• Title/Summary/Keyword: time domain data

Search Result 1,285, Processing Time 0.045 seconds

The Ultimate Bound of Discrete Sliding Mode Control System with Short Sampling Period for DC Motor System (DC 모터 시스템을 위한 짧은 샘플링 시간을 갖는 이산슬라이딩 모드의 최종 수렴범위)

  • Park, Heum-Yong;Jo, Young-Hun;Park, Kang-Bak
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.16 no.3
    • /
    • pp.245-248
    • /
    • 2010
  • Almost all of control schemes proposed so far have been designed in the continuous-time domain theoretically. Actual systems, however, have been implemented in the discrete-time domain since Micro Control Unit(MCU) and/or microprocessors have been used for the controllers. Thus, the overall system turned to be a sampled-data system, and generally speaking, the ultimate error cannot converge to zero in the actual system even though the proposed control algorithm showed the asymptotic stability in the continuous-time domain. In this paper, therefore, the ultimate error bound of a sampled data system with a short sampling period has been investigated. The ultimate error is shown to be related in the sampling period.

Nonlinear Inversion of Time-domain Induced Polarization Data with Negative Apparent Chargeability Data (음의 겉보기 충전성 자료를 포함한 시간영역 유도분극 자료의 비선형 역산)

  • Cho, In-Ky;Kim, Yeon-Jung
    • Geophysics and Geophysical Exploration
    • /
    • v.24 no.4
    • /
    • pp.139-148
    • /
    • 2021
  • Negative apparent chargeability data in time-domain induced polarization (IP) survey are very often considered as noise and rejected before the inversion stage. Negative IP data can, however, occur naturally as a consequence of the distribution of chargeable zones in the ground. In some cases, the negative apparent chargeability values may account for most of the data measured. Negative IP data are caused by the geometry of chargeable zones and electrode positions. Negative apparent chargeability data appear most frequently when a dipole-dipole array is used. In this study, the effect of negative apparent chargeability data on inversion results is analyzed through the numerical 2D time-domain IP modeling and nonlinear inversion. The results demonstrate clearly that negative apparent chargeability data have to be included in the inversion as they contain important information on the distribution of subsurface chargeability.

Performance Analysis of the reconstruction Algorithms in the Stripmap-mode SAR (Stripmap-mode SAR에서의 영상복원 알고리즘의 성능분석)

  • 박현복;김형주;최정희
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2000.11a
    • /
    • pp.29-33
    • /
    • 2000
  • The classical image reconstruction for stripmap SAR is based on the Fresnel approximation which utilizes deramping or chirp deconvolution in the synthetic aperture(slow-time) domain. Another approach in formulating stripmap SAR processing and imaging is based on the SAR wavefront reconsturction theory, and analysis of the SAR signal in the slow-time via the spherical wave Fourier decomposition of the radar radiation pattern. In this paper, we compare the Fresnel approximation and the wavefrong reconstruction methods using simulated stripmap SAR dada.

  • PDF

Localized evaluation of actuator tracking for real-time hybrid simulation using frequency-domain indices

  • Xu, Weijie;Guo, Tong;Chen, Cheng
    • Structural Engineering and Mechanics
    • /
    • v.62 no.5
    • /
    • pp.631-642
    • /
    • 2017
  • Accurate actuator tracking plays an important role in real-time hybrid simulation (RTHS) to ensure accurate and reliable experimental results. Frequency-domain evaluation index (FEI) interprets actuator tracking into amplitude and phase errors thus providing a promising tool for quantitative assessment of real-time hybrid simulation results. Previous applications of FEI successfully evaluated actuator tracking over the entire duration of the tests. In this study, FEI with moving window technique is explored to provide post-experiment localized actuator tracking assessment. Both moving window with and without overlap are investigated through computational simulations. The challenge is discussed for Fourier Transform to satisfy both time domain and frequency resolution for selected length of moving window. The required data window length for accuracy is shown to depend on the natural frequency and structural nonlinearity as well as the ground motion input for both moving windows with and without overlap. Moving window without overlap shows better computational efficiency and has potential for future online evaluation. Moving window with overlap however requires much more computational efforts and is more suitable for post-experiment evaluation. Existing RTHS data from Network Earthquake Engineering Simulation (NEES) is utilized to further demonstrate the effectiveness of the proposed approaches. It is demonstrated that with proper window size, FEI with moving window techniques enable accurate localized evaluation of actuator tracking for real-time hybrid simulation.

A Simplified Time Domain Channel Tracking Scheme in OFDM Systems with Null Sub-Carriers (Null 부반송파를 갖는 OFDM 시스템에서 단순화된 시간영역 채널 추적 방식)

  • Jeon, Hyoung-Goo
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.32 no.4C
    • /
    • pp.418-424
    • /
    • 2007
  • This paper proposes a scheme to track channel response in OFDM systems with null sub-carriers. The proposed channel tracking scheme estimates the channel response first in the frequency domain by using the decision directed data. The time domain channel estimation is then performed to remove additive white Gaussian noise (AWGN) components further. Due to the channel estimation in the frequency domain, no inverse matrix calculation is required in the time domain channel estimation. Computational reduction in the proposed method is about 93%, compared with the conventional time domain channel estimation method. Mean square error (MSE) and bit error rate (BER) performances are evaluated by using computer simulation. The proposed method shows the same performance as that of the conventional time domain channel estimation even though the significant computational reduction.

Radionuclides Transport from the Hypothetical Disposal Facility in the KURT Field Condition on the Time Domain (KURT 부지 환경에 위치한 가상의 처분 시설에서 누출되는 방사성 핵종의 이동을 Time Domain에서 해석하는 방법에 관한 연구)

  • Hwang, Youngtaek;Ko, Nak-Youl;Choi, Jong Won;Jo, Seong-Seock
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.10 no.4
    • /
    • pp.295-303
    • /
    • 2012
  • Based on the data observed and analyzed on a groundwater flow system in the KURT (KAERI Underground Research Tunnel) site, the transport of radionuclides, which were assumed to be released at the supposed position, was calculated on the time-domain. A groundwater pathway from the release position to the surface was identified by simulating the groundwater flow model with the hydrogeological characteristics measured from the field tests in the KURT site. The elapsed time when the radionuclides moved through the pathway is evaluated using TDRW (Time Domain Random Walk) method for simulating the transport on the time-domain. Some retention mechanisms, such as radioactive decay, equilibrium sorption, and matrix diffusion, as well as the advection-dispersion were selected as the factors to influence on the elapsed time. From the simulation results, the effects of the sorption and matrix diffusion, determined by the properties of the radionuclides and underground media, on the transport of the radionuclides were analyzed and a decay chain of the radionuclides was also examined. The radionuclide ratio of the mass discharge into the surface environment to the mass released from the supposed repository did not exceed $10^{-3}$, and it decreased when the matrix diffusion were considered. The method used in this study could be used in preparing the data on radionuclide transport for a safety assessment of a geological disposal facility because the method could evaluate the travel time of the radionuclides considering the transport retention mechanism.

Analysis of Time Domain Active Sensing Data from CX-100 Wind Turbine Blade Fatigue Tests for Damage Assessment

  • Choi, Mijin;Jung, Hwee Kwon;Taylor, Stuart G.;Farinholt, Kevin M.;Lee, Jung-Ryul;Park, Gyuhae
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.36 no.2
    • /
    • pp.93-101
    • /
    • 2016
  • This paper presents the results obtained using time-series-based methods for structural damage assessment. The methods are applied to a wind turbine blade structure subjected to fatigue loads. A 9 m CX-100 (carbon experimental 100 kW) blade is harmonically excited at its first natural frequency to introduce a failure mode. Consequently, a through-thickness fatigue crack is visually identified at 8.5 million cycles. The time domain data from the piezoelectric active-sensing techniques are measured during the fatigue loadings and used to detect incipient damage. The damage-sensitive features, such as the first four moments and a normality indicator, are extracted from the time domain data. Time series autoregressive models with exogenous inputs are also implemented. These features could efficiently detect a fatigue crack and are less sensitive to operational variations than the other methods.

A Comparison of Superimposition Schemes for Spectral Efficiency Improvement of OFDM (OFDM 주파수 효율 증가를 위한 중첩 전송 방법 성능 비교)

  • Lee, Jun-Kyoung;Yang, Jang-Hoon;Kim, Dong-Ku
    • Journal of Advanced Navigation Technology
    • /
    • v.12 no.4
    • /
    • pp.332-340
    • /
    • 2008
  • In this paper, comparisons of the superimposition schemes for orthogonal frequency division multiplexing (OFDM) system are made. The time domain superimposition of data (TDSD) has a tradeoff between the degree of freedom for data transmission and inter-carrier interference (ICI). While SPPT and APSB experiences the increases of interference as the transmit data rate increases, TDSD can effectively improve spectral efficiency by exploiting preprocessing structures which prevents interference between the signals in the different domain. TDSD which we proposed is compared with the conventional superimposition schemes or OFDM, such as SPPT (the superimposed periodic pilot in the time domain) and APSB (the added pilot semi-blind channel estimation) by simulation. As the result, comparing the conventional OFDM, TDSD can increase the spectral efficiency up to about 20% with the superimposition factor M=16 while SPPT has the similar efficiency. APSB has the worst efficiency.

  • PDF

3-D Representation of Cavity Region from Ultrasonic Image Acquired in the Time Domain (시간 영역에서 획득된 초음파 영상의 심내강 영역에 대한 3차원 표현)

  • Won, C.H.;Chae, S.P.;Koo, S.M.;Kim, M.N.;Cho, J.H.
    • Proceedings of the KOSOMBE Conference
    • /
    • v.1997 no.05
    • /
    • pp.119-122
    • /
    • 1997
  • In this paper, we represented the variation of heart cavity area in the space domain by 3-d rendering. We arranged the 2-d sequence of ultrasonic image acquired in the time domain as volumetric data, and extracted heart cavity region from 3-d data. For the segmentation of 3-d volume data, we extracted the cavity region using the method of expanding the cavity region that is same statistical property. By shading which is using light and object normal vector, we visualized the volume data on image plane.

  • PDF

Bilateral Controller for Time-varying Communication Delay: Time Domain Passivity Approach (시변 시간지연 하에서 안정성을 보장하는 양방향 원격제어기 : 시간영역 수동성 기법)

  • Ryu, Jee-Hwan
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.13 no.11
    • /
    • pp.1099-1105
    • /
    • 2007
  • In this paper, modified two-port time-domain passivity approach is proposed for stable bilateral control of teleoperators under time-varying communication delay. We separate input and output energy at each port of a bilateral controller, and propose a sufficient condition for satisfying the passivity of the bilateral controller including time-delay. Output energy at the master port should be less than the transmitted input energy from the slave port with time-delay, and output energy at the slave port should be less than the transmitted input energy from the master port with time-delay. For satisfying above two conditions, two passivity controllers are attached at each port of the bilateral controller. A packet reflector with wireless internet connection is used to introduce serious time-varying communication delay of teleoperators. Average amount of time-delay was about 190(msec) for round trip, and varying between 175(msec) and 275(msec). Moreover some data packet was lost during the communication due to UDP data communication. Even under the serious time-varying delay and packet loss communication condition, the proposed approach can achieve stable teleoperation in free motion and hard contact as well.