A carregar...
Projeto de investigação
Sem título
Financiador
Autores
Publicações
A JSON/HTTP communication protocol to support the development of distributed cyber-physical systems
Publication . Pereira, Fernando; Gomes, Luis; CTS - Centro de Tecnologia e Sistemas; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias
Cyber physical systems are often built using networks of components containing physical and computational resources, enabling the design of distributed applications that collect data from remote sensors and manipulate remote actuators, located on local networks or on far away locations. The communication protocol presented in this paper was designed to support the communication between components of distributed applications. In addition, it includes remote debug and monitoring capabilities, to support the detection and resolution of errors and design mistakes on nodes running on remote locations. Employing the JSON/HTTP standards, the proposed protocol is Web browser friendly, suitable for the creation of Web based applications and user interfaces, but it may be employed on most programming environments that offer libraries to support those standards. As it is based on HTTP, it can easily traverse most firewall configurations and used through proxies. Development of the proposed protocol started on the IOPTTools framework, but the current version was implemented as part of the IOPT-Flow framework, aiming the development of distributed CPS applications based on graphical formalism combining Petri nets and dataflows. Both tool frameworks are available at http://gres.uninova.pt.
A Voltage Controlled Oscillator Using IGZO Thin-Film Transistors
Publication . Keragodu, Tejaswini; Tiwari, Bhawna; Nishtha; Bahubalindruni, Pydi; Goes, Joao; Barquinha, Pedro; DEE2010-A2 Electrónica; CTS - Centro de Tecnologia e Sistemas; DEE - Departamento de Engenharia Electrotécnica e de Computadores; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N)
This paper presents a voltage controlled oscillator (VCO) using amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs). This circuit consists of a high-gain OpAmp, a comparator and a relaxation oscillator. The implemented relaxation oscillator shows a power consumption of 700 μW, when it is simulated with a supply rail of ±5 V. It shows a frequency of oscillation range from 327 to 560 Hz, when the tuning capacitance value varies from 1.6 to 5 pF. On the other hand, the VCO has a power dissipation of 1.3 mW with frequency ranging from 400 to 556 Hz with a controlling voltage from -5 to 5 V. In-house oxide TFT model is used for circuit simulations in Cadence environment. This circuit finds potential applications in large-area flexible systems, namely smart packaging, biomedical and wearable systems, which needs clocks with different frequencies.
On consensus-based distributed blind calibration of sensor networks
Publication . Stanković, Miloš S.; Stanković, Srdjan S.; Johansson, Karl Henrik; Beko, Marko; Camarinha-Matos, Luis M.; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CTS - Centro de Tecnologia e Sistemas; MDPI - Multidisciplinary Digital Publishing Institute
This paper deals with recently proposed algorithms for real-time distributed blind macro-calibration of sensor networks based on consensus (synchronization). The algorithms are completely decentralized and do not require a fusion center. The goal is to consolidate all of the existing results on the subject, present them in a unified way, and provide additional important analysis of theoretical and practical issues that one can encounter when designing and applying the methodology. We first present the basic algorithm which estimates local calibration parameters by enforcing asymptotic consensus, in the mean-square sense and with probability one (w.p.1), on calibrated sensor gains and calibrated sensor offsets. For the more realistic case in which additive measurement noise, communication dropouts and additive communication noise are present, two algorithm modifications are discussed: one that uses a simple compensation term, and a more robust one based on an instrumental variable. The modified algorithms also achieve asymptotic agreement for calibrated sensor gains and offsets, in the mean-square sense and w.p.1. The convergence rate can be determined in terms of an upper bound on the mean-square error. The case when the communications between nodes is completely asynchronous, which is of substantial importance for real-world applications, is also presented. Suggestions for design of a priori adjustable weights are given. We also present the results for the case in which the underlying sensor network has a subset of (precalibrated) reference sensors with fixed calibration parameters. Wide applicability and efficacy of these algorithms are illustrated on several simulation examples. Finally, important open questions and future research directions are discussed.
Continuous reinforcement operator applied to resilience in disaster rescue networks
Publication . Jassbi, Javad J.; Ribeiro, Rita A.; Camarinha-Matos, Luis M.; Barata, José; Gomes, Maria Isabel; CTS - Centro de Tecnologia e Sistemas; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CMA - Centro de Matemática e Aplicações
Resilience measurement can be viewed as a multicriteria hierarchical decision making problem since calculating the final level of resilience involves measuring different criteria, at several hierarchical levels, and then merging the information together. In this paper, a resilience model for disaster rescue networks is discussed with a full-reinforcement operator, denoted continuous reinforcement operator. This approach is tested with different levels of reinforcement and the results are compared with those from a Fuzzy Inference System. The proposed approach offers interesting features to support balanced development of disaster rescue networks and facilitates managerial decisions by imposing standards for criteria to penalize or reward the information fusion process.
On target localization using combined RSS and AoA measurements
Publication . Tomic, Slavisa; Beko, Marko; Dinis, Rui; Bernardo, Luís; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CTS - Centro de Tecnologia e Sistemas; DEE2010-A1 Telecomunicações; DEE - Departamento de Engenharia Electrotécnica e de Computadores; MDPI - Multidisciplinary Digital Publishing Institute
This work revises existing solutions for a problem of target localization in wireless sensor networks (WSNs), utilizing integrated measurements, namely received signal strength (RSS) and angle of arrival (AoA). The problem of RSS/AoA-based target localization became very popular in the research community recently, owing to its great applicability potential and relatively low implementation cost. Therefore, here, a comprehensive study of the state-of-the-art (SoA) solutions and their detailed analysis is presented. The beginning of this work starts by considering the SoA approaches based on convex relaxation techniques (more computationally complex in general), and it goes through other (less computationally complex) approaches, as well, such as the ones based on the generalized trust region sub-problems framework and linear least squares. Furthermore, a detailed analysis of the computational complexity of each solution is reviewed. Furthermore, an extensive set of simulation results is presented. Finally, the main conclusions are summarized, and a set of future aspects and trends that might be interesting for future research in this area is identified.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
5876
Número da atribuição
147324