ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF OUTPUT-FEEDBACK VS LINEAR QUADRATIC REGULATOR

This paper presents analytical and experimental comparisons of three control laws for a laboratory structure designed to simulate large space structures. The first control law is the standard time-invariant linear quadratic regulator with state estimation, which requires model reduction for practical implementation. This model reduction may lead to spillover instability. Two simple direct output feedback controls laws guaranteeing stability are proposed. One minimizes the maximum control force, and the other minimizes the same quadratic performance index as the linear quadratic regulator. The three control laws are found to give comparable performance for the modes retained in the reduced model. However, the standard linear quadratic regulator with state estimation provides almost no margin of stability for the unmodeled modes, whereas the simpler direct feedback laws provide significant stability margins to all modes. The analytical results were verified experimentally using a digital implementation of the control laws. Good agreement between the analytical predictions and experimental measurements was observed. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.