High-frequency line-of-sight jitter rejection via an extended Youla-Kucera parameterization controller in segmented diffractive telescope-Theory and experiment

Line-of-sight jitter caused by mechanical vibrations and disturbances in the transmission medium seriously damages the imaging performance in telescope systems. This paper investigates the problem of high-frequency line-of-sight jitter rejection up to Nyquist frequency in bandwidth-limited control systems due to time delays. Although the piezoelectric ceramic-driven tip-tilt mirror has a wide bandwidth, Large time delays caused by the image sensor for high quality imaging severely restrict the control system's closed-loop bandwidth. The disturbance cannot be sufficiently rejected, especially outside the bandwidth. Based on the Small Gain Theorem, the gain factor and time-delay factor as an extra flexible budget in the YoulaKucera (Y-K) parameterization are derived from decreasing the waterbed effect, improving the closed-loop system stability. Thus, this proposed Y-K method accommodates disturbance rejection frequency inside and outside control bandwidth, which can be extended to the Nyquist frequency. Simulation analyses and Experimental results have been effectively verified in the line-of-sight stabilization control of the segmented lightweight large-scaled diffractive telescope (SLLDT) system.