Back EMF-Based Dynamic Position Estimation in the Whole Speed Range for Precision Sensorless Control of PMLSM

Abstract

Back EMF-based sensorless control strategies for permanent magnet linear synchronous motor (PMLSM) have the potential to simplify the mechatronic system, reduce the cost and prolong the service life. However, the poor performance in the low-to-zero speed region limits their application range. In this paper, a novel back electromotive force (EMF)-based mover position estimator is proposed to achieve consistent good accuracy in the whole speed range including high speed, medium speed, low speeds, temporary standstill, and speed reversals. The three-phase flux linkages are obtained by directly calculating the integration of back EMF. To overcome the curve drift caused by the integrator, this paper proposes a jumping correction algorithm (JCA) and a uniform correction algorithm (UCA). The mover position is calculated from the corrected flux linkages. This paper also realizes a closed-loop sensorless trajectory tracking control system using the proposed position estimator. Experimental results on a PMLSM demonstrate that the proposed position estimator can guarantee stability and accuracy in the whole speed range. Compared with existing back EMF-based methods working only well in high-speed region and usually with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$mm$</tex-math></inline-formula> -level accuracy, the proposed method achieves an accuracy of sub-200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu m$</tex-math></inline-formula> regardless of the reference trajectory, and has exciting prospect in industrial applications.