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1、英 文 翻 译系 别专 业班 级学生姓名学 号指导教师 Control of suspension bridge flutter instability using pole-placement techniqueAbstrat The closed-loop state feedback control scheme by pole-placement technique, which is widely used in control literature, is applied to control the flutter instability of suspension bridge
2、s. When the mean wind speed U at the bridge site increases beyond the critical flutter wind speed, the real part of the dominant pole of the system is forced to a desired negative value by properly designing a state feed back gain matrix to control the flutter instability. The control force, which i
3、s expressed as a product of gain matrix and state vector in modal coordinates, is applied in the form of an active torsional moment in the middle of the bridge span. The values of the state variables are estimated by designing a full order observer system. The application of the control scheme for i
4、ncreasing the critical wind speed for flutter of suspension bridges is demonstrated by considering the Vincent Thomas Bridge as the numerical example. The efficiency of the method for controlling the bridge deck flutter is investigated under a set of parametric variations. The results of the numeric
5、al study show that the control scheme using pole-placement technique effectively brings down the divergent oscillation of the bridge at wind speeds greater than the critical wind speed for flutter, to almost zero value within few seconds. 2004 Elsevier Ltd. All rights reserved.1. Introduction Long-s
6、pan suspension bridges, due to their flexibility and lightness, are much prone to the flutter instability. Flutter is a wind-induced instability in the bridge deck at a critical wind velocity leading to an exponentially growing response. The evaluation of flutter condition of suspension bridges is o
7、ne of the most important phases in the design of these bridges. In recent years, many researchers have focused their attention on increasing the critical flutter wind speed of the cable-supported bridges using different types of control devices. Wilde et al. proposed a passive aerodynamic control of
8、 flutter by adding two additional surfaces to generate stabilizing forces and by putting an additional pendulum to control the torsional motion. Other studies also have been carried out to control the critical flutter wind speed of long-span bridges using eccentric mass on the bridges. In 2002, the
9、authors proposed a passive control of critical flutter wind speed of suspension bridges using a combined vertical and torsional tuned mass damper (TMD)system. The proposed TMD system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetri
10、c modes of the bridge, which get coupled during flutter. Even with these advances, challenges still exist in increasing the critical flutter wind speed by applying reasonable external devices such as active control force or passive control properties, and trying to find practical methods to control
11、the flutter condition of these bridges. In particular, application of pole-placement technique for control of bridge vibration is much less compared to that of optimal control theory . Meirovitch and Ghosh used modal control for suppressing the suspension bridge flutter, but they essentially used op
12、timal control theory in modal space. Since control of bridge flutter is associated with the problem of making the system stable from an unstable state, the pole-placement technique should find as good application for this problem. In this paper, the closed-loop state feedback control method by pole-
13、placement technique, which has been used for other control problems, is applied to stabilize the flutter instability condition of suspension bridges. For this purpose, the equation of motion of the system is obtained by multi-mode finite element modeling (beam element) of the bridge deck using consi
14、stent mass matrix. The consistent mass matrix and structural stiffness matrix are evaluated using energy approach, which duly considers the effects of suspended cables. The final controlled equation of motion of the system is obtained in states space in terms of the generalized modal coordinate vect
15、or. The control force w is considered proportional to the values of the state vector, which are estimated by designing a full-order observer system. The control scheme is applied to suppress the flutter instability of Vincent Thomas Bridge and its effectiveness for flutter control of suspension bridge is investigated for different mean wind speeds through a numerical study. 2. Assumptions The following assumptions are made in the analysis: (1) All stresses in the bridge elements obey the Hookes law, and therefore no material nonlinearity is considered. (2) Th
