• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.199-201
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• 2006

풍력발전기에 있어서 블레이드의 Yaw방향 제어는 끊임없이 변화하는 풍향에 대해 효율의 극대화와 블레이드의 강도 및 진동측면에서 대단히 중요하다. 기존의 블레이드 Yaw 방향 측정은 접촉 및 비접촉 센서가 이용되어왔다. 본 논문에서는 풍력발전기의 원격모니터링 시스템에서 기본적으로 설치되는 카메라를 이용하여 블레이드의 Yaw방향을 측정하는 방법을 제안한다. 블레이드가 풍향에 따라 회전할 때 영상 누적을 행하고, 누적영상에 대해 경계점을 추정하여 타원의 궤적을 추정한다. 추정된 경계점들을 이용하고 최소자승법을 적용하여 타원방정식을 추정하고, 장축과 단축을 연산한다. 장축과 단축의 변화를 이용하여 카메라의 촬영방향의 기준점으로부터 Yaw방향의 변화를 정량적인 값으로 산출하여 이를 바탕으로 Yaw회전각을 추정한다. Yaw 방향 추정의 검증을 위해 블레이드 속도와 Yaw 방향의 제어가 가능한 모형풍력발전기를 제작하고 실험을 통하여 제안한 추정알고리즘의 유효성을 검증한다.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.234-236
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• 2001

자동차 산업의 활성화로 인하여 차량의 연료 소비의 고효율화 및 구동모터의 고정밀 설계 기술의 향상이 대두되고 있는 실정이다. 특히, LPG 차량의 연료 펌프 모터의 고속화, 저진동, 저 소음화의 추세로 인하여 기존의 Brush타입의 DC모터를 대체하기 위한 Brushless DC 모터의 개발이 증대되고 있다. 본 논문에서는 이러한 Brushless DC모터의 고정밀 속도제어 및 빠른 응답 특성을 가지는 제어기를 개발하였으며, 회전자의 위치를 파악하기 위하여 역기전력을 이용한 센서리스형 제어기를 개발하였다. 본 논문에서 개발한 제어기는 가변속도제어범위를 가지며. 2000rpm에서 정격 속도를 가진다. 제어기의 성능 검증을 위하여 정격 속도에서의 단위스텝 응답 특성 실험을 하였으며, 각각의 게인 설정에 따른 제어 성능 실험을 하였다.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.13-18
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• 2011

This thesis is about the result of conducting a specific experiment for the development of noncontact vibration displacement sensor for measuring the spindle vibration that is used for conditional monitoring of machinery. One should be careful when using the eddy current type displacement sensor because the sensitivity of it is different according to the quality of the material. While the probe used for nondestructive inspection adopts the effect of transmitting the material by using the high frequency domain, the eddy current type displacement sensor uses the lower frequency of around 1MHz. Also, while the nondestructive probe uses the method of enhancing output by using the resonance zone, the vibration displacement sensor utilizes the stable zone by avoiding the resonance zone. Since the oscillator of the converter uses the "L" element as Probe, its characteristic changes with the variation of a relevant impedance. In other words, if the length of Probe's Cable gets extended (Impedance increase), the sensitivity declines accordingly. The effect of surrounding temperature was small, but the influence of the quality of Sensor Coil used was high. Moreover, following an experimental demonstration of the phenomenon where the sensitivity decreases as the frequency of the tested material increases from a frequency response test, the maximum frequency that could be measured was approximately 1KHz. It was noted that the degree of precision could be maintained by using the gap of the probe in the linear zone at the installation site.

• Journal of IKEEE
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• v.26 no.3
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• pp.488-493
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• 2022

In manufacturing sites, bearing fault in eletrically driven motors cause the entire system to shut down. Stopping the operation of this environment causes huge losses in time and money. The reason of this bearing defects can be various factors such as wear due to continuous contact of rotating elements, excessive load addition, and operating environment. In this paper, a motor driving environment is created which is similar to the domestic manufacturing sites. In addition, based on the established environment, we propose a dataset for bearing fault detection by collecting changes in vibration characteristics that vary depending on normal and defective conditions. The sensor used to collect the vibration characteristics is Microphone G.R.A.S. 40PH-10. We used various machine learning models to build a prototype bearing fault detection system trained on the proposed dataset. As the result, based on the deep neural network model, it shows high accuracy performance of 92.3% in the time domain and 98.3% in the frequency domain.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.1
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• pp.48-57
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• 2015

In a sodium-cooled fast reactor, which is a Generation-IV reactor, refueling is conducted by rotating, but not opening, the reactor head to prevent a reaction between the sodium, water and air. Therefore, an inspection technique that checks for the presence of any obstacles between the reactor core and the upper internal structure, which could disturb the rotation of the reactor head, is essential prior to the refueling of a sodium-cooled fast reactor. To this end, an ultrasound-based inspection technique should be employed because the opacity of the sodium prevents conventional optical inspection techniques from being applied to the monitoring of obstacles. In this study, a ranging inspection technique using a plate-type ultrasonic waveguide sensor was developed to monitor the presence of any obstacles between the reactor core and the upper internal structure in the opaque sodium. Because the waveguide sensor installs an ultrasonic transducer in a relatively cold region and transmits the ultrasonic waves into the hot radioactive liquid sodium through a long waveguide, it offers better reliability and is less susceptible to thermal or radiation damage. A 10 m horizontal beam waveguide sensor capable of radiating an ultrasonic wave horizontally was developed, and beam profile measurements and basic experiments were carried out to investigate the characteristics of the developed sensor. The beam width and propagation distance of the ultrasonic wave radiated from the sensor were assessed based on the experimental results. Finally, a feasibility test using cylindrical targets (corresponding to the shape of possible obstacles) was also conducted to evaluate the applicability of the developed ranging inspection technique to actual applications.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.17-23
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• 2017

Optical current sensors are suitable for operation in high voltage and high current environments such as power plants due to they are not affected by electromagnetic interference and have excellent insulation characteristics. However, as they operate in a harsh environment such as large temperature fluctuation and mechanical vibration, high reliability of the sensor is required. Therefore, many groups have been working on enhancing the reliability. In this work, an integrated optical current sensor incorporating polarization-rotated reflection interferometer is proposed. By integrating various optical components on a single chip, the sensor exhibits enhanced stability as well as the solution for low-cost optical sensors. Using this, we performed the characterization for the actual field application. By using a large power source, the current of 0.3 kA~36 kA was applied to the photosensor and the linear operation characteristics were observed. The error of the sensor was within $0{\pm}.5%$. Even when operating for a long time, the error range of the sensor was kept within $0{\pm}.5%$. In addition, the measurement of the frequency response over the range of 60 Hz to 10 kHz has confirmed that the 3-dB frequency band of the proposed OCT is well over 10 kHz.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.60-67
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• 2015

The finite element (FE) model updating is a commonly used approach in civil engineering, enabling damage detection, design verification, and load capacity identification. In the FE model updating, acceleration responses are generally employed to determine modal properties of a structure, which are subsequently used to update the initial FE model. While the acceleration-based model updating has been successful in finding better approximations of the physical systems including material and sectional properties, the boundary conditions have been considered yet to be difficult to accurately estimate as the acceleration responses only correspond to translational degree-of-freedoms (DOF). Recent advancement in the sensor technology has enabled low-cost, high-precision gyroscopes that can be adopted in the FE model updating to provide angular information of a structure. This study proposes a FE model updating strategy based on data fusion of acceleration and angular velocity. The usage of both acceleration and angular velocity gives richer information than the sole use of acceleration, allowing the enhanced performance particularly in determining the boundary conditions. A numerical simulation on a simply supported beam is presented to demonstrate the proposed FE model updating approach.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.59-67
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• 2018

In this paper, the test facility for coaxial propellers at low Reynolds developed and validated by measured data. The test equipment was designed to measure the hovering performance of propellers according to distances between the upper/lower propellers. Thrust, torque, rotational speed, vibration, and amperage of upper and lower propellers can be measured separately. The data acquisition system was built to collect signals of sensors, and LabVIEW software was used to control the motor and collect the signal. The hover performance tests of single propellers were preceded for the facility validation, and then the performance values of coaxial propellers were measured according to distances and diameter differences between the upper/lower propellers. The results showed that the high efficiency is achieved at 20%~30% distance between the upper propeller and lower one. The configuration that the upper propeller has shorter diameter than the lower one has the highest efficiency than other configuration.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.4 s.31
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• pp.35-43
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• 2004

Multibeam Echosounder system is the latest technology of a hydrographic survey utilized in producing an electronic nautical chart, obtaining a DEM with high precision, making a moving image by Swath surveying a wide area. As a fundamental study for improving the precision of MBES, we compared and analyzed measurements of DGPS and Motion sensor, and studied for the dynamic characteristics of vessel's movements. DGPS was installed in front and in the rear and on both side or the vessel and surveyed. The receiving precision of surveyed GPS results was obtained to the satisfactory extent that was possible to valuate the accuracy of Motion sensor as 0.0016$^{\circ}$ of the roll value and 0.0009$^{\circ}$ of the pitch value. The relationship between the values of heading, pitch, and roll in Motion sensor and the data of DGPS was proportional correlation. In addition, it is considered that deviations by elements like rapid turning and vibration of the vessel will be occurred, although the correlation of each deviation according to each amount or change is proportional. It is suitable that GPS installs in the central line of the vessel that is less affected than other places by waving because the amount of change in the tide level obtained from GPS survey and the value of heave are similar with the values taken by Motion sensor, and the velocity of GPS is different from installed places. The accuracy of the final result from MBES could be affected by the values of gyro and Motion sensor inputted to MBES processor because there were intervals of 15s and 13s of receiving time in gyro and Motion sensor respectively compared with the real-time measurements of DGPS.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1071-1076
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• 2011

NC machines are generally used for machining operations because of their position accuracy, path accuracy, and machining reaction force. However, some NC machines require a very large space and are expensive. Recently, industrial articulated robot arms with large handling capability and wrist torque have been developed and the corresponding sensor technology has been improved. A machining robot for three-dimensional large curved objects was developed on the basis of an automatic-path-generation method. A self-position-compensation method with a laser displacement sensor was adopted for the six-axis robot developed, because the large articulated robot arms had poor position accuracy. An automatic-path-generation method using specific points was adopted to reduce the number of teaching points and time. In order to determine the proper machining conditions, various machining conditions such as tool rotation speed, cutting angle, cutting depth, and tool moving speed, were evaluated.