Novel algorithm for mover position measurement in linear motion systems

Abstract

In this paper we consider an enhanced position sensing algorithm in linear motion systems, based on permanent magnet tubular linear motors (PMTLM), which became quite widespread in recent years. Unlike traditional systems that convert rotating into linear motion (ball-screw pairs, belt drives and worm-gears) linear motors are deprived of many shortcomings related to mechanical interaction of the machine parts, but, however, they also are characterized by some disadvantages. Currently, one of the most actual scientific problems related to this kind of motor is a find a way to determine the current position of mover along the stator while fitting into strict real time constraints maintaining high accuracy despite all stator and mover imperfections. In this paper, we propose a modified algorithm to determine mover position, using two Hall-effect sensors, which eliminates the need for separate optical or magnetic encoder. Proposed algorithm heavily relies on the use of very large correction tables, created during the calibration, which is done right at the end of motor and stator assembly manufacturing. Proposed algorithm makes it possible to achieve the positioning accuracy within 10 um range, while keeping the usage of additional costly equipment and electronic parts at minimum.