Large segmented telescopes

Abstract

The accurate control of the segments of large segmented telescopes to achieve desired shapes could open the way for the construction of much larger telescopes with much better capabilities. In this article, we consider centralized, decentralized, and overlapping approaches to designing controllers for the shape control of a segmented telescope. In the centralized approach, all the segments and interconnections are considered to be a single dynamical system. In the decentralized case, the interconnections between the segments are neglected for control design purposes. In the overlapping decentralized approach, overlapped segments are considered to be isolated subsystems. In each case, we design controllers using the H∞∞∞ robust control approach. In the centralized control case, the disturbances are rejected over a wide frequency range and all performance requirements are met. The order of the centralized controller, however, is high, which makes it difficult to implement in real time. The decentralized control approach greatly reduces the computational and hardware requirements at the cost of performance deterioration. The overlapping approach trades off between the centralized and decentralized cases that provides sufficient flexibility to meet both performance and computational requirements.