• 전력전자학회논문지
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• 제7권5호
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• pp.472-481
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• 2002

본 논문은 SRG(Switched Reluctance Generator)의 제어를 위하여 순시자속을 이용하여 위치를 추정하고, 추정한 위치에 근거하여 출력전압을 제어하는 방법이 제안되었다. SRG를 제어하기 위해서는 정확한 회전자의 위치정보가 필수적이다. 이러한 위치정보는 일반적으로 엔코더나 레졸버와 같은 정밀한 위치센서로부터 얻어진다. 그러나, 전자기적 간섭(Electromagnetic Interference), 진동, 열, 습도 등의 열악한 환경으로 인하여 정확한 위치를 검출하는데 많은 문제점을 가지고 있다. 따라서 이러한 문제점을 극복하기 위하여 위치·속도센서 없는 SRG의 제어기가 요구되어 진다. 본 논문에서는 SRG를 위한 새로운 위치·속도의 실시간 추정방법이 제안되었다. 순시자속은 측정한 전압과 전류에 의해 계산한 것과 위치와 자속 프로파일로부터 회전자의 위치를 추정하였다. 출력전압은 PID 제어 알고리즘에 의해 일정 제어되었다. 제안된 방법은 시뮬레이션을 통하여 확인하였고, DSP를 적용하여 구현하였다. 실험을 통하여 제안된 방법은 부하가 변동하더라도 일정하게 출력전압을 유지하고, SRG 제어가 안정됨을 확인하였다.

• Journal of Biosystems Engineering
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• 제39권1호
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• pp.21-33
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• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• Journal of Radiation Protection and Research
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• 제22권4호
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• pp.263-272
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• 1997

방사선 작업자의 과피폭을 방지하기 위해 방사선 작업 도중 이상 사태가 발생할 경우 광 음경보가 발생한 후 이상 사태 발생 90분, 발생 30분간의 방사선량과 방사선량율 변화를 저장하고 외부 PC로 데이터를 전송한 후 사고를 분석하여 차후에 같은 유형의 방사선 사고를 사전에 예방할 수 있도록 고안된 방사선 경보장치를 개발하였다. 이 방사선 경보장치의 특징은 넓은 방사선 측정 범위(10mR/h $\sim$ 100 R/h), 방사선 준위의 기록 및 기억, PC와의 data처리 기능, 휴대성, 교정 기능에 의한 높은 정밀도(${\pm}5%$), 인지도가 높은 강력한 경보기능 채택 등이다. 개발된 방사선 경보장치의 물리적 환경 적응시험을 가장 엄격한 ANSI N42.17A의 표준 시험조건에 의거하여 온도, 습도, 진동, 전자기파 간섭 등에 관해 한국표준과학연구원에서 수행하였으며 모든 시험항목을 통과하였다.

• Smart Structures and Systems
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• 제20권5호
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• pp.619-636
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• 2017

Magnetorheological (MR) damper is a type of controllable device widely used in vibration mitigation. This device is highly nonlinear, and exhibits strongly hysteretic behavior that is dependent on both the motion imposed on the device and the strength of the surrounding electromagnetic field. An accurate model for understanding and predicting the nonlinear damping force of the MR damper is crucial for its control applications. The MR damper models are often identified off-line by conducting regression analysis using data collected under constant voltage. In this study, a MR damper model is integrated with a model for the power supply unit (PSU) to consider the dynamic behavior of the PSU, and then a real-time nonlinear model updating technique is proposed to accurately identify this integrated MR damper model with the efficiency that cannot be offered by off-line methods. The unscented Kalman filter is implemented as the updating algorithm on a cyber-physical model updating platform. Using this platform, the experimental study is conducted to identify MR damper models in real-time, under in-service conditions with time-varying current levels. For comparison purposes, both off-line and real-time updating methods are applied in the experimental study. The results demonstrate that all the updated models can provide good identification accuracy, but the error comparison shows the real-time updated models yield smaller relative errors than the off-line updated model. In addition, the real-time state estimates obtained during the model updating can be used as feedback for potential nonlinear control design for MR dampers.

• 한국철도학회논문집
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• 제18권1호
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• pp.15-24
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• 2015

상전도흡인식 자기부상열차는 전자석의 전류를 조정하여 차량과 선로 사이의 간극(공극)을 일정하게 유지한다. 이러한 능동현가장치를 사용하는 자기부상열차에 있어서는 다양한 외란에도 불구하고 부상제어기를 이용한 부상공극을 허용하는 범위 내로 유지하는 것이 핵심기술 중의 하나이다. 특히 차량과 유연한 가이드웨이 사이의 동적상호작용에 의해 발생되는 진동은 저속 및 정지상태에서 부상안정성을 방해하는 중요한 요인으로 작용한다. 본 논문에서는 가이드웨이의 유연성에도 강인한 부상제어기를 개발하기 위하여 차량과 유연 가이드웨이 사이의 연성 동역학 모델을 개발하고, 전자석 및 부상제어기도 포함시키는 통합모델링을 제안하였다. 개발된 통합동역학 모델을 이용하여 가이드웨이의 유연성을 고려한 부상공극 시뮬레이션을 수행하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.187-190
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• 2002

In contrast to conventional electromagnetic motor, USM(Ultrasonic Motor), as piezoelectric ceramic applying ultrasonic mechanical vibration and as frictional-movement type motor, get rotational torque by elastic friction between stator and rotator, The USM, which is small motor without iron cores and coil as a simple structure, has little load weight, has character of high torque at low speed, and can apply a direct drive type without deceleration gear as low speed type. A response of USM from control input is satisfactory, and also generates much torque in low speed driving, and holding torque is much without supplying power. In this study, I designed and made Ultrasonic motor-digital multi controller(USM- DMC) using FPGA chip, A54SX72A made in Actel Corporation. By the minute, USM-DMC can control frequency, duty ratio, and phase difference of USM by llbit digital input from Pc. Therefore, when we use this controller, we can apply to typical parameter, frequency, phase difference, and voltage parameter, to control as well as we can do mixing control like phase-frequency, phase-voltage, frequency-voltage, frequency-phase-voltage, What is more, the strongest point is that it can trace frequency based on optimized frequency because we can input optimized resonant frequency while in motoring.

• 센서학회지
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• 제14권5호
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• pp.322-330
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• 2005

A new type of transducer, piezoelectric floating mass transducer (PFMT) which has advantages of piezoelectric and electromagnetic transducer has been proposed and implemented for the implantable middle ear hearing devices. By the uneven bonding of piezoelectric material to the inner bottom of transducer case, the PFMT can vibrate back-and-forth along the longitudinal axis of the transducer even though the piezoelectric material within the cylindrical case produces only the bilateral expansion and contraction according to the applied electrical signal. To improve efficiency of the PFMT, the multi-layered piezoelectric material has been adapted. The small number of components in the PFMT enables the simple manufacturing and the easy implanting into the middle ear. In order to examine the characteristics of vibration, mechanical modeling and finite element analyses of the proposed transducer have been performed. From the result of theoretical analyses and the measured data from the experiment, it is verified that the implemented PFMT can be used in implantable middle ear hearing devices.

• 환경영향평가
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• 제21권1호
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• pp.1-13
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• 2012

We diagnosed on status and problems of environmental assessment regarding development of offshore wind power, and also on reasonable core assessment items. Most of the coastal wind power are located on the western coastline of Korea and Jeju Island. In the selections of the site for the offshore wind farms, a previous investigations should be conducted with regard to distances from the land, stabilities from external forces (tide, wave, etc.) and topographical changes, and characteristics of the surroundings (distributions of protected area, fishing ground, artificial seagrasses, and shipping traffic). It is needed to assess dispersion of suspended solids, changes of the sea bottom, and impacts on fisheries resources and fishing activities under construction of offshore wind power. Furthermore, the responses of marine organisms to noise and vibration, impacts by electromagnetic fields, impacts on sea birds, hindrances to sea lane routes, and damaged scenery and marine protection areas are thoroughly assessed during operation processes. The consultation criteria in case of development of offshore wind farm is adjusted by focusing marine environmental impact assessment.

• Structural Engineering and Mechanics
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• 제88권2호
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• pp.159-168
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• 2023

Cost-effective high precision hybrid elements are presented in a hierarchical form for dynamic analysis of plates. The costs associated with controlling the vibrations of ferromagnetic plates can be minimized by adequate determination of the amount of electric current and magnetic field. In the present study, the effect of magnetic field and electric current on nonlinear vibrations of ferromagnetic plates is investigated. The general form of Lorentz forces and Maxwell's equations have been considered for the first time to present new relationships for electromagnetic interaction forces with ferromagnetic plates. In order to derive the governing nonlinear differential equations, the theory of third-order shear deformations of three-dimensional plates has been applied along with the von Kármán large deformation strain-displacement relations. Afterward, the nonlinear equations are discretized using the Galerkin method, and the effect of various parameters is investigated. According to the results, electric current and magnetic field have different effects on the equivalent stiffness of ferromagnetic plates. As the electric current increases and the magnetic field decreases, the equivalent stiffness of the plate decreases. This is a phenomenon reported here for the first time. Furthermore, the magnetic field has a more significant effect on the steady-state deflection of the plate compared to the electric current. Increasing the magnetic field and electric current by 10-times results in a reduction of about 350% and an increase of 3.8% in the maximum steady-state deflection, respectively. Furthermore, the nonlinear frequency decreases as time passes, and these changes become more intense as the magnetic field increases.

• 토지주택연구
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• 제7권4호
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• pp.307-314
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• 2016

이 연구는 평소에 주변에 상존하지만 버려지는 미활용 에너지를 수확하여 전기로 생산하는 에너지하베스팅에 관한 것이다. 이 연구에서는 다양한 에너지원들 중에서 도로나 주차장을 주행하는 차량의 진동과 압력을 동시에 활용하는 하이브리드 방식의 에너지 하베스터를 개발하였다. 1단계 연구에서는 프로토타입 에너지하베스터, 이를 개선된 하이브리드 모듈, 그리고 하이브리드 모듈의 성능을 개선한 최종 모듈을 개발하였으며, 그 결과는 이전 논문으로 발표하였다. 본 논문은 최종 개발된 하이브리드 모듈을 실제 주차장에 설치하여 차량의 주행에 따른 압력과 진동, 그리고 차량주행 속도에 따른 발전성능을 측정하고 앞서 발표된 실험실 조건에서의 측정결과와 비교하였다. 선행연구에서 수행한 실험실 조건에서의 에너지블록의 최대전력은 1회 가진시 1.066W, 5회연속 가진시 1.830W로 측정되었다. 반면에 이 연구에서 실시한 실제 주차장 주행차량 속도별 측정결과는 5km/h 주행시 평균 0.310W, 10km/h에서 0.670W, 20km/h에서 1.250W, 30km/h에서 2.1600W로 측정되었다. 즉, 차량의 주행속도가 높을수록 발전성능은 증가하는 것으로 나타났다. 그러나 실험실조건에 대비해서 주행속도 20km/h까지는 발전성능이 떨어지며, 실험실 조건의 1회 가진시 대비해서는 20km/h이상, 그리고 5회연속가진에 대비해서는 30km/h 이상일 때 발전성능이 높은 것으로 측정되었다. 이는 실험실과 실제차량이라는 재하조건의 차이로 사료된다. 따라서 향후 도로용 에너지블록의 적용은 주차장 조건보다는 주행도로용으로 활용하는 것이 효과적일 것으로 사료된다.