Controlling flutter of a cable-stayed bridge with output feedback driven winglets

Abstract

Active control of flutter of a long span cable-stayed bridge is considered in this study. The control action is provided by winglets actuated using constant/variable gain output feedback controllers. Two FE modeling schemes are adopted, namely one element cables, and multi-element cables with each stay-cable discretized into multiple elements to consider the cable vibration effect. Cable discretization results in additional closely spaced modes. Rational function approximation of flat plate flutter derivatives is considered to model aeroelastic forces on deck and winglets. The output feedback controller yields the desired winglet rotation by using vertical and torsional displacements of the deck. Controllability Gramian and response indices are used to obtain the optimal location of winglets, while the best sensor location is obtained based on a combined index. This yields around 40% increase in the stability limit with winglets covering 12% of the central span, and eight measured outputs for feedback. Response indices reduce substantially if a shift from constant to variable gain is performed at a certain wind speed. Controller design based on the one-element model, when applied to the more realistic multi-element model, results in substantially lesser response attenuation. Hence, cable vibration needs to be consider for the controller design. Keywords: Flutter, Cable-stayed bridge, Winglet, Rational function approximation, Variable gain output feedback, Cable vibration.