A Novel Magnetic Rotary Encoder for Servo Motors

概要

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A new type of a magnetic rotary encoder for servomotors is proposed. A salient feature of the proposed encoder is its small size, high resolution, and simple construction. An encoder based on the proposed method having a width of 10mm, a height of 10mm, and a depth of 3mm was developed and is reported here. In addition, the developed encoder has a high resolution of 4096ppr and is capable of detecting absolute angular position. The proposed encoder comprises of a disc magnet magnetized in one direction with all the magnetic domains in the material parallel to each other, a stationary body made up of a magnetically soft material, and four Hall effect devices. This paper describes the configuration of the encoder and the proposed detection process of the rotational position. The characteristics of the prototype encoder are also presented. The accuracy of the encoder depends on the distortion of a pseudo-sinusoidal output waveform, and therefore for achieving high accuracy the distortion of the output waveform should be minimal. The magnetic flux distribution and the output waveform of the encoder were simulated using finite element method (FEM). Based on FEM analysis, the optimal shape of the disc magnet and its housing, relative position of the Hall effect devices and the material of the disc magnet were determined to achieve high performance characteristics.
社団法人電気学会の論文
2006-09-01