Improved two dimensional micro-/nanoradian angle generator with single rotation center located on tilting plane and error compensation of capacitive sensors

An improved two dimensional micro-/nanoradian angle generator (2D-MNAG) with single rotation center located on the tilting plane and error compensation of capacitive sensors is presented in this study. The 2D-MNAG is structured on an optimized flexure hinge with single rotation center in orthogonal axes. The rotation center is located on the center of tilting plane of 2D-MNAG so that there is no linear displacement coupled in the angular output of the tilting plane. Three capacitive sensors are used in the 2D-MNAG to monitor the angular output for feedback control. The principle error of capacitive sensor while used in angle measurement is compensated using an established model, thus to improve the accuracy and repeatability of the angular output. A synthetic output error of 0.212 arcsec of 2D-MNAG is obtained using Monte Carlo simulation while the distance from rotation center to each driving and angle monitoring point is 40 mm with manufacturing and mounting errors in the range of [-0.01, 0.01] mm in rectangular distribution. The performance of the angular output monitoring unit and the strategy for closed-loop control are the key for improving the 2D-MNAG while the mechanical structure and driving unit are optimized.