Research On Control Strategy Of Vehicle Steer-by-Wire Active Steering System Based On Permanent Magnet Synchronous Motor

Active steering by wire system is a new type of steering system.The traditional steering system uses the mechanical structure to connect the steering wheel and steering mechanism,and the mechanical structure in the on-line steering system is replaced by the electronic control system,so the steer-by-wire system can freely design different angular displacement transmission characteristics and torque transmission characteristics,which has an important impact on the future research of vehicle stability,vehicle handling and active safety.In this paper,the design method of variable transmission ratio of active steering by wire system and the stability of control strategy are studied.The main research contents and achievements are as follows:(1)The structure and working principle of permanent magnet synchronous motor and active steering by wire system are analyzed in detail,and the mathematical model of permanent magnet synchronous motor is built.The magnetic field of permanent magnet synchronous motor is simulated by finite element method using electromagnetic field simulation software,and the rationality of magnetic circuit of permanent magnet synchronous motor is verified.The steering wheel assembly and control system of active steering by wire system are built The dynamic model of the steering actuator is established,and the typical working conditions are co simulated with the vehicle simulation software.The simulation results are analyzed,and the correctness of the model is verified.(2)In order to give full play to the advantage that the active steering by wire system can freely design variable transmission ratio,this paper deeply studies the steering characteristics of the active steering by wire system,based on the linear two degree of freedom vehicle model of the active steering by wire system,establishes the relevant mathematical equations,and designs a variable transmission ratio based on the constant yaw rate gain and lateral acceleration gain.The vehicle model with variable transmission ratio is built in the vehicle simulation software,and the simulation of double line shifting condition and angle step input condition is carried out.The simulation results are compared and analyzed.The fuzzy algorithm is used to optimize the variable transmission ratio,and the simulation results are compared with those before optimization,and the rationality of variable transmission ratio is verified.(3)In this paper,an adaptive fuzzy PI control strategy of steer-by-wire with variable transmission ratio is proposed.Combining the advantages of fuzzy control and PI control,an adaptive fuzzy PI steering controller is designed,which takes the difference between the actual vehicle response parameters and the ideal vehicle response parameters as the input variable.Compared with the vehicle model of other control methods,the simulation experiments of sine amplitude input and angle step input are carried out,and the effectiveness of the control strategy is verified.(4)The test bench of active steering by wire system is built.The hardware in the loop test is carried out under sinusoidal input condition and angular step input condition.The experimental data and simulation results are compared and analyzed to verify the rationality of active steering by wire control strategy.