Study On Sensorless State Estimation And Digital Control Of Bearingless Permanent Magnet Synchronous Motor

Bearingless Permanent Magnet Synchronous Motor(BPMSM)is a new type of motor that combines electromagnetic bearing with permanent magnet synchronous motor(PMSM).This kind of motor integrated with rotating and self-suspension function in one body has a wide application prospect in the fields of semiconductor,life sciences,biochemistry,aerospace and other high-tech fields with small volume,light weight,high power density,no lubrication,no wear and no mechanical noise.For the stable suspension operation as well as the rotor field oriented control,accurate detection of rotor position signal is important.Traditional mechanical position or speed sensors not only increase the size and cost of the motor,but also reduce the reliability of the system.Especially under the conditions of high speed or ultra-high speed the bearing motor excellent high-speed performance will be seriously limited.Therefore,based on the establishment of BPMSM mathematical model,this paper studies the state estimation method of BPMSM based on sliding mode observer.The hardware and software design of the BPMSM digital control system is completed.The concrete content includes:(1)The principle of the levitation force in the BPMSM and the electromagnetic coupling relations between the torque winding and the suspension force winding with air gap magnetic field are analyzed.The exact model of the BPMSM levitation force considering rotor eccentricity is established by Maxwell's tensor method.The mathematical model of electromagnetic torque considering rotor eccentricity and suspension winding current is deduced according to electromechanical energy conversion principle.(2)Based on the traditional sliding mode observer,which exists larger chattering,a BPMSM rotor position estimation method based on improved sliding mode observer is proposed.The estimate of back electromotive force is obtained by the sliding mode observer.The rotor position and velocity is extracted from the estimated back electromotive force using the phase-locked loop type position observer with PI-I structure.By using the rotor field orientation control strategy and considering the rotor eccentricity,the simulation model of BPMSM sensorless control system is established by using Matlab/simulink.Simulation results show that the improved method can reduce the chattering and improve the accuracy of the rotor position estimation under the medium and high speed conditions(3)A complete software and hardware implement scheme is provided,and a BPMSM digital control experiment platform based on DSP TMS320F28335 is constructed.Hardware designs of BPMSM digital control system mainly include auxiliary power supply circuit,detection circuit,interface circuit.Software designs of BPMSM digital control system mainly include rotor position and velocity calculation,radial displacement close-loop control algorithm,velocity and current close-loop control algorithm,SVPWM modulation algorithm.BPMSM digital control system software and hardware debugging are made.Through the analysis of the experimental results,the correctness of the proposed design is proved.