Research On Torque Distribution Strategy Of Four-Wheel-Drive Electric Vehicle Based On Driving Intention Identification

With the increasing concern of the nation and society about energy crisis and environmental problems, the development of electric vehicle has entered a new stage. Meanwhile, with the rapid development of automobile technology, people have become increasingly demanding on the performance of the vehicle’s handling stability, economy and security,etc. The drive system of four-wheel drive electric vehicle with in-wheel moters omits the traditional clutch, transmission, etc., and each wheel is driven directly by the in-wheel motor. Thus,it has saved installation space, which greatly improves the efficiency of the transmission system, each wheel torque is independently controllable, and easy to measure, which can achieve an arbitrary assignment of torque according to the actual situation. In order to take full advantages of such vehicles, it should consider the driver’s driving intention, to take appropriate control strategies according to different driving intentions, making the vehicle actual state more consistent with the driver’s expectation, and the vehicle torque distribution depends on demand to improve the performance of the vehicle. From this point of view, the thesis is about the research on torque distribution strategy of the in-wheel motor electric vehicle based on the driving intention identification,the research work is carried out in the following.(1) Analysis of the significance and research status of four-wheel-drive electric vehicles. The structure, characteristics and key technologies of four-wheel independent drive electric vehicle have been introduced, and the development status at domestic and abroad in recent years has been analyzed, and the research status of the driver intention identification and four-wheel drive torque distribution has been reviewed.(2) The establishment of a driving intention identification system. The necessity of driving intention identification has been analyzed,and the driver’s intention has been classified, the factors affecting the operation of the driver have been analyzed, and the best identification parameters for the respective driving intention have been selected.The driving intention fuzzy identification model has been established by fuzzy control theory and methods, and simulation conducted according to real vehicle data.(3) Analysis of the necessity of the torque distribution and its impact on vehicle dynamics, the torque distribution strategy in driving conditions has been proposed. Based on the results of the driver intention identification module,the control system calculates vehicle demand torque, and for the intention to accelerate, turn and cruise, the appropriate torque distribution control strategy has been developed respectively to improve the vehicle’s performance of power and steering stability.(4) Simulation. Using MATLAB/Simulink to build a 15 degrees of freedom vehicle dynamic simulation model, including longitudinal, lateral, vertical, yaw, pitch, roll of the body, the rotation and vertical motion of the four wheels,and front wheels steering. Through importing the driver intention identification model to the vehicle model for a unified identification simulation of a variety of driving intentions in driving condition, the torque control strategy based on driving intention identification has been simulated, and the simulation results have been analyzed.The simulation results show that the driving intention fuzzy identification system designed can accurately identify a variety of driver’s intentions. In the case of low adhesion at low speed,the torque distribution strategy based on the driving intention identification can improve the vehicle performance,though it is not obvious. And at low adhesion and high speed,it can significantly improve the vehicle’s acceleration and steering stability.