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In the optical telescope, the stable precision of the optical path is affected by the structural vibrations. The image sensor with time delay and the micro electro-mechanical system (MEMS) accelerometer with massive drift limit the disturbance suppression performance of the closed loops. The current control methods cannot reject sufficiently vibrations due to the deficiency of the sensors, causality, and stability restrictions. In this study, the frequency-domain fusion virtual multi-loop feedback control system with measured disturbance feedforward method is proposed to suppress more structural vibrations. In spite of the deficiency of the sensors, we propose the frequency-domain fusion virtual gyroscopes (VGYR) to measure extra velocity of the system. The VGYR is estimated from the MEMS accelerometer with drift and corrected by the image sensor, and it replaces the fiber-optical gyroscopes (FOG) on the fast-stable platform because the weight of FOG is not negligible. To suppress more vibrations, the VGYR and the replaced FOG are utilized to build the virtual multi-loop feedback control system with measured disturbance feedforward, because it is not limited by the causality and stability restrictions. Therefore, the proposed method with causal ideal compensator can effectively improve stable precision and suppress much more structural vibrations in the wider frequency range. Detailed comparative experimental results adequately illustrate the advantages and effectiveness of this method.

The Frequency-Domain Fusion Virtual Multi-Loop Feedback Control System with Measured Disturbance Feedforward Method in Telescopes