Integrated optimal dynamics control of 4WS4WD electric ground vehicles with tire-road frictional coefficient estimation

This paper presents a novel integrated optimal dynamics control of 4WS4WD electric vehicles via hierarchical control methodology. In the higher-level design, an LQR controller is proposed to obtain the generalized longitudinal force, lateral force and yaw moment, according to their respective reference values. In the lower-level design, the control signals from the higher-level controller are allocated through a cost function to generate the eight optimal tire forces. A barrier function based on the friction limit circle is proposed to calculate the coefficients in the cost function. The lower-level controller is designed to ensure all the tires work in the stable region while realizing the tracking control of the vehicle dynamics. The tire-road friction coefficient is estimated through the integrated longitudinal force and lateral force, respectively, using a brush tire model. To reduce the estimation error, a novel data fusion function is employed to generate the final estimation value. Finally, the effectiveness of the proposed control and estimation strategies is validated via CarSim-Simulink joint simulation.