is in a stop state and the steering wheel is returned to neutral position. The control unit continuously monitors vehicle speed and steering wheel position, and only operates the actuator when both conditions indicate the need for centering. This replaces continuous spring force application with intermittent actuator activation, significantly reducing power consumption during cruising.
3Device complexity
If rear wheel steering is not allowed when stopped, then the mechanism is simpler, but the rear wheels remain away from neutral position causing aesthetic issues and vehicle meandering
Solution Approach 1:
The patent enables the rear wheel steering system to automatically return itself to the neutral position when the vehicle is stopped and the steering wheel is centered. The control system monitors the steering wheel position and, when neutral is detected during a stop state, activates the actuator to bring the rear wheels to their neutral position. This self-correcting capability ensures aesthetic appearance without requiring continuous external intervention or complex mechanical centering springs.
Data Source
AI summary
An electronic control unit determines the steering direction of rear wheels on the basis of the turning operation direction of a steering wheel when a detected vehicle speed is “0”, i.e. when the vehicle is stopped. If the steering direction of the rear wheels is a return-side steering direction to obtain a neutral steering position, the unit operates a rear wheel-side steering mechanism by driving and controlling an electric motor, whereby allowing return-side stationary steering for the rear wheels.