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Publicações

Publicações por CRIIS

2008

A ZigBee multi-powered wireless acquisition device for remote sensing applications in precision viticulture

Autores
Morais, R; Fernandes, MA; Matos, SG; Serodio, C; Ferreira, PJSG; Reis, MJCS;

Publicação
COMPUTERS AND ELECTRONICS IN AGRICULTURE

Abstract
This paper is part of a long-term effort to introduce precision viticulture in the region of Demarcated Region of Douro. It presents the architecture, hardware and software of a platform designed for that purpose, called MPWiNodeZ. A major feature of this platform is its power-management subsystem, able to recharge batteries with energy harvested from the surrounding environment from up to three sources. It allows the system to sustain operation as a general-purpose wireless acquisition device for remote sensing in large coverage areas, where the power to run the devices is always a concern. The MPWiNodeZ, as a ZigBee (TM) network element, provides a mesh-type array of acquisition devices ready for deployment in vineyards. In addition to describing the overall architecture, hardware and software of the monitoring system, the paper also reports on the performance of the module in the field, emphasising the energy issues, crucial to obtain self-sustained operation. The testing was done in two stages: the first in the laboratory, to validate the power management and networking solutions under particularly severe conditions, the second stage in a vineyard. The measurements about the behaviour of the system confirm that the hardware and software solutions proposed do indeed lead to good performance. The platform is currently being used as a simple and compact yet powerful building block for generic remote sensing applications, with characteristics that are well suited to precision viticulture in the DRD region. It is planned to be used as a network of wireless sensors on the canopy of vines, to assist in the development of grapevine powdery mildew prediction models.

2008

Fast and straightforward method to estimate sub-pixel level displacement field

Autores
Sousa, A; Morais, J; Filipe, V; Jesus, A; Vaz, MAP;

Publicação
COMPUTATIONAL VISION AND MEDICAL IMAGING PROCESSING

Abstract
This paper presents a fast and straightforward method to assess displacement fields on the surface of a planar specimen with sub-pixel resolution. First, pixel level displacements are obtained by cross correlation (CC) of two consecutive images, used as the image similarity measure. Next, sub-pixel displacement information is calculated from the CC coefficients matrix using a similarity interpolation method. Finally, sub-pixel estimation error cancellation is performed. Several experiments were conducted to validate the proposed method effectiveness, applied to chestnuts compression test for quality control purposes.

2008

Restricting IEC 61131-3 Programming Languages for use on High Integrity Applications

Autores
de Sousa, M;

Publicação
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS

Abstract
When developing applications with high integrity requirements, the choice of programming language is of utmost importance. In fact, IEC 61508 includes a table with suggested programming languages for each SIL (Safety Integrity Level). The languages defined in IEC 61131-3 are included in this table, but are only highly recommended for the higher SILs if a subset of the languages are used. In this paper we propose restrictions and changes to the IEC 61131-3 languages that constitute a subset of the languages with the objective of making them appropriate for the development of high integrity applications.

2008

Framework for Management of Replicated IEC 61499 Applications

Autores
Santos, AA; de Sousa, M;

Publicação
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS

Abstract
The IEC 61499 standard defines function blocks with which distributed control applications may be developed, and how these are interpreted and executed. With the distributed nature of the control application, many issues also need to be taken into account. In this paper we propose a replication management framework for IEC 61499 applications, and discuss some mechanisms and protocols that may be used for this purpose.

2008

A Modified Design for the VS-MRAC Based on the Indirect Approach: Stability Analysis

Autores
Oliveira, JB; Araujo, AD;

Publicação
IFAC Proceedings Volumes

Abstract

2008

Design and stability analysis of an indirect variable structure model reference adaptive control

Autores
Oliveira, JB; Araujo, AD;

Publicação
INTERNATIONAL JOURNAL OF CONTROL

Abstract
This paper presents the stability and robustness analysis of an indirect adaptive control based variable structure algorithm for uncertain plants with relative degree one. The indirect approach has been proposed as a way to get an easier design of the switching laws, compared to the direct relationship between the plant transfer function parameters and the physical parameters of the system. Here, a singular perturbation approach is used to establish the robustness of the controller in the presence of unmodelled dynamics and disturbances. It is shown that, for sufficiently small parasitics, the system remains stable with respect to some small residual set.

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