Composite Active Front Steering Controller Design for Vehicle System

The active front steering (AFS) technique is one of the effective methods to handle the stability of a vehicle. In this paper, some AFS control schemes have been proposed. First, a two degree of freedom mathematical model for the vehicle dynamics has been introduced in order to calculate the desired yaw rate. On this basis, the actual sideslip angle is further identified and estimated by constructing a sliding-mode observer. Then, two kinds of baseline AFS controllers are proposed by using PID and terminal sliding mode techniques, such that the actual yaw rate will approach its reference value as closely as possible. To further improve the performance of the closed-loop AFS control system, taking the uncertainties and external disturbances into account, the composite control schemes are developed by combining the previous designed state-feedback controllers and feedforward compensation term generated by the disturbance observer. The effectiveness of the designed AFS control schemes is verified by using the Carsim Software. It has been verified that the performance under two composite controllers is better than both baseline controllers.