Study On Driving Force Control System Of Multi-Wheel-Independent-Drive Electric Vehicle

At present, Multi-Wheel-Independent-Drive (M-WID) Electric Vehicle (EV) is the research hotspot and important development direction in the field of electric vehicle’s technology. It has obvious advantages in vehicle dynamics control and driving force distribution comparing with the vehicles driven by traditional internal combustion engine and the ordinary electric vehicle driven by a single motor. In this thesis, a driving force comprehensive control system is designed for a Two-Wheel-Independent-Drive EV. According to the V development model of control system, the software in the loop simulation is run, the rapid control prototype is established and the wheel hub motor’s test bench is constructed, through which the new development process of EV dedicated control system is explored.Firstly, the driving force comprehensive control strategy is proposed, which integrates electronic differential control and torque coordination control. This comprehensive control strategy can optimize the allocation of driving force according to different working conditions to improve vehicle dynamic performance. The electronic differential control is implemented at low speed steering and the torque coordinated control is implemented at high speed steering. The electronic differential control performs driving torque distribution based on the Ackermann-Jeantand steering model. The torque coordinated control adopts hierarchical control architecture, in which a target designing layer calculates dynamics parameters of stability, a yaw moment determining layer determines required yawing moment, a driving force distribution layer distributes torque of each driving wheel.The vehicle system model, brushless DC motor model and driving force control system model are constructed using CarSim and MATLAB/Simulink software in order to establish an EV dynamics simulation platform. The software in the loop simulation of driving force comprehensive control system is run, which verifies effectiveness of the control system through the CarSim-MATLAB/Simulink co-simulation. The simulation results show that the designed driving force comprehensive control system can effectively improve vehicle’s driving stability under the conditions of high speed line change and so on.After the software in the loop simulation test, the rapid control prototype of Two-Wheel-Independent-Drive EV’s driving force control system is established. Using Compact RIO system as the virtual controller of rapid control prototype, where C-RIO FPGA module and real-time system are designed according to electronic differential control strategy. Using wheel hub motors and motor controllers as the actual control objects of the virtual controller, a bench of wheel hub motor is designed for rapid control prototype.