• Title/Summary/Keyword: natural output

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A Study on the Converter Drive by Means of Series and Parallel Connection (콘버어터 직병렬 접속 운전에 관한 연구)

  • Chung, Yon-Tack;Seo, Yong-Soo;Hwang, Lak-Hoon
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.33 no.9
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    • pp.347-354
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    • 1984
  • This paper presents a method of improving the power factor and , the waveform of A.C line currents and the output waveforms of AC to DC fully bridge converter systems which is achieved by connecting CON I.II and CON III.IV in series and parallel. The basic principle of the CON I.II.III.IV's operation is simple and feasibility of thease converter is proved by experiments. CON I and CON III are constructed of natural commutation, CON II and CON IV are constructed of forced commutation. The experimental results show that the power factor and waveform of the source currents and the output waveforms are improved by the method of connecting converter in series and parallel and driving it in I, II, III, IV quadrant.

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수직형 마이크로 자이로스코프의 연성 진동과 영점 출력

  • 이승엽;전도영;김택현
    • Journal of KSNVE
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    • v.10 no.5
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    • pp.880-885
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    • 2000
  • In a verical type, vibratory gyroscope, the coupled motion between the reference and sensing vibrations causes the zero-point output which means non-zero sensing vibration without angular velocity. This structural coupling leaks to an inherent discrepancy between the natural frequencies of the reference and sensing oscillations, causing the degradation of the sensing performance and dynamic stability. In this paper, the dynamic characteristics associated the coupling phenomenon are theoretically analyzed. Effects of reference frequency and coupling factor on the rotational direction and amplitude of elliptic oscillation are studied. A technique to predict the existence of curve veering of crossing in frequency trajectories is introduced to apply the design of micro gyroscopes with decoupled structures.

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A study on digital signal method of PWM signal by switching position function (PWM 신호의 스위칭 함수에 의한 디지탈 방식에 관한 연구)

  • Chung, Y.T.;Lee, J.S.;Bae, S.J.;Baek, J.H.
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.148-150
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    • 1988
  • The output characteristics of VSI by transistor depend upon bias signal with drive circuit. As the CTI is one of the VSI, takes case PWM output voltage. This Inverter operation is based upon position and negative of sinusoldal PWM signal by carrier triangular wave and compared sine one. Besides, the Inverter operation system required digital signal for microprocessor, sampling method of Inverter driver signals study for get rid of generated signal is error. In the paper, the method of 3 level PWM signal for CTI was studied. This method of signals depend upon caculated switching position of natural sampling with $10^{-6}$ modulation error for time flowchart programs.

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Design of Fuzzy Controller Based on Empirical Knowledge (실험적 지식에 기초한 퍼지제어기 설계)

  • Bae, Hyeon;Kim, Sung-Shin;Kim, Hae-Gyun
    • Proceedings of the KIEE Conference
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    • 2000.07d
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    • pp.2296-2298
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    • 2000
  • Fuzzy control has been researched for application of industrial processes which have no accurate mathematical model and could not controlled by conventional methods because of a lack of quantitative input-output data. Intelligent control approach based on fuzzy logic could directly reflex human thinking and natural language to controller comparing with conventional methods. In this paper, fuzzy controller is implemented to acquire operator's knowledge. The tested system is constructed for sending a ball to the goal position using wind from two DC motors in the path. This system contains non-linearity and uncertainty because of the characteristic of aerodynamics inside the path. Ball position is measured by a vision camera. The system used in this experiment could be hardly modeled by mathematic methods and could not be easily controlled by linear control manners. The controller, in this paper is designed based on the input-output data and experimental knowledge obtained by trials.

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High-order, closely-spaced modal parameter estimation using wavelet analysis

  • Le, Thai-Hoa;Caracoglia, Luca
    • Structural Engineering and Mechanics
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    • v.56 no.3
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    • pp.423-442
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    • 2015
  • This study examines the wavelet transform for output-only system identification of ambient excited engineering structures with emphasis on its utilization for modal parameter estimation of high-order and closely-spaced modes. Sophisticated time-frequency resolution analysis has been carried out by employing the modified complex Morlet wavelet function for better adaption and flexibility of the time-frequency resolution to extract two closely-spaced frequencies. Furthermore, bandwidth refinement techniques such as a bandwidth resolution adaptation, a broadband filtering technique and a narrowband filtering one have been proposed in the study for the special treatments of high-order and closely-spaced modal parameter estimation. Ambient responses of a 5-story steel frame building have been used in the numerical example, using the proposed bandwidth refinement techniques, for estimating the modal parameters of the high-order and closely-spaced modes. The first five natural frequencies and damping ratios of the structure have been estimated; furthermore, the comparison among the various proposed bandwidth refinement techniques has also been examined.

A study on the power system stabilizer using discrete-time adaptive sliding mode control (이산 적응슬라이딩 모드 제어를 이용항 전력계통 안정화 장치에 관한 연구)

  • Park, Young-Moon;Kim, Wook
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.45 no.2
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    • pp.175-184
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    • 1996
  • In this paper the newly developed discrete-time adaptive sliding mode control method is proposed and applied to the power system stabilization problem. In contrast to the conventional continuous-time sliding mode controller, the proposed method is developed in the discrete-time domain and based on the input/output measurements instead of the continuous-time and the full-states feedback, respectively. Because the proposed control method has the adaptivity property in addition to the natural robustness property of the sliding mode control, it is possible to design the power system stabilizer which can overcome both the minor variations of the parameters of the power system and the diverse operating conditions and faults of the power system. Mathematical proof and the various computer simulations are done to verify the performance and stability of the proposed method.

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Output only system identification using complex wavelet modified second order blind identification method - A time-frequency domain approach

  • Huang, Chaojun;Nagarajaiah, Satish
    • Structural Engineering and Mechanics
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    • v.78 no.3
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    • pp.369-378
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    • 2021
  • This paper reviewed a few output-only system identification algorithms and identified the shortcomings of those popular blind source separation methods. To address the issues such as less sensors than the targeted modal modes (under-determinate problem), repeated natural frequencies as well as systems with complex mode shapes, this paper proposed a complex wavelet modified second order blind identification method (CWMSOBI) by transforming the time domain problem into time-frequency domain. The wavelet coefficients with different dominant frequencies can be used to address the under-determinate problem, while complex mode shapes are addressed by introducing the complex wavelet transformation. Numerical simulations with both high and low signal-to-noise ratios validate that CWMSOBI can overcome the above-mentioned issues while obtaining more accurate identified results than other blind identification methods.

Energy harvesting using an aerodynamic blade element at resonant frequency with air excitation

  • Bolat, Fevzi C.;Sivrioglu, Selim
    • Smart Structures and Systems
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    • v.24 no.3
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    • pp.379-390
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    • 2019
  • In this research, we propose an energy harvesting structure with a flexible blade element vibrating at its first mode to maximize the power output of the piezoelectric material. For this purpose, a piezoelectric patch was attached on the blade element used in a small-scale wind turbine, and air load was applied with a suitable angle of attack in the stall zone. The aerodynamic load created by air excitation vibrates the blade element in its first natural frequency and maximizes the voltage output of the piezoelectric patch. The variation of power outputs with respect to electrical resistance, air speed, and extra mass is experimentally investigated for various cases. An analytical model is constituted using a single-mode blade element with piezoelectric patch dynamics, and the power outputs of the obtained model are compared with experimental results.

Vibration-based damage detection in wind turbine towers using artificial neural networks

  • Nguyen, Cong-Uy;Huynh, Thanh-Canh;Kim, Jeong-Tae
    • Structural Monitoring and Maintenance
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    • v.5 no.4
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    • pp.507-519
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    • 2018
  • In this paper, damage assessment in wind-turbine towers using vibration-based artificial neural networks (ANNs) is numerically investigated. At first, a vibration-based ANNs algorithm is designed for damage detection in a wind turbine tower. The ANNs architecture consists of an input, an output, and hidden layers. Modal parameters of the wind turbine tower such as mode shapes and frequencies are utilized as the input and the output layer composes of element stiffness indices. Next, the finite element model of a real wind-turbine tower is established as the test structure. The natural frequencies and mode shapes of the test structure are computed under various damage cases of single and multiple damages to generate training patterns. Finally, the ANNs are trained using the generated training patterns and employed to detect damaged elements and severities in the test structure.

The Economic Effect of Industrial Investment on North Korea Natural Gas and Coal (북한 천연가스산업과 석탄산업 투자에 따른 경제적 파급효과)

  • Kim, Hyoungtae;Chae, Jungmin;Cho, Youngah
    • Journal of Energy Engineering
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    • v.25 no.3
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    • pp.1-8
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    • 2016
  • North Korea is currently undergoing an economic crisis of industrial productivity reduction, which resulted from decreased energy production and economic sanctions due to conflicts with the international society. This paper examined the technological status of North Korea's natural gas and coal industries which are essential sectors for recovery of the economy and North-South cooperation on energy industry. This paper also analyzed investment strategies in North Korean energy industries and calculated the size of economic ripple effect of the investment on North and South Korea. In order to analyze the effect of the investment on North Korean economy, we constructed an inter-industry relation table of North Korea for year 2014 and used an input-output model. The ripple effect of the investment in natural gas and coal industries turned out to be 1.012 billion dollars and 2.742 billion dollars respectively. In order to analyze the ripple effect of the investment on South Korean economy, we constructed an inter-industry relation table of South Korea for year 2013 and used a demand-driven model for inter-industry analysis. As a result, production, added-value and employment inducement coefficients of the investment were calculated as 2.02073, 0.62697 and 8.99409 for the natural gas industry and 2.02130, 0.62701 and 9.00413 for the coal industry respectively.