Research On Direct Yaw Moment Control Of Distributed Drive Electric Vehicle

With the rapid consumption of energy and the tightening of environmental protection policies,more and more attention has been paid to the energy conservation and environmental protection of vehicles,which brings new opportunities for the rapid development of the electric vehicle industry.The distributed drive electric vehicle power is directly transferred from the motor to the wheel,which eliminates the energy loss between the intermediate mechanical transmission parts,and can make full use of the advantages of independent and controllable driving / braking torque of each wheel.Therefore,the direct yaw moment control can be easily realized on the distributed drive electric vehicle.Based on the characteristics of distributed drive electric vehicle,the problem of yaw stability control is studied in this paper.Based on the Carsim and Simulink software,the whole vehicle model of distributed drive electric vehicle is established,including tire model,driver model,steering system model,etc.,and the permanent magnet synchronous motor model is built in Simulink.By using the combined simulation platform of Carsim/Simulink,the vehicle model built in this paper and the vehicle model built in Carsim are tested with high and low adhesion double shift line.Through the comparative analysis of vehicle parameters such as yaw rate,sideslip angle of mass center,the results show that the distributed driving electric vehicle model established in this paper is accurate and effective.A linear two degree of freedom vehicle model is established,and the expected values of yaw rate and sideslip angle of centroid are obtained.By analyzing the mechanism of vehicle instability,the effects of yaw rate and sideslip angle on vehicle stability are studied.Finally,a sliding mode variable structure additional yaw moment controller is designed,which takes yaw rate and sideslip angle as control parameters.The additional yaw moment is added on the basis of the ideal two degree of freedom vehicle model to ensure the driving stability of the vehicle under unstable conditions.Through the sliding mode variable structure control,the deviation of sideslip angle and yaw rate is kept close to zero,Then the required additional yaw moment is obtained,and the decision-making of the additional yaw moment needed to maintain the vehicle stability is realized.The torque distribution method mainly studies the optimal distribution control strategy of driving torque and the distribution control strategy of braking torque based on the sequential quadratic programming method.The objective of driving torque distribution is to minimize the comprehensive utilization of road adhesion,and to consider the constraints of additional yaw moment,road adhesion,maximum motor torque and so on.The optimal distribution of braking torque takes the ratio of each wheel load to the total load as the weight coefficient to realize the optimal distribution control of the vehicle demand braking torque and yaw torque.According to the size of the braking strength,the vehicle braking can be divided into pure motor braking,electro-hydraulic composite braking and pure hydraulic braking.On the basis of the combined simulation platform of Carsim/Simulink,the double lane shifting test of high and low adhesion road under driving condition and the double and single lane shifting test of high adhesion road under braking condition are carried out.Under the driving condition,the simulation results show that the effect of applying control is better than that of no control.Under the control condition,the vehicle speed is stable at the set target speed,and the values of sideslip angle and yaw rate are also small,which improves the driving stability and path following ability of the vehicle.Under the braking condition,the simulation results show that the application of the control has achieved good control effect,which not only improves the braking efficiency of the vehicle,but also effectively improves the driving stability of the vehicle.