The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform

M. Muenchhof - One of the best experts on this subject based on the ideXlab platform.

  • Closed-form minimax time-delay filters for underdamped systems
    Optimal Control Applications & Methods, 2020
    Co-Authors: T. Singh, M. Muenchhof
    Abstract:

    This paper derives closed-form solutions for the parameters of a time-delay filter designed to be robust to uncertainties in frequencies to be cancelled. It is shown that the slope of the Magnitude Plot of the two time-delay filter is zero at the nominal frequency indicating that it is a local maximum. This information is used for deriving the solution of the parameters of the time-delay filter in closed form. Three time-delay filters are also designed which force a zero of the filter to be located at the nominal frequency of the system. Uniform and non-uniform distributions of the penalty over the uncertain regions are permitted in this formulation. The applicability of the proposed technique for the control of multi-mode systems is also illustrated. Copyright © 2006 John Wiley & Sons, Ltd.

  • Closed form minimax time-delay filters for underdamped systems
    Proceedings of the 2004 American Control Conference, 2004
    Co-Authors: T. Singh, M. Muenchhof
    Abstract:

    This paper derives closed form solutions for the parameters of a time-delay filter designed to be robust to uncertainties in frequencies to be cancelled. It is shown that the slope of the Magnitude Plot of the two time-delay filter is zero at the nominal frequency indicating that it is a local maximum. This information is used for deriving the solution of the parameters of the time-delay filter in closed form. Three time-delay filters are also designed which force a zero of the filter to be located at the nominal frequency of the system. The applicability of the proposed technique for the control of multi-mode systems is also illustrated.

T. Singh - One of the best experts on this subject based on the ideXlab platform.

  • Closed-form minimax time-delay filters for underdamped systems
    Optimal Control Applications & Methods, 2020
    Co-Authors: T. Singh, M. Muenchhof
    Abstract:

    This paper derives closed-form solutions for the parameters of a time-delay filter designed to be robust to uncertainties in frequencies to be cancelled. It is shown that the slope of the Magnitude Plot of the two time-delay filter is zero at the nominal frequency indicating that it is a local maximum. This information is used for deriving the solution of the parameters of the time-delay filter in closed form. Three time-delay filters are also designed which force a zero of the filter to be located at the nominal frequency of the system. Uniform and non-uniform distributions of the penalty over the uncertain regions are permitted in this formulation. The applicability of the proposed technique for the control of multi-mode systems is also illustrated. Copyright © 2006 John Wiley & Sons, Ltd.

  • Closed form minimax time-delay filters for underdamped systems
    Proceedings of the 2004 American Control Conference, 2004
    Co-Authors: T. Singh, M. Muenchhof
    Abstract:

    This paper derives closed form solutions for the parameters of a time-delay filter designed to be robust to uncertainties in frequencies to be cancelled. It is shown that the slope of the Magnitude Plot of the two time-delay filter is zero at the nominal frequency indicating that it is a local maximum. This information is used for deriving the solution of the parameters of the time-delay filter in closed form. Three time-delay filters are also designed which force a zero of the filter to be located at the nominal frequency of the system. The applicability of the proposed technique for the control of multi-mode systems is also illustrated.

Omar Aljohani - One of the best experts on this subject based on the ideXlab platform.

  • application of dip to detect power transformers axial displacement and disk space variation using fra polar Plot signature
    IEEE Transactions on Industrial Informatics, 2017
    Co-Authors: Omar Aljohani, A Abusiada
    Abstract:

    While frequency response analysis (FRA) technique has been successfully used to assess the mechanical integrity of active parts within power transformers, it still exhibits some drawbacks including its inability to detect incipient and minor winding deformations and the requirement for an expert to analyze the results. Although several papers have investigated the impact of various faults on the transformer FRA signature, no attempt was made to automate and improve the fault detection accuracy of the current technique. The main contribution of this paper is the presentation of a new approach for the FRA technique through incorporating the Magnitude and phase angle Plots that can be measured using any commercial frequency response analyzer into one polar Plot. Contrary to the current industry practice that only relies on the Magnitude of the measured FRA signature for fault identification and quantification, the proposed polar Plot that comprises more features than the Magnitude Plot will facilitate the use of digital image processing (DIP) techniques to improve the detection accuracy, standardize, and automate the FRA interpretation process. In this regard, three-dimensional models for two three-phase power transformers of different ratings, sizes, and windings structures are modeled using a finite element analysis technique to simulate various levels of axial displacement (AD) and disk space variation (DSV) at different locations of the transformer windings. Impact of minor fault levels on the proposed polar Plot signature is investigated through the application of various DIP techniques. Simulation results are validated through practical measurements on a scaled-down transformer. Results show that the proposed polar Plot along with the DIP technique is able to detect minor fault levels of AD and DSV with high accuracy.

  • Application of digital image processing to detect transformer bushing faults and oil degradation using FRA polar Plot signature
    IEEE Transactions on Dielectrics and Electrical Insulation, 2017
    Co-Authors: Omar Aljohani, Ahmed Abu-siada
    Abstract:

    Frequency Response Analysis (FRA) technique is commonly used to assess the mechanical integrity of power transformer core and windings. A few papers investigating the ability of FRA technique to detect bushing faults and transformer oil degradation can be found in the literatures. However, in all of these papers, only Magnitude of the FRA signature along with visual analysis was used for fault identification and quantification which may lead to inconsistent conclusions for the same FRA signature when interpreted by various personnel. As such, there is an essential need to standardize and automate the FRA interpretation process to improve its reliability and accuracy. This paper is taking a step forward toward this goal through presenting a new FRA interpretation approach by incorporating the Magnitude and phase angle Plots of the measured FRA signature into one polar Plot that comprises more features than the conventional Magnitude Plot currently used for fault diagnosis. Moreover, the proposed polar Plot facilitates the application of digital image processing techniques (DIP) to automate and standardize the whole process. The new proposed technique is assessed through its application to detect minor transformer bushing faults and insulating oil degradations. In this regard, two transformers of different ratings, winding structure and physical dimensions are simulated using 3D finite element analysis to implement various levels of transformer bushing faults and oil degradation. The obtained FRA polar Plots of the two investigated transformers under various bushings and oil health conditions are manipulated using the developed DIP codes to investigate the impact of each fault type / level on the proposed polar Plot signature. Also, Practical measurements are performed to validate simulation results and evaluate the feasibility of the proposed technique. Results show the ability of the proposed technique to automate the detection of minor levels of bushing faults and insulating oil degradation with a high degree of accuracy.

  • Application of Digital Image Processing to Detect Short-Circuit Turns in Power Transformers Using Frequency Response Analysis
    IEEE Transactions on Industrial Informatics, 2016
    Co-Authors: Omar Aljohani, Ahmed Abu-siada
    Abstract:

    Although a frequency response analysis (FRA) technique has been extensively used to detect mechanical deformation within power transformers, interpretation of FRA signature still needs a high level of expertise to identify and quantify faults as there is no FRA interpretation code widely accepted yet. All commercial frequency response analyzers can measure the Magnitude and phase angle of the impedance, admittance, or transfer function of each phase in a wide frequency range; however, only Magnitude is currently used for fault identification and quantification. This paper presents a novel approach for FRA signature interpretation by incorporating the FRA Magnitude and phase Plots into one polar Plot that captures more features of the measured signal than the Magnitude Plot. Digital image processing-based techniques are employed to automate the fault identification and quantification process. To investigate the impact of transformer rating and size on the proposed technique, two transformers of different ratings and physical geometrical dimensions are simulated using 3-D finite-element analysis to emulate transformer real operation. Short-circuit of various fault levels is simulated at various locations within the high-voltage and low-voltage windings of the two transformer models and the obtained FRA polar Plot signature for each case study is analyzed and compared with the healthy signature. Also, practical measurement is conducted to validate the simulation results. Results show that fault level along with fault location can be easily identified using the proposed polar Plot signature along with the developed digital image processing technique.

Ahmed Abu-siada - One of the best experts on this subject based on the ideXlab platform.

  • 3D approach for fault identification within power transformers using frequency response analysis
    IET Science Measurement & Technology, 2019
    Co-Authors: Ahmed Abu-siada, Ibrahim Radwan, Ahmed F. Abdou
    Abstract:

    With the growing pool of aged power transformers, application of the sweep frequency response analysis (SFRA) to assess power transformers' mechanical integrity has been given much attention. One of the research gaps in this field is the lack of reliable and automated techniques to interpret SFRA signatures. Conventional interpretation technique relies on visual inspection and personnel level of expertise, which may lead to inconsistent interpretation for the same signature. Furthermore, current SFRA technique fails in detecting transformer incipient mechanical deformations of low levels. To overcome these limitations, this paper presents a new three-dimensional (3D)-SFRA signature that comprises frequency, Magnitude and phase angle in one Plot. In contrary to the current interpretation practice that relies only on the Magnitude Plot, the proposed 3D signature exhibits more features, which can improve the SFRA identification accuracy. To automate and standardise the fault identification process, a digital image processing code is developed to extract some unique features from the proposed signature. The proposed technique is validated through finite element simulation analysis to detect short-circuit turns, axial displacement and radial deformation of a three-phase 40 MVA transformer and practical feasibility is assessed through its application to detect short-circuit turns of a three-phase 45 MVA transformer.

  • Application of digital image processing to detect transformer bushing faults and oil degradation using FRA polar Plot signature
    IEEE Transactions on Dielectrics and Electrical Insulation, 2017
    Co-Authors: Omar Aljohani, Ahmed Abu-siada
    Abstract:

    Frequency Response Analysis (FRA) technique is commonly used to assess the mechanical integrity of power transformer core and windings. A few papers investigating the ability of FRA technique to detect bushing faults and transformer oil degradation can be found in the literatures. However, in all of these papers, only Magnitude of the FRA signature along with visual analysis was used for fault identification and quantification which may lead to inconsistent conclusions for the same FRA signature when interpreted by various personnel. As such, there is an essential need to standardize and automate the FRA interpretation process to improve its reliability and accuracy. This paper is taking a step forward toward this goal through presenting a new FRA interpretation approach by incorporating the Magnitude and phase angle Plots of the measured FRA signature into one polar Plot that comprises more features than the conventional Magnitude Plot currently used for fault diagnosis. Moreover, the proposed polar Plot facilitates the application of digital image processing techniques (DIP) to automate and standardize the whole process. The new proposed technique is assessed through its application to detect minor transformer bushing faults and insulating oil degradations. In this regard, two transformers of different ratings, winding structure and physical dimensions are simulated using 3D finite element analysis to implement various levels of transformer bushing faults and oil degradation. The obtained FRA polar Plots of the two investigated transformers under various bushings and oil health conditions are manipulated using the developed DIP codes to investigate the impact of each fault type / level on the proposed polar Plot signature. Also, Practical measurements are performed to validate simulation results and evaluate the feasibility of the proposed technique. Results show the ability of the proposed technique to automate the detection of minor levels of bushing faults and insulating oil degradation with a high degree of accuracy.

  • Application of Digital Image Processing to Detect Short-Circuit Turns in Power Transformers Using Frequency Response Analysis
    IEEE Transactions on Industrial Informatics, 2016
    Co-Authors: Omar Aljohani, Ahmed Abu-siada
    Abstract:

    Although a frequency response analysis (FRA) technique has been extensively used to detect mechanical deformation within power transformers, interpretation of FRA signature still needs a high level of expertise to identify and quantify faults as there is no FRA interpretation code widely accepted yet. All commercial frequency response analyzers can measure the Magnitude and phase angle of the impedance, admittance, or transfer function of each phase in a wide frequency range; however, only Magnitude is currently used for fault identification and quantification. This paper presents a novel approach for FRA signature interpretation by incorporating the FRA Magnitude and phase Plots into one polar Plot that captures more features of the measured signal than the Magnitude Plot. Digital image processing-based techniques are employed to automate the fault identification and quantification process. To investigate the impact of transformer rating and size on the proposed technique, two transformers of different ratings and physical geometrical dimensions are simulated using 3-D finite-element analysis to emulate transformer real operation. Short-circuit of various fault levels is simulated at various locations within the high-voltage and low-voltage windings of the two transformer models and the obtained FRA polar Plot signature for each case study is analyzed and compared with the healthy signature. Also, practical measurement is conducted to validate the simulation results. Results show that fault level along with fault location can be easily identified using the proposed polar Plot signature along with the developed digital image processing technique.

Takis Kasparis - One of the best experts on this subject based on the ideXlab platform.

  • Cyclic motion detection for motion based recognition
    Pattern Recognition, 1994
    Co-Authors: Ping-sing Tsai, Katharine Keiter, Mubarak Shah, Takis Kasparis
    Abstract:

    The motion of a walking person is analyzed by examining cycles in the movement. Cycles are detected using autocorrelation and Fourier transform techniques of the smoothed spatio-temporal curvature function of trajectories created by specific points on the object as it performs cyclic motion. A large impulse in the Fourier Magnitude Plot indicates the frequency at which cycles are occurring. Both synthetically generated and real walking sequences are analyzed for cyclic motion. The real sequences are then used in a motion based recognition application in which one complete cycle is stored as a model, and a matching process is performed using one cycle of an input trajectory