| Four-wheeled independent control-by-wire vehicle have gradually entered people’s field of vision with the advantages of high degree of freedom,flexibility,stability and easy integration of intelligent control methods.Although it has many advantages,the drive motor may change the terminal voltage due to poor insulation,winding resistance changes and other reasons,and the reliability of the wire control system is not as good as the mechanical structure,which will increase the probability of actuator failure.Therefore,this paper studies the fault tolerant control strategy for the failure of the singlewheel motor fail and the opposite side dual-wheel motor fail of the four-wheeled independent control-by-wire vehicle that loses part or all of the driving capacity to ensure the stability and dynamics of the vehicle.And improve the driver’s driving experience.The main research contents are as follows:Firstly,a four-wheeled independent control-by-wire vehicle model was established,including a 3-degree-of-freedom body plane motion model,a drive motor model,and a magic tire model.At the same time,the double-shifting test is used as the simulation condition,and the established vehicle model is compared with the state of the car output by the Carsim vehicle model to verify the accuracy of the model.Secondly,a trajectory reference model was established.When a Four-wheeled independent control-by-wire vehicle’s hub motor terminal voltage abnormally causes the motor to lose part or all of its driving ability,it will affect the vehicle’s turning angle,thereby changing the driving track.When performing drive motor fault-tolerant control,you need to refer to the car under fault-free conditions.Track the corner of the target driving path.Therefore,this article is based on the linear 2--degree-of-freedom vehicle model,combined with the active front wheel +active rear wheel steering control strategy,so that the output front and rear wheel angles can be used as the desired angle for fault-tolerant control.Afterward,the fault tolerant control research is carried out to solve the problem of vehicle instability and power loss caused by the failure of the vehicle’s single-wheel or opposite-side two-wheel actuators.When a system failure is detected,determine the failure mode and use the failed wheel as the driven wheel,and then adopt the corresponding control strategy;in order to reduce the complexity,the normal yaw moment is not considered,and the driving force of the normal working wheel is redistributed to control the stability;In order to compensate for the yaw moment ignored by the stability control and increase the driving experience,the direct yaw moment control based on the sliding mode control is introduced,which is parallel to the stability control;to ensure the dynamics of the vehicle and prevent the rear-end collision caused by the failure of the actuator,the dynamic control based on the collision avoidance model is introduced.Finally,take the front and rear wheel angles output by the active front wheel + active rear wheel control as the desired angle,combined with direct yaw moment control,under the doubleline shifting condition,change the road adhesion coefficient and vehicle speed,and set the right front wheel motor fail,front wheel and right rear wheel motor fail,then carry out the simulation experiment.The results show that the fault-tolerant control strategy can keep the stability and tracking ability of the faulty vehicle consistent with the results under the condition of no fault,and can effectively improve the response rate of fault-tolerant control. |
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