This paper presents a new modes switching control method based on a dual-motor centralized and distributed coupling drive system, which can achieve the centralized and distributed coupling drive and reduce the modes switching shock to improve electric vehicle dynamics performance. Initially, the influence of the switching speed on the shock is analyzed and the models of each modes switching stage are established. Furthermore, a stage-by-phase multivariable combination controller based on the control of position, velocity and force of the actuators is designed, and a load torque state observer is developed to estimate system interference. Finally, the shock suppression effect is testified by the upshift process simulation and the experiments of a centralized and distributed coupling drive electric vehicle. The research shows that the peak value of the switching process with the controller is 9 m/s3, which is lower than the recommended value of 10 m/s3. It laid the theoretical foundation for solving the mode switching problem of the centralized and distributed coupling drive electric vehicles.

Introduction

The development of pure electric vehicles is an important way to solve the problems of energy crisis and environmental pollution. The existing drive modes for pure electric vehicles are divided into distributed drive and centralized drive. The centralized drive means that only one drive system is used for the coaxial drive wheels, and the torque balance between the two-side drive wheels is accomplished by a mechanical differential. The research results show that the single-motor direct centralized drive system has the most simple structure but the worst performance; after a two gear transmission has been added, the dynamic performance is improved and the driving range is significantly increased; the main and auxiliary motors drive can further improve the above performance [1]. Although the centralized drive system has good reliability and maturity, it must rely on auxiliary devices for dynamics control [2], which makes the vehicle control system very complicated. The distributed drive means that each drive wheel has an independent drive system, which can separately adjust the output torque and speed of the drive wheel and realize dynamic control without auxiliary systems. It is currently a research hotspot in the field of vehicle dynamics [3]. However, because it is difficult to match a transmission for each drive motor, the vehicle’s driving performance depends entirely on the work of the engine and motors characteristics [4].