Active Four-Wheel-Steering Design for an Advanced Vehicle

The design of a control system to coordinate the steering of the four wheels of an advanced vehicle is described. The Linear Quadratic Gaussian, design process is applied to a directional dynamics model that includes yaw, lateral, and roll degrees-of-freedom for the vehicle and steering rotation degrees-of-freedom for the front and rear wheels. Vehicle oscillations, overshoot, sideslip, and response times to steering inputs are minimized at all forward speeds. Left-to-right steering corrections augment the control design to eliminate tire scrub and squeal in low speed and parking maneuvers. Simulation results illustrate the advantages of active four-wheel-steering over two-wheel-steering and proportional four-wheel-steering and the insensivity of the design to changes in vehicle speed, trim, loading, and tire characteristics.