• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.173-178
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• 1990

로터-베어링축계는 증기및 가스터빈, 터보 발전기, 압축기등 거의 모든 산업 기계류에서 동력 전달의 기본 도구로써 사용되고 있다. 즉 회전에 의한 동력 의전달은 비교적 간단히 대용량의 동력을 효율적으로 전달할 수 있다. 이에 따라 회전기계류에 대한 연구는 산업 혁명 이후 꾸준히 발전되어 온바, 특히 근래에 들어와 산업기계류의 경쟁이 치열하여짐에 따라 산업기계류의 고정 밀화, 고속화, 고신뢰화 요구가 증대하고 있는 현실을 비추어 볼때, 산업 기 계류의 근간을 이루고 있는 로터-베어링 축계의 안정성을 포함한 진동에 관 한 문제는 회전기계류 설계의 주요 기술로써 연구.개발의 필요성이 매우 높 다 하겠다. 회전축계 진동 관련 연구는 두 분야로 대별될 수 있는데 언밸런 스(Unbalance)에 의한 Synchronous진동과 여러가지 원인에 의해 계의 불안 정성을 유발시키는 Nonsynchronous진동으로 나눌 수 있다. 본 연구에서는 이들 연구의 기본이 되는 회전축-베어링계 동특성 해석 프로그램을 개발하 였다. 여러가지 방법이 있으나 여기서는 Holzer가 비틀림 진동에 적용하고, Mykiestad(2)와 Prohl(3)에 의하여 회전축의 횡 진동에 적용된 이후 Lund(4) 등에 의하여 베어링의 영향등이 첨가된 전달 매트릭스 (Transfer Matrix) 방 법을 이용하여 임계속도(Critical Speed), 모우드 형태(Mode shapes)를 예측 하고 불안정 판정(Instability Criteria)등을 할 수 있는 프로그램을 개발하였 다. 특히 Murphy(1)의 다항식 방법(Polynomial Method)에 기본을 두어 기존 의 전달 매트릭스가 가지고 있던 반복, 수렴 시간 문제와 빠뜨리는 임계속도 예측에 대한 개선을 이루었으며 기존 논문과 실험 결과와의 비교 검토를 통 하여 개발된 프로그램의 신뢰성을 검토하였다. 특히, 각종 회전 기계의 소형 화, 경량화 추세에 따라 지반이나 케이싱이 경량이거나 유연하여 회전축과 동적으로 연성된 경우 회전축-베어링-지반으로 이루어진 2중구조의 회전축 계 동특성을 해석할 수 있는 프로그램을 개발하므로서 회전 기계류의 진동 전반에 걸친 문제점에 대한 그 원인과 현상을 명확히 분석하여 국내의 전기 계류의 보다 신뢰성있는 설계 및 제작자료를 확보하는데 기여할 수 있게 하 였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.801-806
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• 2015

Journal bearings support rotors using fluid film between the rotor and the stator. Generally, journal bearings are used in large rotor systems such as turbines in a power plant, because even in high-speed and load conditions, journal bearing systems run in a stable condition. To enhance the reliability of journal-bearing systems, in this paper, we study health-diagnosis algorithms that are based on the supervised learning method. Specifically, this paper focused on defining the unit of features, while other previous papers have focused on defining various features of vibration signals. We evaluate the features of various lengths or units on the separable ability basis. From our results, we find that one cycle datum in the time-domain and 60 cycle datum in the frequency domain are the optimal datum units for real-time journal-bearing diagnosis systems.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.7-16
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• 2007

An axial-type fan which operates at the relative total pressure of 671Pa and static pressure of 560Pa with the flow rate of $416.6m^3/min$ is developed with an optimization technique based on the gradient method. Prior to the optimization of fan blade, a three-dimensional axial-type fan blade is designed based on the free-vortex method along the radial direction. Twelve design variables are applied to the optimization of the rotor blade, and one design variable is selected for optimizing a stator which is located behind of the rotor and is used to support a fan driving motor. The total and static pressure are applied to the restriction condition with the operating flowrate on the design point, and the efficiency is chosen as the response variable to be maximized. Through these procedures, an initial axial-fan blade designed by the free vortex method is modified to increase the efficiency with the satisfaction of the operating condition. The optimized fan is tested to compare the aerodynamic performance with an imported same class fan. The test result shows that the optimized fan operates with the satisfaction of restriction conditions, but the imported fan cannot. From the experimental and numerical test, they show that this optimization method improves the fan efficiency and operating pressures of a fan designed by the classical fan design method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.106-111
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• 2024

A triboelectric nanogenerator is a promising energy harvester operated by the combined mechanism of electrostatic induction and contact electrification. It has attracting attention as eco-friendly and sustainable energy generators by harvesting wasting mechanical energies. However, the power generated in the natural environment is accompanied by low frequencies, so that the output power under such input conditions is normally insufficient amount for a variety of industrial applications. In this study, we introduce a non-contact rotational triboelectric nanogenerator using pedaling and gear systems (called by P-TENG), which has a mechanism that produces high power by using rack gear and pinion gear when a large force by a pedal is given. We design the system can rotate the shaft to which the rotor is connected through the conversion of vertical motion to rotational motion between the rack gear and the pinion gear. Furthermore, the system controls the one directional rotation due to the engagement rotation of the two pinion gears and the one-way needle roller bearing. The TENG with a 2 mm gap between the rotor and the stator produces about the power of 200 ㎼ and turns on 82 LEDs under the condition of 800 rpm. We expect that P-TENG can be used in a variety of applications such as operating portable electronics or sterilizing contaminated water.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.241-245
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• 2006

In this paper, the design and characteristics of a $\pi-shaped$ ultrasonic motor that is applicable to optical zoom operation of a lens system for mobile phones are investigated. Its design and simulation of performances are carried out by FEM (finite element method) commercial software. As a simulation result, by applying voltage with single phase, a combined vibration is produced at the surface of a stator arm. A prototype of the motor is fabricated and its outer size is $8*4*2mm^3$ including the cylindrical steel rod of 2 mm in diameter as the rotor. The motor exhibits a maximum speed of 500 rpm and a power consumption of 0.3 W when driven at 20 Vpp and 64 kHz.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.616-618
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• 2002

A Superconducting Rotary Machine (SRM) is characterized by an air-cored machine with its rotor iron and stator iron teeth removed. For this reason, the SRM is featured by 3D magnetic flux distribution, which decreases in the direction of axis, Therefore, 3D magnetic field analysis method is required to know about characteristic of magnetic field distribution of SRM, In this paper, 3D flux distribution of SRM is calculation by using analytical method. The magnetic field distribution due to the field coils use of the Biot-Savart equation. The magnetic core is represented by magnetic surface polarities. The paper describes the combined use of above methods for the total computation, and compares analytical method and 3D FEM(Finite Element Method) results.

• Journal of Fisheries and Marine Sciences Education
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• v.7 no.1
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• pp.111-126
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• 1995

In general, the electromagnetic transient phenomenon always exists in induction motor(IM) with the torque change. The control performance of IM is very worse than that of D.C motor owing to this transient phenomenon. So many studies about the elimination methods of the transient phenomenon have been making progress. Interesting methods of them are the Field acceleration method(FAM) and the method of impulse addition on the input voltage at the time point of torque change. In this paper, first, the circuit equation of IM is derived from the phase segregation method. The torque equation consisted of the stator and rotor currents is derived from the solving of the circuit equation. As we well known, the transient terms exist in this the torque equation. The method of impulse addition on the input voltage at the instance of torque change is confirmed theoretically for the elimination of the transient phenomenon. With the base on it, the author proposed a real time algorithm to eliminate the transient terms. The control system is consisted of the PI controller with the feedforward of torque change. The author could confirm that the quick stepwise responses of torque and speed can be obtained from response simulations.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2274-2277
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• 2003

A cylindrical permanent magnet inside the four-phase permanent magnet (PM) stepping motor is employed as the rotor. The stator has four teeth around, which its coils are wound. The mode of excitation can be classified into 3 modes: single-phase excitation, two-phase excitation and ministep excitation. The ministep drive is a method to subdivide one step into several small steps by means of electronics. The paper presents the programmable ministep technique drive. This technique decodes the results obtained from the counter to locate the data in Read Only Memory (ROM). The Sinusoidal Pulse Width Modulation (SPWM) is transformed to binary file and saved to the ROM. The experiment is performed with the four-phase PM stepping motor and drives from a two-phase programmable sinusoidal ministep signal, instead of square wave. The results show that the performances of the proposed programmable ministep technique drive have high efficiency, smooth step motion, and high speed response. Moreover, the resolution of sinusoidal ministep signal can be controlled by the input frequency (f command).

• Journal of the Korean Society of Industry Convergence
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• v.23 no.5
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• pp.825-833
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• 2020

Currently, the K-Water uses various valves that can be remotely controlled for optimal water management. Valve system fault can be classified into rotor defects, stator defects, bearing defects, and gear defects of induction motors. If the valve cannot be operated due to a gear fault, the water management operation can be greatly affected. For effective water management, there is an urgent need for preemptive repairs to determine whether gear is damaged through failure prediction diagnosis.. Recently, deep learning algorithms are being applied for valve failure diagnosis. However, the method currently applied has a disadvantage of attaching a vibration sensor to the valve. In this paper, propose a new algorithm to determine whether a fault exists using a convolutional neural network (CNN) based on the voltage and current information of the valve without additional sensor mounting. In particular, a normalized Lisasjous diagram was used to maximize the fault classification performance in the CNN-based diagnostic system.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.249-255
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• 2017

Efficient operation of induction motor at light loads has been getting wide attention recently because the operating of induction motor at light loads occupies big portion of its operating regions in many applications such as environment friendly vehicle. As one of approaches to improve efficiency, Adaptive Maximum Torque Per Amp (Adaptive MTPA) control for induction motor drives has been proposed to achieve a desired torque with the minimum possible stator current. However, the Adaptive MTPA control was validated only at heavy load where, in general, control scheme tends to perform better than at light loads since the error in measurement of sensors is lower and signal to noise is better. Thus, although the performance of a control scheme is good at rated operating point, its performance at light load is somewhat in doubt in practice. This has led to considerable interest in efficiency of Adaptive MTPA control at light loads. This work experimentally demonstrates performance of Adaptive MTPA control at light loads regardless of rotor resistance variation, thus showing its good performance over all operating conditions.