Control techniques or a large segmented reflector

Abstract

The performance of astronomical systems is directly related to the size of their reflectors. Since it is very difficult to cast mirrors larger than 7 meters in diameter from a single piece of glass, to reach unprecedented performance levels, it is planned to construct future optical systems with diameters in the 7-12 meters range from arrays of mirror segments. The problem with segmented optics is to make them behave like the conventional ones made from a single piece of glass. No support structure can provide the mechanical rigidity needed to maintain the position of the mirror segments to such an accuracy. To compensate for the mechanical imperfections, the deformations due to the gravity and thermal loads and to attenuate the seismic or maneuver induced vibrations, the mirror segments must therefore be actively controlled. To study the complex dynamic behavior of large segmented optical systems, NASA has founded a five year project to design and construct a test-bed in the Controls and Structures Laboratory (CSRL) at the California State University, Los Angeles. The CSRL test-bed will serve as a generic experimental facility capable of performing experiments that simulate the complex dynamic behavior of a large segmented optical system. It will be used as an experimental facility for addressing in an integrated way, problems associated with structural dynamics, control of multi-input multi-output systems, optics, electronics, actuators, and sensor design. We describe our latest results regarding robust control, decentralized control, adaptive control and neural network control of the CSRL structure.