Research On Torque Allocation Optimal Control Of Distributed Electric Driving Vehicle

In this paper,a distributed electric driving vehicle with independent e-drive system is taken as the research object,and the research of system modeling,controller solving and joint simulation verification is carried out on the basis of vehicle dynamics and robust control theory.In order to solve the disturbance and uncertainty caused by the state observation error and the uncertain dynamics,the H infinity control of the longitudinal slip rate of the vehicle electric wheel,the robust control of the upper control target of the whole vehicle and the optimal torque allocation method are carried out.It will greatly enhance the vehicle’s skid ability,dynamic performance,lateral stability and robust performance of the control system.The main contents are as follows:First,taking the single wheel of the distributed electric vehicle as the research object,considering the influence of the torque variation and the speed estimation error of the uncontrolled wheel,the longitudinal slip rate control problem is analyzed.The slip ratio state error equation,which includes the torque variation and the speed estimation error of the uncontrolled wheel,is established.Based on the H infinity state feedback theory,the longitudinal slip ratio controller is solved.The slip ratio is controlled near the optimal slip rate while the interference gain is suppressed.In order to verify the effectiveness and robustness of slip rate controller,the simulation test of vehicle speed disturbance is carried out on the split road surface respectively.The experimental results show that the slip ratio controller has strong robustness and the distributed driving vehicle has good driving skid resistance capability.The distributed electric drive system has multiple independent driving elements,that is,redundant configuration.In order to effectively control longitudinal acceleration and lateral attitude control,comprehensive control problems need to be dealt with hierarchically.The longitudinal driving force and the additional yaw moment are taken as the upper driving target,and the robust LQ control method is used to solve the control failure caused by the uncertain dynamics caused by the nonlinear change of the tire side stiffness,and the control problem caused by the uncertainty of the parameter is suppressed.The upper controller determines the longitudinal driving force and the additional yaw moment control target,the lower layer controller establishes the power source constraint,the road adhesion constraint and the driving antiskid constraint,and designs the optimal objective function including the upper controller target and the motor load rate,and transforms the torque allocation problem into a multi-objective linear programming problem.In order to verify the comprehensive performance of torque allocation strategy,the speed following model,drive system,battery model and vehicle control strategy are built in Simulink.The driver steering model,vehicle dynamics model and state observer are built in CarSim,and the joint simulation verification based on CarSim and Simulink is carried out.The simulation tests of high and low speed double line conditions are carried out on low and high attached pavement,and the robust LQ control strategy,the feed forward control strategy and the speed following control strategy are compared.In general,the trend of the speed following control,feed forward control and the robust LQ control proposed in this paper is less deviating from the driver’s driving intention,and the stability and robustness are stronger.