High-Resolution Absolute Position Vernier Shaft Encoder Suitable for High-Performance PMSM Servo Drives

Abstract

Permanent magnet synchronous motor (PMSM) drives are suitable for high-performance servo applications, as in robotics. This, however, requires an accurate position feedback, which is not possible with the existing absolute position encoders, unless one is prepared to compromise on the size of the encoder. This paper proposes a new encoding scheme based on the simple Vernier principle. The proposed scheme improves the resolution of the encoder within limited disk diameter. An improved encoder based on the same principle is also presented with minor modifications to improve the resolution. Computer simulations and experimental work have shown that a suitable modification of the Vernier concept can result in an encoder that is superior to the existing ones. Details of this work are presented.