6-PSS Precision Positioning Stewart Platform for the Space Telescope Adjustment Mechanism

In this paper, the mechanical design, precision control, optimal calibration and experiment of a 6-PSS Stewart adjusting mechanism for space telescope secondary mirror adjustment mechanism is introduced. The modal analysis, static analysis, inverse kinematics modeling and accuracy analysis were performed on the basis of the mechanical design. According to the identification model acquired from the white noise input, the robust controller based on mixed sensitivity is designed for a better robust performance to the model uncertainty and disturbance, and the better disturbance rejection and dynamic characteristics are all verified by the simulation and experiment results. Then, the SMCS optimal method improved by correcting the step size and preventing the crossing of the boundary is applied to the calibration of the Stewart mechanism model. Finally, the effectiveness of the analysis, design and algorithm are all verified by calibration experiments. The results of the system performance test showed that the secondary mirror adjustment system has fine absolute and repeatability positioning accuracy of a single axis, and the system may achieve higher positioning accuracy by decoupling. The precision positioning requirement of Space telescope active optics could be satisfied.