All-Wheel Steering Ratio Adjustment for Stability and Effort
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Solution Overview
Problem
Existing all-wheel steering systems face a trade-off between achieving high vehicle stability and yaw rate damping, which results in high steering effort for the driver, especially at high speeds when the rear and front axles steer equidirectionally.
Innovation Solution
The all-wheel steering system adjusts the front axle steering ratio as a function of the rear axle steering angle, allowing for larger rear axle steering angles without increasing the driver's steering effort by reducing the front axle steering ratio, and incorporates a bend detection unit and driving dynamics control unit to optimize steering ratios based on vehicle speed and cornering intentions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rear axle steering angle is increased to improve vehicle stability and yaw rate damping, then vehicle stability is improved, but the steering effort for the driver increases
Solution Approach 1:
The front axle steering ratio is dynamically adjusted based on the rear axle steering angle. When the rear axle steering angle is large, the front axle steering ratio is reduced, which compensates for the increased steering effort caused by large rear axle steering angles, thereby maintaining both vehicle stability and acceptable steering effort
Solution Approach 2:
The control unit continuously monitors the rear axle steering angle and uses this information to adjust the front axle steering ratio accordingly. This feedback mechanism ensures that the front axle steering ratio is optimized in real-time to compensate for the effects of rear axle steering, resolving the contradiction between stability and steering effort
Data Source
AI summary
An all-wheel steering system for a motor vehicle is described which has an active front axle steering system and an active rear axle steering system. The front axle steering system includes a gear ratio unit which is coupled to a steering wheel. The gear ratio unit is configured to define a front axle steering angle as a function of a steering wheel angle and a front axle steering ratio. In addition, the gear ratio unit is coupled to the rear axle steering system in such a way that the front axle steering ratio is adjustable as a function of a rear axle steering angle. Further, a motor vehicle having such an all-wheel steering system is discussed. Also presented is a method of operating an all-wheel steering system for a motor vehicle.