Research On Yaw Stability Integrated Control Method Of In-wheel Motor Drive Electric Vehicles

Forced by the pressure of energy shortage and environmental degradation,the development of electric vehicles are an inevitable trend of the automobile industry.The in-wheel motor drive electric vehicles,due to the unique structure and performance characteristics,are considered to be the ideal carrier for studying the optimal vehicle dynamic performance.Besides,the in-wheel motor drive electric vehicles have the potential to enhance the active safety of vehicles combined with yaw stability control system,which is becoming the current research hotspot.To improve the vehicle yaw stability,this dissertation research on four in-wheel motor drive electric vehicles configured with active front wheel steering system,mainly focus on the integrated control strategy of active front wheel steering and direct yaw moment and torque distribution problem.Firstly,the seven degrees of freedom nonlinear vehicle dynamic model,based on the idea of modular modeling,which can meet the need of research topic including the longitudinal,lateral and lateral movement of the vehicle and four wheel rotational motions is established.The accuracy and validity of the model are verified,which lays the foundation for the study of the integrated control method of yaw stability in later work.Then,the integrated control system of active front wheel steering and direct yaw moment is studied using hierarchical control structure.The upper controller uses the linear two degrees of freedom vehicle model as the reference model,yaw rate and slip angle taken as control object.Based on the model predictive control theory,tracking the vehicle's desired state,the additional yaw moment and the additional front wheel angle are calculated which can ensure the vehicle stability.For the lower controller,the additional front wheel angle is directly applied to the active front wheel steering actuator,and three kinds of control distribution algorithms are used for torque distribution considering the condition of actuator constraint and tire force coupling problem.At the same time,the situation whether the hydraulic brake system involved in the compensation are analyzed and discussed respectively.Finally,in order to verify the effectiveness and real-time performance of the integrated control system,simulation experiments of typical working conditions are carried out based on the off-line simulation platform and the real-time simulation platform.The results shows that the yaw stability integrated control method proposed in this dissertation has a good control effect,which can improve the yaw stability of the vehicle effectively.