2016 Volume 5 Issue 2 Pages 148-153
A helical motor, which is composed of helically-shaped stator and mover, has various advantages. However, in order to control this motor, we need two encoders to measure the translational position and rotational angle of the mover. This paper describes a method of estimating the gap displacement, which is the relative position of the mover from the center of the stator slot. If we can estimate the gap displacement accurately, one of two encoders used by present helical motors can be removed. Our proposed method uses the relation between the gap displacement and the inductance, which is derived from the mathematical model of the helical motor. In order to estimate the gap displacement, high-frequency voltage is injected into the armature windings and a current of the same frequency component is extracted. The validity of the method is confirmed by numerical simulations and experiments.