Active steering control based on piecewise affine regions

This paper shows that an active front steering control can be designed taking into account the nonlinear behaviour of the tire-road forces considering the vehicle dynamics with respect to the tire sideslip angle and by approximating the tire force characteristics by piecewise affine functions. The proposed control strategy involves the design of two control loops: the first one is a state feedback and it is designed to improve the vehicle dynamics using the pole placement techniques while the second control loop uses a PI control to ensure the tracking of constant yaw rate reference signal on the basis of the yaw rate tracking error despite constant disturbances and parameters uncertainties. Several simulations, including disturbances rejections and step references, are carried out on a standard CarSim D-Class vehicle model to explore the robustness with respect to unmodelled effects such as combined lateral and longitudinal tire forces, pitch, roll and driver dynamics. The simulations confirm that the proposed PWL control can greatly improve the vehicle stability and may be advantageous in very demanding manoeuvres in comparison with the use of the proposed controller designed for the linear region only.