Centralized, decentralized, and overlapping control designs for a segmented telescope

We consider the centralized, decentralized and overlapping approaches to designing controllers for shape control of a segmented telescope. 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 expense of performance deterioration. The overlapping approach is shown to be a trade-off between the centralized and decentralized one and provides sufficient flexibility to meet both performance and computational requirements