Calibration of Rotary Encoders Using a Shift-Angle Method

Abstract

Cross-calibration using an autocollimator and a polygon is the traditional method for calibrating a rotary encoder. These angles, which can be calibrated using this method, are limited by the pitch angle of the polygon, which is 15° for a 24-faced polygon. In this work, we propose a new shift-angle method using the same setup as the traditional method. However, the new method can measure smaller than the pitch angle of the polygon, which is the measurement limitation of the traditional method. The proposed method can calibrate every angle of the rotary encoder. In the experiment, we use an autocollimator and a 24-faced polygon to calibrate the SelfA rotary encoder to verify the proposed shift-angle method. The SelfA rotary encoder, which comprises one rotary encoder and 12 read heads, is calibrated using self-calibration. The difference between the calibration results obtained by applying these two methods to the same SelfA rotary encoder is smaller than ±0.1″.