The problem of active structural acoustic control in an enclosure using radiation mode is investigated. The response of the coupled enclosure is derived in terms of radiation modes. The potential energy in the enclosu...The problem of active structural acoustic control in an enclosure using radiation mode is investigated. The response of the coupled enclosure is derived in terms of radiation modes. The potential energy in the enclosure can be decomposed into independent parts and the radiation modes contribute to potential energy independently. The control strategy for minimizing first G radiation modes with large radiation efficiency is proposed, and the optimal model of control forces is presented. Finally, a numerical simulation for minimizing sound transmission into a rectangular enclosure using the proposed method is conducted. Simulation results indicate that one control force can control one radiation mode and controlling the first four-order radiation modes with four control forces can achieve significant potential energy reduction at the low frequency range.展开更多
The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this pap...The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform （WPT） is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium root structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both Tianjin and E1 Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller.展开更多
The objective of this paper is to investigate the dynamic characteristics of two adjacent building structures interconnected by viscoelastic dampers under seismic excitations. The computational procedure for an analyt...The objective of this paper is to investigate the dynamic characteristics of two adjacent building structures interconnected by viscoelastic dampers under seismic excitations. The computational procedure for an analytical model including the system model formulation, complex modal analysis and seismic time history analysis is presented for this purpose. A numerical example is also provided to illustrate the analytical model. The complex modal analysis is conducted to determine the optimal damping ratio, the optimal damper stiffness and the optimal damper damping of the viscoelastic dampers for each mode of the system. For the damper stiffness and damping with optimal values, the responses can be categorized into underdamped and critically damped vibrations. Furthermore, compared to the viscous dampers with only the energy dissipation mechanism, the viscoelastic dampers with both the energy dissipation and redistribution mechanisms are more effective for increasing the damping ratio of the system. The seismic time history analysis is conducted to assess the effectiveness of the viscoelastic dampers for vibration control. Based on the optimal damping ratio, the optimal damper stiffness, the optimal damper damping of the viscoelastic dampers for a certain mode of the system, and the viscoelastic dampers can be used to effectively suppress the root-mean-square responses as well as the peak responses of the two adjacent buildings.展开更多
For the problem posed by closely spaced modes, this paper defined the MCC (modal correlation criterion) to measure the degree of correlation between close modes. It was proved that structures with certain features ten...For the problem posed by closely spaced modes, this paper defined the MCC (modal correlation criterion) to measure the degree of correlation between close modes. It was proved that structures with certain features tend to have closely clustered modes and the corresponding mode shapes highly correlated. With this understanding, the closed-form expressions for controllability and observability Grammians were adopted to analyze the impacts of actuator/sensor placement on the controllability/observability of highly correlated close modes. On this basis, the problem of actuator/sensor placement, when the optimization criterion is based on modal controllability/observability, was simplified. Moreover, the dimension of the control/measurement vector in independent modal space control for highly correlated close modes was proved to have the potential to be reduced, therefore fewer actuators and sensors were required in this dimension-reduced control strategy. Finally, the desirable vibration suppression for an example structure showed that the theory and methods of this paper were accurate and effective.展开更多
基金Supported by the National Natural Science Foundation of China(50375027,50575041)~~
文摘The problem of active structural acoustic control in an enclosure using radiation mode is investigated. The response of the coupled enclosure is derived in terms of radiation modes. The potential energy in the enclosure can be decomposed into independent parts and the radiation modes contribute to potential energy independently. The control strategy for minimizing first G radiation modes with large radiation efficiency is proposed, and the optimal model of control forces is presented. Finally, a numerical simulation for minimizing sound transmission into a rectangular enclosure using the proposed method is conducted. Simulation results indicate that one control force can control one radiation mode and controlling the first four-order radiation modes with four control forces can achieve significant potential energy reduction at the low frequency range.
基金Supported by National Natural Science Foundation of China (No.51108089,No.90715034 and No.90715032)National Natural Science Foundation of Fujian Province (No.2011J05128)
文摘The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform （WPT） is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium root structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both Tianjin and E1 Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller.
文摘The objective of this paper is to investigate the dynamic characteristics of two adjacent building structures interconnected by viscoelastic dampers under seismic excitations. The computational procedure for an analytical model including the system model formulation, complex modal analysis and seismic time history analysis is presented for this purpose. A numerical example is also provided to illustrate the analytical model. The complex modal analysis is conducted to determine the optimal damping ratio, the optimal damper stiffness and the optimal damper damping of the viscoelastic dampers for each mode of the system. For the damper stiffness and damping with optimal values, the responses can be categorized into underdamped and critically damped vibrations. Furthermore, compared to the viscous dampers with only the energy dissipation mechanism, the viscoelastic dampers with both the energy dissipation and redistribution mechanisms are more effective for increasing the damping ratio of the system. The seismic time history analysis is conducted to assess the effectiveness of the viscoelastic dampers for vibration control. Based on the optimal damping ratio, the optimal damper stiffness, the optimal damper damping of the viscoelastic dampers for a certain mode of the system, and the viscoelastic dampers can be used to effectively suppress the root-mean-square responses as well as the peak responses of the two adjacent buildings.
基金supported by the National Natural Science Foundation of China (Grant No. 10872028)
文摘For the problem posed by closely spaced modes, this paper defined the MCC (modal correlation criterion) to measure the degree of correlation between close modes. It was proved that structures with certain features tend to have closely clustered modes and the corresponding mode shapes highly correlated. With this understanding, the closed-form expressions for controllability and observability Grammians were adopted to analyze the impacts of actuator/sensor placement on the controllability/observability of highly correlated close modes. On this basis, the problem of actuator/sensor placement, when the optimization criterion is based on modal controllability/observability, was simplified. Moreover, the dimension of the control/measurement vector in independent modal space control for highly correlated close modes was proved to have the potential to be reduced, therefore fewer actuators and sensors were required in this dimension-reduced control strategy. Finally, the desirable vibration suppression for an example structure showed that the theory and methods of this paper were accurate and effective.
