| In recent years,with the strong support of government due to environment pollution and energy shortage,the electric vehicles have been rapidly developed.The study object of this paper is four-wheel hub motor drive electric vehicle,it has a great advantage since the four wheel torque can be controlled independently,which have a great influence on handling and stability control of four-wheel hub motor drive electric vehicle.The first part of this paper is to analyze the dynamics of four-wheel hub motor drive electric vehicle.Then,a Co-simulation model have been built,it combines vehicle dynamics simulation model established by using Carsim software,and control strategy model established in MATLAB/Simulink software.The simulation platform can simulate the dynamic response of four-wheel hub motor drive electric vehicle,and meet the requirement of simulation analysis.The second part of this paper analyze the influence elements of stability,the reason of insatiability and its evaluation criteria.A stability control strategy is presented,the strategy consists two parts,(1)the upper level controller:using the linear two degree of freedom vehicle model for reference.Using sliding mode variable structure to calculate the required steering yaw moment.(2)the lower level controller:using the optimization-based distribution method to distribute the torque for each wheel.By simulation in condition of sine sweep steer,double lane change and snake cornering,the effectiveness of the control strategy has been verified.Finally,fail safe based drive mode control strategy is studied.A strategy of single motor fail,two motor and three,four motor fail is presented.The strategy is designed to maintain the vehicle stability by controlling the remaining normal working motor.By simulation in condition of straight line drive and steering drive,the results shown that the fail safe based control strategy can enhance the handling and stability performance of four-wheel hub motor drive electric vehicle. |
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