Effects of assembly errors on axial positioning accuracy for rotating machinery with magnetoresistance-based magnetic encoders

In positioning systems, magnetic scales consisting of magnetoresistive sensors are widely used in the generation of position signals for machine tools. To obtain a precise position, magnetoresistive elements inside the sensor head output sinusoidal signals through the angle between the magnetization vector and the supplied current direction in order to determine the displacement of the system under a saturated magnetic field. With the development of machine tools, magnetic pattern media have evolved from linear encoders to rotary. In this paper, various medium models are built in order to examine the effects of changes in medium size, and the finite element method is used to simulate optimal size of the magnetic ring and assembly tolerances, such as pitch, yaw, and flying height errors. The results demonstrate that pitch angle error dominating among all errors results in the greatest impact on measurement accuracy. The installation of rotating machinery with the magnetoresistance-based magnetic encoders can follow the suggested design rule presented in this paper to optimize these error sources and quantify them accordingly to reduce assembly error.