Research On Yaw Moment Control Method Of Distributed Drive Pure Electric Vehicle

With the increasingly prominent energy and environmental problems,traditional vehicles are more and more difficult to adapt to the new trend of vehicle development,the electric vehicles have brought solutions to these two problems with it.Distributed driven pure electric vehicle removes all intermediate mechanical transmission links from the power unit to the wheels,with outstanding advantages of rapid control and high efficiency,but increased vehicle control difficulty.Vehicle lateral stability control directly affects the safety of vehicle driving at high speed,while the control methods of distributed driven pure electric vehicle are various,this paper is to study the method of the yaw moment control,extending the control methods of vehicle and satisfying the vehicle's driving requirements while achieving lateral stability control of the vehicle.According to the requirements of lateral stability control strategy,a vehicle simulation model based on CarSim and Matlab/Simulink is built,selecting the motor submodule and whose parameters are matched.Designing simulation conditions checks validity of the vehicle model.The reason of vehicle instability is analyzed,and the parameters of vehicle stability state-yaw rate and center of mass side angle are selected.The state output value of the four-wheel two-degree-of-freedom vehicle model are taken as the control objective,establishing a lateral stability controller with two layers of upper and lower structures.The upper controller uses sliding mode control theory,which making the output of vehicle actual state follow the change of the target value,once the vehicle deviates from the predetermined trajectory,the controller will determine the required yaw moment for vehicle tracking control.After judging the instability of the vehicle,the lower level controller based on three different control methods distributes the yaw moment.The first,introducing the hydraulic differential brake control method selects the wheels to be controlled,and using the fuzzy control theory adapts for changes in the actual working conditions of the vehicle,so that the vehicle can reach a stable driving condition.The second,using the quadratic programming method,taking into account tire-surface contact conditions,motor output characteristics and other constraints,with the optimization goal to minimize tire utilization,completes the distribution of the moment between the wheels to ensure the vehicle dynamic while maintaining vehicle stability.The third,based on motor-hydraulic composite braking,introducing yaw moment control and obtaining the braking requirements of each wheel through the distribution of front and rear axle and left and right wheels braking forces.In the case of non-emergency braking,the method,which giving priority to motor braking and the hydraulic brake compensates the surplus,redistributes the single-wheel demand braking force to meet the brake demand and achieves the purpose of torque distribution,thereby correcting the tendency of the vehicle to lose stability.Based on the joint simulation platform of CarSim and Matlab/Simulink,design the simulation conditions,the steering wheel continuous sinusoidal input condition,FMVSS 126 and double lane change condition to verify three different lateral stability control algorithms.The results show that the state of the controlled vehicle can respond to changes in the external input and follow the ideal value to ensure the lateral stability of the vehicle under severe driving conditions.