Development of an optimal control system for longitudinal and lateral stability of an individual eight-wheel-drive electric vehicle

This paper presents an optimal torque allocation control method for an individual eight-wheel-drive electric vehicle to improve longitudinal and lateral stability. The proposed optimal controller is designed as a hierarchical structure with an upper level controller and a lower level controller. The upper controller including human driver model is developed using sliding mode control algorithm, which takes longitudinal velocity, side slip angle and yaw rate as control variables. The lower controller is developed using optimal control algorithm, which optimally allocates the tractive/braking torque to eight in-wheel motors and mechanical brake system independently. Numerical simulation studies, including driver-vehicle-controller in-loop and open-loop simulations, are conducted to investigate the performance of the proposed controller. The simulation results show that the proposed controller significantly improves vehicle longitudinal and lateral stability.