• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.143-146
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• 1999

특정 플랜트내에 원하지 않는 음이나 진동신호를 능동적으로 제어하기 위해 LMS의 Filtered reference와 Filtered error 방법으로 피드포워드 적응제어 시스템을 사용할 때 오차신호의 수렴특성을 플랜트의 추정 임펄스응답의 정확도로써 나타낼 수 있는 식을 제안하고 수치 시뮬레이션과 실험으로 그 유효성에 대해 기술한다. 플랜트내 음향전달계의 추정 임펄스응답의 안정성 평가식은 이미 W. Ren과 P. R. Kumar에 의해 발표되었으나[1], 그 평가방법은 플랜트내의 실제(True) 임펄스응답을 필요로하고있어 수치 시뮬레이션에서는 가능한 방법이지만 임펄스응답의 측정이 불가능한 실제의 적응제어 시스템에 적용하는 것은 곤란하다. 따라서, 플랜트의 추정 임펄스응답을 크로스스펙트럼법(Cross-Spectrum)으로 추정하여 그 임펄스응답을 피드포워드 적응제어 시스템에 적용했을 때 안정성 여부를 평가하고, 또한 오차신호의 수렴특성을 Filtered reference와 Filtered error 방법에서 각각 확인하였다. 수치 시뮬레이션 결과와 실험 결과가 일치함을 확인하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.5
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• pp.436-442
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• 2005

This paper proposes an estimation algorithm to find the moment of inertia, which is essential to design high performance controller for motor drive system. The algorithm finds the moment of inertia observing the position error signal, which contains an error information of moment of inertia, generated by speed observer. Moreover, the proposed algorithm is easily realized in the observer-based speed detection method. The simulation and experimental results are also presented to confirm the performance of moment of inertia estimation method, which shows that the moment of inertia converges to the actual value within several seconds. The speed control responses and the designed speed controller performance match well.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.223-234
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• 2011

For advanced database security, various researches and challenges are being done to keep pace with new information technologies. We suggests new extended access control that make it possible to conform security policies even with uncertain context and purpose. There may be a discrepancy between the syntactic phrase in security policies and that in queries, called semantic gap problem. New access control derive semantic implications from context and purpose hierarchy tree and control the exceed privileges using semantic gap factor calculating the degree of the discrepancy. And then, We illustrate prototype system architecture and show performance comparison with existing access control methods.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.57-67
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• 2012

In this study, design of LCTS(Launch Complex Thermostatting System), which is one of ground support equipments for KSLV-I, is analyzed based on CDP(Critical Design Package) provided by Russia. The thermo-hydraulic design of air preparation compartment and hydraulic design of air heating & distribution compartment performed. Also numerical simulation of air heating & distribution compartment was conducted and compared with actual measurement data. Finally, insulation design of system was analyzed. Designing method of LCTS will be helpful in developing or modifying LCTS for new launch vehicle.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.136-147
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• 1993

The paper describes : ⅰ) Mathematical modeling of poloidal flux to define and calculate the tokamak plasma position based on a property of the plasma boundary which is always a flux surface. Controlling the plasma boundary position is therefore equivalent to equalizing the flux value on several points belonging to a curve tangent to the limiter. ⅱ) Experimental method for determining the outmost poloidal isoflux surface by a linear combination of measurements of magnetic fluxes, fields and field gradients, without requiring knowledge of internal plasma parameters for the feedback control, i.e., with neither corrections for variation in the poloidal beta and the plasma current distribution, nor compensations for the induced currents in the vacuum vessel. ⅲ) Feedback control algorithm for the regulation of plasma boundary position and its electronics hardware based on the PID control theory. ⅳ) Experimental results obtained from the RTP tokamak experiments using the present plasma control system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.2
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• pp.73-80
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• 2003

This Paper Proposes instantaneous following control method to control pulse modulation switching converter by using principle that reset time of integrator is inverse proportion in size of integrator input voltage. proposed control method acts of fixed frequency and control switch calculates time of become turn on and turn off using analog integrator. Duty ratio that express switching time of converter is depended on mean value of switching variable and following time consists in one cycle. Follow to do order exactly stationary state as well as transition state, and controller corrects mean value of control variable and control reference value and control as control error gets into zero. Proposed control method could experimented and know that experiment result and theory are agreeing well through this using the buck converter.

• Journal of IKEEE
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• v.6 no.1 s.10
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• pp.30-39
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• 2002

In this paper, we proposed a new circuit construction method that reduces the number of circuit devices of fuzzy controller. Sasaki had defined a new operator to eliminate the divide circuit comparing with the center of gravity method which often using to design the fuzzy controller. In this paper we obtained the more compacted fuzzy controller's circuit by using the proposed definition of fuzzification and defuzzification than using the Sasaki's method and the fuzzification and defuzzification are reverse operation each other. Using these definitions we exhibit the new design method and circuit structure that can eliminate the bounded product(BP) circuit included in Sasaki's circuit. Using the proposed method to level controlling of the water tank, we verified the fuzzy controller's performance by using existent method and proposed method. As a result that are calculated by using the Proposed fuzzy controller to level controlling of the water tank, total numbers of blocks and devices were decreased. If the number of variables and antecedents are Be11ing larger, this method is more efficient.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.6
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• pp.41-48
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• 2002

This study is on the structural control experiment for a small scale three-story building structure employing on active mass damper subjected to earthquake loading. $\mu$-synthesis controllers, which belong to robust control strategies, were designed and their performance were experimentally verified. Frequency-dependent weighting functions corresponding to disturbance input and controlled output were defined and combined to produce optimal $\mu$-synthesis controllers. The experiment result shows 60-70% reduction in RMS responses under the band-limited white noise excitation and 30-45% reduction in peak responses under the scaled earthquake excitations. Good agreement was obtained between the simulations based on the identified mathematical model and experimental results. And the simulations for the system with uncertainties show that the designed controllers are robust within a specified range of uncertainties.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.2
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• pp.140-148
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• 2000

A robust current control technique with a simple time delayed estimator for a permanent magnet synchronous m motor (PMSM) drive is presented. Among the various CWTent control schemes for a voltage source inverter-fed P PMSM drive, the predictive control is known to give a superior performance. This control technique, however, r requires the full knowledge of machine parameters and operating conditions, and gives an unsatisfactory r response under the parameter mismatch between the motor and controller. To overcome such a limitation, the d disturbances caused by the parameter valiations will be estimated by using a" time delay contTol approach and u used for the computation of the reference voltages by a simple feedforwal"d control. The proposed control $ scheme is implemented on a PMSM using the software of DSP TlVIS:32OC:30 and the effectiveness is verified d through the comparative simulations and experiments.periments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.749-757
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• 2021

In transportation missions using quadrotor, the payload may change the model parameters, such as mass, moment of inertia, and center of gravity. Moreover, if position of the payload is constantly changing during flight, the effect can adversely affect the control performances. To handle this issue, we suggest Model Reference Adaptive Control based on Linear Quadratic Regulator(LQR+MRAC) to compensate the uncertainty caused by payload. Firstly, the mathematical modeling with the fixed payload is derived. Second, Linear Quadratic Regulator (LQR) is used to design the reference model and baseline controller. Also, through the Stability method, Adaptive law is derived to estimate the model parameters. To verify the performance of proposed control scheme, we compared LQR and LQR+MRAC in situations where uncertainties exist. And, when the disturbance exist, the classic MRAC and proposed controller is compared to analyze the transient response and robustness.