CRAS

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This performs research and development activities in autonomous robotic systems, mobile robotics and multi-robot mobile systems for inspection, monitoring and mapping, with applications in security, energy, environment, aquaculture, oceanography, marine biology, resource extraction, among other sectors. These activities are supported by research in perception, navigation, control, localization, coordination, and automatic data acquisition and processing.

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    Hydrodynamic Modeling and Motion Limits of AUV MARES
    ( 2009) Miguel Armando Pinto ; Bruno Miguel Ferreira ; Aníbal Matos ; Nuno Cruz
    This papers addresses the dynamic characterization of the autonomous underwater vehicle MARES. The paper presents the main dynamic properties of this underwater robotic platform as well as the procedures employed to obtain the parameters that define the vehicle model. Furthermore, the paper also presents a detailed characterization of the elementary motions that this vehicle is able to perform.
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    The MARES AUV, A Modular Autonomous Robot for Environment Sampling
    ( 2009) Nuno Cruz ; Patrícia Ramos ; Aníbal Matos
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    Side Scan Sonar Image Segmentation and Feature Extraction
    ( 2009) Bruno Miguel Ferreira ; Aníbal Matos ; Nuno Cruz ; Miguel Armando Pinto
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    Using Side Scan Sonar to Relative Navigation
    ( 2009) Miguel Armando Pinto ; Aníbal Matos ; Bruno Miguel Ferreira ; Nuno Cruz
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    Using Side Scan Sonar for Relative Navigation
    ( 2009) Nuno Cruz ; Miguel Armando Pinto ; Aníbal Matos ; Bruno Miguel Ferreira
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    Control of the MARES Autonomous Underwater Vehicle
    ( 2009) Aníbal Matos ; Bruno Miguel Ferreira ; Miguel Armando Pinto
    This paper focuses the control problem of a nonholonomic autonomous underwater vehicle, moving in the tridimensional space. The dynamic of a body in submarine environments is strongly nonlinear. This implies that classical linear controllers are often inadequate whereby Lyapunov theory is here considered. Methods based in this theory are promising tools to design controllers and are applied to the case of MARES, a small-sized autonomous underwater vehicle. Several controllers based only on Lyapunov theory are determined while others combine linear and nonlinear control theory in order to perform various maneuvers. Aiming to verify the correct performance of controllers, simulations and experiments are carried out.
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    Single beacon navigation: localization and control of the MARES AUV
    ( 2010) Nuno Cruz ; Aníbal Matos ; Bruno Miguel Ferreira
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    Estimation Approach for AUV Navigation Using a Single Acoustic Beacon
    ( 2010) Nuno Cruz ; Bruno Miguel Ferreira ; Aníbal Matos
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    "Experiment@Portugal"
    ( 2011) Maria Teresa Restivo ; Alberto Cardoso ; Alves,J
    The main goal of the Project Experiment@Portugal is to produce a complete survey of Portuguese developments in remote and virtual labs. This knowledge will provide the conditions for joining forces in order to organize a well structured national website integrating a database of available remote and virtual experiments, categorized for sharing purposes, and looking for delivering valuable contents for high schools and for higher education. It is expected that the final result will bring up a solid team able to offer in this domain a Portuguese partner at international level.
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    Monitorização ambiental do emissário submarino da Foz do Arelho usando um veículo submarino autónomo
    ( 2011) Sandra Carvalho ; Aníbal Matos ; Patrícia Ramos ; Nuno Cruz
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    Autonomous Underwater Vehicles
    ( 2011) Nuno Cruz
    Autonomous Underwater Vehicles (AUVs) are remarkable machines that revolutionized the process of gathering ocean data. Their major breakthroughs resulted from successful developments of complementary technologies to overcome the challenges associated with autonomous operation in harsh environments. Most of these advances aimed at reaching new application scenarios and decreasing the cost of ocean data collection, by reducing ship time and automating the process of data gathering with accurate geo location. With the present capabilities, some novel paradigms are already being employed to further exploit the on board intelligence, by making decisions on line based on real time interpretation of sensor data. This book collects a set of self contained chapters covering different aspects of AUV technology and applications in more detail than is commonly found in journal and conference papers. They are divided into three main sections, addressing innovative vehicle design, navigation and con
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    Self-localisation of indoor mobile robots using multi-hypotheses and a matching algorithm
    ( 2013) Pinto,M ; Héber Miguel Sobreira ; António Paulo Moreira ; Hélio Mendonça ; Aníbal Matos
    This paper proposes a new, fast and computationally light weight methodology to pinpoint a robot in a structured scenario. The localisation algorithm performs a tracking routine to pinpoint the robot's pose as it moves in a known map, without the need for preparing the environment, with artificial landmarks or beacons. To perform such tracking routine, it is necessary to know the initial position of the vehicle. This paper describes the tracking routine and presents a solution to pinpoint that initial position in an autonomous way, using a multi-hypotheses strategy. This paper presents experimental results on the performance of the proposed method applied in two different scenarios: (1) in the Middle Size Soccer Robotic League (MSL), using artificial vision data from an omnidirectional robot and (2) in indoor environments using 3D data from a tilting Laser Range Finder of a differential drive robot (called RobVigil). This paper presents results comparing the proposed methodology and an Industrial Positioning System (the Sick NAV350), commonly used to locate Autonomous Guided Vehicles (AGVs) with a high degree of accuracy in industrial environments.
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    Object recognition using laser range finder and machine learning techniques
    ( 2013) Andry Maykol Pinto ; Luís Freitas Rocha ; António Paulo Moreira
    In recent years, computer vision has been widely used on industrial environments, allowing robots to perform important tasks like quality control, inspection and recognition. Vision systems are typically used to determine the position and orientation of objects in the workstation, enabling them to be transported and assembled by a robotic cell (e.g. industrial manipulator). These systems commonly resort to CCD (Charge-Coupled Device) Cameras fixed and located in a particular work area or attached directly to the robotic arm (eye-in-hand vision system). Although it is a valid approach, the performance of these vision systems is directly influenced by the industrial environment lighting. Taking all these into consideration, a new approach is proposed for eye-on-hand systems, where the use of cameras will be replaced by the 2D Laser Range Finder (LRF). The LRF will be attached to a robotic manipulator, which executes a pre-defined path to produce grayscale images of the workstation. With this technique the environment lighting interference is minimized resulting in a more reliable and robust computer vision system. After the grayscale image is created, this work focuses on the recognition and classification of different objects using inherent features (based on the invariant moments of Hu) with the most well-known machine learning models: k-Nearest Neighbor (kNN), Neural Networks (NNs) and Support Vector Machines (SVMs). In order to achieve a good performance for each classification model, a wrapper method is used to select one good subset of features, as well as an assessment model technique called K-fold cross-validation to adjust the parameters of the classifiers. The performance of the models is also compared, achieving performances of 83.5% for kNN, 95.5% for the NN and 98.9% for the SVM (generalized accuracy). These high performances are related with the feature selection algorithm based on the simulated annealing heuristic, and the model assessment (k-fold cross-validation). It makes possible to identify the most important features in the recognition process, as well as the adjustment of the best parameters for the machine learning models, increasing the classification ratio of the work objects present in the robot's environment.
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    Robot@Factory: Localization Method Based on Map-Matching and Particle Swarm Optimization
    ( 2013) Andry Maykol Pinto ; António Paulo Moreira ; Paulo José Costa
    This paper presents a novel localization method for small mobile robots. The proposed technique is especially designed for the Robot@Factory which is a new robotic competition presented in Lisbon 2011. The real-time localization technique resorts to low-cost infra-red sensors, a map-matching method and an Extended Kalman Filter (EKF) to create a pose tracking system that is well-behaved. The sensor information is continuously updated in time and space through the expected motion of the robot. Then, the information is incorporated into the map-matching optimization in order to increase the amount of sensor information that is available at each moment. In addition, a particle filter based on Particle Swarm Optimization (PSO) relocates the robot when the map-matching error is high. Meaning that the map-matching is unreliable and robot is lost. The experiments conducted in this paper prove the ability and accuracy of the presented technique to localize small mobile robots for this competition. Therefore, extensive results show that the proposed method have an interesting localization capability for robots equipped with a limited amount of sensors.
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    Sensing Structure based on Surface Plasmonic Resonance in Single Mode Optical Fibers Chemically Etched
    ( 2013) Luís Carlos Coelho ; José Almeida ; José Luís Santos ; Ferreira,RAS ; Andre,PS ; Diana Viegas
    Many optical systems based on Surface Plasmon Resonance (SPR) have been developed for work as refractometers, chemical sensors or even for measure the thickness of metal and dielectric thin films. These kinds of systems are usually large, expensive and cannot be used for remote sensing. Optical fiber sensors based on SPR has been widely studied for the last 20 years with several configurations mostly using multimode optical fibers with large cores and plastic claddings. Sensors based on SPR present very high sensitivity to refractive index variations when compared to the traditional refractive index sensors. Here we propose a SPR sensor based in a single mode fiber. The fiber end is chemically etched by emersion in a 48% hydrofluoric acid solution, resulting a single mode fiber with the cladding removed in a small section. A resonance dip around 1580 nm was attained in good agreement with the simulation scenario that takes into account the real characteristics of the fiber.
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    Revisiting Lucas-Kanade and Horn-Schunck
    ( 2013) Andry Maykol Pinto ; António Paulo Moreira ; Paulo José Costa ; Miguel Velhote Correia
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    Personalised advertising supported by agents
    ( 2013) Bruno Miguel Veloso ; Sousa,L ; Benedita Malheiro
    This paper reports the development of a B2B platform for the personalization of the publicity transmitted during the program intervals. The platform as a whole must ensure that the intervals are filled with ads compatible with the profile, context and expressed interests of the viewers. The platform acts as an electronic marketplace for advertising agencies (content producer companies) and multimedia content providers (content distribution companies). The companies, once registered at the platform, are represented by agents who negotiate automatically the price of the interval timeslots according to the specified price range and adaptation behaviour. The candidate ads for a given viewer interval are selected through a matching mechanism between ad, viewer and the current context (program being watched) profiles. The overall architecture of the platform consists of a multiagent system organized into three layers consisting of: (i) interface agents that interact with companies; (ii) enterprise agents that model the companies, and (iii) delegate agents that negotiate a specific ad or interval. The negotiation follows a variant of the Iterated Contract Net Interaction Protocol (ICNIP) and is based on the price/s offered by the advertising agencies to occupy the viewer's interval. © Springer International Publishing Switzerland 2013.