• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.574-577
• /
• 2004

This paper presents a hybrid system combining lead rubber bearings and hydraulic actuators controlled by a $\mu-synthesis$ 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 $\mu-synthesis$ method that guarantees the robust performance is considered to enhance the possibility of real applications of the control system. The performances of the proposed control system are compared with those of passive, active, semiactive control systems and hybrid system controlled by a LQG algorithm. Furthermore, 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 performances of the proposed control system are superior to those of passive system and slightly better than those of active and semiactive systems and two hybrid systems show similar control performances. Furthermore, the hybrid system controlled by a f-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.

• 한국인터넷방송통신학회논문지
• /
• 제13권4호
• /
• pp.229-237
• /
• 2013

최근 SOA와 클라우드 컴퓨팅 기반의 IT 서비스에 대한 수요가 증가하면서 서비스 당사자들 간에 SLA(Service Level Agreement, 서비스 수준 협약)에 대한 관심이 증대되고 있다. 통상 SLA는 자연어로 작성된 종이 계약서이다. 상업용 SLA 관리 툴에서 사용하는 SLA는 절차적 언어를 사용하여 계약서 내용을 애플리케이션 안에 암시적으로 구현된다. 이는 SLA 자동화 작업을 어렵게 한다. 또한 계약시스템에 대한 유지관리를 어렵게 하고 새로운 계약 요구사항을 적용하기 위해서는 소스 코드에 대한 광범위한 수정 작업이 뒤따른다. SLA 유지관리 과정에서 발생하는 문제의 근본 원인은 동일한 SLA가 문서형과 실행형으로 이원화 되어 있다는 것이다. 본 논문에서는 이러한 현행 SLA 관리의 문제점을 개선하기 위해서 능동형 SLA(ASLA : Active Service Level Agreement)를 기반으로 하는 능동형 SLM(ASLM : Active Service Level Management) 시스템을 제안한다. 이 시스템에서는 이원화된 SLA 처리 및 관리 과정이 능동형 SLA(ASLA)의 도입으로 일원화될 수 있음을 보였다.

• 한국통신학회논문지
• /
• 제29권4C호
• /
• pp.559-569
• /
• 2004

인터넷 기반의 사이버 공격의 형태가 다양해지고 복잡해지면서 공격자를 탐지하고 신속하게 대응하는 것이 점차 어려워지고 있다. 또한, 기존의 네트워크 보안 메커니즘이 지엽적인 영역에서 방어적인 대응에 치중하고 있는 실정이다. 본 논문에서는 다양한 사이버 공격에 쉽게 대응할 수 있고, 보안 영역 간의 협력을 통해 공격자를 추적하고 고립화할 수 있는 능동적인 대응이 가능한 새로운 네트워크 보안 구조를 제안하고자 한다. 제안된 보안 구조는 능동 네트워크 상에서 능동 패킷 기술을 이용하여 위조 IP 공격이나 DDoS(Distributed Denial of Service) 공격 등을 효과적으로 대응하는 것이 가능하다. 제안된 보안 구조를 기반으로 설계된 능동 보안 관리 시스템은 보안 영역 내에서 능동보안노드와 능동보안관리서버로 구성되며, 다양한 보안 영역 내의 능동보안관리 시스템 간의 협업을 통해 기존의 사이버 공격 대응 방식보다 능동적으로 대응할 수 있다. 능동보안관리 시스템의 적용가능성을 검증하기 위해 테스트베드를 구축하여 실험하였고, 실험 결과를 분석한다.

• 한국통신학회논문지
• /
• 제35권7A호
• /
• pp.669-681
• /
• 2010

본 논문에서는 능동형 RFID (Radio Frequency Identification) 시스템인 ISO/IEC 18000-7 시스템과 저속 WPAN (Wireless Personal Area Network) 표준인 IEEE 802.15.4a에 정의된 UWB (Ultra Wideband) 방식과 CSS (Chirp Spread Spectrum)방식에 대하여 살펴보고, 인식율 및 인식거리를 향상시키기 위하여 매우 넓은 주파수 대역에 걸쳐 상대적으로 낮은 스펙트럼 전력밀도로 다른 시스템과 양립할 수 있는 UWB 기술을 이용하여 정보를 전송하고, USN (Ubiquitous Sensor Network) 응용을 위해 능동형 태그와 센서노드들이 서로 혼재되어 구성된 네트워크에서 릴레이 태그를 릴레이 AP로 이용하여 능동형 태그의 정보뿐 아니라 센서노드의 정보도 전달하는 UWB 기반의 Class 4 능동형 RFID 프로토콜을 제안한다. 기존 ISO/IEC 18000-7 시스템과 제안된 시스템의 성능평가를 위하여 Sensitivity에 의한 인식거리 및 시스템 효율과 같은 항목을 정의하며, MCL (Minimum Coupling Loss) 분석과 SLS (System Level Simulation) 분석을 통해 제안된 시스템의 성능을 비교 및 분석한다.

• 한국인터넷방송통신학회논문지
• /
• 제14권5호
• /
• pp.153-159
• /
• 2014

본 논문에서 제안하는 이동에이전트를 이용한 분산형 절전제어 방법은 다수의 센서와 이동에이전트를 이용하여 능동적 지능적으로 조명장치의 제어(on/off 및 디밍 조절 등)를 가능하게 하여 에너지 절감에 효과적이며, 다양한 능동규칙들의 적용에 의한 원격감시 및 제어기능 추가가 용이하므로 효율적 절전제어시스템 설계 및 구축에 따른 비용절감 등의 효과를 유도한다. 또한, 이동에이전트 기반의 센서네트워크 미들웨어의 기능을 통하여 상황정보나 사용자의 감성 등을 규칙화하여 실시간으로 이벤트 처리 및 제어함으로써 센싱 데이터의 효용성을 향상시킨다. 본 논문의 결과는 다양한 능동적 센서네트워크 응용들의 개발에 있어 제안한 이동에이전트를 이용한 제어시스템의 활용가능성을 제시한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
• /
• pp.462-464
• /
• 2004

ActiveX is the general name for a set of Microsoft Technologies that allows users to re-use code and link individual programs together to suit their computing needs. In addition ActiveX technology Provides a standard model for interapplication communication that different programming language. ActiveX is based on COM(Component Object Model), the COM standard allow developer to create code and application from a multitude of different languages and build a defined interface to that code, making it easily accessible by other application. By using ActiveX, user can access the functionality of other applications running remote computer distributed through the network and communicate over the network to build distributed applications. LabVIEW provides access to other Windows applications using ActiveX technologies. So in this paper we implement distributed application using ActiveX technology for remote control and monitoring.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제53권1호
• /
• pp.24-29
• /
• 2004

A new low cost hybrid active filter for thyristor-controlled rectifier load is presented to overcome the high cost problem of the active or the other hybrid active filters. The proposed hybrid active filter which consists of tuned (5th and 7th harmonics) LC passive filters, power factor improvement(PFI) capacitor bank, and active filter compensates power factor as well as harmonic currents. Since most of harmonic currents are filtered by the passive filter and most of reactive power is compensated by the PFI capacitor bank, the power rating of active filter can be minimized, resulting in cost minimization of the proposed hybrid active filter. A 300kVA hybrid active filter system is implemented and tested using 1MVA thyristor rectifier load to verify the operation and performance.

• Earthquakes and Structures
• /
• 제4권1호
• /
• pp.63-84
• /
• 2013

A semi-active mass damping (SMD) system with magnetorheological (MR) dampers focusing on low- and mid-rise buildings is proposed in this paper. The main purpose of this study is to integrate the reliable characteristics of the traditional tuned mass damper (TMD) and the superior performance of the active mass damper (AMD) to the new system. In addition, the commonly seen solution of deploying dense seismic dampers throughout the structure nowadays to protect the main structure is also expected to switch to the developed SMD system on the roof with a similar reduction performance. In order to demonstrate this concept, a full-size three-story steel building representing a typical mid-rise building was used as the benchmark structure to verify its performance in real life. A numerical model with the interpolation technique integrated was first established to accurately predict the behavior of the MR dampers. The success of the method was proven through a performance test of the designated MR damper used in this research. With the support of the MR damper model, a specific control algorithm using a continuous-optimal control concept was then developed to protect the main structure while the response of the semi-active mass damper is discarded. The theoretical analysis and the experimental verification from a shaking table test both demonstrated the superior mitigation ability of the method. The proposed SMD system has been demonstrated to be readily implemented in practice.

• Structural Engineering and Mechanics
• /
• 제20권2호
• /
• pp.191-207
• /
• 2005

Time delay exists inevitably in active control, which may not only degrade the system performance but also render instability to the dynamic system. In this paper, a novel active controller is developed to solve the time delay problem in flexible structures. By using the independent modal space control method, the differential equation of the controlled mode with time delay is obtained from the time-delay system dynamics. Then it is discretized and changed into a first-order difference equation without any explicit time delay by augmenting the state variables. The modal controller is derived based on the augmented system using the discrete variable structure control method. The switching surface is determined by minimizing a discrete quadratic performance index. The modal coordinate is extracted from sensor measurements and the actuator control force is converted from the modal one. Since the time delay is explicitly included throughout the entire controller design without any approximation, the system performance and stability are guaranteed. Numerical simulations show that the proposed controller is feasible and effective in active vibration control of dynamic systems with time delay. If the time delay is not explicitly included in the controller design, instability may occur.

• Journal of electromagnetic engineering and science
• /
• 제7권4호
• /
• pp.161-168
• /
• 2007

A fast correlative vector direction finding(CVDF) system using active dipole antenna array for mobile direction finding(DF) applications is presented. To develop the CVDF system, the main elements such as active dipole antenna, multi-channel direction finder, and search receiver are designed and analyzed. The active antenna is designed as composite structure to improve the filed strength sensitivity over the wide frequency range, and the multi-channel direction finder and search receiver are designed using DDS-based PLL with settling time of below 35 us to achieve short signal processing time. This system provides the capabilities of the high DF sensitivity over the wide frequency range and allows for high probability of intercept and accurate angle of arrival(AOA) estimation for agile signals. The design and performance analysis according to the external noise and modulation schemes of the CVDF system with five-element circular array are presented in detail.