An Optimal Projection Controller for an Experimental Truss Struct~rel~~

Optimal Projection (OP) reduced order control theory is applied experimentally to a controlled structure testbed. The test structure has twenty-five disturbed modes, and the controller uses four strain sensors to command four noncollocated stress actuators. The best OP design, an 18th order controller derived from a 58th order structnral model, is experimentally found to reduce the broad-band vibration of live 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 (LQG) controller is found to always destabilize high frequency modes. The homotopy algorithm used to solve the OP synthesis equations is described, and its convergence is discussed. Analytical and experimental closed-loop performance for a series of OP and LQG controllers are compared to illustrate the effect of structural dynamic modeling errors on the results.