Disturbance observer based model following controller for four wheel steering vehicles

In this paper, performance limitations of the conventional front wheel steering (FWS) system is analyzed in order to design the controller that can improve the vehicle handling and stability. By adding steering input at the rear wheels, four wheel steering model under the influence of external crosswind disturbance acting on the vehicle is obtained. The disturbance observer (DO) based model following sliding mode controller is designed for modified steering model to achieve ideal vehicle handling. A simulation is carried out to prove the effectiveness of the proposed controller in tracking the dynamics of the system to the desired reference model. Robustness of the proposed controller is also verified against external disturbances and in tracking different steering inputs.