H-INFINITY CONTROL SCHEME FOR CABLE-SUPPORTED BRIDGES SUBJECTED TO SEISMIC EXCITATION

摘要

An active scheme is proposed for vibration control of cable-supported bridges under seismic excitation. The control action is supplied by using a subset of the stay cable as active tendons. Two key problems are discussed, i. e. , formulating a reduced-order model required for controller design and prevention of spillover instability. The H-infinity optimal control theory is used to design the state feedback controller, which incorporates two kinds of filters, i. e. , weighting functions, into the dynamic system to form an augmented plant, where the control gain is determined by solving Riccati equation. Critical modes of vibration, which fall in the predominant frequency range of seismic excitations and contribute much to the displacement response of bridge towers, are selected to be controlled, and the others modes are truncated as model perturbation. The spillover instability due to the truncated modes is avoided by reasonable selection of a class of weighting functions representing the uncertainties of control system. The performance of the control scheme is verified by control simulation of a combined cable-stayed and suspension bridge.