• 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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.435-442
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• 2002

본 연구에서는 사장교의 제어기법 개발을 위한 구조물로 제공되는 벤치마크(benchmark) 사장교에 대해 복합제어 기법을 적용하였다. 이 벤치마크 문제에서는 2003년 완공 예정으로 미국 Missouri 주에 건설 중인 Cape Girardeau 교를 대상 구조물로 고려하였다. Cape Girardeau 교는 New Madrid 지진구역에 위치하고, Mississippi 강을 횡단하는 주요 교량이라는 점 때문에 설계단계에서부터 내진 문제에 대하여 자세하게 고려되었다. 상세 설계도면을 기반으로 하여 교량의 전체적인 거동 특성을 정확하게 나타낼 수 있는 3차원 모델이 만들어졌고, 사장교의 제어 성능에 관련된 평가 기준이 수립되었다. 본 연구에서 사용한 복합제어 기법이란 지진하중으로 인해 구조물에 발생되는 하중을 줄이기 위한 수동제어 기법과 상판변위와 같은 구조물의 응답을 추가적으로 제어하기 위한 능동제어 기법이 결합된 제어방법이다. 수동제어 장치로는 현재 일반적으로 많이 사용되고 있는 납고무받침(lead rubber bearing)을 사용하였다. 능동제어 방법에는 $H_2$/LQG 제어 알고리듬(algorithm)을 사용하였다. 수치해석 결과 제안방법의 성능은 수동제어 방법에 비해 매우 효과적이며, 능동제어 방법에 비해서는 좀더 좋은 제어성능을 나타내었다. 또한, 복합제어 방법은 수동제어 부분 때문에 능동제어 방법에 비해 좀더 신뢰할 수 있는 제어 방법이다. 따라서 제안된 제어방법은 지진하중을 받는 사장교의 제어를 위해 효과적으로 사용될 수 있다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.154-157
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• 2000

Distributed piezoelectric sensor and actuator system has been designed for the active vibration control of shell structure. PVDF is used for the materials of sensor/actuator. To prevent the adverse effect of spillover, distributed modal sensor/actuator system is established. Although shell structure is three-dimensional structure, the PVDF sensor/actuator system can be treated as two-dimensional Finite element programs are developed to consider curved structures having PVDF modal sensor/actuator. The nine-node Mindlin shell element with five nodal degree of freedoms is used for finite element discretization. The electrode patterns and lamination angle of PVDF sensor/actuator are optimized to design the modal sensor/actuator system Genetic algorithm is used for optimization. Sensor is designed to minimize the observation spillover, and actuator is designed to minimize the system energy of the control modes under a given initial condition. Modal sensor/actuator for the first and second modes of singly curved cantilevered shell structure are designed using mentioned methods. Discrete LQG method is used as a control law. Experimental demonstrations of the active vibration control with designed sensor/actuator system have been performed successfully.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.93-101
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• 2016

This study presents a simple genetic algorithm to systematically design a PID controller for a hydraulic positioning system operated by a proportional solenoid valve. The inverse dead-zone compensator with nonlinear characteristics is used to cancel out the dead-zone phenomenon in the hydraulic system. The object function considering overshoot, settling time, and control input is adopted to search for optimal PID gains. The designed PID controller is compared with the LQG/LTR controller to check the performance of the hydraulic positioning system in the time and frequency domains. The experimental results show that the hydraulic servo system with the proposed PID controller responds effectively to the various types of reference input.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.466-471
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• 2008

Structural vibration and noise are hot issues in underwater vehicles such as submarines for their survivability. Therefore, active vibration and noise control of submarine, which can be modeled as hull structure, have been conducted by the use of piezoelectric materials. Traditional piezoelectric materials are too brittle and not suitable to curved geometry such as hull structures. Therefore, advanced anisotropic piezoceramic actuator named as Macro-Fiber Composite (MFC), which can provide great flexibility, large induced strain and directional actuating force is adopted for this research. In this study, dynamic model of the smart hull structure is established and active vibration control performance of the smart hull structure is evaluated using optimally placed MFC. Actuating performance of MFC is evaluated by finite element analysis and dynamic modeling of the smart hull structure is derived by finite element method considering underwater condition. In order to suppress the vibration of hull structure, Linear-Quadratic-Gaussian (LQG) algorithm is adopted. After then active vibration control performance of the proposed smart hull structure is evaluated with computer simulation and experimental investigation in underwater. Structural vibration of the hull structure is decreased effectively by applying proper control voltages to the MFC actuators.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.128-141
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• 1998

We propose the robust nonlinear controller design methodology for the multivariable system which has hard nonlinearities (Coulomb friction, dead-zone, etc) and the structured real parameter uncertainty. The hard nonlinearity can be linearized by the RIDF technique and structured real parameter uncertainty can be modelled as the sense of Peterson-Hollot's quadratic Lyapunov bound. For this system, we apply the robust QLQG/H$_{\infty}$ control and then can obtain four Riccati equations. Because of the system's nonlinearity, however, one Riccati equation contains the nonlinear correction term that is very difficult to solve numerically, In order to treat this problem, using some transformations to Riccati equations, the nonlinear correction term can be eliminated. Then, only two Riccati equations need to design a controller. Finally, the robust nonlinear controller is synthesized via IRIDF techniques. To test this proposed control method, we consider the direct-drive robot manipulator system that has Coulomb frictions and varying inertia.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.364-368
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• 1994

Algebraic matrix Riccati equations of the form, FP+PF$^{T}$ -PRP+Q=0. are analyzed with reference to the stability of closed-loop system F-PR. Here F, R and Q are n * n real matrices with R=R$^{T}$ and Q=Q$^{T}$ .geq.0 (nonnegative-definite). Such equations have been playing key roles in optimal control and filtering problems with R .geq. 0. and also in the solutions of in H$_{\infty}$ control problems with R taking the form R=H$_{1}$$^{T}$ H$_{1}$-H$_{2}$$^{T}$ H$_{2}$. In both cases an existence of stabilizing solution, i.e. the solution yielding asymptotically stable closed-loop system, is an important problem. First, we briefly review the typical results when R is of definite form, namely either R .geq. 0 as in LQG problems or R .leq. 0. They constitute two extrence cases of Riccati to the cases H$_{2}$=0 and H$_{1}$=0. Necessary and sufficient conditions are shown for the existence of nonnegative-definite or positive-definite stabilizing solution. Secondly, we focus our attention on more general case where R is only assumed to be symmetric, which obviously includes the case for H$_{\infty}$ control problems. Here, necessary conditions are established for the existence of nonnegative-definite or positive-definite stabilizing solutions. The results are established by employing consistently the so-called algebraic method based on an eigenvalue problem of a Hamiltonian matrix.x.ix.x.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.476-483
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• 2004

This paper presents a hybrid system combining lead rubber bearings and hydraulic actuators controlled by a μ-synthesis method for seismic response control of a cable-stayed bridge. A hybrid system could alleviate some of restrictions and limitations that exist when each system is acting alone because multiple control devices are operating. Therefore, the overall control performance of a hybrid system may be improved compared to each system, however the overall system robustness may be negatively impacted by active device in the hybrid system or active controller may cause instability due to small margins. Therefore, a f-synthesis method that guarantees the robust performance is considered to enhance the possibility of real applications of the control system. The control performances of the proposed control system are compared with those of passive, active, semiactive control systems and hybrid system controlled by LQG algorithm and an extensive robust analysis with respect to stiffness and mass matrices perturbation and time delay of actuator is performed. Numerical simulation results show that the control performance of the proposed control system is superior to that of the passive system and slightly better than that of the active and semiactive systems and two hybrid systems show similar control performances. Furthermore, the hybrid system controlled by a μ-synthesis method shows the good robustness without loss of control performances. Therefore, the proposed control system could effectively be used to seismically excited cable-stayed bridge which contains many uncertainties.

• Journal of KSNVE
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• v.8 no.4
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• pp.632-642
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• 1998

A method based on finite element discretization is developed for optimizing the polarization profile of PVDF film to create the modal transducer for specific modes. Using this concept, one can design the modal transducer in two-dimensional structure having arbitrary geometry and boundary conditions. As a practical means for implementing this polarization profile without repoling the PVDF film the polarization profile is approximated by optimizing electrode patterns, lamination angles, and poling directions of the multi-layered PVDF transducer. This corresponds to the approximation of a continuous function using discrete values. The electrode pattern of each PVDF layer is optimized by deciding the electrode of each finite element to be used or not. Genetic algorithm, suitable for discrete problems, is used as an optimization scheme. For the optimization of each layers lamination angle, the continuous lamination angle is encoded into discrete value using binary 5 bit string. For the experimental demonstration, a modal sensor for first and second modes of cantilevered composite plate is designed using two layers of PVDF films. The actuator is designed based on the criterion of minimizing the system energy in the control modes under a given initial condition. Experimental results show that the signals from residual modes are successfully reduced using the optimized multi-layered PVDF sensor. Using discrete LQG control law, the modal peaks of first and second modes are reduced in the amount of 12 dB and 4 dB, resepctively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.978-983
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• 2000

This paper presents the system identification of a small-scale building model with an active mass driver and the controller design using Matlab program. As the AMD is a mechanical system which has a dynamic characteristic and whose mass can not be neglected compared to that of the building mass, the AMD-building interaction should be included in the controller design. The system identification is carried out for the AMD-building system with two acceleration inputs of the shaking table and the AMD and single acceleration output of the building. The mathematical model for the AMD-building is obtained and compared with the experimental result. The controller is designed based on the mathematical model using the optimal control algorithm of LQG strategy. The experimental results are compared with the numerical results. It is shown that both results are in good agreement in the system identification and the controlled responses.