• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.47 no.6
• /
• pp.43-50
• /
• 2010

In this paper, the TWTA (Traveling Wave Tube Amplifier) maintenance system for the low altitude surveillance Radar was developed using the embedded Linux system, and its superiority was demonstrated through the performance test. Nowadays, the necessity of maintenance system and reliability testing on military equipments has been increasing steadily. In addition, nonlinear characteristics of the maintenance system for the low altitude surveillance Radar are more likely to have serious problems as well as to slow down durability. Therefore, after analyzing characteristics of RF input-output signal and TWTA, we designed interface circuits between the TWTA equipment and the embedded Linux system. The Linux kernel on the system was optimized to improve the efficiency and reliability. And our new TWTA maintenance system was evaluated in the real field. As a result, the proposed system was contented with desired specifications, and demonstrated military's fighting capabilities. Therefore, our novel system will advance military maintenance technology and will help to develop similar equipments.

• Aerospace Engineering and Technology
• /
• v.2 no.1
• /
• pp.108-116
• /
• 2003

This research presents the design and analysis of PCDU(Power Control & Distribution Unit) of communication satellite. The PCDU of a spacecraft must provide adequate power to each subsystem and payload during mission life, and it also needs high reliability and performance in space environment. A control circuit of the PCDU include bus sensing and filter circuits, error signal amplification circuit, error compensation circuit of SAS(Shunt Assembly Switch) and BPC(Battery Power Converter). The phase margin and DC gain for the designed circuits are analyzed through the frequency response characteristics of the compensated control circuit. And also the transfer function of the battery power converter circuit are discussed at the battery CCCM(Charge Continuous Conduction Mode) and battery C/DCCM(Continuous/Discontinuous Conduction Mode).

• Journal of KIISE:Computing Practices and Letters
• /
• v.5 no.4
• /
• pp.457-466
• /
• 1999

원자력 발전소 계측 제어 시스템, 의료 관련 시스템, 항공 관련 시스템 등 실생활과 밀접한 시스템에 소프트웨어의 사용이 점차 증가하고 있다. 이러한 시스템에서 소프트웨어의 오류는 예기치 않는 사고를 유발하여 인명, 재산상의 심각한 타격을 줄 수 있다. 그러므로 고신뢰도 소프트웨어의 개발 시에는 반드시 시스템의 안전성을 보장해 주어야 한다. 역방향 안전성 분석 방법은 시스템의 안전성을 분석하는 한가지 방법으로서 시스템의 위험 상태를 정의하고 그 위험의 원인들을 추적, 분석함으로써 안전성에 대한 효율적인 분석을 수행할 수 있는 장점을 갖는다. 이 논문에서는 소프트웨어 개발 초기 단계에서 안전성을 분석할 수 있는 방법으로 Colored Petri Nets(CPN)에 기반을 둔 역방향 안전성 분석 방법을 제시한다. 또한 CPN 역방향 안전성 분석 도구인 SAC(Safety Analyzer for CPN)의 설계 및 구현에 대해 언급한다. SAC은 기존의 상용 CPN 모델링 도구인 Design/CPN과 연계하여 사용될 수 있으므로 CPN으로 모델링된 시스템의 안전성을 분석할 수 있다는 장점이 있다. 이 논문에서는 예제로 자동 교통 제어 시스템의 일부를 CPN으로 모델링하고 SAC을 이용한 분석 과정을 기술한다.Abstract In safety-critical systems such as nuclear power plants, medical machines, and avionic systems which are closely related with our livings, the usage of software in the controlling part is growing rapidly. Since software errors in safety-critical systems may cause serious accidents leading to financial or human damages, system safety should be ensured during and after development of a system. A backward safety analysis technique defines system hazards and tries to trace their causes by analyzing system states backward. In this paper, we provide a backward safety analysis technique based on Colored Petri Nets(CPN), which is applicable to the early software development phase. Also Safety Analyzer for CPN(SAC), the supporting tool, is designed and implemented. Since SAC is compatible with Design/CPN, a commercial tool for supporting CPN, it can be applicable to analyze safety in practical problems. As an example, we model a part of the traffic light control system using CPN and analyze safety properties of the model using the SAC tool.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.6 no.6
• /
• pp.865-871
• /
• 2011

DC-DC converter commonly used in photovoltaic systems or fuel cell systems is a boost converter. Among several types of boost converter, the interleaved boost converter with small input and output current ripples is widely used in recent years. Because of small input and output current ripples, the circuit can reduce the size of the input and output capacitors. Thus, instead of conventional electrolytic capacitor, the film capacitor with high reliability can be used and this is the life and reliability of the entire system can be improved. In this paper, the input/output current ripple formulas of the multi-stage interleaved boost converter are derived, and the characteristics in accordance with duty are found out. In order to verify the above mentioned contents, the derived results will make a comparison with the calculated values by using PSIM tool.

• Journal of KIISE:Software and Applications
• /
• v.29 no.12
• /
• pp.926-939
• /
• 2002

The formal specification methods with probability have been demanded in the area of fault real-time systems, in order to specify the uncertainty that the systems can encounter during their execution due to various environmental factors. This paper presents a new formal method with probability. namely Probabilistic Abstract Timed Machine (PATM), in order to analyze and predict system's behavior in dynamical environmental changes, This method classifies the factors into two classes: the variable and the constant. The analysis of system's behavior is performed on the probabilistic reachability graph generated from the ATM specification for the system. The analysis can predict any possibility that the behavior may not satisfy some safety requirements of the system, indicate which variable factors cause such satisfaction, and further recover from this unsatisfying fault state by fixing the variable factors. Consequently the reliability to the fault real-time systems can be improved.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.2
• /
• pp.79-87
• /
• 2010

This is the first of the two papers dealing with reliability analyses for external and internal stability of a quay wall constructed on a special foundation. A new practical reliability analysis method is proposed in this paper to evaluate the quantitative risk associated with external stability of a quay wall constructed on the deep cement mixed ground. The method can consider uncertainties in various design variables. For the risk estimation to external stability of the improved soil-quay wall, three corresponding limit state functions of sliding, overturning and bearing capacity are fully defined by introducing concept of the secondary random variable. Three representative reliability methods, MVFOSM, FORM and MCS are then applied to evaluate the failure probabilities of the three limit state functions explicitly expressed in terms of the basic and secondary random variables. From the reliability analysis results, the failure probabilities obtained from the three approaches are very close to each other, and the sliding failure mode appears to be the most critical when the earthquake loading is under consideration.

• Journal of KIISE
• /
• v.42 no.11
• /
• pp.1339-1348
• /
• 2015

In a distributed system environment based on a service-oriented architecture, separate systems collaborate to achieve the goals of the entire system by using services provided other systems. A service quality violation from using one service can cause runtime system failure in the environment. The existing self-adaptation methods follow fault tolerance mechanism that responds to a failure after a service quality violation. In other words, these methods are limited to responsive action. Therefore, a service-dependability-case based self-adaptation mechanism is necessary to preserve the dependability of the self-adaptive system. This paper demonstrates that the service-dependability-case based self-adaptation mechanism is better than QoS(quality of service)-based self-adaptation with fault tolerance to preserve the dependability of the self-adaptive system. Additionally, this paper suggests a method to present and analyze service dependability by using GSN(Goal Structuring Notation) which is the existing modeling method for the presentation of assurance cases, an action mechanism adapted using an analysis result of service-dependability-cases, a methods of leveraging the service-dependability-case based self-adaptation mechanism by following the service's life cycle, and the framework architecture including the major components and the interactions between the components in the control loop of the self-adaptation process.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.453-454
• /
• 2014

태양광 발전용 AC-모듈에서 발생하는 전력 디커플링을 위해 사용되는 대용량 전해 커패시터는 시스템의 신뢰성을 감소시키므로 최근 보조회로를 이용한 디커플링 기법이 연구되고 있다. 하지만 디커플링 회로의 제어기 오차와 시스템의 효율이 고려될 경우, 태양광 패널에 전력 맥동이 존재하게 되고 이는 인버터 출력 전류를 왜곡시키는 원인이 된다. 본 논문에서는 제어기 오차와 시스템 효율을 고려하여 발생하는 전력 맥동에 대해 분석하고, 이를 저감시키기 위한 전류 왜곡 보상 기법을 제안하였다. 이를 PSIM 시뮬레이션을 통해 그 타당성을 검증하였다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.34 no.8
• /
• pp.348-366
• /
• 2007

Capacity of modem storage devices is becoming larger than yesterday and integration of disk is increasing. It refers that physical errors can damage a lot of digital information on storage devices. So we propose file system test framework in this paper to test integrity and robustness of file systems. We develop the tool for generating bad sectors on disks and the tool which creates all physical errors defined in storage devices. We also develop the tool for immediately monitoring the condition of read and write execution on storage devices. So, by integrating those tools, we develop FORT, test framework for confirming robustness of file system. We analyze robustness of ext3 file systems by FORT. Lastly, we present draft of intelligent system merging file system and device driver's layer architecture.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.7
• /
• pp.1319-1325
• /
• 2006

Urine analysis is basic test in clinical medicine using visual examination by expert nurse. Recently, this test is measured by automatic urine analysis system. But, this system has different results by each instrument. So, a new classification algorithm is required for accurate classify and urine color collection. In this paper, a intelligent color classifier of urine analysis system was designed using neural network algorithm. The input parameters are three stimulus(RGB) after preprocessing using normalization. The fuzzy inference and neural network ware constructed for classify class according to 9 urine test items and $3{\sim}7$ classes. The experiment material to be used a standard sample of medicine. The possibility to adapt classifier designed for urine analysis system was verified as classifying measured standard samples and observing classified result. Of many test items, experimental results showed a satisfactory agreement with test results of reference system.