Vehilce Robust Stability Controller Design Based On Model Predictive Control Theory

In this paper,a vehicle chassis integrated control system is designed to improve the vehicle stability using wheel torque control and steering wheel control,i.e.allocating the desired yaw moment and the lateral force to slip ratios of four wheels and applying additional steering angle.In the designed system,a model predictive controller(MPC),a robust optimal allocation algorithm and a sliding-mode controller are developed to overcome the uncertainty and nonlinearity of the tire-road contact situations.The controller system includes three levels: 1)In the top level,by using designed MPC controller in which a linear time-varying model is used as the inner model,the desired yaw rate and the additional active steering angle are calculated on the basis of a bicycle model and the driver steering input.The prediction and the control horizon are tuned properly to gain satisfactory control effects.2)In the middle level,considering tire nonlinearities and vehicle parameter uncertainties,the parameters in the efficiency matrix are not accurate.Thus,a robust optimal allocation algorithm,which converts the problem into linear programming with constraints,is designed to allocate the desired moment and the lateral force to four wheels and also to apply steering control based on calculated additional steering angles.3)In the bottom level controller,as the estimation of road adhesion coefficient,rolling resistance coefficient,vertical load of tire and rotational inertia may not be accurate,a slidingmode controller with robustness is used to track and maintain the desired slip ratio of each wheel.The performance of the whole controller is verified in MATLAB/Simulink-CarSim co-simulation environment using two kinds of experiments: 1)open-loop manoeuvers experiments with step inputs on roads with high and low adhesion coefficients;2)closed-loop simulation with a default driver model in CarSim under double-lane change condition.Simulations have proved the robustness and performance of the proposed controller.By using the controller proposed in this paper,the vehicle is able to follow the desired yaw rate better with less overshoot and less stable time compared with the vehicle equipped with only the active front wheel steering system and the vehicle without control.