Rule-based torque vectoring distribution strategy combined with slip ratio control to improve the handling stability of distributed drive electric vehicles

Abstract

This study presents a hierarchical control system of handling stability for distributed drive electric vehicles. The desired direct yaw moment (DYM), determined by the upper-level controller, regulates the sideslip angle and yaw rate according to the robust H_∞ control strategy. Meanwhile, the lower-level controller proposed in this research consists of a rule-based torque vectoring distribution and wheel slip ratio control. The proposed rule-based torque vectoring distribution strategy (TVDS) permits drive pattern switching based on the wheel slip ratio and preferentially employs the balanced torque vectoring distribution strategy to achieve DYM, wherein the distributed braking torque is achieved by motor regenerative braking. Here, the wheel with serious slipping was managed in a four-wheel drive pattern by the slip ratio controller. Then, the distribution strategies used for differential braking and proposed rule-based torque vectoring with and without slip ratio control were compared and analyzed in vehicle states and actuator outputs, respectively, by setting CarSim/MATLAB cosimulation under two driving conditions. Results demonstrate that the proposed rule-based TVDS can improve handling stability, energy efficiency, and riding comfort. Wheel locking can be successfully avoided by actuating the wheel slip ratio control, subsequently reducing the road adhesion requirements and improving vehicle handling stability and trajectory tracking accuracy.