Stability control of a road vehicle considering model and parametric uncertainties

Parametric uncertainties due to unknown parameters of the model and unmodelled dynamics are two factors which degrade performance of the vehicle stability control systems. In this paper, a modified sliding mode control system is proposed to enhance the handling performance of a passenger car via differential braking in the presence of the road and model uncertainties. The proposed control system consists of two control loops and stabilises the vehicle via minimising the desired and achieved yaw rates. The inner loop which utilises a sliding mode controller is responsible for calculating the required yaw moment. The outer control loop which plays the role of supervisor controller determines the braking pressure at each wheel. The controller is designed based on the reduced bicycle model and is implemented in a virtual prototype model with sufficient degrees of freedom. The simulations results establish the ability of the proposed control system in vehicle rapid stabilising under a severe manoeuvre. Moreover, robustness of the controller in the presence of vehicle mass and road friction coefficient variations was proved.