Implementation of Embedded Magnetic Encoder for Rotor Position Detection Based on Arbitrary Phase-Shift Phase-Lock Loop

Abstract

Rotor position is essential in control of permanent magnet synchronous motors (PMSMs). In terms of resolution, structural complexity, occupied volume, anti-interference ability, environmental adaptability, and cost, embedded magnetic encoder based on linear Halls owns strong competitiveness. When linear Hall sensors are selectively installed at stator slot openings in extremely compact scenario, signal phase-shift asymmetry between two or three Hall sensors is inevitable. Conventionally, prefilter synchronous reference frame-phase-locked loops exhibit excellent phase-lock ability at fixed frequency (50/60Hz), but become ill when frequency changes especially at zero frequency. In this article, a novel transformation matrix is derived to map the asymmetric phase-shift signals onto two-phase stationary coordinate system. Then, an arbitrary phase shift-phase-locked loop is formed by replacing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Clark</i> transformation with the proposed transformation matrix, which can accurately extract rotor position and speed information in a simple and effective way, avoiding the utilization of complex notch filter. Simulations in continuous domain based on MATLAB and experiments in discrete domain based on an 18-slot/20-pole prototyped PMSM both confirm the effectiveness of the proposed method.