An Absolute Linear Displacement Sensor Based on Orthogonal Dual Traveling Wave Magnetic Field

This paper presents an absolute linear displacement sensor, which is based on orthogonal dual traveling wave magnetic field. The sensor consists of two groups of field coils and inductive coils. Two groups of field coils with ‘
${N}$
’ and ‘
${N}$
-1’ pitches generate two groups of traveling wave magnetic field which move in orthogonal directions. Then, the mixed magnetic field is picked up and induced by two groups of inductive coils. Two roads of electrical traveling wave signals are generated. Absolute position measurement is realized by comparing the phase differences of two groups of electrical signals. Compared with the traditional structure of the absolute sensor, the sensor combines dual tracks into a single track. Accordingly, the width of the sensor can be reduced. In order to be sensed effectively, dual traveling wave magnetic fields move orthogonally. The angular separations with the direction of measurement are 45° and −45°. The structure and measurement principle of the sensor are described in detail. A sensor prototype is fabricated by printed circuit board technology, and the experiment is brought out. The experimental results show that the sensor can achieve absolute displacement measurement, and the measurement accuracy is ±
$15 ~\mu \text{m}$
within the measurement range of 0–80 mm.