MODELING AND CONTROL FOR VIBRATION SUPPRESSION OF A FLEXIBLE ACTIVE STRUCTURE

Theoretical and experimental results of the modeling and control of a flexible ribbed antenna are presented. The antenna consists of eight flexible ribs that constitute an active antenna in the sense that the actuators and sensors are an integral part of the structure. The antenna exhibits closely spaced and repeated modes, thus multi-input, multi-output (MIMO) control is necessary for controllability and observability of the structure. The structure also exhibits a mode localization phenomenon and contains postbuckled members making an accurate finite element model of the structure difficult to obtain. An identified MIMO minimum-order model of the antenna is synthesized from identified single-input, single-output transfer functions curve fit in the frequency domain. The identified model is used to design a positive position feedback and H-infinity controller that increases damping in all of the modes in the targeted frequency range. Because of the accuracy of the open-loop model of the antenna, the closed-loop response predicted by the identified model correlates well with experimental results.