Nonlinear Dynamic Response of Four Wheel Steering Automobiles to Combined Braking and Steering Commands in Collision Avoidance Maneuvers

A nonlinear “bicycle model” of an automobile was used to investigate both conventional front wheel (FWS) and four wheel steering (4WS) automobiles during emergency maneuvers combining braking with steering commands. The model includes a comprehensive, nonlinear tire model.

Two different 4WS control laws were used. The first was an open loop law where the commanded rear wheel steer angle was based on the instantaneous front wheel steer angle. The second, a closed loop law, required a signal comprised of a comparison of yaw rate and front wheel steer angle to command the rear wheel steer angle.

Simulated results of the response to combined hard steering and braking inputs the potential benefits of 4WS in these types of maneuvers - among these are faster and more stable response and improved maneuverability.