Portable Rotary-angle Detector for Industrial Motor Inspection

Several types of precision equipment, such as machine tools and robot arms, rely on precision rotary motion. In this study, we developed a portable rotary-angle detector (PRAD) comprising five optical sensors and one angle ring with a 57-mm diameter to measure the positioning and radial errors of rotary motions. The five optical sensors were installed at equally divided intervals around the angle ring according to the equal division averaged method (EDA-Method) implementation. The grating of the angle ring has 9000 lines, and the signal interpolation of the angle detector system has 4000-fold subdivision. Therefore, the PRAD resolution can be achieved at 0.036 arcsec. Furthermore, a 12-face polygon and an autocollimator with 0.05-arcsec resolution and 0.25-arcsec accuracy were used to check the PRAD performance. The experimental results showed that the structure of the PRAD is simple. However, the difference over 360° is only 0.7 arcsec, indicating that PRAD is suitable for motor inspection in machine tools or robot arms.