Robust nonlinear decoupling and yaw stabilization of 4WS cars

Abstract

Four-wheel steering systems for cars are decoupled in order to split the control problem into two parts: i) the steering problem in which the driver only has to keep a mass point on his planned path and ii) the yaw stabilization problem. The decoupling and stabilization problems are robustly solved by yaw rate feedback. Four-wheel car steering is modelled by a single-track model with nonlinear tire characteristics. A generic constant yaw-rate feedback law for decoupling of lateral and yaw motion is derived. For robust yaw stabilization a velocity scheduled yaw rate feedback to rear-wheel steering is given, by which the linear part of the system gets velocity independent yaw eigenvalues.