Rear Wheel Steering Angle Timing for Yaw Rate Hysteresis
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Solution Overview
Problem
In four-wheel steering systems, hysteresis in yaw rate occurs when shifting from additional turning to cutback turning, causing discomfort for the driver as the front and rear wheels return to the steering neutral position.
Innovation Solution
A steering control device determines a rear wheel steering angle control command to return the rear wheel steering angle to a predetermined angle earlier than the front wheel steering angle, using a steering angle ratio correction value based on vehicle speed to adjust the ratio of rear to front wheel steering angles, thereby reducing yaw rate hysteresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rear wheel steering angle returns to the neutral position at the same time as the front wheel steering angle, then the steering control is simple, but yaw rate hysteresis occurs causing driver discomfort
Solution Approach 1:
The rear wheel steering angle is returned to the neutral position in advance before the front wheel steering angle returns to neutral. This preliminary action eliminates yaw rate hysteresis by ensuring the rear wheels are already neutral when the front wheels complete their return, preventing the lag effect that causes driver discomfort.
Solution Approach 2:
The patent changes the timing parameter of rear wheel steering angle control dynamically. By adjusting when the rear wheels return to neutral relative to the front wheels, the system optimizes the steering response to eliminate hysteresis while maintaining smooth vehicle behavior during cutback turning maneuvers.
2Object-affected harmful factors
If the rear wheel steering angle returns to the neutral position earlier than the front wheel steering angle, then yaw rate hysteresis is reduced, but the steering control complexity increases
Solution Approach 1:
The control system uses feedback from steering angle sensors and yaw rate sensors to determine when to initiate the early return of rear wheel steering angle to neutral. This feedback mechanism automatically adjusts the timing based on actual vehicle state, reducing the need for complex manual control logic while achieving hysteresis elimination.
Solution Approach 2:
The patent implements dynamic steering control where the rear wheel steering angle ratio changes based on steering wheel operation state. The system transitions between different control modes (additional turning, cutback turning, neutral) with smooth interpolation, making the complexity adaptive rather than static and manageable.
Data Source
AI summary
A steering control device, a steering control method, and a steering control system according to the present invention determines a rear wheel steering angle control command for returning a rear wheel steering angle to a predetermined steering angle earlier than a front wheel steering angle when steering wheel operation (that is, operation of a steering wheel) shifts from a state of additional turning to a state of cutback turning, in steering control that steers a rear wheel steering angle of a vehicle in opposite-phase with respect to a front wheel steering angle, and outputs the determined rear wheel steering angle control command to a rear wheel steering device, so that hysteresis of a yaw rate is reduced or eliminated, reducing or eliminating a sense of discomfort given to a driver.