Motion sensorless control of BLDC PM motor with offline FEM info assisted state observer

Abstract

This paper describes a new offline FEM assisted position and speed observer, for brushless dc (BLDC) PM motor drive sensorless control, based on the line-to-line PM flux linkage estimation. The zero-crossing of the line-to-line PM flux linkage occurs right in the middle of two commutation points, which is used as a basis for the position and speed observer. For performance applications, the position between commutation points is obtained by comparing the estimated line-to-line PM flux linkage with the FEM calculated line-to-line PM flux linkage. Even if the proposed observer relies on the fundamental model of the machine, a safe starting strategy under heavy load torque, called I-f control, is used, with seamless transition to the proposed sensorless control. The I-f starting method allows low-speed sensorless control, without knowing the initial position, and without machine parameters identification. Digital simulations and experimental results are shown, demonstrating the reliability of the FEM assisted position and speed observer for BLDC PM motor sensorless control operation.