Measurement of initial phase for movers in magnetically levitated planar actuators

Abstract

Mover position initialization is the prerequisite to realize the precision motion control of magnetically levitated planar actuators (MLPAs), while its basis is the initial phase positioning. In this paper, an estimation algorithm was proposed to position the mover's geometric center as well as the rolling angle in motionless MLPAs. The mechanism was that: based on the linear Hall sensors distributed at different points in the MLPA mover, the magnetic flux density at motionless state was measured, and then the first-order harmonic model of magnetic flux density distribution above the magnet array was used to solve the magnetic field phase and rolling angle at the MLPA's geometric center. Moreover, the positioning precision was improved by adding a redundant sensor and via rational arrangement of sensors, which ensured that data would not be collected at the magnetic field peaks. The experiments indicate that after addition of one redundant sensor, the maximum errors in phase positioning and rolling positioning were both reduced.