Self-Stabilizing Message Routing in Mobile ad hoc Networks

We present a self-stabilizing algorithm for routing messages between arbitrary pairs of nodes in a mobile ad hoc network. Our algorithm assumes the availability of a reliable GPS service, which supplies mobile nodes with accurate information about real time and about their own geographical locations. The GPS service provides an external, shared source of consistency for mobile nodes, allowing them to label and timestamp messages, and thereby aiding in recovery from failures. Our algorithm utilizes a Virtual Infrastructure programming abstraction layer, consisting of mobile client nodes, virtual stationary timed machines called Virtual Stationary Automata (VSAs), and a local broadcast service connecting VSAs and mobile clients. VSAs are associated with predetermined regions in the plane, and are emulated in a self-stabilizing manner by the mobile nodes. VSAs are relatively stable in the face of node mobility and failure, and can be used to simplify algorithm development for mobile networks. Our routing algorithm consists of three subalgorithms: [(1)] a VSA-to-VSA geographical routing algorithm, [2] a mobile client location management algorithm, and [3] the main algorithm, which utilizes both location management and geographical routing. All three subalgorithms are self-stabilizing, and consequently, the entire algorithm is also self-stabilizing

Virtual stationary timed automata for mobile networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 339-347).In this thesis, we formally define a programming abstraction for mobile networks called the Virtual Stationary Automata programming layer, consisting of real mobile clients, virtual timed I/O automata called virtual stationary automata (VSAs), and a communication service connecting VSAs and client nodes. The VSAs are located at prespecified regions that tile the plane, defining a static virtual infrastructure. We present a theory of self-stabilizing emulation and use this theory to prove correct a self-stabilizing algorithm to emulate a timed VSA using the real mobile nodes that are currently residing in the VSA's region. We also specify two important services for mobile networks: motion coordination and end-to-end routing. We split the implementation of the end-to-end routing service into three smaller pieces, consisting of geographic routing and location management services with an end-to-end routing service built on top of them. We provide stabilizing implementations of each of these services using the VSA abstraction, and provide formal correctness analyses for each implementation.by Tina Ann Nolte.Ph.D

Self-stabilizing robot formations over unreliable networks

We describe how a set of mobile robots can arrange themselves on any specified curve on the plane in the presence of dynamic changes both in the underlying ad hoc network and in the set of participating robots. Our strategy is for the mobile robots to implement a self-stabilizing virtual layer consisting of mobile client nodes, stationary Virtual Nodes (VNs), and local broadcast communication. The VNs are associated with predetermined regions in the plane and coordinate among themselves to distribute the client nodes relatively uniformly among the VNs' regions. Each VN directs its local client nodes to align themselves on the local portion of the target curve. The resulting motion coordination protocol is self-stabilizing, in that each robot can begin the execution in any arbitrary state and at any arbitrary location in the plane. In addition, self-stabilization ensures that the robots can adapt to changes in the desired target formation.National Science Foundation (U.S.) (Grant No. CNS-0614993

μGIM - Microgrid intelligent management system based on a multi-agent approach and the active participation of end-users

[ES] Los sistemas de potencia y energía están cambiando su paradigma tradicional, de sistemas centralizados a sistemas descentralizados. La aparición de redes inteligentes permite la integración de recursos energéticos descentralizados y promueve la gestión inclusiva que involucra a los usuarios finales, impulsada por la gestión del lado de la demanda, la energía transactiva y la respuesta a la demanda. Garantizar la escalabilidad y la estabilidad del servicio proporcionado por la red, en este nuevo paradigma de redes inteligentes, es más difícil porque no hay una única sala de operaciones centralizada donde se tomen todas las decisiones. Para implementar con éxito redes inteligentes, es necesario combinar esfuerzos entre la ingeniería eléctrica y la ingeniería informática. La ingeniería eléctrica debe garantizar el correcto funcionamiento físico de las redes inteligentes y de sus componentes, estableciendo las bases para un adecuado monitoreo, control, gestión, y métodos de operación. La ingeniería informática desempeña un papel importante al proporcionar los modelos y herramientas computacionales adecuados para administrar y operar la red inteligente y sus partes constituyentes, representando adecuadamente a todos los diferentes actores involucrados. Estos modelos deben considerar los objetivos individuales y comunes de los actores que proporcionan las bases para garantizar interacciones competitivas y cooperativas capaces de satisfacer a los actores individuales, así como cumplir con los requisitos comunes con respecto a la sostenibilidad técnica, ambiental y económica del Sistema. La naturaleza distribuida de las redes inteligentes permite, incentiva y beneficia enormemente la participación activa de los usuarios finales, desde actores grandes hasta actores más pequeños, como los consumidores residenciales. Uno de los principales problemas en la planificación y operación de redes eléctricas es la variación de la demanda de energía, que a menudo se duplica más que durante las horas pico en comparación con la demanda fuera de pico. Tradicionalmente, esta variación dio como resultado la construcción de plantas de generación de energía y grandes inversiones en líneas de red y subestaciones. El uso masivo de fuentes de energía renovables implica mayor volatilidad en lo relativo a la generación, lo que hace que sea más difícil equilibrar el consumo y la generación. La participación de los actores de la red inteligente, habilitada por la energía transactiva y la respuesta a la demanda, puede proporcionar flexibilidad en desde el punto de vista de la demanda, facilitando la operación del sistema y haciendo frente a la creciente participación de las energías renovables. En el ámbito de las redes inteligentes, es posible construir y operar redes más pequeñas, llamadas microrredes. Esas son redes geográficamente limitadas con gestión y operación local. Pueden verse como áreas geográficas restringidas para las cuales la red eléctrica generalmente opera físicamente conectada a la red principal, pero también puede operar en modo isla, lo que proporciona independencia de la red principal. Esta investigación de doctorado, realizada bajo el Programa de Doctorado en Ingeniería Informática de la Universidad de Salamanca, aborda el estudio y el análisis de la gestión de microrredes, considerando la participación activa de los usuarios finales y la gestión energética de lascarga eléctrica y los recursos energéticos de los usuarios finales. En este trabajo de investigación se ha analizado el uso de conceptos de ingeniería informática, particularmente del campo de la inteligencia artificial, para apoyar la gestión de las microrredes, proponiendo un sistema de gestión inteligente de microrredes (μGIM) basado en un enfoque de múltiples agentes y en la participación activa de usuarios. Esta solución se compone de tres sistemas que combinan hardware y software: el emulador de virtual a realidad (V2R), el enchufe inteligente de conciencia ambiental de Internet de las cosas (EnAPlug), y la computadora de placa única para energía basada en el agente (S4E) para permitir la gestión del lado de la demanda y la energía transactiva. Estos sistemas fueron concebidos, desarrollados y probados para permitir la validación de metodologías de gestión de microrredes, es decir, para la participación de los usuarios finales y para la optimización inteligente de los recursos. Este documento presenta todos los principales modelos y resultados obtenidos durante esta investigación de doctorado, con respecto a análisis de vanguardia, concepción de sistemas, desarrollo de sistemas, resultados de experimentación y descubrimientos principales. Los sistemas se han evaluado en escenarios reales, desde laboratorios hasta sitios piloto. En total, se han publicado veinte artículos científicos, de los cuales nueve se han hecho en revistas especializadas. Esta investigación de doctorado realizó contribuciones a dos proyectos H2020 (DOMINOES y DREAM-GO), dos proyectos ITEA (M2MGrids y SPEAR), tres proyectos portugueses (SIMOCE, NetEffiCity y AVIGAE) y un proyecto con financiación en cascada H2020 (Eco-Rural -IoT)

Exploring the potential of brain-inspired computing

The gap between brains and computers regarding both their cognitive capability and power efficiency is remarkably huge. Brains process information massively in parallel and its constituents are intrinsically self-organizing, while in digital computers the execution of instructions is deterministic and rather serial. The recent progress in the development of dedicated hardware systems implementing physical models of neurons and synapses enables to efficiently emulate spiking neural networks. In this work, we verify the design and explore the potential for brain-inspired computing of such an analog neuromorphic system, called Spikey. We demonstrate the versatility of this highly configurable substrate by the implementation of a rich repertoire of network models, including models for signal propagation and enhancement, general purpose classifiers, cortical models and decorrelating feedback systems. Network emulations on Spikey are highly accelerated and consume less than 1 nJ per synaptic transmission. The Spikey system, hence, outperforms modern desktop computers in terms of fast and efficient network simulations closing the gap to brains. During this thesis the stability, performance and user-friendliness of the Spikey system was improved integrating it into the neuroscientific tool chain and making it available for the community. The implementation of networks suitable to solve everyday tasks, like object or speech recognition, qualifies this technology to be an alternative to conventional computers. Considering the compactness, computational capability and power efficiency, neuromorphic systems may qualify as a valuable complement to classical computation

Optimal Planning of Virtual Inertia Installations to Improve the Power System Frequency Response

In recent years, the power system has seen a fast transformation from one primarily based on fossil energy to one where renewable energy, especially wind and solar power, takes a more significant proportion in the energy profile. With the shift in energy profile come the changes in the electricity generation units. The solar panels and wind turbines replace the synchronous generators in electricity generation. Most solar and wind generation units are converter-interfaced. In contrast, the synchronous generator is connected to the power grid directly. For this reason, the future power system of a high level of renewable penetration will exhibit dynamic properties different from the traditional power system, which poses many challenges. One of the challenges is related to frequency stability. The frequency stability of a traditional power system is secured with a three-level frequency control scheme. The scheme is composed of three frequency regulation mechanisms at different time scales. The fastest control mechanism, named primary frequency control, needs about 5 s to be fully deployed to arrest the frequency drops or overshoots. After that, the other two frequency secondary and tertiary frequency control mechanisms are then slowly deployed to bring the system frequency back to the nominal value. Under this control scheme, the overall active power generation and consumption in a power system get balanced, and the power frequency variation is limited within a narrow range around a nominal value. However, before the primary frequency control is sufficiently deployed, the system relies on the natural inertia response of the synchronous generators to maintain the active power balance at the sacrifice of changes in the generators' rotational speeds. As the power frequency is decided collectively by the rotational speeds of all synchronous generators in the system, larger system inertia means smaller power frequency variation when subject to the same disturbance. Since there is no lack of system inertia in a synchronous generator-dominant power system, the power frequency variation with the help of the tertiary control scheme is usually contained within a limited range. For a future power system with more and more synchronous generators being displaced by converter-interfaced generation (CIG) units, the system inertia decreases. The tertiary frequency control scheme alone can no longer limit the power frequency variation within an acceptable range. For this reason, techniques were proposed to emulate inertia response on a converter-interfaced generation unit. Apart from the level of total system inertia, studies show that the spatial distribution of system inertia can also influence the frequency response. Under this context, a well-planned virtual inertia installation at selected locations can achieve a satisfactory level of improvement on frequency response at a low investment cost. This thesis work aims at developing a systematic method to search for the most economical plan of virtual inertia installations while ensuring a satisfactory level of frequency response. In order to derive the most economical plan of virtual installation, a mathematical optimization problem is proposed with constraints formulated with the help of a newly proposed metric of inertia response that quantifies the influence of inertia on the system frequency response. The formulation of the optimization problem considers all possible combinations of loading and renewable generation profiles. Two methods are proposed to solve the optimization problem of the mixed-integer type. The first one is based on the classic scheme of dynamic programming. The second method adopts a relaxation technique based on the sparsity promotion or Majorize-Minimization (MM) method. Furthermore, parallel and cloud programming techniques are used to facilitate computation speed. Other minor contributions include a design of a supplementary controller on top of the inertia emulation control to improve the voltage stability of a converter-interfaced generation unit. Finally, case studies were conducted on a modified Southeast Australian power system against different types of faults to validate the performance and investment cost of the virtual inertia installation plan givens by the proposed method in comparison with two other methods. The result shows that the virtual inertia installation plan given by the proposed method produces better performance while at lower investment costs

Grid-Connected Renewable Energy Sources

The use of renewable energy sources (RESs) is a need of global society. This editorial, and its associated Special Issue “Grid-Connected Renewable Energy Sources”, offers a compilation of some of the recent advances in the analysis of current power systems that are composed after the high penetration of distributed generation (DG) with different RESs. The focus is on both new control configurations and on novel methodologies for the optimal placement and sizing of DG. The eleven accepted papers certainly provide a good contribution to control deployments and methodologies for the allocation and sizing of DG

Modular event-driven unmanned aerial vehicles control platform

Hoje em dia, os drones estão-se a tornar cada vez mais comuns nas nossas vidas diárias. Com a agilidade, acessibilidade e diversidade dos drones, eles são uma excelente plataforma para transportar dispositivos (p.ex., conjunto de sensores, câmeras, unidades computacionais de pequena dimensão). Assim sendo, são uma excelente ferramenta para tarefas como: explorar e estudar áreas perigosas, monitorizar campos de agricultura, ajudar na detecção e combate de incêndios ou vigiar multidões. Para realizar tais tarefas, ferramentas de automação e integração são essenciais, para que o desenvolvimento se concentre na própria aplicação e não nos problemas relacionados com a integração e automação do sistema do drone. Os drones atualmente disponiveis não são capazes de lidar com tais complexidades de forma tão transparente. Por exemplo, certos niveis de automação são ja possiveis, mas requerem hardware e software especificos do fornecedor; no que toca a integração, alguns já supportam SDK ou API para interagir com o drone, mas mais uma vez com a inconveniência de necessitar de conhecimento prévio sobre os sistemas dos drones. Para responder a estas necessidades, esta tese propõe uma plataforma modular de controlo baseada em eventos para abstrair os processos de automação e integração da complexidade subjacentes aos drones. Enquanto que a plataforma permite que as aplicações controlem e interajam com os drones, a sua complexidade é resolvida dentro da plataforma, simplificando o processo de integração. Além disso, com a plataforma proposta, a automação e funcionalidades do drone podem ser estendidas para estender as funcionalidades de drones mais limitados. A plataforma desenvolvida foi testada em diferentes cenários, tanto ao nível das suas funcionalidades como ao nível da analise de desempenho. Os resultados mostram que, além das funcionalidades suportadas, a plataforma consegue suportar o controlo e gestão de pelo menos até 64 drones em simultâneo sem ter modificações significativas nos atrasos de comunicação e throughput.Nowadays, drones are becoming more common in our daily lives. Since drones are agile, a ordable and diverse, they make an excellent platform to carry devices around (e.g., sensor arrays, cameras, small computers). With these capabilities, they become an excellent tool for tasks like: explore and study hazardous areas, agriculture monitoring, help on the detection and ght in res, and crowd surveillance. To perform such tasks, automation and integration tools are a must have, so that the development can focus on the application itself and not on the issues related with the integration and automation of the drone system. Current available drones are not capable of properly handling such complexities in a seamless way. For instance, some levels of automation are already possible, but require vendor speci c hardware and software; for integration, some o er SDK or API interactions, but once again with the inconvenience of requiring extensive knowledge about drone systems to implement. To address these issues, this thesis proposes a modular event-driven control platform to abstract automation and integration processes from the underlying complexities of the drones, while the platform lets the applications control and interact with the drones. The drones' complexities are resolved within the platform, therefore simplifying integration process. Moreover, with the proposed platform, drone automation and functionality can be extended across distinct brands of drones, while some may already support some features, others may not, and in that case the platform modules may intervene to extend the features of less capable drones. The developed platform has been tested in di erent scenarios, such as in terms of its functionalities and in terms of performance analysis. The results show that, besides the supported functionalities, the platform is able to handle the control and management of at last 64 simultaneous drones without signi cant changes in the communication delays and throughput.Mestrado em Engenharia Informátic

Design and implementation of virtual network testbeds for routing protocols

In this project, we present the design and implementation of virtual network testbeds for studying routing changes. A virtual network testbed is a computer network that is completely created in software, while routing changes directly impact on the reliability and the reachability information of the network. We used testbeds to emulate a small and a large-scale network on a single Linux machine. These emulated networks allow the study of network behavior and operations which are examined using two routing protocols: Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). We implemented a fifteen-node network to study RIP, and a model of the GÈANT network to examine OSPF in virtual network testbeds. Each testbed represents an autonomous system (AS) or an intra-domain environment. Therefore, these environments provided us with the opportunities to evaluate routing changes in an AS. We used the testbeds to compare the routing of the original network with the new routing of the missing links and routers to see what changes occur. The GÈANT network is the large-scale network used for investigations in this project. We then used our emulation results of the large-scale network to compare with the simulation work for the same network topology-the GÈANT network, and confirmed that our emulation studies also identified important links and routers in the same network. --P.ii.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b162504