A wireless sensor network platform for structural health monitoring: enabling accurate and synchronized measurements through COTS+custom-based design

Structural health monitoring has long been identified as a prominent application of Wireless Sensor Networks (WSNs), as traditional wired-based solutions present some inherent limitations such as installation/maintenance cost, scalability and visual impact. Nevertheless, there is a lack of ready-to-use and off-the-shelf WSN technologies that are able to fulfill some most demanding requirements of these applications, which can span from critical physical infrastructures (e.g. bridges, tunnels, mines, energy grid) to historical buildings or even industrial machinery and vehicles. Low-power and low-cost yet extremely sensitive and accurate accelerometer and signal acquisition hardware and stringent time synchronization of all sensors data are just examples of the requirements imposed by most of these applications. This paper presents a prototype system for health monitoring of civil engineering structures that has been jointly conceived by a team of civil, and electrical and computer engineers. It merges the benefits of standard and off-the-shelf (COTS) hardware and communication technologies with a minimum set of custom-designed signal acquisition hardware that is mandatory to fulfill all application requirements.

Overcoming the objectification of western classical music with the concept of music as a process

Dissertation to obtain the degree of Master in Music - Artistic Interpretation

A sensor classification strategy for robotic manipulators

In practice the robotic manipulators present some degree of unwanted vibrations. The advent of lightweight arm manipulators, mainly in the aerospace industry, where weight is an important issue, leads to the problem of intense vibrations. On the other hand, robots interacting with the environment often generate impacts that propagate through the mechanical structure and produce also vibrations. In order to analyze these phenomena a robot signal acquisition system was developed. The manipulator motion produces vibrations, either from the structural modes or from endeffector impacts. The instrumentation system acquires signals from several sensors that capture the joint positions, mass accelerations, forces and moments, and electrical currents in the motors. Afterwards, an analysis package, running off-line, reads the data recorded by the acquisition system and extracts the signal characteristics. Due to the multiplicity of sensors, the data obtained can be redundant because the same type of information may be seen by two or more sensors. Because of the price of the sensors, this aspect can be considered in order to reduce the cost of the system. On the other hand, the placement of the sensors is an important issue in order to obtain the suitable signals of the vibration phenomenon. Moreover, the study of these issues can help in the design optimization of the acquisition system. In this line of thought a sensor classification scheme is presented. Several authors have addressed the subject of the sensor classification scheme. White (White, 1987) presents a flexible and comprehensive categorizing scheme that is useful for describing and comparing sensors. The author organizes the sensors according to several aspects: measurands, technological aspects, detection means, conversion phenomena, sensor materials and fields of application. Michahelles and Schiele (Michahelles & Schiele, 2003) systematize the use of sensor technology. They identified several dimensions of sensing that represent the sensing goals for physical interaction. A conceptual framework is introduced that allows categorizing existing sensors and evaluates their utility in various applications. This framework not only guides application designers for choosing meaningful sensor subsets, but also can inspire new systems and leads to the evaluation of existing applications. Today’s technology offers a wide variety of sensors. In order to use all the data from the diversity of sensors a framework of integration is needed. Sensor fusion, fuzzy logic, and neural networks are often mentioned when dealing with problem of combing information from several sensors to get a more general picture of a given situation. The study of data fusion has been receiving considerable attention (Esteban et al., 2005; Luo & Kay, 1990). A survey of the state of the art in sensor fusion for robotics can be found in (Hackett & Shah, 1990). Henderson and Shilcrat (Henderson & Shilcrat, 1984) introduced the concept of logic sensor that defines an abstract specification of the sensors to integrate in a multisensor system. The recent developments of micro electro mechanical sensors (MEMS) with unwired communication capabilities allow a sensor network with interesting capacity. This technology was applied in several applications (Arampatzis & Manesis, 2005), including robotics. Cheekiralla and Engels (Cheekiralla & Engels, 2005) propose a classification of the unwired sensor networks according to its functionalities and properties. This paper presents a development of a sensor classification scheme based on the frequency spectrum of the signals and on a statistical metrics. Bearing these ideas in mind, this paper is organized as follows. Section 2 describes briefly the robotic system enhanced with the instrumentation setup. Section 3 presents the experimental results. Finally, section 4 draws the main conclusions and points out future work.

Single-objective spreading algorithm

This paper addresses the problem of finding several different solutions with the same optimum performance in single objective real-world engineering problems. In this paper a parallel robot design is proposed. Thereby, this paper presents a genetic algorithm to optimize uni-objective problems with an infinite number of optimal solutions. The algorithm uses the maximin concept and ε-dominance to promote diversity over the admissible space. The performance of the proposed algorithm is analyzed with three well-known test functions and a function obtained from practical real-world engineering optimization problems. A spreading analysis is performed showing that the solutions drawn by the algorithm are well dispersed.

Automated design of microwave discrete tuning differential capacitance circuits in Si-integrated technologies

A genetic algorithm used to design radio-frequency binary-weighted differential switched capacitor arrays (RFDSCAs) is presented in this article. The algorithm provides a set of circuits all having the same maximum performance. This article also describes the design, implementation, and measurements results of a 0.25 lm BiCMOS 3-bit RFDSCA. The experimental results show that the circuit presents the expected performance up to 40 GHz. The similarity between the evolutionary solutions, circuit simulations, and measured results indicates that the genetic synthesis method is a very useful tool for designing optimum performance RFDSCAs.

From design-for-test to design-for-debug-and-test: analysis of requirements and limitations for 1149.1

The increasing complexity of VLSI circuits and the reduced accessibility of modern packaging and mounting technologies restrict the usefulness of conventional in-circuit debugging tools, such as in-circuit emulators for microprocessors and microcontrollers. However, this same trend enables the development of more complex products, which in turn require more powerful debugging tools. These conflicting demands could be met if the standard scan test infrastructures now common in most complex components were able to match the debugging requirements of design verification and prototype validation. This paper analyses the main debug requirements in the design of microprocessor-based applications and the feasibility of their implementation using the mandatory, optional and additional operating modes of the standard IEEE 1149.1 test infrastructure.

Design state exploration applied to the development of a remote lab for projectile launch experiments

This paper describes the application of Design State Exploration techniques in the development of a remote lab for projectile motion experiments. The application was enabled by the existence of two independent teams: one composed of a series of internships that started first and another with two grantees that started a few months later. The paper presents evidence on how this approach provided gains in the development process conducted by the second team that benefited from design state exploration studies performed by the first team. This particular aspect is highlighted in relation to the work already presented in the 10th Remote Engineering and Virtual Instrumentation (REV) conference.

Using SysML in systems design

System of systems involves several secondary systems working together with its creation gathering the knowledge of several distinct disciplines and teams, each one with their own background and methods, leading to a difficult communication between them. SysML, a language originated from UML, enables that communication, without background interference, with the use of a rich notation for systems design. This paper analyzes its use through the experience gained in the design of a chemical system with SysML.

Addressing software impact in the design of remote laboratories

Remote Laboratories or WebLabs constitute a first-order didactic resource in engineering faculties. However, in many cases, they lack a proper software design, both in the client and server side, which degrades their quality and academic usefulness. This paper presents the main characteristics of a Remote Laboratory, analyzes the software technologies to implement the client and server sides in a WebLab, and correlates these technologies with the characteristics to facilitate the selection of a technology to implement a WebLab. The results obtained suggest the adoption of a Service Oriented Laboratory Architecture-based approach for the design of future Remote Laboratories so that client-agnostic Remote Laboratories and Remote Laboratory composition are enabled. The experience with the real Remote Laboratory, WebLab-Deusto, is also presented.

Particle swarm design of digital circuits

Swarm Intelligence (SI) is the property of a system whereby the collective behaviors of (unsophisticated) agents interacting locally with their environment cause coherent functional global patterns to emerge. Particle swarm optimization (PSO) is a form of SI, and a population-based search algorithm that is initialized with a population of random solutions, called particles. These particles are flying through hyperspace and have two essential reasoning capabilities: their memory of their own best position and knowledge of the swarm's best position. In a PSO scheme each particle flies through the search space with a velocity that is adjusted dynamically according with its historical behavior. Therefore, the particles have a tendency to fly towards the best search area along the search process. This work proposes a PSO based algorithm for logic circuit synthesis. The results show the statistical characteristics of this algorithm with respect to number of generations required to achieve the solutions. It is also presented a comparison with other two Evolutionary Algorithms, namely Genetic and Memetic Algorithms.

Automated synthesis procedure of RF discrete tuning differential capacitance circuits

The paper presents a RFDSCA automated synthesis procedure. This algorithm determines several RFDSCA circuits from the top-level system specifications all with the same maximum performance. The genetic synthesis tool optimizes a fitness function proportional to the RFDSCA quality factor and uses the epsiv-concept and maximin sorting scheme to achieve a set of solutions well distributed along a non-dominated front. To confirm the results of the algorithm, three RFDSCAs were simulated in SpectreRF and one of them was implemented and tested. The design used a 0.25 mum BiCMOS process. All the results (synthesized, simulated and measured) are very close, which indicate that the genetic synthesis method is a very useful tool to design optimum performance RFDSCAs.

Estudo de atirantamentos ancorados no plano perpendicular às fachadas de Alvenaria. Análise de proposta de dimensionamento

O conceito de atirantamento surgiu no contexto de promover a interação global dos edifícios, nomeadamente, estabelecer as referidas ligações, de modo a prevenir o derrubamento para o exterior das paredes de fachada, perante a ocorrência de ação sísmica ou assentamento das fundações. Neste sentido, o presente trabalho tem como objetivo, estudar o comportamento dos atirantamentos ancorados no plano perpendicular das fachadas, quando solicitados à tração. No entanto, como as alvenarias são elementos heterogéneos, houve necessidade de desarticular os atirantamentos e estudar cada uma das partes que o compõe: tirantes injetados em alvenarias e sistemas de ancoragem. Em primeiro lugar, foi elaborado um estudo preliminar sobre tirantes injetados em alvenarias, o qual incidiu no seu dimensionamento, na análise de sensibilidade, apresentação de um caso de estudo e comparação de resultados. Numa segunda fase fez-se uma revisão bibliográfica dos tipos de Sistemas de Ancoragens mais comuns, onde foram mencionados alguns aspetos, nomeadamente a importância, o objetivo e condições da sua aplicação. Por último, associaram-se as duas componentes e foram estudados os Atirantamentos. Fezse um estudo da sua utilização e do seu interesse de aplicação. Foi também analisada uma forma de metodologia de dimensionamento, quando inseridos em alvenarias de tijolo e pedra. Finalizado este estudo foram traçadas as conclusões e sugeridas perspetivas futuras.

Aplicação de metodologias Lean ao fabrico de elevadores

Num mercado cada vez mais competitivo, torna-se fundamental para as empresas produzirem mais com menos recursos, aumentando a eficiência interna, através da otimização dos seus processos. Neste contexto aparece o Lean Manufacturing, metodologia que tem como objetivo criar valor para os stakeholders, através da eliminação de desperdício na cadeia de valor. Este projeto descreve a análise e a formulação de soluções do processo de produção de um Módulo de Serviço, produto que faz parte do sistema elétrico de um elevador. Para análise do problema utilizamos técnicas e ferramentas lean, tais como, o value stream mapping (VSM), o diagrama de processo e o diagrama de spaghetti. Para formulação do problema usamos o value stream design (VSD), a metodologia 5S, o sistema Kanban e a criação de fluxo contínuo, através do conceito takt time, do sistema Pull, da definição do processo pacemaker, da programação nivelada (Heijunka), do conceito pitch time e da caixa de nivelamento (Heijunka Box). Com este projeto pretendemos demonstrar que a implementação de um fluxo unitário de peças através da filosofia Lean Manufacturing, acrescenta qualidade ao produto, cria flexibilidade, aumenta a produtividade, liberta áreas de produção, aumenta a segurança, reduz o custo com o stock e aumenta a motivação organizacional.

Aparato para experimentação remota do lançamento de projéteis

Num sistema de ensino cada vez mais exigente, a experimentação assume um papel fundamental na aquisição e validação do conhecimento. No ensino da Física, a necessidade de compreender a influência do meio num dado conceito teórico leva a que a experimentação tenha um carácter obrigatório. Neste contexto, surgem três cenários capazes de suportar a aprendizagem dos conceitos teóricos adquiridos. A simulação que faz uso da velocidade e capacidades de cálculo do computador para obter o resultado de uma experiência, a experimentação tradicional em laboratório, na qual o aluno executa, presencialmente, a sua experiência e por último a experimentação remota, que permite a execução de uma experiência real sem a presença física do aluno. Esta dissertação apresenta o projeto de um aparato para experimentação remota do “Lançamento de projéteis”. De forma a providenciar um meio de ensino de Física mais flexível, o aparato desenvolvido permite, aos alunos, a determinação da aceleração da gravidade e o estudo da dependência do movimento de um projétil num conjunto de parâmetros. Este aparato, operado remotamente, é acedido via web, onde primeiramente é reservado um intervalo de tempo. O conjunto de parâmetros (“Bola”, “Altura de lançamento” e “Ângulo de lançamento”) da máquina permite suportar vários cenários de ensino da Física, com diferentes complexidades.

Discretization of complex-order algorithms for control applications

In this article we describe several methods for the discretization of the differintegral operator sa, where α = u + jv is a complex value. The concept of the conjugated-order differintegral is also introduced, which enables the use of complex-order differintegrals while still producing real-valued time responses and transfer functions. The performance of the resulting approximations is analysed in both the time and frequency domains. Several results are presented that demonstrate its utility in control system design.