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RISS 인기검색어
- 검색키워드
- 저자 : David Alaluf (검색결과 4 건)
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Control-structure interaction in piezoelectric deformable mirrors for adaptive optics
Wang, Kainan,Alaluf, David,Mokrani, Bilal,Preumont, Andre Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.6
This paper discusses the shape control of deformable mirrors for Adaptive Optics in the dynamic range. The phenomenon of control-structure interaction appears when the mirror becomes large, lowering the natural frequencies $f_i$, and the control bandwidth $f_c$ increases to improve the performance, so that the condition $f_c{\ll}f_i$ is no longer satisfied. In this case, the control system tends to amplify the response of the flexible modes and the system may become unstable. The main parameters controlling the phenomenon are the frequency ratio $f_c/f_i$ and the structural damping ${\zeta}$. Robustness tests are developed which allow to evaluate a lower bound of the stability margin. Various passive and active strategies for damping augmentation are proposed and tested in simulation.
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Fanhao Meng,Jingjun Yu,David Alaluf,Bilal Mokrani,André Preumont 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.1
This paper addresses the problem of damage detection in suspension bridge hangers, with an emphasis on the modal flexibility method. It aims at evaluating the capability and the accuracy of the modal flexibility method to detect and locate single and multiple damages in suspension bridge hangers, with different level of severity and various locations. The study is conducted numerically and experimentally on a laboratory suspension bridge mock-up. First, the covariance-driven stochastic subspace identification is used to extract the modal parameters of the bridge from experimental data, using only output measurements data from ambient vibration. Then, the method is demonstrated for several damage scenarios and compared against other classical methods, such as: Coordinate Modal Assurance Criterion (COMAC), Enhanced Coordinate Modal Assurance Criterion (ECOMAC), Mode Shape Curvature (MSC) and Modal Strain Energy (MSE). The paper demonstrates the relative merits and shortcomings of these methods which play a significant role in the damage detection of suspension bridges.
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Active tendon control of suspension bridges: Study on the active cables configuration
Zhui Tian,Bilal Mokrani,David Alaluf,Jun Jiang,Andre Preumont 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.5
In a previous study, the potential of damping suspension bridges with active stay cables has been evaluated on a numerical model of a suspension bridge, and demonstrated experimentally on a laboratory mockup. In this paper, we extend our study to explore two different configurations of the active stay-cables: one classical configuration, corresponding to attaching the active stay-cables between the top of the pylons and the deck (configuration I) and, another configuration, consisting of attaching the stay-cables between the base of the pylons and the catenary (configuration II). The analysis confirmed that both configurations are effective with a slight superiority of the second configuration. The study is conducted numerically and experimentally on a suspension bridge mock-up, by considering two types of active stay-cables. The experimental results confirmed the numerical predictions, and demonstrated the effectiveness of the second configuration.
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Active tendon control of suspension bridges
André Preumont,Matteo Voltan,Andrea Sangiovanni,Bilal Mokrani,David Alaluf 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.1
The paper first reviews the theory of active tendon control with decentralized Integral Force Feedback (IFF) and collocated displacement actuator and force sensor; a formal proof of the formula giving the maximum achievable damping is provided for the first time. Next, the potential of the control strategy for the control of suspension bridges with active stay cables is evaluated on a numerical model of an existing footbridge; several configurations are investigated where the active cables connect the pylon to the deck or the deck to the catenary. The analysis confirms that it is possible to provide a set of targeted modes with a considerable amount of damping, reaching s=15% . Finally, the control strategy is demonstrated experimentally on a laboratory mock-up equipped with four control stay cables equipped with piezoelectric actuators. The experimental results confirm the excellent performance and robustness of the control system and the very good agreement with the predictions.
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