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Publicações

Publicações por CRAS

2015

Sensing Structure Based on Surface Plasmon Resonance in Chemically Etched Single Mode Optical Fibres

Autores
Coelho, L; de Almeida, JMMM; Santos, JL; Ferreira, RAS; Andre, PS; Viegas, D;

Publicação
PLASMONICS

Abstract
Many optical systems based on surface plasmon resonance (SPR) have been developed for working as refractometers, chemical sensors or even for measuring the thickness of metal and dielectric thin films. Sensors based on SPR present very high sensitivity to refractive index (RI) variations when compared to the traditional RI sensors. However, these kinds of systems are usually large, expensive and therefore cannot be used for remote sensing. Optical fibre sensors based on SPR are usually implemented using multimode optical fibres cope with the requirements for remote sensing. In this section a new type of SPR sensor based in a single mode fibre (SMF) is proposed. A section of the SMF was chemically etched by emersion in a 48 % hydrofluoric acid solution, resulting in a tapering effect, with the cladding removing while the core is kept intact. Simulation results are in good agreement with the experimental spectral resonance dip attained around 1550 nm. Sensitivities of 3800 and 5100 nm/RIU were achieved for the reflection and for the transmission modes, respectively, for RI in the 1.33 to 1.37 range.

2015

Towards a Reliable Monitoring Robot for Mountain Vineyards

Autores
dos Santos, FN; Sobreira, H; Campos, D; Morais, R; Moreira, AP; Contente, O;

Publicação
2015 IEEE INTERNATIONAL CONFERENCE ON AUTONOMOUS ROBOT SYSTEMS AND COMPETITIONS (ICARSC)

Abstract
Crop monitoring and harvesting by ground robots on mountain vineyards is an intrinsically complex challenge, due to two main reasons: harsh conditions of the terrain and reduced time availability and unstable localization accuracy of the GPS system. In this paper is presented a cost effective robot that can be used on these mountain vineyards for crop monitoring tasks. Also it is explored a natural vineyard feature as the input of a standard 2D simultaneous localization and mapping approach (SLAM) for feature-based map extraction. In order to be possible to evaluate these natural features for mapping and localization purposes, a virtual scenario under ROS/Gazebo has been built and described. A low cost artificial landmark and an hybrid SLAM is proposed to increase the localization accuracy, robustness and redundancy on these mountain vineyards. The obtained results, on the simulation framework, validates the use of a localization system based on natural mountain vineyard features.

2015

Deriving Mechanical Structures in Physical Coordinates from Data-Driven State-Space Realizations

Autores
dos Santos, PL; Ramos, JA; Azevedo Perdicoulis, TP; de Carvallio, JLM;

Publicação
2015 AMERICAN CONTROL CONFERENCE (ACC)

Abstract
In this article, the problem of deriving a physical model of a mechanical structure from an arbitrary state-space realization is addressed. As an alternative to finite element formulations, the physical parameters of a model may be directly obtained from identified parametric models. However, these methods are limited by the number of available sensors and often lead to poor predictive models. Additionally, the most efficient identification algorithms retrieve models where the physical parameters are hidden. This last difficulty is known in the literature as the inverse vibration problem. In this work, an approach to the inverse vibration problem is proposed. It is based on a similarity transformation and the requirement that every degree of freedom should contain a sensor and an actuator (full instrumented system) is relaxed to a sensor or an actuator per degree of freedom, with at least one co-located pair (partially instrumented system). The physical parameters are extracted from a state-space realization of the former system. It is shown that this system has a symmetric transfer function and this symmetry is exploited to derive a state-space realization from an identified model of the partially instrumented system. A subspace continuous-time system identification algorithm previously proposed by the authors in [1] is used to estimate this model from the IO data.

2015

Modelling a gas pipeline as a repetitive process: controllability, observability and stability

Autores
Azevedo Perdicoulis, TP; Jank, G; dos Santos, PL;

Publicação
MULTIDIMENSIONAL SYSTEMS AND SIGNAL PROCESSING

Abstract
In this paper, the gas dynamics within the pipelines is modelled as a repetitive process with smoothing. Controllability and observability criteria when the system is steered through initial and boundary data, which is achieved by an adequate choice of the homogeneity, are obtained. From the point of view of the technical applications, it seems to make more sense to consider boundary data controls as for instance in the management of high pressure gas networks. Stability criteria suitable computer simulations are also included.

2015

Nash equilibrium with wave dynamics and boundary control

Autores
Azevedo Perdicoulis, TP; Jank, G; Lopes dos Santos, PL;

Publicação
2015 IEEE 9TH INTERNATIONAL WORKSHOP ON MULTIDIMENSIONAL (ND) SYSTEMS (NDS)

Abstract
In this paper, the gas dynamics within the pipelines is written as a wave repetitive process, and modify it in a way that the dynamics is influenced by p decision makers, namely the boundary conditions. We obtain sufficient criteria for the existence of boundary equilibrium controls as well as controllability of the different agents and observability of the system when this is steered through initial and boundary data. From the point of view of some applications it seems to make sense to consider boundary data controls, e.g. in high pressure gas networks management.

2015

Boundary control of discrete repetitive processes with smoothing: controllability, observability and disturbance attenuation

Autores
Azevedo Perdicoulis, TP; Jank, G; dos Santos, PL;

Publicação
MULTIDIMENSIONAL SYSTEMS AND SIGNAL PROCESSING

Abstract
In this paper, we proffer an explicit representation of solutions for a specific class of linear repetitive processes with smoothing. This representation is used to obtain direct controllability and observability criteria of this same class of discrete time 2-D systems. Not only classical controllability properties are considered, where control of the system is obtained by choosing its inhomogeneity appropriately, but also controllability of the system by steering it through boundary data control. From the point of view of technical applications, for instance in high pressure gas network modelling (see Azevedo-PerdicoA(0)lis and Jank in Proceedings of n-DS, international workshop on multidimensional systems, Thessaloniki. 2009), it seems to be more reliable to consider boundary data controls. Therefore, in this paper we emphasise boundary data control properties of the system. A disturbed optimal boundary control problem with a quadratic criterion is also solved.

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