Large Telescope Primary Mirror Position Detection And Control

When large-aperture telescope is tracking target, the attitude of primary mirror is changing constantly. Due to the great weight of the primary mirror, different attitudes will lead to deformation of the support structure, and the relative position of the main mirror in the mirror chamber will change.This will affect the telescope image quality. So the primary mirror position needs to be controlled, to make the relativeposition between the main mirror and the mirror chamber be unchanged. This paper designed the primary mirror position detection and control system on the basis of summarizing basic primary mirrorsupportingprinciples of the large-aperture telescope.It has an important significance for large-aperture telescope in the actual designing and producting process.This paper introduced the large telescope primary mirror supporting principles, and analysed hydraulic supporting system.The overall plan which using hydraulic system to support the primary mirror was determined. According to attitude changes, the primary mirror position detection system was designed, which can detect and solve the primary mirror position from 5 degrees of freedom in real-time. And this change was fed back to the hydraulic control system, which can make the hydraulic system calibrate the position of the main mirror according to the deviation.The primary mirror position control system was designed on the basis of the character of hydraulic supporting system. And position control model of hydraulic system was established.The PID controller was used. Double closed-loop control simulation of the primary mirror position control system was carried out and the good results were obtained.The experimental platform was set up.Panasonic series servo motor and the corresponding driver was used to control the hydraulic supporting system. The position sensors were used to test performance of servo electric cylinder and components of hydraulic supporting system. A closed-loop regulation is produced of a loop composing of the adjusting hydraulic cylinder and a single supporting hydraulic cylinder. Control method which is double closed-loop control including speed loop and position loop was determined. Then the primary mirror was placed on the hydraulic supporting platform and the position of the primary mirror was controlled to achieve responses which meet requirements of the experimental index.The large-aperture telescope primary mirror position detection and control system designed in this paper has high precision and good control performance.The system can be applied to practical work and provide technical accumulation for larger telescope developing in future.