Closed-Loop Identification of Flexible Structures: An Experimental Example

Abstract

The application of a closed-loop identie cation procedure to a e exible structure, the Jet Propulsion Laboratory Control Structure Interaction Phase B testbed, is described. The approach is based on an indirect, closed-loop identie cation procedure, recently developed by Van den Hof and Schrama (Van den Hof, P. M., and Schrama, R. J., “ An Indirect Method for Transfer Function Estimation from Closed-Loop Data,” Automatica, Vol. 29, No. 6, 1993,pp.1523 ‐1527),whichgivesaconsistentmodelestimateinthecasewherethesystemnoise/outputdisturbance model is not accurate. The procedure is modie ed and applied, in the frequency domain, to closed-loop data from a e exible structure control experiment. The results of the analysis are compared to a purely open-loop frequencydomain identie cation approach. Enhancements to the experimental cone guration are also discussed. EEDBACK control for active vibration suppression is an area of signie cant importance to large spaceborne structures. The majorityofcontroldesigntechniquesappliedtothisproblemrequire a mathematical model of the system, compatible with the proposed design methodology. The identie cation of such models has been an area of active research interest within the e exible structure control design community. This paper examines a closed-loop approach to this problem, using frequency-domain data. Several identie cation approaches have received widespread attention, and for the most part, these are open-loop techniques. The