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 distributed-driven electric vehicle (DEV). The nonlinear dynamics and tire model of the DEV are constructed. Moreover, the single-point preview optimal curvature model with the proportional-integral-derivative (PID) process is developed to simulate the driver's behavior. By using coordinated control and sliding mode control, a three-layer hierarchical control system was developed. In the upper level, the integral two degree-of-freedom (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 path-tracking accuracy and that vehicle stability under limited conditions is improved efficiently. Moreover, the safety under actuator failure is enhanced.