Rotation angle sensing system using magnetostrictive alloy Terfenol-D and permanent magnet

Abstract

In this study, we developed a rotation angle sensor using the polycrystalline magnetostrictive alloy Terfenol-D, an SmCo permanent magnet, and a commercial dial gauge. The magnetostriction ΔL/L value was measured based on the variation in the electrical resistance of a strain gauge fixed on Terfenol-D. The merit of this system is that it is non-contact and can convert the measured electrical resistance directly into the angle of rotation. The ΔL/L was proportional to the distance x between Terfenol-D and the SmCo magnet. The deviation of the measured points from the fitting linear line was ±0.4%, which corresponds to ± 1.4°per 360°rotation.The developed system is suitable for rotation angle sensors. We also performed the actuation of this sensor system in variable state and compared this sensor system with giant magnetoresistance or Hall sensors; the rotational angle, maximum speed, and errors are not significantly different from those of other sensing types.