Study On Electric Power Steering System With Recirculating Ball Type Based On Permanent Magnet Synchronous Motor

In recent years,with the popularization of automobiles,people have higher and higher requirements for the portability,flexibility,stability and safety of automobile driving,and the safety and handling stability of automobile driving have a direct relationship with the performance of automobile steering system.However,there are many problems in the traditional power steering system.At this time,the electric power Steering(EPS)system came into being.It is assisted by the motor output torque to complete the steering operation.It not only meets the above requirements for car driving,but also has the advantages of environmental protection and energy saving.It is widely used in various types of vehicles.Electric power steering system plays an important role in the development of power steering technology.In this paper,permanent magnet synchronous motor(PMSM)is selected as the assist motor of electric power steering system.Based on this,the electric power steering system with recirculating ball type is researched,mainly includes:(1)The structural composition and working principle of the electric power steering system are briefly introduced.The control principle of the permanent magnet synchronous motor is analyzed,and the control method of implementing the d-axis current to 0 is determined.(2)The steering resistance torque of the vehicle in the in-situ steering and the normal steering of the vehicle is analyzed,and the structure of the EPS system of the target vehicle is simplified.On this basis,the dynamic mathematical model of each part of the cycle ball electric power steering system is established.(3)According to the working requirements,the three control modes of the electric power steering system with recirculating ball type used in the target vehicle are analyzed and studied.For the assistant control,the conventional PID control strategy and the PID control strategy based on genetic algorithm optimization are formulated.In response to the lack of returnability at a low speed and the overshoot of returnability at a high speed,a return-to-center control strategy was developed.Aiming at the problem of poor road feel when the car is driving at high speed,the damping control strategy of the electric power steering system is formulated.(4)The simulation models of the EPS system are built in the environment of Matlab/simulink.The simulation and analysis of three kinds of control of the EPS system are carried out.The simulation results show that the optimized PID assist control based on genetic algorithm optimization has better target current traceability and higher steering stability than conventional PID assist control.After the EPS system is added to the return-to-center control,the steering wheel can always return to the middle position quickly,and the system stability is also enhanced,whether it is at low speed steering or high speed steering.The addition of damping control at high speeds reduces steering sensitivity and improves driver's road feel and driving safety.(5)With the single-chip microcomputer TMS320F28035 as the core,the EPS controller prototype was developed.In order to verify the performance of the controller prototype,the basic performance test bench of the recirculating ball EPS system based on LabVIEW was developed.According to the relevant test standards,the input torque/output torque test,input torque/motor current characteristic test,forward no-load torque test and function test were carried out on the basic performance test bench of the recirculating ball EPS system.The test results show that it meets the relevant industry standards.