FEM assisted position and speed observer for BLDC PM motor drive sensorless control, with experiments

In this paper, the authors propose and investigate a FEM assisted position and speed observer for brushless d.c. PM motor drive sensorless control, based on the line-to-line PM flux linkage estimation. The line-to-line PM flux may be estimated using measured currents and line-to-line voltages. The zero-crossing of the line-to-line PM flux linkage occurs right in the middle of two commutation points. The time period from one commutation point to zero-crossing is equal with the time period from zero-crossing to the next commutation point, at constant or slowly varying speed. This is used as a basis for the position and speed observer. For performance applications, in the present paper, the position between commutation points is obtained by comparing the estimated line-to-line PM flux with a look-up table, which contains the position versus FEM calculated line-to-line PM flux. A simulation model and experimental results are shown, demonstrating the reliability of FEM assisted position and speed observer for BLDC PM motor.