• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.2057-2059
• /
• 2001

A nonlinear adaptive speed controller is designed for induction motors. Only the measurement of the stator current is used to design the controller and the observers. The sliding mode cascade observer is introduced to estimate the stator current and its time derivatives. The open-loop observer are designed to estimate the rotor flux and its time derivatives. The adaptive observer is also designed to estimate the rotor resistance. Sequentially, the rotor speed can be calculated using these estimated values. It is shown that the estimation errors of the corresponding states and the parameter converge to the specified residual set. It is also shown that the speed controller using these estimates is performed well. The experimental results are represented to investigate the validity of the proposed observer and controller.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1276-1278
• /
• 2005

In this paper, we propose an adaptive sliding mode observer-based control of induction motors with uncertainties. The proposed adaptive sliding mode flux observer generates estimates both for the unknown parameters(load torque and rotor resistance) and for the unmeasured state variable (rotor fluxes); they converge to the corresponding true value under persistency of excitation which actually holds in typical operating conditions. The proposed controller guarantees speed tracking and bounded signals for every initial condition of the motor. Simulations show that all estimation errors tend quickly to zero so that high tracking performances are achieved both for speed and rotor flux.

• Proceedings of the KIPE Conference
• /
• 2010.11a
• /
• pp.259-260
• /
• 2010

This paper presents the sensorless and MPPT control algorithm for a 100kW tidal energy system. The proposed algoritm is estimated the rotor position and generator speed using adaptive sliding mode observer. The vector control of generator at the machine side converter and the converter at the grid side are controlled to obtain maximum torque and to regulate unity power factor respectively. Psim simulation is used for validity of proposed control algorism.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.24 no.1
• /
• pp.33-39
• /
• 2019

We propose a mechanical parameter estimation algorithm for surface-mounted permanent magnet synchronous motors (SPMSMs) using a sliding-mode observer (SMO) and an adaptive filter. The SMO estimates system disturbances in real time, which contain the information on mechanical parameters. A desirable feature that distinguishes the proposed estimation algorithm from other existing mechanical parameter estimators is that the adaptive filter estimates electromagnetic torque to improve the estimation performance. Moreover, the SMO acts as a low-pass filter to suppress the chattering effect, which enables the smooth output signals of the SMO. We verify the mechanical parameter estimation performance for SPMSM by conducting extensive experiments for the proposed algorithm.

• Journal of Auto-vehicle Safety Association
• /
• v.15 no.2
• /
• pp.13-20
• /
• 2023

This paper presents a fault tolerant control strategy for Steer-by-Wire (SbW) systems. Among many problems to be solved before commercialization of SbW systems, maintaining reliability and fault tolerance in such systems are the most pressing issues. In most previous studies, dual steering motors are used to achieve actuation redundancy. However, relatively few studies have been conducted to introduce fault tolerant control strategies using rear wheel steering system. In this work, an actuator fault in front wheel steering is compensated by active rear wheel steering. The proposed fault tolerant control algorithm consists of disturbance observer and sliding mode control. The fault tolerant control performance of the proposed approach is validated via computer simulation studies with Carsim vehicle dynamics software and MATLAB/Simulink.

• Journal of Korea Water Resources Association
• /
• v.50 no.4
• /
• pp.253-261
• /
• 2017

A lot of nonstationary frequency analyses have been studied in recent years as the nonstationarity occurs in hydrologic time series data. In nonstationary frequency analysis, various forms of probability distributions have been proposed to consider the time-dependent statistical characteristics of nonstationary data, and various methods for parameter estimation also have been studied. In this study, we aim to introduce a parameter estimation method for nonstationary Gumbel distribution using ensemble empirical mode decomposition (EEMD); and to compare the results with the method of maximum likelihood. Annual maximum rainfall data with a trend observed by Korea Meteorological Administration (KMA) was applied. As a result, both EEMD and the method of maximum likelihood selected an appropriate nonstationary Gumbel distribution for linear trend data, while the EEMD selected more appropriate nonstationary Gumbel distribution than the method of maximum likelihood for quadratic trend data.

• Korean Journal of Remote Sensing
• /
• v.36 no.2_2
• /
• pp.365-377
• /
• 2020

Continuous monitoring and immediate response is essential to protect the national maritime territory and maritime resources from the activities of illegal ships. Synthetic Aperture Radar (SAR) images with a wide range of images are effective for maritime surveillance asthe weather and day-night conditions rarely affect to image acquisition. However, an effective ship detection is not easy due to the huge data size of SAR images and various characteristics such as the speckle noise. In this study, the Human Visual Attention System (HVAS) algorithm was applied to KOMPSAT-5 to extract the initial targets, and the SAR-Split algorithm depending on the imaging modes was used to remove false alarms. The detected targets were finally selected by the Constant False Alarm Rate (CFAR) algorithm and matched with the ship's Automatic Identification System (AIS) information. Overall, the detected targets were well matched with AIS data, but some false alarms by ship wakes were observed. The detection rate was about 80% in ES mode and about 64% in ST mode. It is expected that the developed ship detection algorithm will contribute to the construction of a wide area maritime surveillance network.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.5
• /
• pp.495-503
• /
• 1997

In this paper, the E-polarized electromagnetic scattering problems by a resistive strip grating with tapered resistivity on 3 dielectric layers are analyzed to find out the effects for the tapered resistivity of resistive strip and the relative permittivity and thickness of 3 die- lectric layers by applying the Fourier-Galerkin moment methods. The induced surface current density is expanded in a series of Jacobi-polynomial ${P^{(\chi,\beta)}}_p$(.) of the order $\alpha$= 0 and $\beta$=1 as a kind of orthogonal polyomians, and the tapered resistivity assumes to vary linearly from 0 at one edge to finite resistivity at the other edge. The normalized reflected and transmitted powers are obtained by varying the tapered resistivity and the relative permittivity and thickness of dielectric layers. The sharp variation points are observed when the higher order modes are transferred between propagating and evanescent modes, and in general the local minimum positions occur at less grating period for the more relative permittivity of dielectric layers. It should be noted that the patterns of the normalized reflected and transmitted powers for the tapered resistivity are very much different from those of the uniform resistivity and perfectly conducting cases. The proposed method of this paper cna solve the scattering problems for the tapered resistive, uniform resistive, and PEC strip cases.

• Korean Journal of Optics and Photonics
• /
• v.32 no.4
• /
• pp.147-152
• /
• 2021

We report high-power continuous-wave operation of a Yb-doped fiber laser at 1070 nm, pumped by high-power laser diodes at 976 nm. Based on theoretical calculation of the stimulated Raman scattering and temperature distribution in the fiber, we construct a bidirectionally pumped Yb-fiberlaser system incorporating a pair of fiber Bragg gratings and a cladding light stripper. The fiber laser yields 3.0 kW of continuous-wave output at 1070 nm in a diffraction-limited beam with M² ≈ 1.26 for 4.1 kW of incident pump power, corresponding to a slope efficiency of 81.5%. The prospects for further power scaling are discussed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.2
• /
• pp.332-350
• /
• 2019

Zonal hydrographic section measurements at $39.7^{\circ}N$ were conducted between $129.0^{\circ}E$ and $131.3^{\circ}E$ from August 7 to 25 in 2017 using an underwater glider. The glider traveled about 440 km for about 18 days along the 106 line of the regular shipboard measurements in the National Institute of Fishery Science (NIFS) and obtained twice a hydrographic section with high horizontal resolution. Even under the strong East Korea Warm Current with maximum speed of 0.8 m/s across the section, the glider successfully maintained the designated path within an RMS distance of 400 m. By comparing with the NIFS shipboard hydrographic section, it is confirmed that high spatial resolution measurements obtained from a glider were necessary to properly observe front and eddy variability in the East Sea where a typical spatial scale is smaller than the open oceans. From the glider section measurements, a new lens-shaped eddy was found in the thermocline. The lens-shaped anticyclonic eddy had 10~13 km in horizonal width and about 200 m in height like a typical submesoscale eddy resided within the thermocline, which was firstly named as Korea intrathermocline eddy (Keddy). The Keddy has the distinguishing characteristics of a typical intrathermocline eddy, such as a central core with anomalously weak stratification, a convex shaped lens bounded by the stratification anomaly, an interior maximum of velocity at 170 m, no surface appearance of the geopotential field, a small or comparable horizontal width relative to the first baroclinic Rossby radius of deformation, and the Rossby nubmer of 0.7.