Design of Primary-Mirror Position Control System in Large Telescope

A design method of a primary-mirror position control system based on motor-driven hydraulic support is proposed to meet the high precision requirements of the primary mirror position in mirror imaging of a 4 m large telescope. Firstly, the composition of the primary-mirror position control system is introduced, and the mathematical model of each structure is established. Furthermore, a primary-mirror position controller is designed based on the first-order dynamic sliding mode control and a linearly extended observer. Finally, the system is simulated. The results show that the maximum tracking error of each support area is less than 0.5 mu m when the tilt axis moves at a uniform speed of 1 (degrees) center dot s(-1). Besides, in the case of sinusoidal guidance of the tilt axis, the maximum tracking error is 1 mu m, which is better than the tracking error (13 mu m) of the traditional proportional integral control. The results satisfy the design requirements of the proposed system in the 4 m large telescope, providing a reference for the design of a primary-mirror position control system in a large telescope.