Research On Active Optics Control System Of Thin Mirror

The thin mirror active optics technology is one of the key technologies in the construction of large aperture telescopes.The principle is to use force actuator to correct the distorted mirror surface in real time,so as to maintain good surface.The control accuracy of the thin mirror active optics system is one of the key factors that affects the surface.Based on the thin mirror active optics project of Nanjing Astronomical Instrument Co.,Ltd.,this paper studies the thin mirror active optics control system with a 1m diameter standard mirror,and improves the accuracy and rapidity of the correction force of the force actuator by using digital signal processing algorithms and control algorithms.The following work has been completed.Based on the analysis of the active support system,the design of force actuator and the performance of hardware,the control scheme of the thin mirror active optics system based on CAN bus is proposed,and the design of the overall control scheme is completed.The force signal collected in the thin mirror active optics control system is analyzed,and the principles of several filters are compared.Finally,the LMS adaptive filter is selected,and the test experiment is carried out.The results show that the LMS adaptive filter can deal with noise well,and make the force signal more smooth and stable,which can improve the control accuracy of the system.Based on the analysis of the control scheme and the structure of the stepper motor,the fuzzy PID control algorithm is selected to control the output of the force actuator.The principle of PID and fuzzy PID is introduced,especially the process of fuzzy PID.Finally,the two algorithms are compared.The results show that the system with fuzzy PID control has better performance.Based on.Net framework and C#language,the software of thin mirror active optics control system is designed and developed.The functions of force sensor data receiving and displaying,output force setting of support point,control command sending and tracking curve drawing are realized.The functions include receiving and displaying force data,setting support force,sending control command and drawing tracking curve.The performance of the thin mirror active optics control system is tested,including the force actuator linearity,force resolution and fuzzy PID control.The results show that the thin mirror active optics control system designed in this paper can meet the requirements of the active optics control system and has good stability,robustness and response characteristics.