• 한국공작기계학회논문집
• /
• 제11권2호
• /
• pp.17-23
• /
• 2002

A cylindrical capacitance-type spindle displacement sensor was developed and its effectiveness as a system to monitor cutting forces during hard turning was tested in this research. The sensor was installed between the face of spindle cover and the chucking element and measured pure radial motion of the spindle under the condition with presence of roundness error at measured surface. To prove the effectiveness of the developed system hard aiming tests using ceramic inserts and tool steel as workpiece were conducted. The workpiece was hardened up to 65 Rc. The variations of pure radial motion of the spindle ware measured during the cutting tests. The signals from the sensor showed the same pattern of cutting force variations from the tool dynamometer due to the progress of tool wear. As the flank wear of the ceramic tool increased both static component of cutting forces and the amount of center shift of spindle orbit increased, Results from the research showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to monitor cutting conditions and tool performance in the un-manned machining center.

• Journal of Power Electronics
• /
• 제18권1호
• /
• pp.234-250
• /
• 2018

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.

• 한국가스학회지
• /
• 제3권2호
• /
• pp.53-61
• /
• 1999

가스설비의 안전성을 위협하는 여러 요소들 중의 하나는 지반 침하 현상이다. 지반 침하는 천연가스 공급배관 뿐 아니라 인수기지 및 공급관리소 등 당 공사 전 설비에 공통적으로 적용되는 위험 요소이다. 따라서 본 연구에서는 침하를 감시하기 위하여 GPS(Global Positioning System) 기술을 적용코자 하였다. GPS기술을 당 설비에 적용하기 전에 GPS의 정밀도와 현장적용 타당성을 검증하기 위하여 모의 시험장치를 이용하여 변위측정 능력 및 정밀도를 측정하여 보았다. 그 결과 수 mm급의 3차원 변위 측정이 가능하다는 것이 입증되었다. 한국가스공사에서 운영하고 있는 가스공급관리소 중 침하가 우려되는 2곳에 GPS 설비를 설치하여 수개월간 배관의 변위량을 측정하여 본 결과, 연간 수 mm의 움직임이 있음을 확인하져다. 실험결과로 부터 GPS 시스템이 가스설비의 침하 및 변형감시 현장 업무에 적용 가능하다는 결론을 얻었다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제6권4호
• /
• pp.299-312
• /
• 2006

This paper presents the results of a novel test structure for process control monitor for uncooled IR detector technology of microbolometer arrays. The proposed test structure is based on resistive network configuration. The theoretical model for resistance of this network has been developed using 'Compensation' and 'Superposition' network theorems. The theoretical results of proposed resistive network have been verified by wired hardware testing as well as using an actual 16x16 networked bolometer array. The proposed structure uses simple two-level metal process and is easy to integrate with standard CMOS process line. The proposed structure can imitate the performance of actual fabricated version of area array closely and it uses only 32 pins instead of 512 using conventional method for a $16{\times}16$ array. Further, it has been demonstrated that the defective or faulty elements can be identified vividly using extraction matrix, whose values are quite similar(within the error of 0.1%), which verifies the algorithm in small variation case(${\sim}1%$ variation). For example, an element, intentionally damaged electrically, has been shown to have the difference magnitude much higher than rest of the elements(1.45 a.u. as compared to ${\sim}$ 0.25 a.u. of others), confirming that it is defective. Further, for the devices having non-uniformity ${\leq}$ 10%, both the actual non-uniformity and faults are predicted well. Finally, using our analysis, we have been able to grade(pass or fail) 60 actual devices based on quantitative estimation of non-uniformity ranging from ＜ 5% to ＞ 20%. Additionally, we have been able to identify the number of bad elements ranging from 0 to ＞ 15 in above devices.

• 대한전기학회논문지:전력기술부문A
• /
• 제49권8호
• /
• pp.412-417
• /
• 2000

TV ghost interference can be described as passive interference by the conducting part of transmission lines. In order to survey this interference from large-sized overhead EHV (extra high voltage) transmission line, TV reception quality was measured in the vicinity of that before and after construction. Instrumentation system was composed of ghost analyzer, TV received field intensity meter, VHF/UHF antennas, TV monitor and so on. The system is installed inside the vehicle. TV field intensity and PDUR (Perceived Desired wave to Undersired wave Ratio) are measured to evaluate TV ghost by using the system and vehicle. As the results, the useful data, which can be used to evaluate the effect of TV ghost interference from transmission lines could be obtained. In this paper, it is shown that the range of TV ghost interference from transmission lines can vary according to the frequency of TV electromagnetic wave, an incidence angle to the line and the other conditiions. At present, we are making efforts to establish a PDUR guideline for transmission lines.

• 전기전자학회논문지
• /
• 제7권2호
• /
• pp.197-209
• /
• 2003

현행 TV 신호는 HDTV나 컴퓨터 모니터에서 사용하는 encoding 기술과는 완전히 다르다. 다시 말하면 기존의 아날로그 TV에서는 Interlace 방식을 사용하는 반면 HDTV 및 컴퓨터 모니터에서는 Interlace 방식 대신 Progressive 방식을 사용한다. 따라서 Interlace 방식을 사용하는 미디어의 신호를 Progressive 방식을 사용하는 미디어에서 사용하기 위해서는 보간 알고리즘이 필요하다. 보간 알고리즘으로는 ELA(Edge-Based Line Average) 알고리즘이 보편적으로 사용된다. 본 논문에서는 ELA 알고리즘의 수평 및 수직 윤곽선 복원 단점을 개선시킨 ADI(Adaptive De-interlacing Interpolation) 알고리즘을 사용하여 Interlace 방식의 YUV 디지털 신호를 Progressive 방식의 RGB 디지털 신호로 변환시켜 주는 주사선 변환 ASIC 칩을 설계하였다. 설계 언어로는 VHDL이 사용되었다.

• 한국소음진동공학회논문집
• /
• 제18권7호
• /
• pp.701-710
• /
• 2008

Including a TV set and a monitor, personal audio system is raising a great interest. In this study, we applied a method to make a good bright zone around the user and dark zone to other region by maximizing the ratio of sound energy between the bright and dark zone. It has been well known as acoustic contrast control. We have attempted to use a line loudspeaker array system to localize the sound in our listening zone. It depends on the size of the zone and array parameters, for example, array size, loudspeaker unit spacing, wave length of sound. We have considered these parameters as spatial variables and studied the effects. And we have found that each spatial variable has its own characteristic and shows very different effect. Genetic algorithms are introduced to find out the optimum value of spatial variables. As a result, we can improve the result of the acoustic contrast control by optimum value of spatial variables.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제50권11호
• /
• pp.562-568
• /
• 2001

In this paper, we described the export system to monitor and diagnose 765KV power apparatus. To develop this expert system, we studied the knowledge bases and data bases for 765KV transformer and GIS. In order to make the reliable inference of knowledge base and the good MMI(Man Machine Interface), the data bases were consisted of the tables of power apparatus information, limit level value, measured input data, inference result and diagnosis result. The knowledge base had various rules to infer the conditions of transformer and GIS. We applied both the forward chaining and backward chaining methods to these rules of system for good inferences. This paper describes the applied methods for expert system. Also, this developed system was tested with dissolved gas analyzing result and the result was shown.

• Journal of the Optical Society of Korea
• /
• 제15권1호
• /
• pp.96-102
• /
• 2011

Simultaneous measurements using a scanning spectrograph system and transmissometer were performed for the first time over an urban site in Gwangju, Korea, to derive the ambient $NO_2$ volume mixing ratio. The differential slant column densities retrieved from the scanning spectrograph system were converted to volume mixing ratios using the light traveling distance along the scanning line of sight derived from the transmissometer light extinction coefficients. To assess the performance of this system, we compared the derived $NO_2$ volume mixing ratios with those measured by an in situ chemiluminescence monitor under various atmospheric conditions. For a cloudless atmosphere, the linear correlation coefficient (R) between the two data sets (i.e., data derived from the scanning spectrograph and from the in situ monitor) was 0.81; the value for a cloudy atmosphere was 0.69. The two sets of $NO_2$ volume mixing ratios were also compared for various wind speeds. We also consider the measurement errors, as estimated from an error propagation analysis.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.1038-1042
• /
• 2002

Monitoring of the drill wear and hole quality change is conducted during the drilling process. Cutting force measured by tool dynamometer is a evident feature estimating abnormal state of drilling. One major difficulty in using tool dynamometer is that the work piece must be mounted on the dynamometer, and thus the machining process is disturbed and discontinuous. Acoustic transducer do not disturb the normal machining process, and provide a relatively easy way to monitor a machining process for industrial application. For this advantage, AE signal is used to estimate the abnormal state. In this study vision system is used to detect flank wear tendency and hole quality, there are many formal factors in hole quality decision circularity, cylindricity, straightness, and so on, but these are difficult to measure in on-line monitoring. The movement of hole center and increasement of hole diameter is presented to determine hole quality As the results of this experiment, AE RMS signal and measurements by vision system are shown the similar tendency as abnormal state of drilling. And detection of the abnormal states using BPNs was achieved 96.4% reliability.