Research On Control Method Of Joystick Steer By Wire For Distributed Drive Electric Vehicle

Each wheel of distributed drive electric vehicle can drive independently and turn independently.Compared with traditional vehicles,it has more advantages of freedom than traditional vehicles,which is conducive to improve the stability of vehicle operation and has important significance in the form of vehicle layout.For the control lever type line control steering system,the driver can control the swing of the control lever,which can make the driver feel the steering feedback more intuitively when steering,reduce the complexity of the vehicle steering control,improve the vehicle comfort and slow down the fatigue time of the driver.The control of the electric vehicle with the distributed drive of the control rod type of the line control steering will be significantly different from the traditional steering wheel steering vehicles.The Project is sponsored by " Liaoning Bai Qian Wan Talents Program",the project studies the control method of the control of the control of the lever type of wire control steering based on the National Natural Science Foundation Project(51675257),taking the control rod type line control to distributed drive electric vehicle as the research object,It provides theoretical basis and technical support for the development of the real vehicle of the distributed drive electric vehicle with the control rod type line control.The main contents of this thesis are as follows:(1)Build the vehicle model.The thesis analyzes the working composition and working principle of the distributed drive electric vehicle of the control rod type line control steering,establishes the simulation model of the control rod type electric vehicle with the software matlab/simulink and Car Sim,including the application of matlab/simulink to build the system model of the driving motor and the steering electric machine,and the car body,tire,suspension,braking and other system models by using the software of casim,The results are helpful for simulation experiments.(2)The design of the angle transmission ratio of the control rod type line control steering system.For the steering angle ratio of the front wheel of the control rod type line control steering system,the design is mainly aimed at the fixed gain.The influence of vehicle speed and angle of control lever on the diagonal transmission ratio is analyzed.The ideal control strategy of front wheel angle transmission ratio is designed.For the transmission ratio of rear wheel steering angle,the segmented control mode is adopted,and the vehicle speed is used as the switching condition.When the vehicle speed is low,the angle relation between the front and rear wheels is obtained by the two degree of freedom model,and the ratio of the front and rear wheel steering is determined to realize the design of the rear wheel angular transmission ratio;When the vehicle speed is high,the control algorithm at low speed can not guarantee the stable driving of the car due to the influence of tire side deflection force and axle load transfer.Therefore,the fuzzy control method is used to determine the change of the rear wheel angle in high speed.The above methods can improve the maneuverability of the control lever type line control steering system and ensure the good stability in the high speed condition.(3)The research on the failure control of the line control steering system.The failure condition of steering motor is analyzed,and the corresponding solutions for different motor failures are given to improve the safety of vehicle driving.In view of the failure of a steering motor system,it is easier to realize differential steering by using the advantage of four wheel independent control of distributed drive electric vehicle.Therefore,differential torque is adopted to ensure the normal steering of the vehicle and improve the driving safety of the vehicle.(4)The experimental results are verified.The control strategy of steering ratio of the steering ratio of the electric vehicle with the control rod type line control is verified by using the driving simulator hardware on the loop test bench.The real vehicle verification under low speed is carried out by using the experimental vehicle.The results show that the control method studied in this thesis can improve the vehicle driving stability and the algorithm has good real-time performance.