Enhanced Interpolated-DFT for Synchrophasor Estimation in FPGAs: Theory, Implementation, and Validation of a PMU Prototype

The literature on the subject of synchrophasor estimation (SE) algorithms has discussed the use of interpolated discrete Fourier transform (IpDFT) as an approach capable to find an optimal tradeoff between SE accuracy, response time, and computational complexity. Within this category of algorithms, this paper proposes three contributions: 1) the formulation of an enhanced-IpDFT (e-IpDFT) algorithm that iteratively compensates the effects of the spectral interference produced by the negative image of the main spectrum tone; 2) the assessment of the influence of the e-IpDFT parameters on the SE accuracy; and 3) the discussion of the deployment of IpDFT-based SE algorithms into field programmable gate arrays, with particular reference to the compensation of the error introduced by the free-running clock of A/D converters with respect to the global positioning system (GPS) time reference. The paper finally presents the experimental validation of the proposed approach where the e-IpDFT performances are compared with those of a classical IpDFT approach and to the accuracy requirements of both P and M-class phasor measurement units defined in the IEEE Std. C37.118-2011

Robust Position-based Visual Servoing of Industrial Robots

Recently, the researchers have tried to use dynamic pose correction methods to improve the accuracy of industrial robots. The application of dynamic path tracking aims at adjusting the end-effector’s pose by using a photogrammetry sensor and eye-to-hand PBVS scheme. In this study, the research aims to enhance the accuracy of industrial robot by designing a chattering-free digital sliding mode controller integrated with a novel adaptive robust Kalman filter (ARKF) validated on Puma 560 model on simulation. This study includes Gaussian noise generation, pose estimation, design of adaptive robust Kalman filter, and design of chattering-free sliding mode controller. The designed control strategy has been validated and compared with other control strategies in Matlab 2018a Simulink on a 64bits PC computer. The main contributions of the research work are summarized as follows. First, the noise removal in the pose estimation is carried out by the novel ARKF. The proposed ARKF deals with experimental noise generated from photogrammetry observation sensor C-track 780. It exploits the advantages of adaptive estimation method for states noise covariance (Q), least square identification for measurement noise covariance (R) and a robust mechanism for state variables error covariance (P). The Gaussian noise generation is based on the collected data from the C-track when the robot is in a stationary status. A novel method for estimating covariance matrix R considering both effects of the velocity and pose is suggested. Next, a robust PBVS approach for industrial robots based on fast discrete sliding mode controller (FDSMC) and ARKF is proposed. The FDSMC takes advantage of a nonlinear reaching law which results in faster and more accurate trajectory tracking compared to standard DSMC. Substituting the switching function with a continuous nonlinear reaching law leads to a continuous output and thus eliminating the chattering. Additionally, the sliding surface dynamics is considered to be a nonlinear one, which results in increasing the convergence speed and accuracy. Finally, the analysis techniques related to various types of sliding mode controller have been used for comparison. Also, the kinematic and dynamic models with revolutionary joints for Puma 560 are built for simulation validation. Based on the computed indicators results, it is proven that after tuning the parameters of designed controller, the chattering-free FDSMC integrated with ARKF can essentially reduce the effect of uncertainties on robot dynamic model and improve the tracking accuracy of the 6 degree-of-freedom (DOF) robot

Sound field synthesis for line source array applications in large-scale sound reinforcement

The thesis deals with optimized large-scale sound reinforcement using line source arrays. This is treated as a sound field synthesis problem. The synthesis of a virtual source via the line source array allows for audience adapted wavefront shaping. For practical array designs and setups this is affected by the deployed loudspeakers and their arrangement, its electronic control and spatial aliasing occurrence. The influence of these parameters is discussed with array signal processing revisiting the Wavefront Sculpture Technology and proposing Wave Field Synthesis as a suitable control method.Die Arbeit beschäftigt sich mit optimaler Beschallung großer Auditorien mit Line Source Arrays. Das Problem wird mit Schallfeldsynthese beschrieben. Die Synthese einer virtuellen Quelle mit einem Line Source Array ermöglicht eine für das Auditorium angepasste Wellenfront. In der Praxis wird dies beeinflusst von den verwendeten Lautsprechern, ihrer Anordnung, ihrer Ansteuerung und räumlichem Aliasing. Der Einfluss der Parameter wird mit Array-Signalverarbeitung diskutiert, wofür Wavefront Sculpture Technology aufgegriffen und Wellenfeldsynthese als Ansteuerungsmethode vorgeschlagen wird

DFT-based Synchrophasor Estimation Algorithms and their Integration in Advanced Phasor Measurement Units for the Real-time Monitoring of Active Distribution Networks

The increasing penetration of Distributed Energy Resources (DERs) at the low and medium-voltage levels is determining major changes in the operational procedures of distribution networks (DNs) that are evolving from passive to active power grids. Such evolution is causing non-negligible problems to DN operators (DNOs) and calls for advanced monitoring infrastructures composed by distributed sensing devices capable of monitoring voltage and current variations in real-time. In this respect, Phasor Measurement Units (PMUs) definitely represent one of the most promising technologies. Their higher accuracy and reporting rates compared to standard monitoring devices, together with the possibility of reporting time-tagged measurements of voltage and current phasors, enable the possibility to obtain frequent and accurate snapshots of the status of the monitored grid. Nevertheless, the applicability of such technology to DNs has not been demonstrated yet since PMUs where originally conceived for transmission network applications. Within this context, this thesis first discusses and derives the requirements for PMUs expected to operate at power distribution level. This study is carried out by analyzing typical operating conditions of Active Distribution Networks (ADNs). Then, based on these considerations, an advanced synchrophasor estimation algorithm capable of matching the accuracy requirements of ADNs is formulated. The algorithm, called iterative-interpolated DFT (i-IpDFT) improves the performances of the Interpolated-DFT (IpDFT) method by iteratively compensating the effects of the spectral interference produced by the negative image of the spectrum and at the same time allows to reduce the window length up to two periods of a signal at the nominal frequency of the power system. In order to demonstrate the low computational complexity of such an approach, the developed algorithm has been subsequently optimized to be deployed into a dedicated FPGA-based PMU prototype. The influence of the PMU hardware components and particularly the effects of the stability and reliability of the adopted UTC-time synchronization technology have been verified. The PMU prototype has been metrologically characterized with respect to the previously defined operating conditions of ADNs using a dedicated PMU calibrator developed in collaboration with the Swiss Federal Institute of Metrology (METAS). The experimental validation has verified the PMU compliance with the class-P requirements defined in the IEEE Std. C37.118 and with most of the accuracy requirements defined for class-M PMUs with the exception of out of band interference tests

Recent Advances and Future Trends in Nanophotonics

Nanophotonics has emerged as a multidisciplinary frontier of science and engineering. Due to its high potential to contribute to breakthroughs in many areas of technology, nanophotonics is capturing the interest of many researchers from different fields. This Special Issue of Applied Sciences on “Recent advances and future trends in nanophotonics” aims to give an overview on the latest developments in nanophotonics and its roles in different application domains. Topics of discussion include, but are not limited to, the exploration of new directions of nanophotonic science and technology that enable technological breakthroughs in high-impact areas mainly regarding diffraction elements, detection, imaging, spectroscopy, optical communications, and computing

Sonar ultrassónico para cegos com sonificação de obstáculos

In this master’s thesis it is intended to develop a portable device that can be used by people with visual impairment in the echolocation of obstacles. This device must be capable of transmitting and detecting ultrasound signals to work as a sonar and still allow its operation as a parametric speaker capable of performing the sonification of obstacles. To do this, it was necessary to develop a Sigma-Delta ADC in FPGA that allows a high density in the independent acquisition of a large number of channels in a small device. Tests performed with the developed Sigma-Delta ADC revealed low distortion and good signal-to-noise ratio, comparable to same type ADCs available on the market. The path for the construction of the device is, then, open.Nesta tese de mestrado pretende-se desenvolver um dispositivo portátil que possa ser usado por pessoas com deficiência visual na ecolocalização de obstáculos. Este dispositivo deverá ser dotado de capacidade de emissão e deteção de ultrassons para funcionar como um sonar e permitir ainda o seu funcionamento como altifalante paramétrico capaz de realizar a sonificação dos obstáculos. Para tal, foi necessário desenvolver uma ADC Sigma-Delta em FPGA que permita uma alta densidade na aquisição independente de um grande número de canais num dispositivo de pequenas dimensões. Os testes realizados com a ADC Sigma-Delta revelaram uma baixa distorção e uma boa relação sinal ruı́do, comparáveis às ADCs do mesmo tipo existentes no mercado. Está assim preparado o caminho para a construção do dispositivo.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest

Novel low cost synchronisation network for spread spectrum systems

Spread Spectrum systems are found in many flavours, used in many applications and have existed since the early days of radio communications. The properties of spread spectrum do however place restrictions on the design, and often make the implementation expensive and complex. When using spread spectrum to provide a basic communications infrastructure, many factors need to be considered. These include supplying the appropriate technology at the right cost. To achieve this a trade-off against performance is often required. One of the more difficult aspects of Spread Spectrum design is the synchronisation of the spreading waveform. The primary characteristic of pseudonoise sequence synchronisation is the need for two levels of synchronisation namely acquisition (course synchronisation) and tracking (fine synchronisation). In these networks (the term network is used to describe a circuit or system throughout the thesis.) a decision is required to switch between the two synchronisation modes. The two layer structure of the typical pseudonoise sequence synchronisation network can increase the overall cost of spread spectrum systems. The objective of the research was therefore to find solutions to reduce the overall cost and complexity of the synchronisation network. The synchronisation structure should perform acquisition and tracking in a single structure, and thereby be low cost. To achieve the primary objective of this dissertation a. mixture of theory, simulations and practical implementation was used. The basis of the investigation was a time-variant spectral evaluation of pseudonoise sequences. It is shown that by multiplying a differentiated pseudonoise sequence with another pseudonoise sequence, useful information is obtained that can form the basis of a synchronisation network

The development of a nanoscale Coulter counter for rapid genetic sequence recognition

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 195-205).The goal of this thesis is the development of a nanoscale Coulter counter for the direct electrical detection of specific genetic sequences of deoxyribonucleic acid (DNA); the general approach used to accomplish sequence recognition is a refinement of the resistive pulse technique. Commercial Coulter counters fabricated with sub-micrometer apertures can size particles with roughly twenty nanometers of resolution. The characterization of DNA, which is more than an order of magnitude smaller than this resolution limit, requires the development of a detection system with a two nanometer limiting aperture. To help develop the techniques and instrumentation explored in this thesis, the biological toxin, alpha hemolysin, was implemented as "prototype" limiting aperture. With the practical knowledge gained from using a toxin channel, a general model for the nanopore as a low-noise sensor was developed. With this model, two broad goals were achieved. The first achievement was the development of novel genetic recognition strategies that exploit the properties of the nanopore within the limitations imposed by DNA structure and existing channel geometries. The second achievement was the design and prototyping of novel interface picoammeter for the measurement of the current fluctuations associated with DNA translocation through a nanopore. Although the instrumentation and methods developed in this thesis are limited to genetic sequence recognition, the hope is that elements of this work will be integrated with the development of silicon nanopores to achieve rapid de novo DNA sequencing in the future.by Timothy Allman Denison.Ph.D