Research On Of Sensorless Disturbance Reject Control Of Servo Motor At Low Speed

Because of their simple structure,high efficiency and low torque ripple,permanent magnet synchronous motors(PMSM)have been widely concerned in the industrial field.The control system of PMSM has very high requirements on the position information of the rotor,and the position and speed are usually acquired by position sensor.However,the use of position sensors limits the application of the system in some extreme conditions.Therefore,the research of sensorless control has become a hot issue in the motor control system.In high speed condition,the motor position estimation is often based on the back EMF estimation method.However,under the condition of low speed,back electromotive force of motor is too small,resulting the signal-to-noise ratio of the back electromotive force greatly reduced,which can't accurately estimate the position signal based on back EMF method.Therefore,the low speed sensorless control of permanent magnet synchronous motor is a tough point in the control of sensorless control.In this paper,research statuses of permanent magnet synchronous motor sensorless control technology are summarized,which indicates that in the field of sensorless control of permanent magnet synchronous motor,position and speed estimation of low speed and the stable operation is a big difficulty.Therefore,this article launches a deeply study on the sensorless stablility control of PMSM at low speed,in which the location estimation algorithm is employed based on high frequency signal injection method.To solve the influence of carrier wave uncertainty to the observer gain and SNR by the traditional signal processing methods,this paper proposes a combination of short time Fourier transform and special coordinate system of the position error signal extraction method.This paper designs a short time Fourier transform(STFT)method based on hanning window and the rotor error information is extracted through STFT and special coordinate system.Finally through a mechanical model of the feedforward torque observer the position and speed is estmated.In view of system dynamic performance degradation problems caused by the high frequency injection method under low speed condition,high frequency injection combined with vector control under sensorless control method is proposed.The speed loop of sensorless vector controller is designed.The current loops of ADRC are designed,and the advantages of the current controller are analyzed.Finally,the simulation of two real-time simulation systems,dSPACE and RT-LAB,is used to verify the proposed method.