• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.123-132
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• 2017

A smart tuned mass damper (TMD) was developed to provide better control performance than a passive TMD for reduction of earthquake induced-responses. Because a passive TMD was developed decades ago, optimal design methods for structural parameters of a TMD, such as damping constant and stiffness, have been developed already. However, studies of optimal design method for structural parameters of a smart TMD were little performed to date. Therefore, parameter studies of structural properties of a smart TMD were conducted in this paper to develop optimal design method of a smart TMD under seismic excitation. A retractable-roof spatial structure was used as an example structure. Because dynamic characteristics of a retractable-roof spatial structure is changed based on opened or closed roof condition, control performance of smart TMD under off-tuning was investigated. Because mass ratio of TMD and smart TMD mainly affect control performance, variation of control performance due to mass ratio was investigated. Parameter studies of structural properties of a smart TMD was performed to find optimal damping constant and stiffness and it was compared with the results of optimal passive TMD design method. The design process developed in this study is expected to be used for preliminary design of a smart TMD for a retractable-roof spatial structure.

• Journal of KIISE
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• v.42 no.11
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• pp.1404-1409
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• 2015

In this paper, we present a novel approach to analyzing large-scale JavaScript applications statically by tuning the analysis scalability, possibly sacrificing soundness. For a given sound static baseline analysis of JavaScript programs, our framework allows users to define a sound approximation of selected executions that they wish to analyze, and it derives a tuned static analysis that can analyze the selected executions practically. The selected executions serve as parameters of the framework by taking a trade-off between the scalability and the soundness of the derived analyses. We formally describe our framework in the abstract interpretation setting and present two instances of the framework.

• Proceedings of the KSPS conference
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• 2006.11a
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• pp.80-83
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• 2006

The purpose of this paper is to build a pronunciation lexicon with estimated likelihoods of the phonetic rules based on the phonetic realizations and therefore to improve the performance of CSR using the dictionary. In the baseline system, the phonetic rules and their application probabilities are defined with the knowledge of Korean phonology and experimental tuning. The advantage of this approach is to implement the phonetic rules easily and to get stable results on general domains. However, a possible drawback of this method is that it is hard to reflect characteristics of the phonetic realizations on a specific domain. In order to make the system reflect phonetic realizations, the likelihood of phonetic rules is reestimated based on the statistics of the realized phonemes using a forced-alignment method. In our experiment, we generates new lexica which include pronunciation variants created by reestimated phonetic rules and its performance is tested with 12 Gaussian mixture HMMs and back-off bigrams. The proposed method reduced the WER by 0.42%.

• Journal of Navigation and Port Research
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• v.34 no.2
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• pp.117-122
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• 2010

Since fuzzy controllers are nonlinear, it is more difficult to set the controller gains and to analyse the stability compared to conventional PID controllers. This paper proposes a fuzzy PD+I controller for tracking control which uses a linear fuzzy inference(product-sum-gravity) method based on a conventional linear PID controller. In this scheme the fuzzy PD+I controller works similar to the control performance as the linear PD plus I(PD+I) controller. Thus it is possible to analyse and design an fuzzy PD+I controller for given systems based on a linear fuzzy PD controller. The scaling factors tuning scheme, another topic of fuzzy controller design procedure, is also introduced in order to fine performance of the fuzzy PD+I controller. The scaling factors are adjusted by a real-coded genetic algorithm(RCGA) in off-line. The simulation results show the effectiveness of the proposed fuzzy PD+I controller for tracking control problems by comparing with the conventional PID controllers.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2299-2301
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• 2000

In this paper, the design of PID controller using Neural networks for the control of non-linear system is presented. First, non-linear system is identified using BPN(Backpropagation Network) algorithm. This identified model is connected to the PID controller and the parameters of PID controller are updated to the direction of reducing the difference between the identified model output and model reference output in arbitrary input signal. Therefore, identified model output tracks the model reference output in an acceptable error range and the parameters of controller are updated adaptively. The output of the system has a good performance in case of both noisy and noiseless model reference and we can control the system stable in off-line when the dynamics of the system is changed.

• Journal of Power Electronics
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• v.15 no.1
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• pp.160-176
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• 2015

This paper presents a method of designing optimal integer- and fractional-order proportional-integral-derivative (FOPID) controllers for a boost converter to gain a set of favorable characteristics at various operating points. A Pareto-based multi-objective optimization approach called strength Pareto evolutionary algorithm (SPEA) is used to obtain fast and low overshoot start-up and dynamic responses and switching stability. The optimization approach generates a set of optimal gains called Pareto set, which corresponds to a Pareto front. The Pareto front is a set of optimal results for objective functions. These results provide designers with a trade-off look-up table, in which they can easily choose any of the optimal gains based on design requirements. The SPEA also overcomes the difficulties of tuning the FOPID controller, which is an extension to the classic integer-order PID controllers and potentially promises better results. The proposed optimized FOPID controller provides an excellent start-up response and the desired dynamic response. This paper presents a detailed comparison of the optimum integer- and the fractional-order PID controllers. Extensive simulation and experimental results prove the superiority of the proposed design methodology to achieve a wide set of desired technical goals.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.300-306
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• 2004

This paper reports a novel tunable bandpass filter using two-state switched inductor with direct-contact MEMS switches for wireless LAN applications. In our filter configuration, the switched inductor is implemented to obtain more stable and much larger frequency tuning ratio compared with variable capacitor-based tunable filter. The proposed tunable filter was fabricated using a micromachining technology and electrical performances of the fabricated filter were measured. The filter consists of spiral inductors, MIM capacitors and direct-contact type MEMS switches, and its frequency tunability is achieved by changing the inductance that is induced by ON/OFF actuations of the MEMS switches. The actuation voltage of the MEMS switches was measured of 58 V, and they showed the insertion loss of 0.1 dB and isolation of 26.3 dB at 2 GHz, respectively. The measured center frequencies of the fabricated filter were 2.55 GHz and 5.1 GHz, respectively. The passband insertion loss and 3-dB bandwidth were 4.2 dB and 22.5 % at 2.55 GHz, and 5.2 dB and 23.5 % at 5.1 GHz, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.231-237
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• 2016

This paper presents a multiband low phase noise CMOS VCO with wide frequency tunability using switched bondwire inductor bank. The combination of bondwire inductor and CMOS switch transistor enhances frequency tunability and improves phase noise characteristics. The proposed multiband VCO operates from 2.3GHz to 6.3GHz with phase noise of -136dBc/Hz and -122dBc/Hz at 1 MHz offset frequency, respectively. Switched bondwire inductor bank shows high quality factor(Q) at each frequency band, which allows better tradeoff between phase noise and power consumption. The proposed VCO is designed in TSMC 0.18um CMOS process and consumes 7.2 mW power resulting in figure of merit(FOM) of -189.3dBc/Hz at 1 MHz offset from 6GHz carrier frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.423-429
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• 2007

The clock recovery module of gap filler for satellite DMB is proposed. Proposed module sustains the output frequency of 10 MHz whether the received signal from the satellite is unstable or cut off within 0.5 sec. The advantages of this module is without frequency tuning at regular interval and low material cost. This module is fabricated by using CPLD as clock recovery IC and new type of loop filter for satisfying the fast lock time and long hold over time simultaneously. The measured performance of the fabricated module has a holdover time of 11 sec at frequency stability less than 0.01 ppm, and phase noise of -113 dBc/Hz at 100 Hz offset.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1726-1733
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• 2015

In order to study the effect of the high-altitude and dusty weather in northwest of China on the corona characteristics of transmission lines, a corona caged based experimental system with sandy and dusty flow condition is numerically investigated and designed. This system overcomes the difficulties caused by harsh environment and offers easy usage for off-site tests. The design parameters are mainly determined by the characteristics of strong sandstorm in northwest region and test requirements. By the comparison of numerical simulation of the particle diffusion in four programs with rectangular or circular air-duct, a practical technology, which introduces swirl to control the particle diffusion length, is obtained. Accordingly, the structure of round air-duct with swirl elbow in inlet and outlet of high level segment is selected as final program. Systems of control and measurement are designed at the same time. Field tuning results show that the test system could ensure the range of sandy and dusty coverage. The wind speed, sandy and dusty concentration could be controlled and meet the requirements of accuracy. The experimental system has many features, such as simple structure, easy to be assembled, disassembled, transported and operated, small space occupied.