Robust control of the servo system of Leighton Chajnantor Telescope under high wind speed

The Caltech Submillimeter Observatory telescope (CSO) will be moved from Mauna Kea, Hawaii to Chajnantor Plateau, Chile in 2022, and renamed as Leighton Chajnantor Telescope (LCT). The altitude of the new site of LCT is 5050 m, and the average wind speed is about 10 m/s. However, the pointing accuracy of LCT will be improved to 1 arc-second (rms), and the rotating speed of LCT's antenna will be improved to 2 degrees/sec, in order to achieve its new scientific aim of large survey in the sub-millimeter waveband. More precise pointing accuracy and faster rotating speed under higher wind speed makes the servo control of LCT very challenging, because both the steady-state and the transient performances of the servo control system are required to get improved under larger disturbance, while the mechanical structure of LCT is less rigid due to the adoption of lean and optimized design. To solve this problem, in this work, a state-space model of the LCT servo control system is constructed, and the Davenport wind disturbance model for LCT is also constructed for simulating wind disturbance. To improve the stability and controllability, a robust controller of the servo system is designed based on H-infinity control theory with considering the disturbance of high wind speed. Simulation analysis verifies the capability of the designed controller for improving LCT's pointing accuracy and its antenna's rotating speed. This research is of good significance for the refurbishment of LCT and the achievement of its new scientific aim.