Control designs for an adaptive optics system

In this paper we designed a sequence of controllers of increasing complexity to control the adaptive optics system. The controllers were designed using an experimentally identified plant model. The simplest controllers were of the PID type and were simple to design using SISO methodologies (root locus, Bode plots, etc.). We then analyzed each controller using singular value (SV) Bode plots, and showed that each controller met the performance requirements of high bandwidth and good error rejection characteristics. We also designed a controller based on the H^∞ control design technique. The H^∞ controller offers better performance than the PID designs, in that it retains the low frequency disturbance rejection characteristics, meets the high bandwidth requirement, and has smaller peaking and less spreading in the singular value Bode plot. One of the criticisms of the modern control methods is that they produce high order, highly complex controllers. Using model reduction techniques, we demonstrated that the original 60th order H^∞ controller can reduced to a 24th order controller with little loss of performance. Thus, the reduced order H^∞ controller has better performance than the PLD counterpart of the same order