Verification of the Usefulness of Eccentric Structure in the Magnetic Encoders Using a Multipole Magnet

Abstract

It is more difficult for magnetic encoders to achieve a higher resolution than optical encoders. The resolution can be improved by multipolarizing the magnet, however the absolute angle cannot be calculated. Using the eccentric rotation of a 4-pole magnet, the authors simultaneously achieved high resolution and absolute angle calculation for a magnetic encoder. In this paper, we propose a high-resolution magnetic absolute encoder using an 8-pole magnet. The higher the eccentricity of the magnet, the easier it is to calculate the offset required to calculate the absolute angle. However, as the eccentricity increases, the angle error increases. The relationship between eccentricity and angle error is clarified, and an appropriate eccentricity is examined.