Fault-tolerant Filter based on an Evolvable Hardware Technique : A case study

This work addresses the problem of providing fault tolerance to an eighth order low-pass filter, employing the principles of evolvable hardware. The filter under study is implemented through the cascade connection of four biquadratic filters in a field programmable analog device. The reconfiguration process of the filter involves the execution of a genetic algorithm (GA) in an external computer, after a fault detected. To perform the test of the filter, we assume that the method of transient analysis is applied. The GA performance is evaluated by fault simulation, employing a parametric fault model. The fault simulation results show that GA finds solutions that meet the established restrictions and presents relatively short run times.Sociedad Argentina de Informática e Investigación Operativ

Air Coupled Impact Echo Testing of Buried Concrete Pipes

Concrete pipes constitute an integral part of the buried infrastructure, and non-destructive testing (NDT) plays an important role in their maintenance effort. Impact echo (IE) is a well-established NDT technique that is widely used for the investigation of concrete structures. In this technique, the thickness (or resonant) frequency is first measured by inducing (compression) P-wave into the structure using an impact source and recording the elastic wave generated using an accelerometer. From the knowledge of P-wave velocity of the medium, the unknown thickness and subsurface defects are then established. To effectively apply this technique, the transducer should be properly coupled with the surface. However, this often becomes a difficult task due to the poor surface quality of concrete. Alternatively, instead of capturing the elastic wave with a contact-based transducer the leaky acoustic wave that accompany the elastic wave is captured with a microphone and the thickness frequency is calculated. This non-contact variation of IE is called the air-coupled IE (ACIE) and it has been shown to be effective for testing plate like concrete structures (e.g., pavements and bride decks). In this dissertation, the feasibility of ACIE for the NDT of buried concrete pipe is investigated. The investigations are conducted in two stages. First, numerical modelling is conducted to test the effectiveness in pipes and then experimental validations are conducted. A structural-acoustic coupled finite element model is created using the COMSOL Multiphysics software, and the propagation of elastic and acoustic waves in a fluid-filled concrete pipe is simulated for standalone and buried pipe. The effectiveness of ACIE is studied when a pipe is surrounded by soil. Two types of soil surrounding the pipe studied to learn more about the quality of the data that might be anticipated from ACIE technique inside the pipe. Using these models, various aspects of ACIE are studied and its performance against the conventional IE is compared. Following the numerical verifications, two laboratory tests setups are constructed with a standalone and buried reinforced concrete pipes (RCP) and ACIE is demonstrated using them. The (unknown) wall thickness is calculated in each case and the results are compared against the conventional contact-based technique. While the presence of soil caused energy losses which affected the amplitude of acoustic wave, it was enough to be detected with good signal to noise ratio. Several enhancements to improve the performance of this technique are studied. For instance, a way to improve the signal-to noise ratio of the acoustic signal is investigated using noise suppressers. For rapid implementation of technique and fast data gathering a semi-automated ACIE setup is also developed. Finally, the ability of the technique to detect several commonly occurring problems in a concrete pipe is investigated. In summary, ACIE technique shows promising results for buried pipe testing

Geração automática de padrões para teste estrutural de circuitos analógicos

Os vultuosos incrementos de complexidade e de funcionalidade que os circuitos eletrônicos atuais apresentam em relação aos seus antecessores deram-se através da miniaturização dos componentes. Essa redução das dimensões incrementou os desafios impostos pelas etapas de projeto e fabricação, aumentando, por consequência, a importância da etapa de teste. Ao mesmo tempo em que os testes precisam ter boa qualidade, apresentando elevadas coberturas de falhas e baixa yield loss, o custo também é um fator primordial a ser levado em consideração. A metodologia de teste baseado em especificação se mostra como uma opção mais cara que a de teste baseado em defeitos. Entretanto, o ônus da opção mais barata está no possível decréscimo da qualidade do teste e da maior dificuldade na determinação das melhores configurações de testes a serem utilizadas. Nesse contexto, nota-se que os circuitos analógicos estão atrás dos digitais quando o assunto é a determinação dessas configurações de teste, pois, enquanto os circuitos digitais possuem, já há bastante tempo, ferramentas para determinação de vetores de teste otimizados, essa determinação, para testes analógicos, ainda não é totalmente automatizada (KABISATPATHY; BARUA; SINHA, 2005). De posse dessas informações, o presente trabalho consiste no desenvolvimento de uma ferramenta que vise amenizar essa discrepância entre circuitos analógicos e digitais. A ferramenta foi desenvolvida em MATLAB de modo a automatizar simulações SPICE de circuitos e, por fim, também de forma automatizada, analisar todos os resultados e chegar na conclusão de quais configurações de testes correspondem ao conjunto mais otimizado para aquele circuito dentro das condições simuladas. Nessa ferramenta, deve-se entrar com a descrição SPICE do circuito e do modelo de falhas que se deseja adotar, sendo esse composto por falhas paramétricas e catastróficas, cujas respectivas impedâncias e desvios são escolhidas pelo usuário. A ferramenta desconsidera que uma falha possa mascarar a outra e, por isso, cria uma descrição SPICE do circuito para cada uma das falhas de maneira individual. Através da simulação de todos os circuitos com falha e do circuito fault free, juntamente com a posterior comparação dos resultados, a ferramenta cria o dicionário de falhas. Esse dicionário contém as informações de quais falhas podem ser detectadas em cada um dos nós e para cada um dos possíveis sinais de entrada. Com ele, a ferramenta determina quais são as coberturas de falhas nos nós e qual o melhor conjunto testes. As funcionalidades da ferramenta foram avaliadas através de estudos de caso que consistiram na determinação de configurações de teste otimizadas para um amplificador totalmente diferencial de dois estágios e um filtro passa-baixas de segunda ordem composto pela conexão de dois estágios de primeira ordem em cascata. No primeiro caso, o amplificador apresentou cobertura de falhas máxima de 63,88%, porém com auxílio de funcionalidades da ferramenta, observou-se, que utilizando um nó interno do circuito como nó de teste, essa cobertura de falhas é aumentada para 73,22%. No segundo caso, do filtro passa-baixas de segunda ordem, a cobertura de falhas alcançada foi de 87,15%. Subsequentemente, foram investigadas as possibilidades de execução de um teste transiente adicional e da execução de testes nos amplificadores do circuito em malha aberta, ambas as análises buscavam o aumento da cobertura de falhas.The great increases in complexity and functionality that modern electronic circuits present in relation to their past generations happened through the miniaturization of their components. This dimension reduction has increased the challenges posed by project and fabrication phases, increasing therefore, the importance of the test phase. While the tests must be of good quality, presenting high fault coverage and low yield loss, the cost must also be a prime factor to be considered. The methodology of specification-based test presents itself as a more expensive option than the defect-based test. However, the burden of the cheapest option is the possible decrease of test quality and the greater difficulty in determining the best test configuration to be used. In this context, it is noted that determination of test configurations for analog circuits, is a step behind of the digital counterparts. This is because, while for digital circuits there are tools for optimized test vector determination, this determination, for analog tests, is still not totally automated (KABISATPATHY; BARUA; SINHA, 2005). Given this information, this work consists in the development of a tool that aims to soften this discrepancy between analog and digital circuits. A tool was developed in MATLAB in a way to automate SPICE circuit simulations and, finally, also in automated form, analyze the results and arrive at a conclusion about what test configurations correspond to the best optimized set for that circuit within the simulated conditions. In this tool, one must enter the SPICE circuit description and the fault model that one wishes to adopt, being the model composed of parametric and catastrophic faults, and whose respective impedances and deviations are chosen by the user. The tool disregards that one fault might mask the other and, therefore, creates an individual fault SPICE circuit description for each one. Through the simulation of all faulty circuits and the fault free circuit, along with a posterior result comparison, the tool creates the fault dictionary. This dictionary contains the information of which faults may be detected in each of the nodes (used as test point) and for each of the possible input signals. Finally, with the dictionary, the tool determines the fault coverage in each node and which are the best tests sets. The functionalities of the tool were evaluated through case studies that consisted in the determination of the optimized test configuration for a two-stage fully differential amplifier and a second order low pass filter. In the first case, the amplifier presented an initial fault coverage of 63,88%. However, with the assistance of the tool, it was observed that, using an internal node of the circuit as test node, this fault coverage increases to 73,22%. In the second case study (second order low pass filter), the fault coverage reached 87,15%. Subsequently, the execution of an additional transient test and the execution of tests in the amplifiers with open loop circuit were investigated; both the analysis searched for an increase in fault coverage. The transient test resulted in the detection of a single additional fault, however the test of the amplifiers operating in open lop resulted in a significant increase in fault coverage, reaching 92,36%

Radar Technology

In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design

Recent Advances in Signal Processing

The signal processing task is a very critical issue in the majority of new technological inventions and challenges in a variety of applications in both science and engineering fields. Classical signal processing techniques have largely worked with mathematical models that are linear, local, stationary, and Gaussian. They have always favored closed-form tractability over real-world accuracy. These constraints were imposed by the lack of powerful computing tools. During the last few decades, signal processing theories, developments, and applications have matured rapidly and now include tools from many areas of mathematics, computer science, physics, and engineering. This book is targeted primarily toward both students and researchers who want to be exposed to a wide variety of signal processing techniques and algorithms. It includes 27 chapters that can be categorized into five different areas depending on the application at hand. These five categories are ordered to address image processing, speech processing, communication systems, time-series analysis, and educational packages respectively. The book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity