Research On Permanent Magnet Synchronous Motor Drive System Of Electric Hydraulic Power Steering

The power steering motor,as a part of the electric hydraulic power steering(EHPS)system,drives the oil pump to push the power piston to achieve the task of power steering.The research object of this thesis is a permanent magnet synchronous machine(PMSM)for power-assisted steering,with a rated power of 1.5k W,using a position sensorless control algorithm,and running at a constant speed and variable load after the automobile is started.To achieve the requirement,this thesis studies an off-line parameter identification method and a sensorless control algorithm of PMSM,where a set of power steering motor drive system software and hardware is designed,and experimental verifications are conducted.The main research contents of this thesis are as follows:1.The composition of the automobile power steering system and the advantages and disadvantages of different structures are analyzed.Then,the characteristics of the EHPS,and hence the basic control requirements of the power steering PMSM drive system are clarified.2.The existing PMSM parameter identification methods and sensorless control algorithms are suummarize,combined with the operating conditions of the power steering PMSM,and then the model reference adaptive system(MRAS)is determined as the sensorless control method of this thesis.3.The principle of off-line identification of PMSM parameters and its implementation method are analylzed.Then,an off-line identification of stator resistance,direct-axis inductance,quadrature-axis inductance,and permanent magnet flux linkage is conducted,and consequently,the effectiveness of the algorithm is verified by comparing the identification results with actual values.4.The model reference adaptive system(MRAS)control method based on back EMF is investigated,where both simulations and experiments for the operating conditions of power steering PMSM are conducted,focusing on the robust performance under the conditions of starting with load,variable load and changing motor parameters.5.Aiming at the reversal phenomenon in the motor starting process,a PMSM rotor pre-positioning method based on sector judgment is proposed,which can effectively avoid the rotor reversal,and the effectiveness of this method is verified by experiments.6.A set of power steering PMSM software and hardware platform is built,including power supply system,self-locking circuit,IGBT drive circuit,high-speed CAN transceiver circuit and other circuits that meet the automotive scene;a PCANExplorer-based host computer control platform is designed for controlling and checking the state of the motor and observing the experimental data.