Research On Controller Of Steering-by-wire Execution Module Based On Redundant Fault Tolerant

As the key technology of automatic driving,Steer-By-Wire technology cancels the mechanical connection between the steering wheel and steering gear in the traditional steering,and uses the way of communication instead,which realizes the decoupling of driver's operation and vehicle movement.However,the electronization of the system also reduces the controllability when the steering fails,especially for the Steer-By-Wire execution module,in which the failure of the main components directly affects the steering of the vehicle.In this paper,the controller of the Steer-By-Wire execution module is studied to ensure the basic functions of stable and accurate steering.At the same time,the fault diagnosis and redundancy fault tolerance of the sensor are studied and designed to make the controller have the redundancy fault tolerance function of the Angle information and further ensure the reliability of the Angle information.Firstly,the overall structure of the Steer-By-Wire execution module was designed,and the brushless DC motor was taken as the steering motor.Then,the mechanical part dynamics model of the Steer-By-Wire execution module and the mathematical model of the brushless DC motor were established,and the driving mode and control strategy of the motor were designed.Considering the advantage of flexible design of Steer-By-Wire,the variable transmission ratio of steering was designed based on the vehicle two-degree-of-freedom dynamics model.Combined with the above mathematical models,the correctness of the model of Steer-By-Wire execution module is verified by using the co-simulation of Carsim and Simulink.Secondly,combining the established dynamic model and the vehicle two-degree-of-freedom model,the state matrix and the observation matrix are derived,and the front wheel angle estimator based on the Adaptive Unscented Kalman Filter algorithm is designed.The fault characteristics were analyzed according to the estimated steering Angle,steering Angle sensor information and linear displacement sensor information,and a fault diagnosis strategy was designed based on residual error and residual error sequence.Furthermore,a redundant fault tolerant system based on adaptive weighted fusion is designed according to the fault information and the characteristics of residual sequence.A Simulink model of Adaptive Unscented Kalman Filter,fault diagnosis and redundancy fault-tolerant system is built,and the validity of the sensor redundancy fault-tolerant system is verified by simulation.Then this paper analyzes the hardware modules and functions that the controller needs to have,including communication with the host computer,corner control of the DC brushless motor,sensor redundancy and fault tolerance,etc.,using the F28335 of the TMS320C28 X series as the main chip to complete the main Research and design of chip system,power supply circuit,drive circuit,sensor sampling circuit,etc.,and make control board for corresponding test.On the basis of the hardware circuit,the software development and design of the control system was carried out,and the overall design of the system,the communication program,the program for converting the signal to the corner after acquisition,and the redundant fault-tolerant program were completed,and the controller with the required functions is realized.Finally,the paper designs the test bed of the Steering-By-Wire execution module,carries out the motor angle follow-up test,fault diagnosis and redundant fault-tolerant test.The designed controller is debugged and functionally verified.The test results show that the controller can better control the motor.The position tracking of the sensor is equipped with the fault diagnosis and redundant fault tolerance functions of the sensor,which meets the design requirements.