Driving Force Hierarchical Control Strategy For Multi-Wheel-Independent-Drive Electric Vehicle

Multi-Wheel-Independent-Drive Electric Vehicle (MWEV) has better performance in vehicle dynamics because it’s driving torque can be independently and accurately controlled in real-time. However, there come many challenges, with abandoning the traditional mechanical connection driving, such as how to control each-wheel driving torque reasonably and improve the safety of electric connection driving.Nowadays, the real-time performance, safety and effect of control allocation are still far away from satisfaction, although many researches on hierarchical control strategy of driving force control are studied. In addition, few scholars have integrated acceleration slip regulation and coordinate control into hierarchical control strategy, and there is not a general simulation-test platform on design of MWEV’s driving control system.A general CarSim-MATLAB/Simulink co-simulation-test platform is designed and used to verify the driving control strategy of MWEV. Also a general experiment test platform with a driving force cRIO controller is established to verify the correctness of simulation model.The simulation and test platform consists of CarSim vehicle dynamics module library, vehicle drive control module library, motor module library and "driver-vehicle-road" observer module. Therefore, this platform is able to quickly and conveniently match different types of motors and driving force control strategies for different EVs. In addition, it also provides driving force control simulation under a variety of complex conditions. This simulation and test platform shorten the development cycle by solving the problem that an EV needs to compare different designs, build different models and repeatedly match drive control system in its research period.In addition, in order to satisfy structural, real-time performance and safety reqirements of MWEV, driving force hierarchical control systems of four-wheel-independent-drive and two-wheel-independent-drive EVs are designed based on the simulation and test platform. This hierarchical control system includes a target layer, an allocation layer and a stability layer. The effectiveness of driving force hierarchical control system is verified by the simulation test under high speed line-change and μ-split road conditions.Finally, a traditional vehicle with engine is refited as a Rear-Wheel-Independent-Drive Electric Vehicle in consideration of structural constraints and power matching. This general experiment test platform with a cRIO controller can quickly change different control strategies in host computers to verify the correctness of vehicle model and the effectiveness of driving force control strategy. This paper provides good ideas and platform on the research of MWEV’s driving force control strategy.