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

Back electromotive force (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 article, a novel back 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 article proposes a jumping correction algorithm and a uniform correction algorithm. The mover position is calculated from the corrected flux linkages. This article 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 the stability and accuracy in the whole speed range. Compared with the existing back EMF-based methods working only well in high-speed region and usually with mm-level accuracy, the proposed method achieves an accuracy of sub-200 mu m regardless of the reference trajectory, and has exciting prospect in industrial applications.

Automated summary

This article proposes a novel back EMF-based mover position estimator that achieves consistent high accuracy in the entire speed range. The three-phase flux linkages are obtained by directly calculating the integration of back EMF. To overcome the curve drift caused by the integrator, jumping correction and uniform correction algorithms are proposed. The experimental results demonstrate that the proposed position estimator guarantees stability and accuracy in the whole speed range, with a sub-200 μm accuracy regardless of the reference trajectory, which has exciting prospects in industrial applications.