Optimal Torque Distribution for the Stability Improvement of a Four Wheel Distributed Driven Electric Vehicle Using Coordinated Control

Abstract

This paper presented an optimal torque distribution scheme for the stability improvement of a distributeddriven electric vehicle (DEV). The nonlinear dynamics and tire model of the DEV are constructed. Moreover, the singlepoint preview optimal curvature model with the proportionalintegralderivative (PID) process is developed to simulate the driver's behavior. By using coordinated control and sliding mode control, a threelayer hierarchical control system was developed. In the upper level, the integral two degreeoffreedom (DOF) linear model is used to compute the equivalent yaw moment for vehicle stability. With the actuators' restrictions, the middle level solved the linear quadratic regulator (LQR) problem via a weighted least square (WLS) method to optimally distribute the wheel torque. In the lower level, a slip rate controller (SRC) was presented to reallocate the actual torques based on the sliding mode method. The simulation results show that the proposed scheme has high pathtracking accuracy and that vehicle stability under limited conditions is improved efficiently. Moreover, the safety under actuator failure is enhanced.