ISEP – LSA – Comunicações em eventos científicos
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Percorrer ISEP – LSA – Comunicações em eventos científicos por autor "Almeida, José Miguel"
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- Application of Visual-Inertial SLAM for 3D Mapping of Underground EnvironmentsPublication . Ferreira, António Bernardo; Almeida, José Miguel; Silva, EduardoThe underground scenarios are one of the most challenging environments for accurate and precise 3d mapping where hostile conditions like absence of Global Positioning Systems, extreme lighting variations and geometrically smooth surfaces may be expected. So far, the state-of-the-art methods in underground modelling remain restricted to environments in which pronounced geometric features are abundant. This limitation is a consequence of the scan matching algorithms used to solve the localization and registration problems. This paper contributes to the expansion of the modelling capabilities to structures characterized by uniform geometry and smooth surfaces, as is the case of road and train tunnels. To achieve that, we combine some state of the art techniques from mobile robotics, and propose a method for 6DOF platform positioning in such scenarios, that is latter used for the environment modelling. A visual monocular Simultaneous Localization and Mapping (MonoSLAM) approach based on the Extended Kalman Filter (EKF), complemented by the introduction of inertial measurements in the prediction step, allows our system to localize himself over long distances, using exclusively sensors carried on board a mobile platform. By feeding the Extended Kalman Filter with inertial data we were able to overcome the major problem related with MonoSLAM implementations, known as scale factor ambiguity. Despite extreme lighting variations, reliable visual features were extracted through the SIFT algorithm, and inserted directly in the EKF mechanism according to the Inverse Depth Parametrization. Through the 1-Point RANSAC (Random Sample Consensus) wrong frame-to-frame feature matches were rejected. The developed method was tested based on a dataset acquired inside a road tunnel and the navigation results compared with a ground truth obtained by post-processing a high grade Inertial Navigation System and L1/L2 RTK-GPS measurements acquired outside the tunnel. Results from the localization strategy are presented and analyzed.
- Ball Sensing in a Leg Like Robotic KickerPublication . Logghe, Jonas; Dias, André; Almeida, José Miguel; Martins, Alfredo; Silva, EduardoThe trend to have more cooperative play and the increase of game dynamics in Robocup MSL League motivates the improvement of skills for ball passing and reception. Currently the majority of the MSL teams uses ball handling devices with rollers to have more precise kicks but limiting the capability to kick a moving ball without stopping it and grabbing it. This paper addresses the problem to receive and kick a fast moving ball without having to grab it with a roller based ball handling device. Here, the main difficulty is the high latency and low rate of the measurements of the ball sensing systems, based in vision or laser scanner sensors.Our robots use a geared leg coupled to a motor that acts simultaneously as the kicking device and low level ball sensor. This paper proposes a new method to improve the capability for ball sensing in the kicker, by combining high rate measurements from the torque and energy in the motor and angular position of the kicker leg. The developed method endows the kicker device with an effective ball detection ability, validated in several game situations like in an interception to a fast pass or when chasing the ball where the relative speed from robot to ball is low. This can be used to optimize the kick instant or by the embedded kicker control system to absorb the ball energy.
- BLUECOM+: Cost-effective broadband communications at remote ocean areasPublication . Campos, Rui; Oliveira, Tiago; Cruz, Nuno; Matos, Anibal; Almeida, José MiguelThe ocean and the Blue Economy are increasingly top priorities worldwide. The immense ocean territory in the planet and its huge associated economical potential is envisioned to increase the activity at the ocean in the forthcoming years. The support of these activities, and the convergence to the Internet of Things paradigm, will demand wireless and mobile communications to connect humans and systems at remote ocean areas. Currently, there is no communications solution enabling cost-effective broadband Internet access at remote ocean areas in alternative to expensive, narrowband satellite communications. This paper presents the maritime communications solution being developed in the BLUECOM+ project. The BLUE-COM+ solution enables cost-effective broadband Internet access at remote ocean areas using standard wireless access technologies, e.g., GPRS/UMTS/LTE and Wi-Fi. Its novelty lies on the joint use of TV white spaces for long range radio communications, tethered balloons for lifting communications nodes high above the ocean surface, multi-hop relaying techniques for radio range extension, and standard access networks at the ocean. Simulation results prove it is possible to reach radio ranges beyond 100 km and bitrates in excess of 3 Mbit/s using a two-hop land-sea communications chain.
- Environmental modeling with precision navigation using ROAZ autonomous surface vehiclePublication . Ferreira, Hugo Miguel; Almeida, Carlos; Martins, Alfredo; Almeida, José Miguel; Dias, André; Silva, Guilherme; Silva, EduardoThe use of robotic vehicles for environmental modeling is discussed. This paper presents diverse results in autonomous marine missions with the ROAZ autonomous surface vehicle. The vehicle can perform autonomous missions while gathering marine data with high inertial and positioning precision. The underwater world is an, economical and environmental, asset that need new tools to study and preserve it. ROAZ is used in marine environment missions since it can sense and monitor the surface and underwater scenarios. Is equipped with a diverse set of sensors, cameras and underwater sonars that generate 3D environmental models. It is used for study the marine life and possible underwater wrecks that can pollute or be a danger to marine navigation. The 3D model and integration of multibeam and sidescan sonars represent a challenge in nowadays. Adding that it is important that robots can explore an area and make decisions based on their surroundings and goals. Regard that, autonomous robotic systems can relieve human beings of repetitive and dangerous tasks.
- Towards a Mobile Three-dimensional Modelling System for Underground StructuresPublication . Ferreira, António Bernardo; Almeida, José Miguel; Silva, EduardoThis paper addresses the three-dimensional modelling of large scale underground galleries, such as traffic tunnels and mines. This work employs techniques from mobile robotics to achieve an autonomous mobile modelling system, adapted to general underground environments. So far, the state-of-the-art methods in underground modelling remain restricted to environments in which pronounced geometric features are abundant. This limitation is a consequence of the scan matching algorithms used to solve the localization and registration problems. This work aims to extend the modeling capability to structures characterized by uniform geometry and smooth surfaces, as is the case of road and train tunnels. A visual monocular Simultaneous Localization and Mapping (MonoSLAM) approach based on the Extended Kalman Filter (EKF) and complemented by the introduction of inertial measurements in the prediction step, allows our system to build threedimensional models and localize himself over long distances, using exclusively sensors carried on board a mobile platform. By feeding the Extended Kalman Filter with inertial data we were able to overcome the major problem related with MonoSLAM implementations, known as scale factor ambiguity, which emerges from the absence of metric measurements in monocular images. The monocular visual features used in MonoSLAM were extracted by the SIFT algorithm, and inserted directly in the EKF mechanism according to the Inverse Depth Parametrization. Through the 1-Point RANSAC (Random Sample Consensus) wrong frame-to-frame feature matches were rejected. To build the model, vertical cross-sections of the gallery, acquired by a laser range finder sensor, are placed on a common reference frame using the estimated localization. The system was tested based on a dataset acquired inside a real road tunnel. Results from the localization strategy and the modelling process are presented.