Research On Direct Yaw Moment Control For In-wheel Motor Electric Vehicles

The problems of energy scarcity and environmental pollution are becoming more an more serious because of the rapid development of automobile industry.Therefore,the development of new energy vehicles has seen the dawn.Compared to traditional vehicles,electric vehicles have a very significant advantage in solving the serious shortage of energy and improving economic efficiency.Therefore,the research of electric vehicle has become a hot topic both at home and abroad.The main advantage of distributed wheel drive is that all motor drives are independently controllable,which provides many conveniences for dynamic control research.Because most of the traffic accidents are caused by vehicle instability,vehicle safety issues have always been a concern of all sectors of society.Therefore,this paper focuses on the direct yaw moment control strategy of distributed-drive electric vehicles.The main contents are as follows:First,on the basis of the vehicle related parameters and dynamics,in view of the direct yaw moment control strategy,ignored the pitch and vertical motion of the suspension system and the body and other factors,established an eight-degree-of-freedom dynamics model,UniTire nonlinear tire model,motor model,steering system model,etc.Moreover,build the simulation model on MATLAB/Simulink platform and verify it.Secondly,the effects of the vehicle yaw rate and centroid slip angle on handing stability of the vehicle and the main factors that cause vehicle instability are introduced respectively.A linear two-degree-of-freedom model of vehicle is established,which is used as an ideal model for reference.The Kalman filter algorithm and the extended Kalman filter algorithm are introduced respectively,and the extended Kalman filter is used to estimate the slip angle of the centroid.The estimated values are simulated under two different conditions.Finally,the control principle of direct yaw moment control is analyzed.Based on the ideal linear two-degree-of-freedom model,we determine the ideal value of the slip angle and the yaw rate of the centroid.The additional yaw controller based on fuzzy control and "feedforward + feedback" is designed respectively.At the same time,the allocation strategy of the additional yaw moment is also introduced.On the MATLAB/Simulink platform,a simulation model of the vehicle's direct yaw moment control system is established based on the vehicle's eight-degrees of freedom simulation model and the simulation model of each controller.And in the steering wheel angle step input conditions and double-shift conditions to simulate,fuzzy control and "feedforward + feedback" control of the two control strategies were compared simulation to verify the control strategy control effect.