Four-Wheel Steering Control for Phase Synchronization Stability
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Solution Overview
Problem
In four-wheel steering vehicles, a phase difference between front and rear wheel steering angles during turning back operations leads to impaired steering stability and deteriorated turning responsiveness when the rear wheels are controlled in phase with the front wheels.
Innovation Solution
A steering control device that adjusts the rear wheel steering angle based on the front wheel steering angle by dividing the integrated change in the rear wheel steering angle into two sections: one where the front wheel steering angle increases and another where it remains constant or decreases, to maintain phase synchronization and improve stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the rear wheels are controlled to be in phase with the front wheels, then the steering stability is improved, but the turning responsiveness deteriorates
Solution Approach 1:
The patent applies dynamics by making the rear wheel steering angle control adaptable to different steering conditions. The control unit dynamically adjusts the rear wheel steering angle based on the steering angle command value and its rate of change, allowing the system to transition between in-phase control (for stability) and delayed control (for responsiveness) depending on the steering situation.
Solution Approach 2:
The patent changes the control parameter from a fixed in-phase relationship to a variable relationship where the rear wheel steering angle is adjusted based on the steering angle command value and its derivative. This parameter change allows the system to optimize both stability and responsiveness by modulating the rear wheel angle according to real-time steering conditions.
2Speed
If a phase difference is introduced to improve turning responsiveness, then the initial stage steering responsiveness improves, but a phase difference occurs during turning back operations
Solution Approach 1:
The control system dynamically adjusts the rear wheel steering angle based on the steering angle command value and its rate of change. During initial steering, the system introduces an appropriate phase difference to improve responsiveness, while during turning back operations, it reduces the phase difference to maintain stability, achieving adaptive control throughout the steering cycle.
Solution Approach 2:
The control unit calculates the rear wheel steering angle in advance based on the steering angle command value and its derivative, allowing the system to prepare for upcoming steering changes. This preliminary action enables smooth transitions between different steering phases without introducing harmful phase differences during turning back operations.
Data Source
AI summary
Provided is a steering control device and a steering control method that can suppress the deterioration of the turning responsiveness at the initial stage of steering that may occur in a four-wheel steering vehicle and improve the steering stability when the front and rear wheels of the four-wheel steering vehicle are controlled in the same phase. A steering control device 1 of a vehicle that controls a rear wheel steering angle based on a front wheel steering angle includes a control unit 19 that controls an amount obtained by dividing an integrated value of a change in the rear wheel steering angle in a second steering section where an absolute value of the front wheel steering angle is constant and/or decreases by a time to be larger than an amount obtained by dividing an integrated value of a change in the rear wheel steering angle in a first steering section where the absolute value of the front wheel steering angle increases by a time.