Research On Handling Stability Control Of All-wheel Independent Drive Vehicle Based On Differential Steering

Each wheel drive/brake torque of all-wheel independent drive electric vehicle is controllable independently,and the response is quick and accurate.It provides an advantageous platform for the realization of various new concepts,technologies and dynamic control.In this paper,aiming at the current situation that the reliability of steering by wire(SBW)system of all-wheel independently driven electric vehicles equipped with SBW system is difficult to be guaranteed,the author focuses on the danger situation of SBW system failure and the lack of vehicle handling stability,and conducts some research on the control recovery of vehicle handling stability based on differential steering technology.Firstly,according to the research needs,a vehicle dynamics simulation model including the differential steering system model was built based on the MATLAB/Simulink simulation platform,and the simulation comparative analysis was conducted.Secondly,based on the original SBW system of the vehicle,the overall design of the differential steering system is carried out to ensure that in case of SBW system failure,the differential steering system can replace the original system to independently conduct steering action,so that the vehicle can drive according to the expected driving purpose and restore its handling stability.The characteristics of the differential steering control system are analyzed.Select the steering rack displacement as the controlled output,and the torque difference between the left and right steering wheel of the front axle as the control input.Considering the system nonlinear characteristics,control performance requirements and practical application requirements,a differential steering nonlinear controller including steady-state,feedforward and feedback control links is designed based on the three-step method nonlinear control theory,and the simulation verification under typical working conditions is carried out.Aiming at the problem that the differential steering can make the driver regain the control of the vehicle,but its control stability is obviously different from that of the normal steering vehicle,this paper studies the control of the vehicle's control stability based on the differential steering,aiming to make the differential steering vehicle have the same or similar control stability as the normal steering vehicle.Firstly,the vehicle stability control strategy based on the combination of yaw rate and side slip angle was proposed,and the LQR vehicle stability controller with self-adjusting weight was designed based on the linear quadratic optimal control theory.On the one hand,it is used for the deviation compensation control of the differential steering so that when the differential steering is involved in the work,the handling stability of the vehicle is as consistent as possible with that of the normal steering vehicle.On the other hand,it is used for the vehicle stability control to ensure the differential steering vehicle running stability.Secondly,considering the execution conflict between differential steering and vehicle stability control,the coordination control was studied.Based on the conflict analysis,a coordination control scheme was proposed,and a coordination controller was designed based on the extension control theory.Finally,the effectiveness of the control strategy was verified by simulation.Finally,the double-hub motors experimental platform was designed and built.Based on the experimental platform and the NI PXI real-time platform,the hardware in the loop simulation experiment is carried out jointly with CarSim and LabVIEW,and the effectiveness of motor torque tracking control and differential steering control strategy is verified.Design and modify hub motor type all-wheel independent drive electric vehicle experimental platform.The Compact-RIO virtual controller was used to develop the prototype of the whole vehicle rapid control,and the vehicle test was carried out to verify the effectiveness of the differential steering.