• Wind and Structures
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• v.2 no.3
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• pp.201-251
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• 1999

Flexible structures may experience excessive levels of vibration under the action of wind, adversely affecting serviceability and occupant comfort. To ensure the functional performance of a structure, various design modifications are possible, ranging from alternative structural systems to the utilization of passive and active control devices. This paper presents an overview of state-of-the-art measures that reduce the structural response of buildings, including a summary of recent work in aerodynamic tailoring and a discussion of auxiliary damping devices for mitigating the wind-induced motion of structures. In addition, some discussion of the application of such devices to improve structural resistance to seismic events is also presented, concluding with detailed examples of the application of auxiliary damping devices in Australia, Canada, China, Japan, and the United States.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.152-158
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• 2010

Generally, the AC electrified railway systems have the power quality problems that are induced from the harmonic currents and the reactive power. This paper presents a single-phase hybrid active filter adopting a SRF(synchronous-reference-frame) control for improving power quality in the AC electrified railway systems. The single-phase hybrid active filter can compensate the harmonic currents and the reactive power through the proposed SRF control algorithm. The proposed control algorithm can extract the third and fifth harmonics through the MSRF(multiple-synchronous-reference-frames) which is used to apply the three-phase systems. Therefore, the hybrid active filter can compensates only the high-frequency harmonic currents whereas the passive filter compensates the low-frequency harmonic currents. Also, the proposed SRF control algorithm can compensate the reactive power by the closed-loop control. The Validity and the effectiveness of the proposed SRF control method for the hybrid active filter are illustrated through the simulation results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.5
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• pp.221-229
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• 2003

This paper suggests a control algorithm of 3-phase 3-wire series active power filter. This suggested algorithm can compensate source harmonics and reactive power in 3-phase 3-wire power distribution systems. These harmonics are generated by nonlinear loads such as diode rectifiers and thyristor converters. This control algorithm extracts a compensation voltage reference from performance function without phase transformation. Therefore, this control algorithm is simpler than any other conventional control algorithms. 3-phase 3-wire series active power filters which have a harmonic voltage source and a harmonic current source are manufactured and experiments are carried out to verify the effectiveness of suggested control algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.876-879
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• 1996

The vibration of an attractive magnetic levitation(Maglev) vehicle transportation system is caused by the irregularity of the guideway track and the performance of the suspensions of the Maglev system. It is essential for us to give attention to the secondary suspension of the vehicle system as it determines the ride quality. In order to improve the ride quality and running stability, active secondary suspensions have been developed and applied to the vibration problems. This paper analyzes the performance of the active secondary suspension which is applied to an attractive magnetic levitation vehicle system running on a rough track. The dynamics of the suspension system and the optimal control problems are studied. According to the transient and frequency response analyses to the track disturbance, the ride quality of an attractive Maglev vehicle has been improved by applying the designed LQR active controller, and it has been confirmed that this improvement was also influenced by the configuration of the system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.156-161
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• 1992

Over the past twenty years, the concept of structural control has been investigated for the application to large civil engineering structures. At the early years, passive control systems, such as tuned mass damper(TMD) and tuned liquid mass bamper(TLD), have been utilized to reduce the wind induced vibrations of tall buildings, decks and pylons of long-span bridges. More recently, the active control concept has been applied to reducing the structural vibration and increasing the human comfortness in tall buildings during strong wind. In this study, the effectiveness of the active tuned mass damper(ATMD) has been investigated for reducing vibration of large structures during strong earthquake. Stochastic optimal control theory has been employed. Example analyses are carried out through analytical simulation studies.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.159-161
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• 1994

A new control technique which generates high-quality sinusoidal output voltage from a single-phase resonant do link inverter suitable for the UPS systems is presented. The inverter output voltage control system has the PID controller with a minor loop of the filter inductor current and tile feedforward controller. The proposed control scheme also solves resonant voltage overshoot without any additional switch or passive component, resulting in pulses with uniform amplitude and high efficiency. Experimental results in the case of linear and nonlinear loads are presented to confirm the usefulness of the Proposed control algorithms.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.511-518
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• 2006

In this study, seismic response mitigation effect of an MR damper generating response-dependent frictional force is investigated. It has been reported in previous studies that passively operated MR damper with constant input current doesn't show better control performance than semi-active MR damper with varying input current calculated by control algorithms such as linear quadratic regulator and sliding mode control. However, in order to operate the MR damper semi-actively, other control systems besides the damper itself such as sensors for measuring structural responses and controller for calculating optimal input current are necessary, which deteriorate the economical efficiency. This study presents a MR damper generating frictional force of which magnitude is controlled in accordance to the displacement and velocity transferred to the damper. Numerical analyses results indicate that the performance of the response dependent MR damper is closely related with the range of the friction force and it can be designed to short better control performance than the passive MR damper.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.442-453
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• 2016

A significant source of vibration in helicopters is the main rotor system, and it is a technical challenge to reduce the vibration in order to ensure the comfort of crew and passengers. Several types of passive devices have been applied to conventional helicopters in order to reduce the vibration. In recent years, helicopter manufacturers have increasingly adopted active vibration control systems (AVCSs) due to their superior performance with lower weight compared with passive devices. AVCSs can also maintain their performance over aircraft configuration and flight condition changes. As part of the development of AVCS software for light civil helicopter (LCH) applications, a test bench is constructed and vibration control tests and simulations are performed in this study. The test bench, which represents the airframe, is excited using a pair of counter rotating force generators (CRFGs) and a multiple input single output (MISO) AVCS that consists of three accelerometer sensors and a pair of CRFGs; a filtered-x least mean square (LMS) algorithm is applied for the vibration reduction. First, the vibration control tests are performed with uniform sensor weights; then, the change in the control performance according to changes in the sensor weight is investigated and compared with the simulation results. It is found that the vibration control performance can be tuned through adjusting the weights of the three sensors, even if only one actuator is used.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.557-563
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• 2007

Rain-wind induced cable vibration can cause serious problems in cable-stayed bridge. External dampers attached to the cables have become widely accepted as an effective means for stay-cable vibration suppression. For very long stay-cables, however, such damper systems are rendered ineffective, as the dampers need be attached near the end of cables for aesthetic reasons. A recent study by the authors proposed that a movable anchorage system is replaced direct fixed support of the cable with a support through a bearing and damper. This paper extends the previous work by adding active control system to mitigate the cable vibration. The response of a cable with the proposed active control system is obtained and then compared to those of the cable with and without an external passive damper. The results show that the active control system can provide superior protection than the passive control system for a cable vibration.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11
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• pp.3020-3033
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• 1999

Role-Based Access Control(RBAC) security policy is being widely accepted not only as an access control policy for information security but as both a natural modeling tool for management structure of organizations and flexible permission management framework in various commercial environments. Important functions provided by the current RBAC model are to administrate the information on the components of RBAC model and determine whether user's access request to information is granted or not, and most researches on RBAC are for defining the model itself, describing it in formal method and other important properties such as separation of duty. As the current RBAC model which does not define the definition, design and operation for applications is not suitable for automated information systems that consist of various applications, it is needed that how applications should be designed and then executed based on RBAC security model. In this paper, we describe dynamic properties of session which is taken for a passive entity only activated by users, as a vehicle for building and executing applications in an automated information systems. And, a framework for session-oriented separation of duty property, application design and operation is also presented.