Research On Stability Control Of In-wheel Motor Drive Vehicle Considering The Single Motor Fault

The electric vehicle driven by in-wheel motors has many advantages,such as more efficient,energy saving,large space,flexible control.Compared with the traditional chassis design,the electric vehicles driven by in-wheel motors integrated the hub motor in the four wheel system,which increases the complexity of the system and the number of actuators,and the frequent failure rate also increases significantly.For electric vehicles driven by in-wheel motors,the single wheel motor fault is frequently happening,which seriously affects the vehicle stability and endangers the driving safety of the vehicle.Therefore,according to the feature that the torque of each in-wheel motors is independently controllable,focusing on the single motor fault,the stability control of vehicle under fault condition is studied in this thesis.First,based on the driving characteristics of electric vehicles driven by in-wheel motors,the dynamic model of the electric vehicles with in-wheel motors is established in Carsim/Simulink.On the basis of this,the torque output fault of the single wheel electric wheel is defined,and the vehicle dynamics model under this fault state is established.Then the stability control decision of electric vehicles driven by in-wheel motors is studied.According to different control ideologies,the vehicle stability control system is divided into two kinds that are based on torque compensation and based on control allocation respectively.Then the fault diagnosis observer is bulit,and according to the observer and on-board sensor system,the application of design decisions is designed,to complete the overall framework of the in-wheel motor drive vehicle stability control system.For the torque compensation control,first of all,according to the nonlinear Triple-Step control theory,the stability control problem is refined as the steady state control,the feedforward and feedback control.And the corresponding steady-state control,feedforward control and PI feedback control are designed so as to develop Triple-Step torque compensation controller.Then,based on the robustness analysis of the model estimation error and the model prediction error in the controller design process,it is demonstrated that Triple-Step torque compensation controller is ISS(Input-to-state stability).Finally,through the simulation analysis,the control effect of Triple-Step control method is verified.For control rules and allocation control,first of all,considering the position of fault wheel,the upper-layer control strategy is designed,and then according to the control strategy,the lower-layer controller is designed,which contains the torque tracking controller and the optimal torque distribution stability controller.The former can make the vehicle quickly get out of the fault state,and the structure is simple and the control response is fast.The latter can effectively with the stability of the vehicle,and make the vehicle with a certain driving response.Finally,the simulation analysis is carried out under J-turn conditions with different speeds.The simulation results demonstrate that the control system can reduce the vehicle risk under the fault condition through the stability control,and ensure vehicle driving safety.Finally,a test vehicle platform is developed,and a rear wheel motor drive electric vehicle is designed.The control effect of optimal torque distribution control in vehicle stability control strategy is verified through the real vehicle test,which lays the foundation for further research on stability control in the future.