• Title, Summary, Keyword: linear time-varying system

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Harmonics Analysis for Electric Arc Furnace According to the Operation Condition (전기 아크로 운전 상태에 따른 고조파 해석)

  • Kim, Jae-Chul;Park, Kyung-Ho;Park, Hyun-Teak;Moon, Jong-Fil;Im, Sang-Kug;Son, Hag-Sig
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.18 no.5
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    • pp.118-125
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    • 2004
  • The use of electric arc furnace has been increasing as the steel consumption is increasing and the operation technique of electric arc furnace are developing. But as the use of electric arc furnace is increased, the furnace have produced the adverse effects of power quality: voltage and current harmonics, voltage and current imbalances, low power factor, and voltage flicker. One of the power quality problems, the harmonic have the characteristics of the time-varying and non-linear. This paper analyzed the harmonics for the various operation conditions of electric arc furnace. The power system model with electric arc furnace have been made, and the harmonic's effects on the power system has been analyzed according to the various operating conditions, first melting, second melting, so on. Also, the filter reducing the harmonic components have been designed and its effects on the power system have been examined.

The Contribution of Innovation on Productivity and Growth in Korea (기술혁신이 생산성과 경제성장에 미치는 영향)

  • Kim, Byung-Woo
    • Journal of Korea Technology Innovation Society
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    • v.11 no.1
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    • pp.72-90
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    • 2008
  • What has been the contribution of industrial innovation to economic growth? Typically, the issue has been approached with growth-accounting methods augmented to include a "stock of knowledge". An independent estimate of the rate of return to R&D is found in order to impute patents granted to the accumulation of knowledge. Griliches(1973) then uses a regression approach to assess the effect of an R&D variable on the computed TFP growth rate. The regression coefficient on the R&D variable would provide an estimate of the social rate of return to R&D. The related studies tend to show high social rates of return to R&D, typically in a range of 20 to 40 % per year. We need to provide multiple equation dynamic system for productivity and innovation in Korean economy in state space form. A wide range of time series models, including the classical linear regression model, can be written and estimated as special cases of a state space specification. State space models have been applied in the econometrics literature to model unobserved variables like productivity. Estimation produces the following results. Considering the goodness of fit, we can see that the evidence is strongly in favor of the range $0.120{\sim}0.135$ for the elasticity of TFP to R&D stock in the period between 1970's and the early 2000's.

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High Gain Observer-based Robust Tracking Control of LIM for High Performance Automatic Picking System (고성능 자동피킹 시스템을 위한 선형 유도 모터의 고이득 관측기 기반의 강인 추종 제어)

  • Choi, Jung-Hyun;Kim, Jung-Su;Kim, Sanghoon;Yoo, Dong Sang;Kim, Kyeong-Hwa
    • Journal of Korean Institute of Intelligent Systems
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    • v.25 no.1
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    • pp.7-14
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    • 2015
  • To implement an automatic picking system (APS) in distribution center with high precision and high dynamics, this paper presents a high gain observer-based robust speed controller design for a linear induction motor (LIM) drive. The force disturbance as well as the mechanical parameter variations such as the mass and friction coefficient gives a direct influence on the speed control performance of APS. To guarantee a robust control performance, the system uncertainty caused by the force disturbance and mechanical parameter variations is estimated through a high gain disturbance observer and compensated by a feedforward manner. While a time-varying disturbance due to the mass variation can not be effectively compensated by using the conventional disturbance observer, the proposed scheme shows a robust performance in the presence of such uncertainty. A Simulink library has been developed for the LIM model from the state equation. Through comparative simulations based on Matlab - Simulink, it is proved that the proposed scheme has a robust control nature and is most suitable for APS.

Use of Adaptive Meshes in Simulation of Combustion Phenomena

  • Yi, Sang-Chul;Koo, Sang-Man
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • pp.285-309
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    • 1996
  • Non oxide ceramics such as nitrides of transition metals have shown significant potential for future economic impact, in diverse applications in ceramic, aerospace and electronic industries, as refractory products, abrasives and cutting tools, aircraft components, and semi-conductor substrates amid others. Combustion synthesis has become an attractive alternative to the conventional furnace technology to produce these materials cheaply, faster and at a higher level of purity. However he process os highly exothermic and manifests complex dynamics due to its strongly non-linear nature. In order to develop an understanding of this process and to study the effect of operational parameters on the final outcome, numerical modeling is necessary, which would generated essential knowledge to help scale-up the process. the model is based on a system of parabolic-hyperbolic partial differential equations representing the heat, mass and momentum conservation relations. The model also takes into account structural change due to sintering and volumetric expansion, and their effect on the transport properties of the system. The solutions of these equations exhibit steep moving spatial gradients in the form of reaction fronts, propagating in space with variable velocity, which gives rise to varying time scales. To cope with the possibility of extremely abrupt changes in the values of the solution over very short distances, adaptive mesh techniques can be applied to resolve the high activity regions by ordering grid points in appropriate places. To avoid a control volume formulation of the solution of partial differential equations, a simple orthogonal, adaptive-mesh technique is employed. This involves separate adaptation in the x and y directions. Through simple analysis and numerical examples, the adaptive mesh is shown to give significant increase in accuracy in the computations.

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Control Algorithm Characteristic Study of Cooling System for Automotive Fuel Cell Application. (차량용 연료전지 냉각시스템 제어 알고리즘 특성 연구)

  • Han, Jae Young;Park, Ji Soo;Yu, Sangseok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.1
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    • pp.39-45
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    • 2016
  • Thermal management of a fuel cell is important to satisfy the requirements of durability and efficiency under varying load conditions. In this study, a linear state feedback controller was designed to maintain the temperature within operating conditions. Due to the nonlinearity of automotive fuel cell system, the state feedback controller results in marginal stable under load condition from $0.5A/cm^2$ to $0.7A/cm^2$. A PWM (Pulse Width Modulation) and the modified state feedback controller are applied to control the temperature under the load condition from $0.5A/cm^2$ to $0.7A/cm^2$. The cooling system model is composed of a reservoir, radiator, bypass valve, fan, and a water pump. The performance of the control algorithm was evaluated in terms of the integral time weighted absolute error (ITAE). Additionally, MATLAB/SIMULINK$^{(R)}$ was used for the development of the system models and controllers. The modified state feedback controller was found to be more effective for controlling temperature than other algorithms when tested under low load conditions.

Determination of Phase Velocity Dispersion Curve and Group Velocity of lamb Waves Using Backward Radiation (후방복사를 이용한 램파의 위상속도 분산과 군속도의 측정)

  • 송성진;권성덕;정용무;김영환
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.1
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    • pp.61-68
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    • 2003
  • The guided wave has been widely employed to characterize thin plates and layered media. The dispersion curves of phase and group velocities are essential for the quantitative application of guided waves. In the present work, a fully automated system for the measurement of backward radiation of LLW has been developed. The specimen moves in two dimensional plane as well as in angular rotation. The signals of backward radiation of LLW were measured from an elastic plate in which specific modes of Lamb wave were strongly generated. Phase velocity of the corresponding modes was determined from the incident angle. The generated Lamb waves propagated forward and backward with the leakage of energy into water. Backward radiated LLW was detected by the same transducer and its frequency components were analyzed to extract the related information to the dispersion curves. The dispersion curves of phase velocity were measured by varying the incident angle. Moving the specimen in the linear direction of LLW propagation, group velocity was determined by measuring the transit time shift in the ultrasonic waveform.

Experimental Results on an Underwater Acoustic Digital Transceiver Based on DSP (수중 음향 디지털 송수신기의 DSP 구현 및 실험적 고찰)

  • 박종원;최영철;이덕환;김시문;김승근;임용곤
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.296-299
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    • 2003
  • In this paper, an underwater acoustic digital transceiver is designed and implemented by a multiple DSPs system. We have designed a QPSK transmitter based on look-up table and 13-symbols Barker code is used for frame synchronization. Channel distortions are compensated by a wide-band beamformer based on FIR filter and an adaptive equalize. with RLS algorithm. Uniform linear array (ULA) with four elements is used for the spartial signal processing. 1/2 convolutional code and Viterbi decoder are implemented to overcome time-varying multi-path fading. Also, we show experimental results in the underwater anechoic basin at KRISO/KORDl and Goseong, Donghae and Soyang lake of Kangwon-do.

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LMS based Iterative Decision Feedback Equalizer for Wireless Packet Data Transmission (무선 패킷데이터 전송을 위한 LMS기반의 반복결정 귀환 등화기)

  • Choi Yun-Seok;Park Hyung-Kun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.7
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    • pp.1287-1294
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    • 2006
  • In many current wireless packet data system, the short-burst transmissions are used, and training overhead is very significant for such short burst formats. So, the availability of the short training sequence and the fast converging algorithm is essential in the adaptive equalizer. In this paper, the new equalizer algorithm is proposed to improve the performance of a MTLMS (multiple-training least mean square) based DFE (decision feedback equalizer)using the short training sequence. In the proposed method, the output of the DFE is fed back to the LMS (least mean square) based adaptive DEF loop iteratively and used as an extended training sequence. Instead of the block operation using ML (maximum likelihood) estimator, the low-complexity adaptive LMS operation is used for overall processing. Simulation results show that the perfonnance of the proposed equalizer is improved with a linear computational increase as the iterations parameter in creases and can give the more robustness to the time-varying fading.

Real-time Fault Diagnosis of Induction Motor Using Clustering and Radial Basis Function (클러스터링과 방사기저함수 네트워크를 이용한 실시간 유도전동기 고장진단)

  • Park, Jang-Hwan;Lee, Dae-Jong;Chun, Myung-Geun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.6
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    • pp.55-62
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    • 2006
  • For the fault diagnosis of three-phase induction motors, we construct a experimental unit and then develop a diagnosis algorithm based on pattern recognition. The experimental unit consists of machinery module for induction motor drive and data acquisition module to obtain the fault signal. As the first step for diagnosis procedure, preprocessing is performed to make the acquired current simplified and normalized. To simplify the data, three-phase current is transformed into the magnitude of Concordia vector. As the next step, feature extraction is performed by kernel principal component analysis(KPCA) and linear discriminant analysis(LDA). Finally, we used the classifier based on radial basis function(RBF) network. To show the effectiveness, the proposed diagnostic system has been intensively tested with the various data acquired under different electrical and mechanical faults with varying load.

Couette-Poiseuille flow based non-linear flow over a square cylinder near plane wall

  • Bhatt, Rajesh;Maiti, Dilip K.;Alam, Md. Mahbub;Rehman, S.
    • Wind and Structures
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    • v.26 no.5
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    • pp.331-341
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    • 2018
  • A numerical study on the flow over a square cylinder in the vicinity of a wall is conducted for different Couette-Poiseuille-based non-uniform flow with the non-dimensional pressure gradient P varying from 0 to 5. The non-dimensional gap ratio L (=$H^{\ast}/a^{\ast}$) is changed from 0.1 to 2, where $H^{\ast}$ is gap height between the cylinder and wall, and $a^{\ast}$ is the cylinder width. The governing equations are solved numerically through finite volume method based on SIMPLE algorithm on a staggered grid system. Both P and L have a substantial influence on the flow structure, time-mean drag coefficient ${\bar{C}}_D$, fluctuating (rms) lift coefficient ($C_L{^{\prime}}$), and Strouhal number St. The changes in P and L leads to four distinct flow regimes (I, II, III and IV). Following the flow structure change, the ${\bar{C}}_D$, $C_L{^{\prime}}$, and St all vary greatly with the change in L and/or P. The ${\bar{C}}_D$ and $C_L{^{\prime}}$ both grow with increasing P and/or L. The St increases with P for a given L, being less sensitive to L for a smaller P (< 2) and more sensitive to L for a larger P (> 2). A strong relationship is observed between the flow regimes and the values of ${\bar{C}}_D$, $C_L{^{\prime}}$ and St. An increase in P affects the pressure distribution more on the top surface than on bottom surface while an increase in L does the opposite.