• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.59-62
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• 1992

Power system fault transient signals are highly distorted due to the presence of high frequency components in the voltage and current signals and an exponentially decaying dc-offset component in the current signals. Modern protective relays have to make reliable fast decisions about the nature of a fault in the presence of such transients. To use a dc-offset removing filter makes relay algorithms much fast and reliable for detecting a fault. In this paper, several dc-offset removing filters are described, and characteristics of them are compared.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.430-434
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• 2001

Virtual manufacturing system is integrated computer model that represents the precise and whole structure of manufacturing system and simulates its physical and logical behavior in operation.[1] A virtual machine is computer model that represents a CNC machine tool and one of core elements of virtual manufacturing system. In this paper, it is emphasized that a virtual machine must be web-based system for serving information to all attendants in a real machine tool without the restriction of time or location, and then in the fault diagnosis, one of important modules of a virtual machine, the methods of both using the controller signal and web-based expert system are proposed.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.176-180
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• 1992

At the KACC'91 conference, we proposed a method of automatic detection of shape of the faulty holes of a shadow mask which is used in a cathode-ray tube of a color television. In this method, the image data are taken from two areas of the mask with CCD camera. Comparing the shape of holes in these two areas by use of a signal processing technique, we can find any fault in the shape of holes. This paper describes the effect of smoothing filters of effectively finding the faulty holes from the difference image data. A computer simulation and actual experiment with a shadow mask have shown that this method of fault detection is very effective for practical use.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.99-105
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• 1994

k-bounded circuits are combinational circuits proposed by Fujiwara whose subcircuits are partitioned in a way that they form a tree and have some restricted k inputs respectively. Fujiwara proposed a O($16^{k}m$) fault detection algorithm for k-bounded circuits where m is the number of signal lines in the circuit. This algorithm is very ineffective to be applied to real circuits, even for small values of k. In this paper, it is shown that a single stuck-at fault in k-bounded circuits can be detected in O($2^{k}m$)time, and multiple stuck-at faults are detected in O($4^{k}m$) time by using thable lookup and imput partitionsing.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1115-1127
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• 2010

Several methods have been applied to detect winding faults (turn-to-turn short). The representative approaches have been focusing on current signals. The current signal can give important information to extract features and to detect faults. In this study, current sensors were installed to measure signals for fault detection of BLDC motors. Therefore, it is necessary to select proper feature extraction methods among the popular methods that use current signals.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.65-71
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• 2007

According to the survey, abnormal condition of the system is the main source for interrupting an elevator service, especially faults in worm gears used for the traction machine. Worm gear is popularly used in traction machine for middle and low speed elevators. Elevators need high reliability and stability, because they are closely related to human life. Usually, traction machine is applied to drive the elevators that have height about 35 m and it is an important mechanical unit for riding quality in elevators. There are some research results about types of vibration fault for worm gear in International Association Elevator Engineers (IAEE). But this study concerns with diagnosis of various faults in elevator worm gear using vibration signal. The analysis of fault characteristics is compared with previous researches in traction machine.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.624-629
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• 2014

The purpose of this study is to carry out the task of engine hesitation which occurred intermittently in driving due to the defective CKPS of LPI vehicles. As the result of the wrong data from the equipment of D-logger, the signal error of CKPS caused the engine hesitation. We performed a study in the followings to analyze and investigate the cause effectively. First, we have investigated the control wiring harness and connector pin contact defect inspection. Second, we have inspected the defection of CKPS separately. From this study, it was found that the engine hesitation were caused by the bad durability and we have showed how to diagnosis the fault of the engine hesitation intermittently while driving. Therefore, it is determined that we have to improve the durability of the CKPS through a strict quality control and to increase the reliability.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.343-346
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• 2000

When a feedback bridging fault is activated, oscillation may be generated in output signal lines. If the oscillation is generated, the fault may not be detected by logic testing. Thus, in the past we proposed a current sensor to detect feedback bridging faults by supply current testing. The sensor circuit design requires the maximum frequency of oscillation which is generated when feedback bridging fault is excited as a specification. In this paper, an estimation method of the oscillation frequency is proposed. Also, it is shown by some experiments that the frequency obtained by the method can be used for the sensor design.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.359-362
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• 2000

In this paper, we propose a test pattern generation algorithm on the basis of the identification of undetectable faults for Speed-Independent(SI) asynchronous control circuits. The proposed methodology generates tests from the specification of a target circuit, which describes the behavior of the circuit in the form of Signal Transition Graph (STG). The proposed identification method uses only topological information of a target circuit and reachability information of a fault-free circuit, which is generated in the form of Binary Decision Diagram(BDD) during pre-processing. Experimental results show that high fault coverage over single input stuck-at fault model is obtained for several synthesized SI circuits and the use of the identification process as a preprocessing decreases execution time of the proposed test generation with negligible costs.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.509-512
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• 1995

The relaying algorithm to calculate the fault distance from only transient signal at faults in T/L is presented. In this paper. At faults the oscillation frequency components exist in both voltage and current and these components minimize the input impedance shown in fault point. The equivalent source impedance shown in relaying point is needed to calculate the fault distance using these components. To source impedance, the reflection coefficient between forward wave and backward and the Prony's analysis is also employed to extract the oscillation frequency component from transient signals. The case study show that the new distance relaying algorithm satisfies the high operation speed and high accuracy even if the algorithm uses only transient signals.