A two-dimensional homopolar linear DC motor with new position detectors

This paper presents a novel two-dimensional homopolar linear DC motor (LDM) which can realize motion two-dimensionally. For precise position control purposes, two kinds of position detecting methods are proposed. The position in one direction is detected by means of a capacitive sensor with a feedback loop which makes the output of the sensor largely immune to the variation of gaps between electrodes. The position detection in the other direction is achieved by exploiting the inductance difference between the two driving coils, instead of using an independent sensor. From the experimental results, good thrust distributions and satisfactory linearity of the detecting methods are obtained. The maximum detecting error is 0.9% and 1.7% respectively.