Acquired Angle Error Correction Based on Variation of an Angle Detection Signal Intensity in Rotary Encoders

Abstract

Rotary encoders are used in various machines to measure the angular position of a rotating axis. Therefore, rotary encoders are required not only to be highly accurate, but also usable in various environments. When using a rotary encoder on a machine, acquired angle errors occur due to the eccentricity between the encoder and the machine, the deformation of the scale, and the shaft runout of the rotation axis. Various methods have been adopted to reduce such angle errors. However, these methods have problems such as the large size and high cost of the encoder, the necessity of additional devices for measuring, and increasing installation labor, so the environment in which they can be implemented is limited. In this study, we have proposed a method to correct the acquired angle errors based on variation of an angle detection signal intensity in the sensor head. This method can correct the errors on the machine without using multiple sensor heads or additional devices. The angle error estimated by this method is compared with that measured by the external equipment of a reference encoder. While the maximum angle error was 28.36″ without correction, the residual error with correction of the acquired error can be reduced to 1.75″ or less. From this result, the proposed method can improve the measurement accuracy of the rotary encoder already installed on the machine. Therefore, this method is an effective means for achieving both high rotational accuracy on machines and ease of correcting an error in rotary encoder machines.