• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.57-64
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• 2015

In this paper, a model reference adaptive control (MRAC) scheme is applied for the precise and robust motion control of a pneumatic system with load variation. The reference model for MRAC is designed systematically using linear quadratic Gaussian control with loop transfer recovery (LQG/LTR). The sigmoid function of inverse velocity is used to compensate for the nonlinear friction force between the sliding parts. The experimental results show that MRAC effectively overcame the limit of the PID controller when there was unknown disturbance, including abrupt load variation and model uncertainty in the pneumatic control system.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.9
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• pp.707-713
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• 2003

We investigate the ultrasonic gas flow meter for the measurement of gas volume quantity, which passing through pipe, using the transit time difference method. We have designed a receiving system of an ultrasonic signal and hardware system of a flow meter Also, we have designed an experimental system for the characteristic test and calibration of a gas flow meter system. We have developed an ultrasonic gas flow meter, which has a measurement uncertainty within $\pm$ 1.7 %. For the test, we have compared our system with a difference pressure type flow meter for a few months in the real field. Through the test, we have confirmed that our system have a good reliability and durability. Also, we have confirmed that our system follows very well the variation of gas volume quantity, which was measured by a difference pressure type flow meter.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.19-24
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• 2013

In this paper, the Superconductor flywheel energy storage system (SFESS) was used for the load frequency control (LFC) of an interconnected 2 area power system. The robust SFESS controller using quantitative feedback theory (QFT) was designed to improve control performance in spite of parameter uncertainty and unexpected disturbances. An overlapping decomposition method was applied to simplify SFESS controller design for the interconnected 2 area power system. The model for simulation of the interconnected 2 area power system included the reheat steam turbine, governor, boiler dynamics and nonlinearity such as governor deadband and generation rate constraint (GRC). To verify robust performance of proposed SFESS controller, dynamic simulation was performed under various disturbances and parameters variation of power system. The results showed that the proposed SFESS controller was more robust than the conventional method.

• Journal of the Korea Safety Management & Science
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• v.8 no.1
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• pp.165-179
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• 2006

Flextime system labor problem appeared by social issue going through a late 97s economic crisis. The most important thing among gravity is that act for factor who do to magnify gulf between rich and poor because do so that may polarize labor market at central part and neighborhood and makes preservation of society integration hardly social economy enemy of flextime system worker's spread. Furthermore, new economy surrounding has attribute that deepen uncertainty social bipolarization according as order by 21th century information-oriented society, globalization, knowledge base economy. Therefore, role of the country that control spread of flextime system in fixed level is more important first of all and application of employment insurance may do that have important meaning and social deliquescence.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.207-214
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• 2001

In Korea, the multi-dwelling residential buildings are most popular housing system that is reinforced concrete shear wall system. However, the serviceability and safety of the system have been decreased because of the errors in design or construction and inadequate maintenance. In addition the safety of the system cannot be evaluated reasonably because the system is analyzed by the deterministic approach. Therefore, this study is aimed to analyze reinforced concrete shear walls by the reliability approach considering uncertainty based on the probability theory. In this study, a reliability analysis program using MATLAB is developed by combining AFOSM and Sampling Method for the reinforced concrete shear walls within feasible design area. The reasonable reliability index β of ultimate limit states for RC shear walls are calculated automatically using this developed program with the measured data those have means and standard deviations in the field. The ultimate states are compression failure, tension failure, governing compression, and governing bending of the reinforced concrete shear walls respectively. To estimate the safety of the system using developed program can be used to predict residual life-time of the system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1094-1101
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• 2006

Recently, a ultra-precision stage is widely used in the fields of the nano-technology, specially in AFMs(Atomic Force Microscope) and STMs(Scanning Tunneling Microscope). In this paper, the ultra-precision stage which consists of flexure hinges, piezoelectric actuator and ultra-precision linear encoder, is designed and developed. The system transfer function of the ultra-precision stage system was derived from the step responses of the system using system identification tool. A $H_{\infty}$ controller was designed using loop shaping method to have robustness for the system uncertainty and external disturbances. For the designed controller, simulations were performed and it was applied to the ultra-precision stage system. From the experimental results it was found that this stage could be controlled with less than 5nm resolution irrespective of hysteresis and creep.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.12
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• pp.580-585
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• 2005

The recovery time of developing SFCL(Superconducting Fault Current Limiter) has an uncertainty. In general, the recovery time is estimated at 1 sec and more, even though the progress of SFCL technology is considered. However, auto reclosing time of circuit breaker is 0.3 or 0.5 sec in Korean power system. It is impossible to apply only one SFCL to power system because the recovery time is over the reclosing time of protection system. This study proposes two new SFCL systems for power system application. The proposed systems consider auto reclosing action for the protection in practical power system and consist of tow parallel SFCLs.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.609-612
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• 2008

Since most of the industries have adopted automation system, the industrial disaster has been declined sharply. Also automation system has offered many benefits such as productivity and assured quality. However, the construction industry is still relying on man power and because of this there are many victims occurring due to the industrial disaster. Construction industry has to overcome uncertainty of incidents and changing natural surroundings to actualize automation. Therefore, the efficient working plan and intelligent decision making process are needed to run more developed techniques and automations. Specially to decline the rate of industrial accidents occurred in basic construction in earth work, the automation via excavator is necessary and also the development of planning process system is too. This research is to establish Task Planning System to prevent disaster which is used for planning automated earth work.

• Smart Structures and Systems
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• v.10 no.4_5
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• pp.375-391
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• 2012

This paper reports the structural health monitoring benchmark study results for the Canton Tower using Bayesian methods. In this study, output-only modal identification and finite element model updating are considered using a given set of structural acceleration measurements and the corresponding ambient conditions of 24 hours. In the first stage, the Bayesian spectral density approach is used for output-only modal identification with the acceleration time histories as the excitation to the tower is unknown. The modal parameters and the associated uncertainty can be estimated through Bayesian inference. Uncertainty quantification is important for determination of statistically significant change of the modal parameters and for weighting assignment in the subsequent stage of model updating. In the second stage, a Bayesian model updating approach is utilized to update the finite element model of the tower. The uncertain stiffness parameters can be obtained by minimizing an objective function that is a weighted sum of the square of the differences (residuals) between the identified modal parameters and the corresponding values of the model. The weightings distinguish the contribution of different residuals with different uncertain levels. They are obtained using the Bayesian spectral density approach in the first stage. Again, uncertainty of the stiffness parameters can be quantified with Bayesian inference. Finally, this Bayesian framework is applied to the 24-hour field measurements to investigate the variation of the modal and stiffness parameters under changing ambient conditions. Results show that the Bayesian framework successfully achieves the goal of the first task of this benchmark study.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.18-18
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• 2010

Methods of the characteristics evaluation of turbo-molecular pumps (TMP) are well-defined in the international measurement standards such as ISO, PNEUROP, DIN, JIS, and AVS. The Vacuum Center in the Korea Research Institute of Standards and Science has recently designed, constructed, and established the integrated characteristics evaluation system of TMPs based on the international documents by continuously pursuing and acquiring the reliable international credibility through measurement perfection. The measurement of TMP pumping speed is normally performed with the throughput and orifice methods dependent on the mass flow regions. However, in the UHV range of the molecular flow region, the high uncertainties of the gauges, mass flow rates, and conductance are too critical to precisely accumulate reliable data. With UHV gauges of uncertainties less than 15% and a calculated conductance of the orifice, about 35% of pumping speed uncertainties are experimentally derived in the pressure range of less than $10^{-6}$ mbar. In order to solve the uncertainty problems of pumping speeds in the UHV range, we introduced an SRG with 1% accuracy and a constant volume flow meter (CVFM) to measure the finite mass flow rates down to $10^{-3}$ mbar-L/s with 3% uncertainty for the throughput method. In this way we have performed the measurement of pumping speed down to less than $10^{-6}$ mbar with an uncertainty of 6% for a 1000 L/s TMP. In this article we suggest that the CVFM has an ability to measure the conductance of the orifice experimentally with flowing the known mass through the orifice chambers, so that we may overcome the discontinuity problem encountering during introducing two measurement methods in one pumping speed evaluation sequence.