A Study on Position Estimation Error in Sensorless Control of PMSM Based on Back EMF Observation Method

In this paper, one of the reasons of position estimation error is pointed out, i.e. the chattering of sliding mode observer (SMO). In order to reduce the buffeting of SMO, the permanent magnet synchronous machine (PMSM) sensorless control based on back electromotive force (EMF) observation method is analyzed. Continue function, saturation function, integral function and sigmoid function are compared with traditional switching function in detail. Low-pass filters (LPFs) are added to the output of SMO. A phase locked loop (PLL) is used to replace arctangent function to prevent SMO disturbance from being further amplified, and the corresponding angle compensation algorithm is studied. Through the comparison of simulation results, it is proved that the performance of sigmoid function is the best among these functions.