Optimal projection control of an experimental truss structure

Optimal projection reduced-order control theory is applied experimentally to a controlled structure testbed. The test structure has 25 disturbed modes, and the controller uses four strain sensors to command four noncollocated stress actuators. The best optimal projection design, an 18th-order controller derived from a 58th-order structural model, is experimentally found to reduce the broad-band vibration of five independent pointing error measures by as much as 66% without saturating the actuators and without destabilizing high-frequency modes. A similar reduced-order linear quadratic Gaussian controller is found to always destabilize high-frequency modes. The homotopy algorithm used to solve the optimal projection synthesis equations is described and its convergence is discussed. Analytical and experimental closed-loop performance for a series of optimal projection controllers are compared to equivalent linear quadratic Gaussian controllers to illustrate the effect of structural dynamic modeling errors on the results.

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