Recursos de colección

Estudo Geral - Universidade de Coimbra (19.630 recursos)

ESTUDO GERAL é a designação do repositório digital da produção científica da Universidade de Coimbra, com o objectivo de divulgar conteúdos digitais de natureza científica de autores ligados à Universidade de Coimbra. A sua criação insere-se no movimento de Acesso Livre à Literatura científica (Open Access), ao qual o Conselho de Reitores das Universidades Portuguesas aderiu em 2006 e que a Universidade de Coimbra subscreveu. À semelhança de outras grandes universidades nacionais e internacionais, a UC tem o maior interesse em aumentar a sua presença na rede informática mundial, sendo cada vez mais - e também por essa via - um emissor de conhecimento e cultura.

FCTUC Eng.Electrotécnica - Artigos em Revistas Internacionais

Mostrando recursos 1 - 20 de 71

  1. A web spatial decision support system for vehicle routing using Google Maps

    Santos, Luís; Coutinho-Rodrigues, João; Antunes, Carlos Henggeler
    This article presents a user-friendly web-based Spatial Decision Support System (wSDSS) aimed at generating optimized vehicle routes for multiple vehicle routing problems that involve serving the demand located along arcs of a transportation network. The wSDSS incorporates Google Maps™ (cartography and network data), a database, a heuristic and an ant-colony meta-heuristic developed by the authors to generate routes and detailed individual vehicle route maps. It accommodates realistic system specifics, such as vehicle capacity and shift time constraints, as well as network constraints such as one-way streets and prohibited turns. The wSDSS can be used for “what-if” analysis related to possible changes to input parameters such as vehicle...

  2. Using SSM for structuring decision support in urban energy planning

    Coelho, Dulce; Antunes, Carlos Henggeler; Martins, António Gomes

  3. Low-Cost Method for the Estimation of the Shape of Quadric Mirrors and Calibration of Catadioptric Cameras

    Gonçalves, Nuno; Araújo, Helder
    This paper tackles the problem of the quadric mirror estimation of omnidirectional imaging systems, as well as the poses of the camera relative to the mirror and to the world reference system. These estimates are obtained for quadric-shaped mirrors (including elliptic, parabolic, hyperbolic and spherical mirrors) where the position of the camera and mirror is unconstrained (fully non central configurations). The apparent contour of the mirror can be used to reduce the uncertainty in the estimation. Although it can enhance both the accuracy of the estimation (allowing the method to converge from farther initial configurations) and also its performance, its use is not strictly required. The...

  4. Geometric Properties of Central Catadioptric Line Images and Their Application in Calibration

    Barreto, João P.; Araújo, Helder
    In central catadioptric systems, lines in a scene are projected to conic curves in the image. This work studies the geometry of the central catadioptric projection of lines and its use in calibration. It is shown that the conic curves where the lines are mapped possess several projective invariant properties. From these properties, it follows that any central catadioptric system can be fully calibrated from an image of three or more lines. The image of the absolute conic, the relative pose between the camera and the mirror, and the shape of the reflective surface can be recovered using a geometric construction based on the conic loci where...

  5. Hand movement recognition based on biosignal analysis

    Wojtczak, Pawel; Amaral, Tito G.; Dias, Octavio P.; Wolczowski, Andrzej; Kurzynski, Marek

  6. Applications of information theory, genetic algorithms, and neural models to predict oil flow

    Ludwig Jr., Oswaldo; Nunes, Urbano; Araújo, Rui; Schnitman, Leizer; Lepikson, Herman Augusto

  7. Data fusion and path-following controllers comparison for autonomous vehicles

    Nunes, Urbano; Bento, L.
    Abstract This paper presents a comparative study of two path-following controllers developed for guiding autonomous vehicles in semi-structured outdoor environments. Part of this paper is focused on the performance of two path-following controllers, which are implemented using two different approaches, the first using fuzzy logic and the second using chained systems theory. The control effort and the errors magnitude along the path are evaluated in a comparative way. A magnetic guidance system for autonomous vehicles navigation in semi-structured outdoor environments is also described, integrating redundant encoders data and absolute positioning data provided by on-board magnetic sensors and magnetic markers buried...

  8. Multi-Class Measurement Based Admission Control for a QoS Framework with Dynamic Resource Management

    Bohnert, Thomas; Monteiro, Edmundo
    The advent of a Premium Service (PS) featuring Internet is still pending, mainly due its difficult deployment. But do we really need Quality of Service like PS? Likely no. We are therefore investigating an alternative QoS model, which is more flexible to deploy at the expense of looser QoS guarantees. We call it a Better-than-Best-Effort (BBE) service. What distinguishes our approach from traditional ones is dynamic resource management based on measurements and ruled by Perceptual QoS. What yet has been missing was Admission Control (AC) and in this paper we present our latest advance. Based on the existence of measurements...

  9. A Stereovision Method for Obstacle Detection and Tracking in Non-Flat Urban Environments

    Yu, Qian; Araújo, Helder; Wang, Hong
    Obstacle detection is an essential capability for the safe guidance of autonomous vehicles, especially in urban environments. This paper presents an efficient method to integrate spatial and temporal constraints for detecting and tracking obstacles in urban environments. In order to enhance the reliability of the obstacle detection task, we do not consider the urban roads as rigid planes, but as quasi-planes, whose normal vectors have orientation constraints. Under this flexible road model, we propose a fast, robust stereovision based obstacle detection method. A watershed transformation is employed for obstacle segmentation in dense traffic conditions, even with partial occlusions, in urban...

  10. Multisensor Demining Robot

    Rachkov, Michael Yu.; Marques, Lino; Almeida, Aníbal T. de
    The paper describes an advanced multisensor demining robot. The robot transport system is based on a simple structure using pneumatic drive elements. The robot has robust design and can carry demining equipment up to 100 kg over rough terrains. Due to the adaptive possibilities of pedipulators to obstacles, the robot can adjust the working position of the demining sensors while searching for mines. The detection block consists of a metal detector, an infrared detector, and a chemical explosive sensor. The robot is controlled by means of an on-board processor and by an operator remote station in an interactive mode. Experimental...

  11. Robust Control for Steer-by-Wire Vehicles

    Bajçinca, N.; Cortesão, R.; Hauschild, M.
    The design and analysis of steer-by-wire systems at the actuation and operational level is explored. At the actuation level, robust force feedback control using inverse disturbance observer structure and active observer algorithm is applied to enhance the robustness vs non-modelled dynamics and uncertain driver bio-impedance. At the operational level, the robustness aspects vs parameter uncertainties in vehicle dynamics and driver bio-impedance are issued and for a given target coupling dynamics between driver and vehicle the design task is converted to a model-matching problem. H8 techniques and active observer algorithms are used to design the steer-by-wire controller. Robustness issues at both...

  12. Introduction: Proof-theoretic Semantics

    Kahle, Reinhard; Schroeder-Heister, Peter
    Without Abstract

  13. A Fast Firing Binaural System for Ultrasonic Pattern Recognition

    Moita, Fernando; Lopes, Ana; Nunes, Urbano
    Abstract A binaural sonar configuration with capability to detect and identify walls, edges and corners on real-time is presented in this work. A new multi-echo ultra-fast firing method increases the sonar acquisition rate, and provides crossed measurements without interference. A feature map is built on-line using Bayesian updating and classification rules. Three classifiers are implemented and analyzed: minimum risk (MR), maximum a posteriori (MAP), and minimum distance (MD). Experimental results of ultrasonic reflector recognition, using data collected in a specular indoor environment are presented in the paper.

  14. Reducing Motion Inaccuracies on a Mobile Robot

    Araújo, Rui; Almeida, A. T. de
    In this article we present two algorithms, for reducing the effects of control-space quantisation errors on a Khepera mobile robot. Specifically, we consider that control-space quantisation is present, when there is only a finite set of available robot wheels velocities. Thus the velocities of the robot wheels can not be chosen from any point in a continuous set. The first algorithm can be used to perform pure rotations (no translation) of the mobile robot while reducing the effects of these errors. The second algorithm can be used to perform robust straight-line motions, between the mobile robot current position, and a...

  15. A meta-model for multiobjective routing in MPLS networks

    Craveirinha, José; Girão-Silva, Rita; Clímaco, João
    Abstract MPLS (Multiprotocol Label Switching) enables the utilisation of explicit routes and other advanced routing mechanisms in multiservice packet networks, capable of dealing with multiple and heterogeneous QoS (Quality of Service) parameters. Firstly the paper presents a discussion of conceptual and methodological issues raised by multiobjective routing optimisation models for MPLS networks. The major contribution is the proposal of a multiobjective routing optimisation framework for MPLS networks. The major features of this modelling framework are: the formulation of a three-level hierarchical routing optimisation problem including network and service performance objectives, the inclusion of fairness objectives in the different levels of...

  16. Olfactory coordinated area coverage

    Larionova, Svetlana; Almeida, Nuno; Marques, Lino; Almeida, A. de
    Abstract This paper proposes an olfaction based methodology to automatically cover an unknown area enabling the decoupled cooperation of a group of floor cleaning mobile robots. This method is based on the utilisation of low cost chemical sensors in cleaning mobile robots, in order to differentiate clean from dirty areas. The experimental results show that the use of olfactory capabilities allows to efficiently cover and clean a certain area, and demonstrate the possibility of coordinating several mobile robots without the need of expensive sensing capabilities, map building or complex algorithms for task scheduling.

  17. An interactive method for multiple objective linear fractional programming problems

    Costa, João Paulo
    Multiple objective linear fractional programming (MOLFP) is an important field of research. Using some branch and bound techniques, we have developed a new interactive method for MOLFP that drastically reduces the computational effort needed, while providing guidance for the decision maker in the choice of his/her preferred solutions. The basic idea of the computation phase of the algorithm is to optimize one of the fractional objective functions while constraining the others. Several linear programming problems, organized in a tree structure, are generated as the search evolves. The whole idea is simple and it results in a fast and very intuitive...

  18. Particle swarm-based olfactory guided search

    Marques, Lino; Nunes, Urbano; Almeida, A. de
    Abstract This article presents a new algorithm for searching odour sources across large search spaces with groups of mobile robots. The proposed algorithm is inspired in the particle swarm optimization (PSO) method. In this method, the search space is sampled by dynamic particles that use their knowledge about the previous sampled space and share this knowledge with other neighbour searching particles allowing the emergence of efficient local searching behaviours. In this case, chemical searching cues about the potential existence of upwind odour sources are exchanged. By default, the agents tend to avoid each other, leading to the emergence of exploration...

  19. On Kalman Active Observers

    Cortesão, Rui
    Abstract The paper introduces the Active Observer (AOB) algorithm in the framework of Kalman filters. The AOB reformulates the Kalman filter to accomplish model-reference adaptive control based on: (1) A desired closed loop system. (2) An extra equation to estimate an equivalent disturbance referred to the system input. An active state is introduced to compensate unmodeled terms, providing a feedforward compensation action. (3) Stochastic design of the Kalman matrices. Stability analysis with model errors is discussed. An example of robot force control with an external and unknown nonlinear disturbance is presented (SISO system). Another example of model-matching control for steer-by-wire...

  20. On the Geometry of Rolling and Interpolation Curves on S n , SO n , and Grassmann Manifolds

    Hüper, K.; Silva Leite, F.
    Abstract We present a procedure to generate smooth interpolating curves on submanifolds, which are given in closed form in terms of the coordinates of the embedding space. In contrast to other existing methods, this approach makes the corresponding algorithm easy to implement. The idea is to project the prescribed data on the manifold onto the affine tangent space at a particular point, solve the interpolation problem on this affine subspace, and then project the resulting curve back on the manifold. One of the novelties of this approach is the use of rolling mappings. The manifold is required to roll on...

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