Research Of Torque Coordinated Control And Stability Analysis Of In-wheel Motors Electric Vehicles

With the rapid development of the automobile industry and the urgent need for convenient transportation,the speed of vehicles is gradually increasing.Therefore,the stability of the vehicle under high-speed extreme conditions and the operability during driving are highly valued by people.Traditional cars are dominated by mechanical control,and intelligent algorithms cannot be integrated.The control methods are limited by traditional mechanical structures and face a development crisis.On the other hand,with the increasing prosperity of the world economy,the production capacity and reserves of oil are increasingly unable to meet the development needs of human beings,which also makes traditional vehicles face an energy crisis.At the same time,traditional cars will emit a large amount of toxic and harmful gases into the atmosphere through exhaust gas,pollute the environment and produce haze,which will cause traditional cars to face environmental crisis.In response to the various crises faced by traditional cars at this stage,researchers have designed a variety of electric vehicles to meet the green and efficient development needs of vehicles.The in-wheel motors electric vehicles has a completely different driving form from the traditional car,eliminating the mechanical devices such as the clutch,the transmission and the transmission shaft in the conventional automobile.The power supply and stability control of the vehicle are all completed by the in-wheel motor,the control is more flexible,providing a completely new solution for vehicle stability control,is a very promising research direction.In this dissertation,the seven-degree-of-freedom(7DOF)dynamics model of the vehicle is established based on the standard coordinate system of the vehicle,and the wheel dynamics model is established to analyze the influence of the force generated by the wheel on the stability of the vehicle.Considering the influence of the road surface and the tire on the vehicle,the UA tire model is introduced,which provides a good simulation experiment platform for verifying the control algorithm proposed in the following dissertation.The vehicle stability controller used in this dissertation is a layered control architecture mode.Firstly,according to the control requirements of the vehicle,the target values of the yaw rate and the sideslip angle are determined,and the analysis method of the instability energy ratio is introduced to analyze whether the vehicle is in an unstable state.Then,in the upper controller,the direct yaw moment of demand is obtained by the improved dynamic sliding mode control method.The control method uses the exponential approach law,the dynamic sliding mode control method and the function substitution method to eliminate the chattering in the sliding mode control,and the timeliness and anti-interference of the sliding mode control are effectively improved.In order to improve the robustness of sliding mode control and improve the convergence speed of sliding mode variables,the adaptive dynamic sliding surface control method is combined with error-oriented adaptive adjusting for high-precision tracking.In the lower controller,taking into account the driving ability of the in-wheel motor within the scope of the adhesion constraint,the minimum wear of the road surface is used as the objective function combined with the elimination method to reasonably distribute the torque,and the maximum torque estimation system and the anti-skid drive system are added.Based on the seven-degree-of-freedom vehicle model,the proposed algorithm is simulated and analyzed under different road conditions and working conditions.The simulation results show that the designed steering stability control system can effectively control the stability and maneuverability of the vehicle,and increase the road surface adhesion ability of the wheel under the premise of improving the vehicle driving capability,with less loss and energy saving.