Supporting real-time distributed computer-controlled systems with multi-hop P-NET networks

Fieldbus communication networks aim to interconnect sensors, actuators and controllers within process control applications. Therefore, they constitute the foundation upon which real-time distributed computer-controlled systems can be implemented. P-NET is a fieldbus communication standard, which uses a virtual token-passing medium-access-control mechanism. In this paper pre-run-time schedulability conditions for supporting real-time traffic with P-NET networks are established. Essentially, formulae to evaluate the upper bound of the end-to-end communication delay in P-NET messages are provided. Using this upper bound, a feasibility test is then provided to check the timing requirements for accessing remote process variables. This paper also shows how P-NET network segmentation can significantly reduce the end-to-end communication delays for messages with stringent timing requirements.

Distributed computing for the factory-floor: a real-time approach using WorldFIP networks

Field communication systems (fieldbuses) are widely used as the communication support for distributed computer-controlled systems (DCCS) within all sort of process control and manufacturing applications. There are several advantages in the use of fieldbuses as a replacement for the traditional point-to-point links between sensors/actuators and computer-based control systems, within which the most relevant is the decentralisation and distribution of the processing power over the field. A widely used fieldbus is the WorldFIP, which is normalised as European standard EN 50170. Using WorldFIP to support DCCS, an important issue is “how to guarantee the timing requirements of the real-time traffic?” WorldFIP has very interesting mechanisms to schedule data transfers, since it explicitly distinguishes periodic and aperiodic traffic. In this paper, we describe how WorldFIP handles these two types of traffic, and more importantly, we provide a comprehensive analysis on how to guarantee the timing requirements of the real-time traffic.

Aplicação de redes neuronais artificiais à deteção e isolamento de falhas em processos industriais

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Layered smart grid architecture approach and field tests by ZigBee technology

This paper presents a layered Smart Grid architecture enhancing security and reliability, having the ability to act in order to maintain and correct infrastructure components without affecting the client service. The architecture presented is based in the core of well design software engineering, standing upon standards developed over the years. The layered Smart Grid offers a base tool to ease new standards and energy policies implementation. The ZigBee technology implementation test methodology for the Smart Grid is presented, and provides field tests using ZigBee technology to control the new Smart Grid architecture approach. (C) 2014 Elsevier Ltd. All rights reserved.

Demux devices based on A-SiC:H

In this paper we present results about the functioning of a multilayered a-SiC:H heterostructure as a device for wavelength-division demultiplexing of optical signals. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photogenerated carriers. Band gap engineering was used to adjust the photogeneration and recombination rates profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption and carrier collection in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. This photocurrent is used as an input for a demux algorithm based on the voltage controlled sensitivity of the device. The device functioning is explained with results obtained by numerical simulation of the device, which permit an insight to the internal electric configuration of the double heterojunction.These results address the explanation of the device functioning in the frequency domain to a wavelength tunable photocapacitance due to the accumulation of space charge localized at the internal junction. The existence of a direct relation between the experimentally observed capacitive effects of the double diode and the quality of the semiconductor materials used to form the internal junction is highlighted.

Autonomous guided vehicles applied to industrial engineering and management studies

This article presents a framework to an Industrial Engineering and Management Science course from School of Management and Industrial Studies using Autonomous Ground Vehicles (AGV) to supply materials to a production line as an experimental setup for the students to acquire knowledge in the production robotics area. The students must be capable to understand and put into good use several concepts that will be of utmost importance in their professional life such as critical decisions regarding the study, development and implementation of a production line. The main focus is a production line using AGVs, where the students are required to address several topics such as: sensors actuators, controllers and an high level management and optimization software. The presented framework brings to the robotics teaching community methodologies that allow students from different backgrounds, that normally don’t experiment with the robotics concepts in practice due to the big gap between theory and practice, to go straight to ”making” robotics. Our aim was to suppress the minimum start point level thus allowing any student to fully experience robotics with little background knowledge.

In situ evaluation of single-cell lysis by cytosol extraction observation through fluorescence decay and dielectrophoretic trapping time

We present a new method for lysis of single cells in continuous flow, where cells are sequentially trapped, lysed and released in an automatic process. Using optimized frequencies, dielectrophoretic trapping allows exposing cells in a reproducible way to high electrical fields for long durations, thereby giving good control on the lysis parameters. In situ evaluation of cytosol extraction on single cells has been studied for Chinese hamster ovary (CHO) cells through out-diffusion of fluorescent molecules for different voltage amplitudes. A diffusion model is proposed to correlate this out-diffusion to the total area of the created pores, which is dependent on the potential drop across the cell membrane and enables evaluation of the total pore area in the membrane. The dielectrophoretic trapping is no longer effective after lysis because of the reduced conductivity inside the cells, leading to cell release. The trapping time is linked to the time required for cytosol extraction and can thus provide additional validation of the effective cytosol extraction for non-fluorescent cells. Furthermore, the application of one single voltage for both trapping and lysis provides a fully automatic process including cell trapping, lysis, and release, allowing operating the device in continuous flow without human intervention.

Study on the properties of piezoelectric materials and manganese-based oxide perovskites /

Perovskite type piezoelectric and manganese oxide materials have gained a lot of attention in the field of device engineering. Lead zirconium titananium oxide (PbZri.iTiiOa or PZT) is a piezoelectric material widely used as sensors and actuators. Miniaturization of PZTbased devices will not only perfect many existing products, but also opens doors to new applications. Lanthanum manganese oxides Lai-iAiMnOa (A-divalent alkaline earth such as Sr, Ca or Ba) have been intensively studied for their colossal magnetoresistance (CMR) properties that make them applicable in memory cells, magnetic and pressure sensors. In this study, we fabricate PZT and LSMO(LCMO) heterostructures on SrTiOa substrates and investigate their temperature dependency of resistivity and magnetization as a function of the thickness of LSMO(LCMO) layer. The microstructure of the samples is analysed through TEM. In another set of samples, we study the effect of application of an electric field across the PZT layer that acts as an external pressure on the manganite layer. This verifies the correlation of lattice distortion with transport and magnetic properties of the CMR materials.

Imagerie à haut contraste et caractérisation d'exoplanètes par la spectroscopie intégrale de champ

Cette thèse porte sur l’amélioration des techniques d’imagerie à haut-contraste permettant la détection directe de compagnons à de faibles séparations de leur étoile hôte. Plus précisément, elle s’inscrit dans le développement du Gemini Planet Imager (GPI) qui est un instrument de deuxième génération pour les télescopes Gemini. Cette caméra utilisera un spectromètre à champ intégral (SCI) pour caractériser les compagnons détectés et pour réduire le bruit de tavelure limitant leur détection et corrigera la turbulence atmosphérique à un niveau encore jamais atteint en utilisant deux miroirs déformables dans son système d’optique adaptative (OA) : le woofer et le tweeter. Le woofer corrigera les aberrations de basses fréquences spatiales et de grandes amplitudes alors que le tweeter compensera les aberrations de plus hautes fréquences ayant une plus faible amplitude. Dans un premier temps, les performances pouvant être atteintes à l’aide des SCIs présentement en fonction sur les télescopes de 8-10 m sont investiguées en observant le compagnon de l’étoile GQ Lup à l’aide du SCI NIFS et du système OA ALTAIR installés sur le télescope Gemini Nord. La technique de l’imagerie différentielle angulaire (IDA) est utilisée pour atténuer le bruit de tavelure d’un facteur 2 à 6. Les spectres obtenus en bandes JHK ont été utilisés pour contraindre la masse du compagnon par comparaison avec les prédictions des modèles atmosphériques et évolutifs à 8−60 MJup, où MJup représente la masse de Jupiter. Ainsi, il est déterminé qu’il s’agit plus probablement d’une naine brune que d’une planète. Comme les SCIs présentement en fonction sont des caméras polyvalentes pouvant être utilisées pour plusieurs domaines de l’astrophysique, leur conception n’a pas été optimisée pour l’imagerie à haut-contraste. Ainsi, la deuxième étape de cette thèse a consisté à concevoir et tester en laboratoire un prototype de SCI optimisé pour cette tâche. Quatre algorithmes de suppression du bruit de tavelure ont été testés sur les données obtenues : la simple différence, la double différence, la déconvolution spectrale ainsi qu’un nouvel algorithme développé au sein de cette thèse baptisé l’algorithme des spectres jumeaux. Nous trouvons que l’algorithme des spectres jumeaux est le plus performant pour les deux types de compagnons testés : les compagnons méthaniques et non-méthaniques. Le rapport signal-sur-bruit de la détection a été amélioré d’un facteur allant jusqu’à 14 pour un compagnon méthanique et d’un facteur 2 pour un compagnon non-méthanique. Dernièrement, nous nous intéressons à certains problèmes liés à la séparation de la commande entre deux miroirs déformables dans le système OA de GPI. Nous présentons tout d’abord une méthode utilisant des calculs analytiques et des simulations Monte Carlo pour déterminer les paramètres clés du woofer tels que son diamètre, son nombre d’éléments actifs et leur course qui ont ensuite eu des répercussions sur le design général de l’instrument. Ensuite, le système étudié utilisant un reconstructeur de Fourier, nous proposons de séparer la commande entre les deux miroirs dans l’espace de Fourier et de limiter les modes transférés au woofer à ceux qu’il peut précisément reproduire. Dans le contexte de GPI, ceci permet de remplacer deux matrices de 1600×69 éléments nécessaires pour une séparation “classique” de la commande par une seule de 45×69 composantes et ainsi d’utiliser un processeur prêt à être utilisé plutôt qu’une architecture informatique plus complexe.

Metglas thin film based magnetostrictive transducers for use in long period fibre grating sensors

Metallic glass alloy Metglas 2826 MB based amorphous magnetic thin films were fabricated by the thermal evaporation technique. Transmission electron micrographs and electron diffraction pattern showed the amorphous nature of the films. Composition of the films was analyzed employing x-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy techniques. The film was integrated to a long period fibre grating. It was observed that the resonance wavelength of the fibre grating decreased with an increase in the magnetic field. Change in the resonance wavelength was minimal at higher magnetic fields. Field dependent magnetostriction values revealed the potential application of these films in magnetostrictive sensor devices

Metglas thin film based magnetostrictive transducers for use in long period fibre grating sensors

Metallic glass alloy Metglas 2826 MB based amorphous magnetic thin films were fabricated by the thermal evaporation technique. Transmission electron micrographs and electron diffraction pattern showed the amorphous nature of the films. Composition of the films was analyzed employing X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy techniques. The film was integrated to a long period fibre grating. It was observed that the resonance wavelength of the fibre grating decreased with an increase in the magnetic field. Change in the resonance wavelength was minimal at higher magnetic fields. Field dependent magnetostriction values revealed the potential application of these films in magnetostrictive sensor devices.

Design and Implementation of a Flexible Robot

This robot has low natural frequencies of vibration. Insights into the problems of designing joint and link flexibility are discussed. The robot has three flexible rotary actuators and two flexible, interchangeable links, and is controlled by three independent processors on a VMEbus. Results from experiments on the control of residual vibration for different types of robot motion are presented. Impulse prefiltering and slowly accelerating moves are compared and shown to be effective at reducing residual vibration.

Virtual Model Control of a Hexapod Walking Robot

Since robots are typically designed with an individual actuator at each joint, the control of these systems is often difficult and non-intuitive. This thesis explains a more intuitive control scheme called Virtual Model Control. This thesis also demonstrates the simplicity and ease of this control method by using it to control a simulated walking hexapod. Virtual Model Control uses imagined mechanical components to create virtual forces, which are applied through the joint torques of real actuators. This method produces a straightforward means of controlling joint torques to produce a desired robot behavior. Due to the intuitive nature of this control scheme, the design of a virtual model controller is similar to the design of a controller with basic mechanical components. The ease of this control scheme facilitates the use of a high level control system which can be used above the low level virtual model controllers to modulate the parameters of the imaginary mechanical components. In order to apply Virtual Model Control to parallel mechanisms, a solution to the force distribution problem is required. This thesis uses an extension of Gardner`s Partitioned Force Control method which allows for the specification of constrained degrees of freedom. This virtual model control technique was applied to a simulated hexapod robot. Although the hexapod is a highly non-linear, parallel mechanism, the virtual models allowed text-book control solutions to be used while the robot was walking. Using a simple linear control law, the robot walked while simultaneously balancing a pendulum and tracking an object.

Teaching an Old Robot New Tricks: Learning Novel Tasks via Interaction with People and Things

As AI has begun to reach out beyond its symbolic, objectivist roots into the embodied, experientialist realm, many projects are exploring different aspects of creating machines which interact with and respond to the world as humans do. Techniques for visual processing, object recognition, emotional response, gesture production and recognition, etc., are necessary components of a complete humanoid robot. However, most projects invariably concentrate on developing a few of these individual components, neglecting the issue of how all of these pieces would eventually fit together. The focus of the work in this dissertation is on creating a framework into which such specific competencies can be embedded, in a way that they can interact with each other and build layers of new functionality. To be of any practical value, such a framework must satisfy the real-world constraints of functioning in real-time with noisy sensors and actuators. The humanoid robot Cog provides an unapologetically adequate platform from which to take on such a challenge. This work makes three contributions to embodied AI. First, it offers a general-purpose architecture for developing behavior-based systems distributed over networks of PC's. Second, it provides a motor-control system that simulates several biological features which impact the development of motor behavior. Third, it develops a framework for a system which enables a robot to learn new behaviors via interacting with itself and the outside world. A few basic functional modules are built into this framework, enough to demonstrate the robot learning some very simple behaviors taught by a human trainer. A primary motivation for this project is the notion that it is practically impossible to build an "intelligent" machine unless it is designed partly to build itself. This work is a proof-of-concept of such an approach to integrating multiple perceptual and motor systems into a complete learning agent.

Plasma polymerization of C[subscript 4]F[subscript 8] thin film on high aspect ratio silicon molds

High aspect ratio polymeric micro-patterns are ubiquitous in many fields ranging from sensors, actuators, optics, fluidics and medical. Second generation PDMS molds are replicated against first generation silicon molds created by deep reactive ion etching. In order to ensure successful demolding, the silicon molds are coated with a thin layer of C[subscript 4]F[subscript 8] plasma polymer to reduce the adhesion force. Peel force and demolding status are used to determine if delamination is successful. Response surface method is employed to provide insights on how changes in coil power, passivating time and gas flow conditions affect plasma polymerization of C[subscript 4]F[subscript 8].