• Title, Summary, Keyword: MR damper

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Control of Smart Base-isolated Benchmark Building using Fuzzy Supervisory Control (퍼지관리제어기법을 이용한 스마트 면진 벤치마크 건물의 제어)

  • Kim, Hyun-Su;Roschke P. N.
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.4
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    • pp.55-66
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    • 2005
  • The effectiveness of fuzzy supervisory control technique for the control of seismic responses of smart base isolation system is investigated in this study. To this end, first generation base isolated building benchmark problem is employed for the numerical simulation. The benchmark structure under consideration is an eight-story base isolated building having irregular plan and is equipped with low-damping elastometric bearings and magnetorheological (MR) dampers for seismic protection. Lower level fuzzy logic controllers (FLC) for far-fault or near-fault earthquakes are developed in order to effectively control base isolated building using multi-objective genetic algorithm. Four objectives, i.e. reduction of peak structural acceleration, peak base drift, RMS structural acceleration and RMS base drift, are used in multi-objective optimization process. When earthquakes are applied to benchmark building, each of low level FLCs provides different command voltage and supervisory fuzzy controller combines two command voltages io one based on fuzzy inference system in real time. Results from the numerical simulations demonstrate that base drift as well as superstructure responses can be effectively reduced using the proposed supervisory fuzzy control technique.

Seismic protection of smart base-isolated structures using negative stiffness device and regulated damping

  • Bahar, Arash;Salavati-Khoshghalb, Mohsen;Ejabati, Seyed Mehdi
    • Smart Structures and Systems
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    • v.21 no.3
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    • pp.359-371
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    • 2018
  • Strong seismic events commonly cause large drift and deformation, and functionality failures in the superstructures. One way to prevent functionality failures is to design structures which are ductile and flexible through yielding when subjected to strong ground excitations. By developing forces that assist motion as "negative stiffness forces", yielding can be achieved. In this paper, we adopt the weakening and damping method to achieve a new approach to reduce all of the structural responses by further adjusting damping phase. A semi-active control system is adopted to perform the experiments. In this adaptation, negative stiffness forces through certain devices are used in weakening phase to reduce structural strength. Magneto-rheological (MR) dampers are then added to preserve stability of the structure. To adjust the voltage in MR dampers, an inverse model is employed in the control system to command MR dampers and generate the desired control forces, where a velocity control algorithm produces initial required control force. An extensive numerical study is conducted to evaluate proposed methodology by using the smart base-isolated benchmark building. Totally, nine control systems are examined to study proposed strategy. Based on the numerical results of seven earthquakes, the use of proposed strategy not only reduces base displacements, base accelerations and base shear but also leads to reduction of accelerations and inter story drifts of the superstructure. Numerical results shows that the usage of inverse model produces the desired regulated damping, thus improving the stability of the structure.

Smart Platform for Microvibration Control of High-Tech Industry Facilities

  • Kim, Hyun-Su;Kang, Joo-Won
    • International journal of steel structures
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    • v.17 no.1
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    • pp.155-164
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    • 2017
  • Recently, the microvibrations of high technology facilities resulting from nearby traffic loads have attracted significant attention. Considerable research aimed at protecting high-tech equipment due to nearby road and rail traffic has focused on vibration isolation systems. These isolation systems include passive-base isolation systems, smart base isolation systems, passive mounts, and active tables that are used mainly to isolate a small quantity of high-tech equipment. In this study, a smart platform was developed to control the microvibrations of high-technology facilities. Train-induced ground acceleration was generated as a nearby traffic load and a magnetorheological damper was used to compose a smart isolation platform. A fuzzy logic controller was used as a control algorithm that was optimized using a multi-objective genetic algorithm. The microvibration control performance of a smart isolation platform was compared with that of a conventional passive isolation platform. A series of parametric studies were performed to optimize the design of a passive isolation platform. Numerical analysis showed that a smart isolation platform can effectively control the microvibrations of a high-technology facility subject to train-induced excitation.

Real-time hybrid testing using model-based delay compensation

  • Carrion, Juan E.;Spencer, B.F. Jr.
    • Smart Structures and Systems
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    • v.4 no.6
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    • pp.809-828
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    • 2008
  • Real-time hybrid testing is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with time-dependent components. Real-time hybrid testing is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for time delays and actuator time lag is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid testing in which time delay/lag compensation is implemented using model-based response prediction. The efficacy of the proposed strategy is verified by conducting substructure real-time hybrid testing of a steel frame under earthquake loads. For the initial set of experiments, a specimen with linear-elastic behavior is used. Experimental results agree well with the analytical solution and show that the proposed approach and testing system are capable of achieving a time-scale expansion factor of one (i.e., real time). Additionally, the proposed method allows accurate testing of structures with larger frequencies than when using conventional time delay compensation methods, thus extending the capabilities of the real-time hybrid testing technique. The method is then used to test a structure with a rate-dependent energy dissipation device, a magnetorheological damper. Results show good agreement with the predicted responses, demonstrating the effectiveness of the method to test rate-dependent components.

Development of Rehabilitation Training System Using Unstable Flatform with Magneto-Rheological Damper (MR 댐퍼 적용 불안정판을 이용한 재활 훈련시스템 개발)

  • Choi, Youn-Jung;Piao, Yong-Jun;Heo, Min;Kwon, Tae-Kyu;Hwang, Ji-Hye;Kim, Dong-Wook;Kim, Nam-Gyun
    • Journal of Institute of Control, Robotics and Systems
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    • v.14 no.2
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    • pp.197-204
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    • 2008
  • The purpose of this paper was to develop a rehabilitation training system which is controlled by electric currents to the Magneto-Rheological dampers system. This system provided the function for the training of the unbalance of the lower extremities. 10 subjects executed the tracing and moving exercises which are presented through the display monitor and confirmed own the capability of performance on the task. The electromyographies of the four muscles in lower extremities were recorded and analyzed in the time and frequency domain the muscles of interest were rectus femoris, biceps femoris, gastrocnemius, tibialis anterior. The experimental results showed that subjects had a task under feedback mode then subjects improve the capability of performance, increasing the in time, decreasing the out time and the distance of body shift. The moving average EMG, spectral energy of four muscle is lower the feedback mode than the constant mode. This could aid the hemiplegic patients to train more easily.

Development of a Linear Motor Dynamometer for Positioning Control Performance Test (Linear모터의 위치 제어 성능 시험을 위한 Dynamometer 개발)

  • Roh Chang-Yul;Rho Myung-Hwan;Kim Ju-Kyung;Park Jong-Jin;Lee Eung-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.5
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    • pp.609-614
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    • 2006
  • Recently linear motor has been used mainly for high speed feeding performance of machine tools. The advantages of linear motor are not only high speed but high accuracy, because it is not required the coupling and ballscrew for converting rotary to liner motion. Before applying in different moving system, the dynamometer is necessary to test the performance. In Korea, the linear motor is producing in a couple of company However, the liner motor dynamometer is not commercialized yet, like as rotary motor dynamometer. In this paper, a linear motor dynamometer is designed and manufactured using a MR damper. The dynamometer system developed in this study could be used for testing the positioning accuracy fur different loading conditions, traction forces, dynamic performance and so on.

Semi-active damped outriggers for seismic protection of high-rise buildings

  • Chang, Chia-Ming;Wang, Zhihao;Spencer, Billie F. Jr.;Chen, Zhengqing
    • Smart Structures and Systems
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    • v.11 no.5
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    • pp.435-451
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    • 2013
  • High-rise buildings are a common feature of urban cities around the world. These flexible structures frequently exhibit large vibration due to strong winds and earthquakes. Structural control has been employed as an effective means to mitigate excessive responses; however, structural control mechanisms that can be used in tall buildings are limited primarily to mass and liquid dampers. An attractive alternative can be found in outrigger damping systems, where the bending deformation of the building is transformed into shear deformation across dampers placed between the outrigger and the perimeter columns. The outrigger system provides additional damping that can reduce structural responses, such as the floor displacements and accelerations. This paper investigates the potential of using smart dampers, specifically magnetorheological (MR) fluid dampers, in the outrigger system. First, a high-rise building is modeled to portray the St. Francis Shangri-La Place in Philippines. The optimal performance of the outrigger damping system for mitigation of seismic responses in terms of damper size and location also is subsequently evaluated. The efficacy of the semi-active damped outrigger system is finally verified through numerical simulation.

Research on Hyperparameter of RNN for Seismic Response Prediction of a Structure With Vibration Control System (진동 제어 장치를 포함한 구조물의 지진 응답 예측을 위한 순환신경망의 하이퍼파라미터 연구)

  • Kim, Hyun-Su;Park, Kwang-Seob
    • Journal of Korean Association for Spatial Structures
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    • v.20 no.2
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    • pp.51-58
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    • 2020
  • Recently, deep learning that is the most popular and effective class of machine learning algorithms is widely applied to various industrial areas. A number of research on various topics about structural engineering was performed by using artificial neural networks, such as structural design optimization, vibration control and system identification etc. When nonlinear semi-active structural control devices are applied to building structure, a lot of computational effort is required to predict dynamic structural responses of finite element method (FEM) model for development of control algorithm. To solve this problem, an artificial neural network model was developed in this study. Among various deep learning algorithms, a recurrent neural network (RNN) was used to make the time history response prediction model. An RNN can retain state from one iteration to the next by using its own output as input for the next step. An eleven-story building structure with semi-active tuned mass damper (TMD) was used as an example structure. The semi-active TMD was composed of magnetorheological damper. Five historical earthquakes and five artificial ground motions were used as ground excitations for training of an RNN model. Another artificial ground motion that was not used for training was used for verification of the developed RNN model. Parametric studies on various hyper-parameters including number of hidden layers, sequence length, number of LSTM cells, etc. After appropriate training iteration of the RNN model with proper hyper-parameters, the RNN model for prediction of seismic responses of the building structure with semi-active TMD was developed. The developed RNN model can effectively provide very accurate seismic responses compared to the FEM model.

Real-time hybrid simulation of smart base-isolated raised floor systems for high-tech industry

  • Chen, Pei-Ching;Hsu, Shiau-Ching;Zhong, You-Jin;Wang, Shiang-Jung
    • Smart Structures and Systems
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    • v.23 no.1
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    • pp.91-106
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    • 2019
  • Adopting sloped rolling-type isolation devices underneath a raised floor system has been proved as one of the most effective approaches to mitigate seismic responses of the protected equipment installed above. However, pounding against surrounding walls or other obstructions may occur if such a base-isolated raised floor system is subjected to long-period excitation, leading to adverse effects or even more severe damage. In this study, real-time hybrid simulation (RTHS) is adopted to assess the control performance of a smart base-isolated raised floor system as it is an efficient and cost-effective experimental method. It is composed of multiple sloped rolling-type isolation devices, a rigid steel platen, four magnetorheological (MR) dampers, and protected high-tech equipment. One of the MR dampers is physically tested in the laboratory while the remainders are numerically simulated. In order to consider the effect of input excitation characteristics on the isolation performance, the smart base-isolated raised floor system is assumed to be located at the roof of a building and the ground level. Four control algorithms are designed for the MR dampers including passive-on, switching, modified switching, and fuzzy logic control. Six artificial spectrum-compatible input excitations and three slope angles of the isolation devices are considered in the RTHS. Experimental results demonstrate that the incorporation of semi-active control into a base-isolated raised floor system is effective and feasible in practice for high-tech industry.

A Study on Control of a Soft Recoil System for Recoil Force Reduction (사격충격력 저감을 위한 연식주퇴계의 제어에 관한 연구)

  • Shin, Chul-Bong;Bae, Jae-Sung;Hwang, Jai-Hyuk;Kang, Kuk-Jeong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.560-564
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    • 2007
  • In order to reduce the level of recoil force, new recoil technology must be employed. The present study discusses a soft-recoil mechanism that can reduce dramatically the recoil force. The dynamics of the soft-recoil system with hydraulic dampers are described and simulated. The results of the simulation show that FOOB system can reduce the recoil force and the recoil stroke compared to conventional systems. However, the FOOB system is not able to perform well when the fault modes happen. Hence, this study uses the MR damper to achieving FOOB under fault modes.

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