• Structural Engineering and Mechanics
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• 제40권2호
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• pp.233-243
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• 2011

This paper presents a theoretical study of a model predictive control (MPC) strategy employed in semi-active control system with magnetorheological (MR) dampers to reduce the responses of seismically excited structures. The MPC scheme is based on a prediction model of the system response to obtain the control actions by minimizing an objective function, which can compensate for the effect of time delay that occurred in real application. As an example, a 5-story building frame equipped with two 20 kN MR dampers is presented to demonstrate the performance of the proposed MPC scheme for addressing time delay and reducing the structural responses under different earthquakes, in which the predictive length l = 5 and the delayed time step d = 10, 20, 40, 60, 100 are considered. Comparison with passive-off, passive-on, and linear quadratic Gaussian (LQG) control strategy indicates that MPC scheme exhibits good control performance similar to the LQG control strategy, both have better control effectiveness than two passive control methods for most cases, and the MPC scheme used in semi-active control system show more effectiveness and robustness for addressing time delay and protecting structures during earthquakes.

• Structural Engineering and Mechanics
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• 제36권2호
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• pp.181-195
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• 2010

Coupled building control is a viable method to protect tall buildings from seismic excitation. In this study, the semi-active control of a building complex is investigated for mitigating seismic responses. The building complex is formed of one main building and one podium structure connected through Magneto-Rheological (MR) Dampers and Tuned Mass Damper. The conventional semi-active control techniques require a primary controller as a reference to determine the desired control force, and modulate the input voltage of the MR damper by comparing the desired control force. The fuzzy logic directly determines the input voltage of an MR damper from the response of the MR damper. The control performance of the proposed fuzzy control technique for the MR damper is evaluated for the control problem of a seismically-excited building complex. In this paper, a building complex that include a 14-story main building and an 8-story podium structure is applied as a numerical example to demonstrate the effectiveness of semi-active control with Magneto-Rheological dampers and its comparison with the passive control with the Tuned Mass Damper and two uncoupled buildings and hybrid semi-active control including the Tuned Mass Damper and Magneto-Rheological dampers while they are subject to the earthquake excitation. The numerical results show that semi-active control and hybrid semi-active control can significantly mitigate the seismic responses of both buildings, such as displacement and shear force responses, and fuzzy control technique can effectively mitigate the seismic response of the building complex.

• 한국소음진동공학회논문집
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• 제14권1호
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• pp.17-23
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• 2004

The semi-active suspension system is getting widely adopted in passenger vehicles for its ability to improve ride comfort over the passive suspension system while not degrading driving safety. A key to the success is to develop practical controllers that yield performance enhancement over the passive damper under various driving conditions. To this end, several control strategies have been studied and evaluated in this research in consideration of practical aspects such as nonlinearity and dynamics of the damper. From simulation results. it has been observed that, with the proposed control schemes, ride comfort can be significantly upgraded while suppressing degradation of driving safety.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.607-612
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• 2007

A conventional passive TMD is only effective when it is tuned properly. In many practical applications, inevitable off-tuning of a TMD occurs because the mass in a building floor could change by moving furnishings, people gathering, etc. When TMDs are off tuned, TMDs their effectiveness is sharply reduced. This paper discusses the application of MR-TMD, semi-active damper, for the reduction of floor vibrations due to machine and human movements. Here, the groundhook and skyhook algorithm are applied to a single degree of freedom system representative of building floors. And displacement and velocity base control method are applied to reduce t100r vibration. The performance of the STMD is compared to that of the equivalent passive TMD. Comparison of the results demonstrates the efficiency and robustness of STMD with respect to equivalent TMD.

• Smart Structures and Systems
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• 제23권6호
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• pp.695-702
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• 2019

The number of cable-stayed bridges has been increasing worldwide, causing issues in maintaining the structural safety and integrity of bridges. The stay cable, one of the most critical members in cable-stayed bridges, is vulnerable to wind-induced vibrations owing to its inherent low damping capacity. Thus, vibration mitigation of stay cables has been an important issue both in academia and practice. While a semi-active control scheme shows effective vibration reduction compared to a passive control scheme, real-world applications are quite limited because it requires complicated equipment, including for data acquisition, and power supply. This study aims to develop an Arduino-based integrated cable vibration control system implementing a semi-active control algorithm. The integrated control system is built on the low-cost, low-power Arduino platform, embedding a semi-active control algorithm. A MEMS accelerometer is installed in the platform to conduct a state feedback for the semi-active control. The Linear Quadratic Gaussian control is applied to estimate a cable state and obtain a control gain, and the clipped optimal algorithm is implemented to control the damping device. This study selects the magnetorheological damper as a semi-active damping device, controlled by the proposed control system. The developed integrated system is applied to a laboratory size cable with a series of experimental studies for identifying the effect of the system on cable vibration reduction. The semi-active control embedded in the integrated system is compared with free and passive mode cases and is shown to reduce the vibration of stay-cables effectively.

• 한국항공우주학회지
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• 제38권9호
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• pp.882-889
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• 2010

수동형 진동제어 방식과 같이 시스템이 안정되며, 수동형에 비해 높은 제진 효과가 기대되는 반능동 진동제어 방식은 시스템의 안정화가 요구되는 우주구조물의 제진방법에 유효한 진동제어 방식중 하나이다. On-Off 제어방식에 근거한 반능동 제어는 On-Off 스위칭 시에 전달력의 불연속성으로 인한 chattering을 발생시킬 수 있으며, 이는 탑재체 구조물의 고유진동수와의 커플링으로 인하여 지향성능을 저하시키는 원인으로 작용할 수 있다. 본 논문에서는 chattering 영향 최소화를 통한 지향성능향상을 목적으로 LQ(Linear Quadratic)이론에 기반한 가변 감쇠형 반능동 제어기법을 제안하였다. 시뮬레이션 결과는 본 논문에서 제안한 반능동 제어기법은 기존의 skyhook와 LQ를 기반으로 하는 Bang-Bang 반능동 제어기법과 비교하여 높은 진동절연 성능을 나타내고 있다.

• 한국지진공학회논문집
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• 제10권1호
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• pp.51-62
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• 2006

다양한 원인에 의해서 발생하는 구조물의 동적응답을 감소시키기 위하여 현재까지 여러 가지 형태의 동조질량감쇠기(Tuned Mass Damper; TMD)가 개발되었고 이에 대한 많은 연구가 수행되어 왔다. 본 연구에서는 구조물의 응답에 따라서 실시간으로 TMD의 감쇠를 변화시킬 수 있는 준능동 TMD(Semi-active TMD; STMD)의 제어성능을 다양한 형태의 하중을 적용하여 해석적으로 검토하였다. STMD를 구성하는 준능동 감쇠기의 감쇠력을 조절하기 위하여 skyhook 제어알고리즘을 이용하였다. 조화하중 및 임의의 동적하중을 직접가력하중과 지반진동하중 형태로 단자유도 구조물에 가하여 STMD와 일반적인 TMD의 제어성능을 비교하였다. 또한, 주구조물의 질량의 변화에 따른 TMD 및 STMD의 제어성능의 견실성을 비교하였다. 그리고, 가변감쇠장지 뿐만 아니라 MR 감쇠기를 사용한 STMD의 제어성능도 평가하여 새로운 진동제어장치로서의 활용가능성을 검토하였다. 수치해석을 수행한 결과 STMD는 TMD에 비하여 조화하중 및 임의의 동적하중에 대해서 매우 뛰어난 제어성능을 보이는 것을 확인할 수 있었다.

• 한국정밀공학회지
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• 제17권1호
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• pp.34-44
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• 2000

In this paper, a modified skyhook control for the semi-active Macpherson suspension system is investigated. A new model for the semi-active type suspension, which incorporates the rotational motion of the unsprung mass, is introduced and an output feedback control law using the skyhook control method is derived. The gains in the skyhook controller are adaptively adjusted by estimating the road conditions. Because two vertical acceleration sensors, one for the sprung mass and another for the unsprung mass, are used rather than using the angle sensor for the rotational motion of the control arm, the relative velocity of the rattle space is filtered using the acceleration signals. For testing the control performance, the actual damping force has been incorporated via the hardware-in-the-loop simulations. The performances of a passive damper and a semi-active damper are compared. Simulation results are provided.

• Earthquakes and Structures
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• 제11권6호
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• pp.1077-1099
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• 2016

One of the main shortcomings in the current passive base isolation system is lack of adaptability. The recent research and development of a novel adaptive seismic isolator based on magnetorheological elastomer (MRE) material has created an opportunity to add adaptability to base isolation systems for civil structures. The new MRE based base isolator is able to significantly alter its shear modulus or lateral stiffness with the applied magnetic field or electric current, which makes it a competitive candidate to develop an adaptive base isolation system. This paper aims at exploring suitable control algorithms for such adaptive base isolation system by developing a close-loop semi-active control system for a building structure equipped with MRE base isolators. The MRE base isolator is simulated by a numerical model derived from experimental characterization based on the Bouc-Wen Model, which is able to describe the force-displacement response of the device accurately. The parameters of Bouc-Wen Model such as the stiffness and the damping coefficients are described as functions of the applied current. The state-space model is built by analyzing the dynamic property of the structure embedded with MRE base isolators. A Lyapunov-based controller is designed to adaptively vary the current applied to MRE base isolator to suppress the quake-induced vibrations. The proposed control method is applied to a widely used benchmark base-isolated structure by numerical simulation. The performance of the adaptive base isolation system was evaluated through comparison with optimal passive base isolation system and a passive base isolation system with optimized base shear. It is concluded that the adaptive base isolation system with proposed Lyapunov-based semi-active control surpasses the performance of other two passive systems in protecting the civil structures under seismic events.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.191-194
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• 1997

Passive, semi-active and active dampers have been used to dissipate energy in mechanical systems. Semi-active dampers have higher performance than passive dampers and require lower power to operate than active dampers. Its damping characteristics can be changed appropriately for varying conditions. In this paper, we developed a semi-active damper based on Magnetorheological(MR) fluid. MR fluid has a variable damping characteristics proportional for the magnetic field intensity. It has several advantages such as high strength, low viscosity, robustness in impurities and wide temperature range of operational stability. We designed a constrained rotary MR damper base on valve mode which can dissipate more energy per unit volume. The system with Bingham characteristics is obtained and proved by the experiment.