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Publications

2009

Distributed DBP: A (m,k)-firm Based Distributed Approach for QoS Provision in IEEE 802.15.4 Networks

Authors
Semprebom, T; Montez, C; Moraes, R; Vasques, F; Custodio, R;

Publication
2009 IEEE CONFERENCE ON EMERGING TECHNOLOGIES & FACTORY AUTOMATION (EFTA 2009)

Abstract
IEEE 802.15.4/Zigbee is one of the most widespread Wireless Sensor Network technologies. It may work either in beacon-enabled mode or in beaconless mode. When operating in beacon-enabled mode, it divides the superframe in sixteen equally-sized time slots, where the request for slot allocation is achieved through a CSMA/CA approach. This allocation method does not allow the provision of any service differentiation scheme, which is required for the transfer of time constrained messages. This paper proposes a QoS provision approach with minimal changes to existing protocols. Our approach improves the CSMA/CA algorithm by assigning decentralized priorities based on the (m,k)-firm task model. In this paper, a set of experimental results is presented and compared with the traditional approach currently offered by the standard. This set of experiments highlight the promising behavior of the proposed approach, when dealing with high network load scenarios.

2009

Accelerometer-Based Control of an Industrial Robotic Arm

Authors
Neto, P; Pires, JN; Moreira, AP;

Publication
RO-MAN 2009: THE 18TH IEEE INTERNATIONAL SYMPOSIUM ON ROBOT AND HUMAN INTERACTIVE COMMUNICATION, VOLS 1 AND 2

Abstract
Most of industrial robots are still programmed using the typical teaching process, through the use of the robot teach pendant. In this paper is proposed an accelerometer-based system to control an industrial robot using two low-cost and small 3-axis wireless accelerometers. These accelerometers are attached to the human arms, capturing its behavior (gestures and postures). An Artificial Neural Network (ANN) trained with a back-propagation algorithm was used to recognize arm gestures and postures, which then will be used as input in the control of the robot. The aim is that the robot starts the movement almost at the same time as the user starts to perform a gesture or posture (low response time). The results show that the system allows the control of an industrial robot in an intuitive way. However, the achieved recognition rate of gestures and postures (92%) should be improved in future, keeping the compromise with the system response time (160 milliseconds). Finally, the results of some tests performed with an industrial robot are presented and discussed.

2009

Optical Fibre Sensing and Analytical Imaging with Semiconductor Nanocrystals

Authors
Jorge, PAS; Maule, C; Rodrigues, H; Esteves da Silva, JCGE; Farahi, F;

Publication
ICTON: 2009 11TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, VOLS 1 AND 2

Abstract
Semiconductor nanocrystals have unique optical properties that make them promising alternatives to traditional dyes in many luminescence based analytical techniques. An overview of the more relevant progresses in the application of quantum dots (QDs) as analytical probes in optical fibre sensing and imaging application will be addressed. Experimental results regarding the use of QDs as self-referenced multiplexed probes for chemical sensing and analytical imaging will be presented.

2009

A DHT-based approach for Path Selection and Message Forwarding in IEEE 802.11s Industrial Wireless Mesh Networks

Authors
Pinheiro, M; Sampaio, S; Vasques, F; Souto, P;

Publication
2009 IEEE CONFERENCE ON EMERGING TECHNOLOGIES & FACTORY AUTOMATION (EFTA 2009)

Abstract
Wireless Mesh Networks (WMNs) are a promising communication technology that may offer greater flexibility and reliability, when compared to traditional wireless networks. WMNs open up new applications domains, but still need to find efficient mechanisms to deal with scalability and timeliness requirements. This paper proposes a scheme for Path Selection and Message Forwarding in IEEE 802.11s networks, that is suitable to be used in industrial environments. We present the DHT-based Cluster Routing Protocol (DCRP), a routing protocol based on DHTs, clustering of nodes and use of proxies. DCRP allows to improve the overall network performance by reducing the time required for path selection and the number of communication hops in large sized networks.

2009

Reliable Communication for DuST Networks

Authors
Rosset, V; Souto, P; Vasques, F;

Publication
2009 IEEE CONFERENCE ON EMERGING TECHNOLOGIES & FACTORY AUTOMATION (EFTA 2009)

Abstract
We present a family of reliable broadcast protocols designed to take advantage of the dual scheduling TDMA (DuST) scheme provided by current state-of-the-art automotive control networks such as FlexRay. These protocols are a complement to FlexRay's native communication services, which do not provide sufficient fault tolerance for safety-critical applications. A reliability evaluation of the proposed protocols carried out with the help of the probabilistic model checker PRISM shows that the proposed protocols can achieve reliability levels suitable for safety-critical applications.

2009

Using a Prioritized Medium Access Control Protocol for Incrementally Obtaining an Interpolation of Sensor Readings

Authors
Andersson, B; Pereira, N; Tovar, E; Gomes, R;

Publication
PROCEEDINGS OF THE SEVENTH INTERNATIONAL WORKSHOP ON INTELLIGENT SOLUTIONS IN EMBEDDED SYSTEMS

Abstract
This paper addresses sensor network applications which need to obtain an accurate image of physical phenomena and do so with a high sampling rate in both time and space. We present a fast and scalable approach for obtaining an approximate representation of all sensor readings at high sampling rate for quickly reacting to critical events in a physical environment This approach is an improvement on previous work in that after the new approach has undergone a startup phase then the new approach can use a very small sampling period.

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