The Study Of Control Technologies Base On Analog Circuits For Fast Steering Mirror

In free-space optical communication system, ATP(Acquisition, Tracking, Pointing, referred to as ATP)technologies are usually used to achieve real-time observation of the moving target so as to establish good communication links. Because the satellite platform jitter interference is the biggest factor that affects the tracking accuracy of ATP system, ATP system needs high control bandwidth to suppress platform disturbances and improve the tracking accuracy. The composite axis structure is usually adopted in the ATP system to compose coarse and fine tracking mode. And fast steering mirror(FSM), as the control core of the fine tracking part in ATP system, should have enough responding speed and high control bandwidth in order to effectively restrain residual high-frequency error of coarse tracking.Firstly, this paper conducted deep research of the current situation and development trend of FSM. Then the paper proposed analog control methods to meet the requirements of rapid development and application of FSM on large diameter, large reflector travel angle range and high control bandwidth based on the development situation and research trend of fast steering mirror. The current situation of the development of FSM control technology was introduced in detail and the shortcomings of the prior technologies were illustrated. The deep analysis of the factors affecting the fast steering mirror system servo control bandwidth was made in this paper. And on the basis of this, selection and analysis of controllers and sensors for fast steering mirror system were made. Based on the analysis of the working principles of FSM, the transfer function of fast steering mirror was obtained through the mathematical modeling and the methods of model measurement. The paper analyzed and concluded the mature digital control, providing the solutions for the difficulties of implementation of analog control methods.This paper focused on the characteristics of analog control methods in improving FSM control bandwidth. How to improve the control bandwidth of FSM while ensuring the stability and tracking accuracy was studied. The difficulties of achieving analog controller were analyzed which was referred to the resonant. The final scheme was to use an analog notch filter to eliminate the structural resonance of fast steering mirror. The analog controller and interface circuits were designed and achieved and simulation analysis was made for analog circuits in TINA. Based on the principles of the circuits mentioned above, the printed circuit board(PCB) of the hardware was successfully implemented.The hardware circuit of FSM experimental system was built and a FSM system testing was carried out. Experimental results showed that: the hardware circuit of analog notch filter can successfully eliminate the structure resonance of fast steering mirror, expanding the control bandwidth of the system. However, the phase change caused by the notch filter limited the increase of bandwidth. The open-loop characteristics of FSM system in each frequency band was relatively flat after the elimination of resonance. The test results of the closed-loop characteristics of FSM system adopted pure analog control circuits showed that the FSM control bandwidth reached 50 Hz and the error signal suppression bandwidth reached 32 Hz and the tracking accuracy was 32 urad. It still needs further studies to improve the performance of the analog control circuits.