Development of the principle for the angle measurement using the two-track scale

摘要

Our study aims to develop the miniaturization angle measurement device applied to a principle of the super high accurate angular measurement. A rotary table requires a rotational positioning with high accuracy, for example, processing a material on a rotary table like a machining center. It is necessary to measure the angle indicated by the rotary table due to control this positioning. The angle accuracy of the rotary table is generally determined by a rotary encoder installed on it. The rotary encoder is one of the angle measurement devices, and it is important to improve the performance of the rotary encoder for the rotational positioning with high accuracy. There are two methods to improve the angle accuracy of the rotary encoder. One method is the way to decrease the angle error directly using the high-performance parts constructing the rotary encoder. The other method is self-calibration to detect and correct the angle error by itself. These methods realize the angle accuracy 0.1 to 0.4 [arcsec] in the one rotation. However, it is limited to improve the angle accuracy using these methods. Therefore, we proposed the new principle which can realize the angle accuracy 0.01 [arcsec] without these methods, the super high accurate angular measurement principle, and developed the angle measurement device based on this new principle. However, on the theory of new principle, the device had the problem that its size grows up due to use the two rotary encoders. Therefore, we propose the principle of the super high accurate angular measurement to apply to the miniaturization angle measurement device installed the special scale disk in this paper. This scale is consisted of two-track scale lines of which the pitches are different.