• Title/Summary/Keyword: Nonlinearity compensation

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Nonlinearity Detection and Compensation in Radio over Fiber Systems Using a Monitoring Channel

  • Kim, Sung-Man
    • Journal of information and communication convergence engineering
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    • v.13 no.3
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    • pp.167-171
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    • 2015
  • A radio over fiber (RoF) system is a kind of analog optical transmission system and considered as a strong candidate for the next-generation fronthaul link in the future mobile network. In RoF systems, nonlinearity compensation is essential to increase the link capacity. In this paper, we propose a nonlinearity detection and compensation scheme using a monitoring channel in RoF systems. A monitoring channel is added at the transmitter site and used for transmitting a reference signal in an RoF transmission. The nonlinearity in the RoF transmission is detected by comparing the received monitoring signal and the original reference signal at the receiver site. Finally, the nonlinearity is compensated at the receiver by giving the reverse function of the detected nonlinearity. Our results show that the proposed scheme can almost remove the error vector magnitude degradation induced by the nonlinearity in the RoF system.

Nonlinearity-Compensation Extended Kalman Filter for Handling Unexpected Measurement Uncertainty in Process Tomography

  • Kim, Jeong-Hoon;Ijaz, Umer Zeeshan;Kim, Bong-Seok;Kim, Min-Chan;Kim, Sin;Kim, Kyung-Youn
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.1897-1902
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    • 2005
  • The objective of this paper is to estimate the concentration distribution in flow field inside the pipeline based on electrical impedance tomography. Special emphasis is given to the development of dynamic imaging technique for two-phase field undergoing a rapid transient change. Nonlinearity-compensation extended Kalman filter is employed to cope with unexpected measurement uncertainty. The nonlinearity-compensation extended Kalman filter compensates for the influence of measurement uncertainty and solves the instability of extended Kalman filter. Extensive computer simulations are carried out to show that nonlinearity-compensation extended Kalman filter has enhanced estimation performance especially in the unexpected measurement environment.

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Nonlinearity compensation for laser interferometer using adaptive algorithm (적응형 알고리즘에 의한 레이저 간섭계의 비선형성 오차 보정)

  • Lee, Woo-Ram;Hong, Min-Suk;Choi, In-Sung;You, Kwan-Ho
    • Proceedings of the KIEE Conference
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    • 2006.04a
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    • pp.234-236
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    • 2006
  • Because of its long measurement range and ultra-precise resolution. the heterodyne laser interferometer systems are very common in various industry area such as semiconductor manufacturing. However the periodical nonlinearity property caused from frequency mixing is an obstacle to improve the high measurement accuracy in nanometer scale. In this paper to minimize the effect of nonlinearity, we propose an adaptive nonlinearity compensation algorithm. We first compute compensation parameters using least square (LS) with the capacitance displacement sensor as a reference input. We then update the parameters with recursive LS (RLS) while the values are optimized to modify the elliptical phase into circular one. Through comparison with some experimental results of laser system, we demonstrate the effectiveness of our proposed algorithm.

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PMD Effect on the Clock-based Optimum Dispersion Compensation Monitoring Technique

  • Kim, Sung-Man
    • Journal of the Optical Society of Korea
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    • v.13 no.1
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    • pp.112-115
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    • 2009
  • We investigate the effect of polarization-mode dispersion (PMD) on the optimum dispersion compensation (ODC) monitoring and nonlinear penalty in optical transmission systems. We report that PMD may reduce the fiber nonlinearity. We also report that the monitoring error of the clock-based ODC monitoring technique decreases after the first-order PMD compensation. A simple explanation of this phenomenon is shown.

Dead Time Compensation Scheme Independent of Parameter Variations in an Inverter-fed PMSM Drive (파라미터 변화에 무관한 인버터 구동 PMSM의 데드타임 보상 기법)

  • Kim, Kyeong-Hwa
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.4
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    • pp.124-134
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    • 2011
  • A new dead time compensation scheme that can exactly estimate the dead time and inverter nonlinearity under parameter variations is proposed for a PWM inverter-fed PMSM drive. The proposed scheme uses the fact that the sixth harmonic component in total disturbance estimated under the presence of various uncertainties is mainly caused by the dead time and inverter nonlinearity. The total disturbance due to the parameter variations as well as the dead time and inverter nonlinearity is estimated by the adaptive scheme. The sixth harmonic component is extracted from this total disturbance through harmonic analysis. The obtained sixth harmonic is processed by the PI controller to estimate the disturbance caused by the dead time and inverter nonlinearity in the stationary reference frame. The effectiveness of the proposed scheme is verified. Without requiring an additional hardware, the proposed scheme can effectively compensate the dead time and inverter nonlinearity even under the parameter variations.

Nonlinearity error compensation in heterodyne laser interferometer using Dual-EKF (Dual-EKF를 이용한 헤테로다인 레이저 간섭계의 비선형 오차보정)

  • Lee, Sang-Chul;Lee, Woo-Ram;You, Kwan-Ho
    • Proceedings of the IEEK Conference
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    • 2009.05a
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    • pp.310-312
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    • 2009
  • The heterodyne laser interferometer has been widely used in precise measurement field. However, the accuracy is limited by the nonlinearity error caused from incomplete laser sources and nonideal optical components. In this paper, we propose the Dual-EKF which estimates states and weights simultaneously to improve the resolution of heterodyne laser interferometer. As a proof, we demonstrate the effectiveness of our proposed method through experimental results.

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Ultra-Precision Position Control of Piezoelectric Actuator System Using Hysteresis Compensation (히스테리시스 보상을 이용한 압전구동기의 초정밀 위치제어)

  • 홍성룡;이병룡
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.85-88
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    • 2000
  • In this paper, the ultra precision positioning system for piezoelectric actuator using hysteresis compensation has been developed. Piezoelectric actuators exhibit limited accuracy in tracking control due to their hysteresis nonlinearity. The main purpose of the proposed controller is to compensate the hysteresis nonlinearity of the piezoelectric actuator. The controller is composed of a PD, hysteresis compensation and neural network part in parallel manner, at first, the excellent tracking performance of the neural network controller was verified by experiments and was compared with the classical PD controller.

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Saturation Compensation of a DC Motor System Using Neural Networks

  • Jang, Jun-Oh;Ahn, Ihn-Seok
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.5 no.2
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    • pp.169-174
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    • 2005
  • A neural networks (NN) saturation compensation scheme for DC motor systems is presented. The scheme that leads to stability, command following and disturbance rejection is rigorously proved. On-line weights tuning law, the overall closed loop performance and the boundness of the NN weights are derived and guaranteed based on Lyapunov approach. The simulation and experimental results show that the proposed scheme effectively compensate for saturation nonlinearity in the presence of system uncertainty.

Nonlinearlity Compensation of Heterodyne laser interferometer based on LMS (LMS를 이용한 헤테로다인 레이저 간섭계 비선형성 보정)

  • Jeong, Pil-Joong;Lee, Woo-Ram;You, Kwan-Ho
    • Proceedings of the KIEE Conference
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    • 2007.10a
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    • pp.283-284
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    • 2007
  • In this paper we introduce a compensation of nonlinearity Heterodyne laser interferometer. The Laser Interferometer is used for length measurement in various industries. However, it has nonlinearity error caused by the imperfect optical equipment. This acts as an obstacle in the measurement improvement. We propose an adaptive error compensation using least mean square(LMS) to improve precision.

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Nonlinearity Compensation in the Secondary Path of Active Noise Control Systems Using An Inverse Adaptive Volterra Filtering (역 적응 볼테라 필터링을 이용한 능동 소음 제어 시스템의 2차 경로 비선형 특성 적응 보상)

  • Jeong I.S.;Lee I.H.;Nam S.W.
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.53 no.12
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    • pp.827-833
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    • 2004
  • In active noise control (ANC) systems, the error-reduction performance of the conventional Filtered-X Least Mean Square (FXLMS) algorithm may be affected by nonlinear distortions in the secondary path such as in the power amplifiers, loudspeakers and transducers. In this paper, a nonlinear FXLMS algorithm with high error-reduction performance is proposed to compensate for undesirable nonlinearities in the secondary-path of ANC systems by employing the inverse Volterra filtering approach. In particular, the proposed approach is based on the utilization of the conventional P-th order inverse approach to nonlinearity compensation in the secondary path of ANC systems. Finally, the simulation results showed that the proposed approach yields a better nonlinearity compensation performance for the ANC systems with a nonlinear secondary path than the conventional FXLMS.