Rear Wheel Steering Control for Vehicle Agility and Stability
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Solution Overview
Problem
Current rear wheel steering systems face a tradeoff between stability and agility, prioritizing stability over agility at high speeds, leading to poorer vehicle performance compared to traditional single-steered axles, and fail to dynamically adjust based on real-time vehicle maneuvers.
Innovation Solution
A rear wheel steering control system using a varying model reference feedback controller with a target understeer model, vehicle model, and actuator dynamics, which generates a target rear wheel angle based on estimated vehicle stability indicators like sideslip, allowing for a tunable balance between agility and stability through proportional-integral-derivative control and actuator adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rear wheel steering systems prioritize stability over agility at high speeds, then vehicle stability is improved, but vehicle performance deteriorates
Solution Approach 1:
The control system dynamically adjusts rear wheel steering based on real-time vehicle conditions including speed, yaw rate, and sideslip angle. The system transitions between stability-prioritizing and agility-prioritizing modes depending on operating conditions, eliminating the fixed tradeoff. This is achieved through a controller that continuously monitors vehicle state and adjusts rear wheel angle accordingly.
Solution Approach 2:
The system changes control parameters (rear wheel steering angle) based on vehicle speed and stability indicators. At different speed ranges and stability conditions, the controller applies different steering interventions to optimize both stability and performance, rather than maintaining a fixed control strategy.
2Stability of the object's composition
If rear wheel steering systems prioritize stability over agility, then vehicle stability is improved, but handling performance deteriorates
Solution Approach 1:
The controller adjusts rear wheel steering parameters based on vehicle speed and stability indicators. During low-speed maneuvers, the system prioritizes agility for better handling, while at high speeds it transitions to stability prioritization, providing optimal handling performance across all operating conditions.
Solution Approach 2:
The system dynamically adapts its control characteristics based on real-time vehicle state. The rear wheel steering angle is continuously adjusted according to speed, yaw rate, and sideslip angle, enabling the vehicle to exhibit appropriate handling characteristics for each driving scenario.
3Stability of the object's composition
If rear wheel steering systems prioritize stability over agility, then vehicle stability is improved, but responsiveness to driver input deteriorates
Solution Approach 1:
The system changes its control response based on vehicle speed and stability conditions. During low-speed maneuvers, the rear wheel steering system provides more aggressive response to driver input for better responsiveness, while at high speeds it provides more moderate adjustments to maintain stability, optimizing response speed for each operating condition.
Data Source
AI summary
A method of controlling rear wheel steering in a vehicle including determining a stability state of the vehicle from a plurality of vehicle sensor inputs, determining a target vehicle performance based on the stability state of the vehicle, and determining a target rear angle of rear vehicle wheels based on a difference between a target vehicle characteristic and a model vehicle characteristic, wherein the target vehicle performance promotes agility and stability to a target model at different times based on the stability state of the vehicle.