A PZT Actuated 6-DOF Positioning System for Space Optics Alignment

Due to limitations in the fabrication technology, the large aperture space optical mirror is always spliced into several small segments rather than fabricated monolithically. To guarantee the imaging quality of the system, each segment needs to be aligned at micron-level precision with millimeter-level range. For this purpose, a PZT actuated six-axis high-precision positioning system, which consists of three serially connected parallel mechanisms is proposed in this article. Compared with previous 6-DOF positioning solutions, such as a Stewart platform, the proposed design features a relatively compact structure and straightforward kinematics. To realize long stroke and fine resolution simultaneously, bridge-type amplifiers are employed to enhance the stroke of the PZT actuation, and the flexure hinges are utilized to eliminate friction and backlash. The performance of the amplifier under two kinds of external loads are analyzed so that the amplifiers could be designed according to the application conditions. Furthermore, it can be found that the displacement sensors must be employed at the output end of the actuation module to eliminate the input coupling that commonly exists in the compliant mechanisms. The feasibility of the design is validated by finite-element analysis and experiment study. The maximum stroke is 2.1 mm in the Z-axis, and the finest resolution is 0.5 μm in X- and Y-axis.