• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.173-179
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• 2017

This paper proposes a robust impedance controller for high-DOF robots. The model-based control of a higher DOF robot uses a numerical dynamic model because the analytical dynamic model is difficult to be derived and this means that modeling error is inevitable. The impedance control in the task space is affected by joint motions and has more difficulties in the higher DOF robots. In addition, the disturbances must be decoupled in the control of high DOF robot. This paper proposes a robust impedance controller based on integral sliding mode control (ISMC) and disturbance observer(DOB) for high-DOF robot manipulator. The ISMC is used to improve the robustness of the impedance control and to preserve its nominal performance. DOB is also employed to cancel the effects of input disturbances and to reduce the maximum gain of the ISMC which eventually determines the input chattering size.

• The Korean Journal of Applied Statistics
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• v.32 no.6
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• pp.837-849
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• 2019

Latent class models (LCM) are useful tools to draw hidden information from categorical data. This model can also be interpreted as a mixture model with multinomial component distributions. In some cases, however, an available dataset may contain both categorical and count or continuous data. For such cases, we can extend the LCM to a mixture model with both multinomial and other component distributions such as normal and Poisson distributions. In this paper, we consider a LCM for the data containing categorical and count data to analyze the Drug Review dataset which contains categorical responses and text review. From this data analysis, we show that we can obtain more specific hidden inforamtion than those from the LCM only with categorical responses.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.461-466
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• 2002

Fiber-optic comb filters using a side-polished fiber coupler are proposed as multi-channel isolation filters on wavelength division multiplexing systems. We have demonstrated that the coupling efficiency between two waveguides is improved by the intermediate coupling layer in spite of the decrease of the optical power transfer between two waveguides due to the high-order modes of the overlay waveguide coupled with the side-polished single-mode fiber. When LiNbO$_3$with a 200-${\mu}{\textrm}{m}$-thickness was applied as a planar-overlay-waveguide, the comb filtering characteristics with a 4 nm-channel-spacing were achieved and the maximum power coupling occurred at the 1-${\mu}{\textrm}{m}$-thickness and the refractive index in range 1.52 to 1.53 of an intermediate coupling layer. If the intermediate coupling layer is optimized, an extinction ratio with more than 20 dB can be obtained. These experimental results are in good agreement with the BPM simulation.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.391-398
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• 2004

Far-ultraviolet Imaging Spectrograph (FIMS) is the main payload of the Korea's first scientific micro satellite STSAT-1, which was launched at Sep. 27 2003 successfully. Major objective of FIMS is observing hot gas in the Galaxy in FUV bands to diagnose the energy flow models of the interstellar medium. Supernova remnants, molecular clouds, and Aurora emission in the geomagnetic pole regions are specific targets for pointing observation. Although the whole system was calibrated before launch, it is essential to perform on-orbit calibration for data analysis. For spectral calibration, we observed airglow lines in the atmosphere since they provide good spectral references. We identify and compare the observed airglow lines with model calculations, and correct the spectral distortion appeared in the detector system to improve the spectral resolution of the system.

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.177-180
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• 2006

We observed $2.1218{\mu}m$ $H_2$ 1-0 S(1) emission from H II region A, which is located just next to Sgr A East and one of the nearest star forming regions to the Gatactic center. Cooled Grating Spectrometer 4 (CGS4) at the 3.8 m United Kingdom Infrared Telescope (UKIRT) was used with aa echelle grating at a velocity resolution of ${\sim}$ 18km s^{-1}$ and an angular resolution of ${\sim}$ 2 arcsec. Comparing the distributions and kinematics of the observed $H_2$ emission with radio continuum and $NH_3$ emission, we find no evidence that this H II region is interacting with Sgr A East. This conclusion supports that the star formation in this region has not been stimulated by the blast wave of Sgr A East.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.1027-1035
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• 2021

We presents a design of 3U cubesat MIMAN (Monochrome imaging for monitoring aerosol by nano-satellite) for aerosol monitoring mission with high spatial resolution. The main objective of MIMAN mission is to take images of aerosols around Korea and to provide auxiliary data for GK 2B cloud masking. For this mission, we derived mission requirements and constraints for the MIMAN mission. We designed the mission architecture and concept of operations. To reduce risk factors in space operation, we considered the safety of the communication. In every operation modes, UHF communication is available so that the cubesat can operate based on the ground commands. So, we can handle every problem at the ground station during mission operations. Based on the mission and concept of operations, we confirmed that the system design satisfied the system requirements. We designed the system interface considering data flow of each hardware, and evaluated the safety of the system with system budget analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.161-172
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• 1997

In this paper, electromagnetic scattering by a perfectly conducting strip grating on dielectric multilayers is analyzed for the normalized reflected and transmitted power by applying the Fourier-Galeakin moment method. The induced current density is expanded in a series of multiplication of chebyshev polynomials of the first kind and functions with appropriate edge boundary condition, the continuous condition of electromagnetic field is applied in the boundary planes. The confirm the validity of the proposed method, the nor- malized reflected and transmitted power obtained by varying the relative permittivity and thickness of each dielectric layers are evaluated and compared with those of the existing numerical method and a paper, and then the numerical results in this paper are in good agreement with those of the existing numerical method and the paper. The sharp variation position in the geometrically normalized reflected and transmitted power can be moved by the incident angle, grating period, and the relative permittivity and thickness of the dielectric multilayers, these sharp variation points which are called the Wood's anomaly of the Geome- trically normalized reflected power are observed as a main factor when the reflected powers of the higher order mode are transitted between propagating and evanescent modes, and the local minimum positions are slightly moved to the left hand direction in which grating period is getting small according to the increase of the relative permittivity of dielectric layers.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.953-959
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• 2018

This paper deals with controlling surge oscillations of a mooring vessel system under large external disturbances such as wind, waves and currents. A control synthesis based on Sliding Mode Control (SMC) with a Super-Twisting Algorithm (STA) has been applied to suppress nonlinear surge oscillations of a two-point mooring system. Despite the advantages of robustness against parameter uncertainties and disturbances for SMC, chattering is the main drawback for implementing sliding mode controllers. First-order SMC shows convergence within the desired level of accuracy, in which chattering is the main obstacle related to the destructive phenomenon. Alternatively, STA completely eliminates chattering phenomenon with high accuracy even for large disturbances. SMC based on STA is an effective tool for the motion control of a nonlinear mooring system because it avoids the chattering problems of a first-order sliding mode controller. In addition, the error trajectories of controlled mooring systems implemented by means of STA form in the bounded region. Finally, the control gain effect of STA can be observed in sliding surface and position trajectory errors.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.2
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• pp.131-142
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• 2015

In order to support the development of a cost-effective river bathymetric system, this research has focused on modeling GPS observables, which are obtained by array of five single-frequency receivers (i.e., two references and three rovers) to estimate the high accurate kinematic position, and the surveying vessel altitude. Also, by applying all GPS measurements as multiple-baselines with constraining rover baselines, we derived the socalled ‘kinematic network model.’ From the model, the integer-constrained least-squares (LS) for position estimation and the implicit LS for attitude determination were implemented, while a series of simulation tests with respect to the baseline lengths around 2km performed to demonstrate its accuracy analysis. The on-the-fly (OTF) ambiguity resolution tests revealed that ninety-nine percents of time-to-fix-first ambiguity (TTFF) can be decided in less than two seconds, when the positioning accuracy of ambiguity-fixed solutions was assessed as the greater than or equal to one and two centimeters in horizontal and vertical, respectively. Comparing to the GPS-derived attitudes, the achievable accuracy gradually descended in sequence of yaw, pitch and roll due to the antenna geometric configuration. Furthermore, the RMSE values for the baseline lengths of three to six meters were within ±1′for yaw, and less than ±10′and ±20′for pitch and roll, respectively, but those of between six to fifteen meters were less than ±1′for yaw, ±5′for pitch, and ±10′for roll.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.7
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• pp.669-672
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• 2012

This paper investigates an algorithm for robust fault diagnosis in robot manipulators. The TOSM (Third Order Sliding Mode observer) provides both theoretically exact observation and unknown fault identification without filtration. The EOI (Equivalent Output Injections) of the TOSM observers can be used as residuals for the problem of fault diagnosis and to identify the unknown faults. The obtained fault information can be used for fault detection, isolation as well as fault accommodation to the self-correcting failure system. The computer simulation results for a PUMA 560 robot are shown to verify the effectiveness of the proposed strategy.