| In order to solve the energy crisis and environmental pollution caused by traditional vehicles,governments pay more and more attention to the research and development of electric vehicles.Because in-wheel motor drive electric vehicle has the advantages of short transmission,independent and controllable wheel torque and vehicle dynamics control freedom,it has become an important direction of electric vehicle development.However,how to give full play to the advantages of distributed drive and improve the active safety of vehicles under extreme working conditions still needs to carry out in-depth research on vehicle lateral stability evaluation and control methods.The research innovations of this paper mainly include the following two aspects:1)In order to solve the problem of saturation of output torque amplitude and response speed of hub motor,combined with the second-order nested saturation model,an anti-saturation fuzzy sliding mode controller is proposed;2)In order to reduce the intervention of active safety control system to improve ride comfort and vehicle dynamic stability,a torque distribution cooperative control strategy based on balanced torque vector and differential braking is proposed.Firstly,aiming at the problem of output torque saturation and response speed limitation of hub motor,an upper controller of lateral stability based on anti-saturation fuzzy sliding mode control strategy is established.The co-simulation results of AMESim and MATLAB/Simulink show that the proposed control strategy can strictly limit the amplitude and change rate of direct yaw moment and improve the reliability of torque distribution control.Secondly,based on the double line method of sideslip-sideslip velocity phase plane and the nonlinear partial least squares regression method,the modeling method of stability boundary parameters on vehicle speed,front wheel angle and road adhesion coefficient is proposed.The accuracy analysis results show that the proposed method has high modeling accuracy and can provide decision-making basis for subsequent torque distribution and coordinated control.Thirdly,in order to reduce the sense of intervention of the active safety control system and improve the safety line under extreme working conditions,a torque distribution cooperative control method based on balanced torque vector distribution and differential braking is proposed.The weight coefficients of the two allocation methods are dynamically adjusted according to the vehicle instability risk.Finally,the control performance is verified by simulation and hardware in the loop simulation test.The results show that the proposed anti-saturation control strategy can reliably realize the direct yaw moment;the proposed coordinated control strategy can improve the safety and ride comfort of vehicles under extreme working conditions. |
