Standalone Rear Wheel Steering Control for Braking Stability
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Solution Overview
Problem
Existing vehicles with integrated Rear Wheel Steering (RWS) systems face instability during straight-ahead braking and turning, leading to potential collisions and reduced follow-up performance due to fixed rear wheel angles, which do not adjust relative to front wheels.
Innovation Solution
A standalone-type RWS control apparatus and method that uses sensors to detect vehicle states, calculating toe-in and rear wheel steering angles to independently control left and right rear wheels, applying toe-in control during straight-ahead braking and same or reverse phase control during turning to improve stability and follow-up performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fixed rear wheel angles are used in existing vehicles, then the structure is simple, but straight-ahead driving stability during braking deteriorates
Solution Approach 1:
The patent implements dynamic rear wheel angle adjustment based on vehicle operating conditions. The control unit varies the rear wheel steering angle according to vehicle speed, steering angle, and braking status, transforming the fixed rear wheel configuration into a dynamic system that adapts to different driving scenarios, thereby improving straight-ahead stability during braking while maintaining manageable system complexity through conditional control strategies
Solution Approach 2:
The patent changes the rear wheel steering angle parameter based on detected vehicle states. By monitoring vehicle speed, steering angle, and braking status, the system adjusts the rear wheel angle parameter in real-time, applying toe-in control during straight-ahead braking and phase-reversed control during turning maneuvers, thus resolving the contradiction between stability improvement and system complexity
2Speed
If rear wheels are steered in opposite direction from front wheels at low speed, then rotation radius decreases, but turning stability deteriorates due to trajectory formation
Solution Approach 1:
The patent dynamically switches between same-phase and reverse-phase rear wheel steering based on vehicle speed and steering conditions. At low speeds during turning, the system may apply reverse-phase steering to reduce rotation radius, while at higher speeds or during stable turning conditions, it transitions to same-phase steering to improve turning stability and prevent trajectory formation issues, thus resolving the contradiction between rotation radius and turning stability
Solution Approach 2:
The control unit predicts potential trajectory formation issues during turning by monitoring steering angle and vehicle speed, and proactively adjusts the rear wheel steering phase and angle magnitude in advance to prevent instability before it occurs, maintaining both compact rotation radius and turning stability
3Device complexity
If integrated RWS minimizes actuator interference during braking, then system complexity is reduced, but straight-ahead driving stability deteriorates
Solution Approach 1:
The patent applies specific parameter changes to the rear wheel steering angle during straight-ahead braking conditions. When braking is detected through the braking status signal, the system applies a predetermined toe-in angle to the rear wheels, moving lateral force inward to enhance stability. This targeted parameter adjustment during specific conditions improves stability without requiring continuous complex actuator control
Solution Approach 2:
The system uses feedback from the braking status signal and vehicle speed sensor to determine when to apply toe-in control. The control unit continuously monitors these parameters and activates rear wheel steering adjustment only when braking conditions are detected, creating a simple yet effective feedback-based control strategy that improves stability without excessive system complexity
Data Source
AI summary
Disclosed herein is an apparatus for controlling standalone-type rear wheel steering (RWS), which includes a vehicle speed detection unit for detecting a vehicle speed by communicating with a sensor installed in a vehicle or an Electronic Control Unit (ECU); a steering angle and steering angular velocity detection unit for detecting steering angles and steering angular velocities of front and rear wheels by communicating with a sensor installed in the vehicle or the ECU; a master cylinder pressure detection unit for detecting a master cylinder pressure by communicating with a sensor installed in the vehicle or the ECU; and a controller for determining braking or turning of the vehicle using the information detected using the sensors or received from the ECU, calculating the amount of toe-in when the vehicle is braking or calculating a rear wheel steering angle when the vehicle is turning, and controlling the RWS based thereon.