Analysis and comparison of two-dimensional permanent-magnet arrays for planar motor

This paper investigates three kinds of permanent-magnet arrays used in planar motors with polarity centers distributed in the lattices of a matrix. The magnetic field of every kind of magnet array is analyzed by analytical methods. First, we give a Laplace equation of magnetic scalar potential and a series of boundary conditions. Then, we derive the analytical expressions of magnet field strength and magnet flux density in the air gap of each kind of magnet array by the method of separation of variables. Finally, we compare the three types of magnet arrays on the basis of the analytical solutions.

I. Introduction

Compared with the conventional two-dimensional (2-D) positioning device with cumbersome stacked arrangements, the 2-D positioning device with a planar motor possesses advantages such as direct driving, low friction, no backlash, high accuracy, and so on. Until now, many types of planar motors have been proposed. However, according to their principles, most of the planar motors can be classified into three types, i.e., variable reluctance planar motor, induction planar motor, and synchronous permanent-magnet planar motor (SPMPM) [1]. Among them, the SPMPM has the advantages of low cost, simple structure, high-power conversion ratio, etc. And it has been attracting more and more attention of the academic field and the engineering field.