Document Type dissertation Author Name Liu, Wei URN etd-031005-105004 Title Vibration Control of Large Scale Flexible Structures Using Magnetorheological Dampers Degree PhD Department Mechanical Engineering Advisors Zhikun Hou, Advisor Michael A. Demetriou, Co-Advisor John Sullivan, Committee Member James Hu, Committee Member Mark Richman, Graduate Committee Rep Keywords MR Dampers Flexible Structures Structural Vibration Control Date of Presentation/Defense 2005-03-02 Availability unrestricted
Structural vibration control (SVC) of large scale structures using the magnetorheological (MR) dampers are studied. Some key issues, i.e. model reduction, suppression of spillover instability, optimal placement of actuators and sensors, modeling of the MR dampers and their applications in SVC system for large scale structures, are addressed in this work.
A new model reduction method minimizing the error of a modal-truncation based reduced order model (ROM) is developed. The proposed method is implemented by using a Genetic Algorithm (GA), and can be efficiently used to find a ROM for a large scale structure. The obtained ROM has a finite H2 norm and therefore can be used for H2 controller design. The mechanism of the spillover instability is studied, and a methodology to suppress the spillover instability in a SVC system is proposed. The suggested method uses pointwise actuators and sensors to construct a controller lying in an orthogonal space spanned by the several selected residual modes, such that the spillover instability caused by these residual modes can be successfully suppressed. A GA based numerical scheme used to find the optimal locations for the sensors and actuators of a SVC system is developed. The spatial H2 norm is used as the optimization index. Because the spatial H2 norm is a comprehensive index in evaluating the dynamics of a distributed system, a SVC system using the sensors and actuators located on the obtained optimal locations is able to achieve a better performance defined on a distributed domain. An improved model of MR dampers is suggested such that the model can maintain the desired hysteresis behavior when noisy data are used. For the simulation purpose, a numerical iteration technique is developed to solve the nonlinear differential equations aroused from a passive control of a structure using the MR dampers. The proposed method can be used to simulate the response of a large scale structural system with the MR dampers. The methods developed in this work are finally verified using an industrial roof structure. A passive and semi-active SVC systems are designed to attenuate the wind-induced structural vibration inside a critical area on the roof. The performances of the both SVC systems are analyzed and compared. Simulation results show that the SVC systems using the MR dampers have great potentials in reducing the structural vibration of the roof structure.
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