Research On Path Tracking And Differential Steering Multi-objective Control For In-wheel Motor Drive Vehicle

The in-wheel motor drive vehicles eliminate the traditional mechanical transmission system,and the four-wheel torques are controllable independently.At the same time,the in-wheel motor drive vehicles have the advantages of rapid torque response and flexible control,which show great potential in the vehicle longitudinal and lateral dynamics control,vehicle active safety control,differential steering control and vehicle stability control.Aiming at the aspect of the active safety control,the path tracking control system of in-wheel motor drive vehicle is designed based on the dynamic extension boundary decision to assist the driver to track the designed path under the premise of ensuring the stability of the vehicle.The designed control system contains decision layer,control layer and execution layer.Based on the neural network algorithm,the dynamic extension boundaries which vary with vehicle speed,road curvature and road adhesion coefficient is designed in the decision layer,which divides different dangerous degrees into different control regions.The path tracking controller,the electronic differential controller and their coordinated control strategy are designed in the control layer,and the path tracking control,electronic differential control and the coordinated control are carried out among different control regions.The different torque distribution modes are divided according to the current road adhesion coefficient,vehicle speed,and lateral acceleration in the execution layer,and the stability distribution,economic distribution,joint distribution are carried out among different torque distribution modes.The effectiveness of designed path tracking control system is verified by Car Sim/Simulink joint simulation.In the research process of the active safety control of in-wheel motor drive vehicles such as the path tracking control system,the dynamic performances of the vehicle itself can't be ignored,especially for the in-wheel motor drive vehicle with differential steering.The differential steering has the impact on the vehicle longitudinal and lateral dynamics.Therefore,the further research on the multi-objective control of differential steering is carried out in this thesis.The dynamics model of the in-wheel motor drive vehicle with differential steering including the longitudinal and lateral motion degrees of freedom is established comprehensively considering the vehicle differential steering dynamics characteristics,vehicle longitudinal dynamics characteristics and vehicle lateral dynamics characteristics.With the characteristics that the model's parameters such as the vehicle speed and the front steering wheel angle are nonlinear and time-varying in the vehicle's different driving time,the Takagi-Sugeno fuzzy method is adopted.Based on the analysis of vehicle longitudinal and lateral dynamic characteristics of differential steering,the high front-wheel steering angle tracking accuracy,the ideal vehicle lateral stability performance and the ideal vehicle longitudinal dynamic response performance are taken as the control objectives.The multi-objective control architecture based on the LMI method is adopted to design the generalized 2H/H? multi-objectives output feedback differential steering controller,which can ensure the longitudinal and lateral dynamic performance under the premise of ensuring the front-wheel steering angle tracking accuracy.The effectiveness of designed multi-objective controller is verified by Car Sim/Simulink joint simulation.Finally,the differential steering control program based on the Labview and NI Compact Rio architecture is designed for the four in-wheel motors drive test vehicle.The differential steering experiment under the angular step input and sine input conditions are carried out respectively,and the ideal experiment results are obtained.