Two-degree-of-freedom vehicle steering controllers design based on four-wheel-steering-by-wire

Four-Wheel-Steering (4WS) and steer-by-wire were combined into Four-Wheel-Steering-By-Wire (4WSBW) to improve the vehicle manoeuvrability and stability. To make the vehicle response follow the desired response under various vehicle speeds, the steering feedforward controller of 4WSBW was designed. A feedback controller as standard H∞ control problem was applied to stabilise the vehicle system with various tyre cornering stiffnesses. Thus the feedback controller was designed by converting it into the control problem of Linear Parameter Varying (LPV) system for resolving Riccati equations in real time. Simulations show the effectiveness of the designed controllers with the different vehicle speeds and tyre cornering stiffness.