Loading...
20 results
Search Results
Now showing 1 - 10 of 20
- BoaVista – Sensor Dedicado de Visão Artificial Baseado em Hardware (Re)configurávelPublication . Lima, Luís; Almeida, José; Martins, Alfredo; Silva, EduardoEste artigo aborda o projecto de um sistema de visão dedicado para robótica móvel autónoma, que beneficia das capacidades de execução paralela do hardware reconfigurável, processando em “pipeline” as imagens provenientes de um sensor de imagem CMOS de alto desempenho em simultâneo com a aquisição das mesmas. Apresentamos um sistema com a capacidade de adquirir e processar imagens com resoluções de 640x480 a uma taxa de 60 fps, baixo custo e capaz de disponibilizar para o sistema central apenas a informação pretendida extraída da imagem. Este ponto, permite libertar os recursos computacionais do robot traduzindo-se em reduções de consumo significativas e consequente aumento da autonomia energética do mesmo.
- Master's in autonomous systems: an overview of the robotics curriculum and outcomes at ISEP, PortugalPublication . Silva, Eduardo; Almeida, José; Martins, Alfredo; Baptista, João Paulo; Neves, Betina CamposRobotics research in Portugal is increasing every year, but few students embrace it as one of their first choices for study. Until recently, job offers for engineers were plentiful, and those looking for a degree in science and technology would avoid areas considered to be demanding, like robotics. At the undergraduate level, robotics programs are still competing for a place in the classical engineering graduate curricula. Innovative and dynamic Master’s programs may offer the solution to this gap. The Master’s degree in autonomous systems at the Instituto Superior de Engenharia do Porto (ISEP), Porto, Portugal, was designed to provide a solid training in robotics and has been showing interesting results, mainly due to differences in course structure and the context in which students are welcomed to study and work
- High-Accuracy Low-Cost RTK-GPS for an Unmanned Surface VehiclePublication . Matias, B.; Oliveira, H.; Almeida, José; Dias, André; Ferreira, H.; Martins, Alfredo; Silva, EduardoThis work presents a low cost RTK-GPS system for localization of unmanned surface vehicles. The system is based on the use of standard low cost L1 band receivers and in the RTKlib open source software library. Mission scenarios with multiple robotic vehicles are addressed as the ones envisioned in the ICARUS search and rescue case where the possibility of having a moving RTK base on a large USV and multiple smaller vehicles acting as rovers in a local communication network allows for local relative localization with high quality. The approach is validated in operational conditions with results presented for moving base scenario. The system was implemented in the SWIFT USV with the ROAZ autonomous surface vehicle acting as a moving base. This setup allows for the performing of a missions in a wider range of environments and applications such as precise 3D environment modeling in contained areas and multiple robot operations.
- Structured Light System Calibration for Perception in Underwater TanksPublication . Lopes, Flávio; Silva, Hugo; Almeida, José; Silva, EduardoThe process of visually exploring underwater environments is still a complex problem. Underwater vision systems require complementary means of sensor information to help overcome water disturbances. This work proposes the development of calibration methods for a structured light based system consisting on a camera and a laser with a line beam. Two different calibration procedures that require only two images from different viewpoints were developed and tested in dry and underwater environments. Results obtained show, an accurate calibration for the camera/projector pair with errors close to 1 mm even in the presence of a small stereos baseline.
- Decentralized Target Tracking based on Multi-Robot Cooperative TriangulationPublication . Dias, André; Capitan, J.; Merino, L.; Almeida, José; Lima, Pedro; Silva, EduardoTarget tracking with bearing-only sensors is a challenging problem when the target moves dynamically in complex scenarios. Besides the partial observability of such sensors, they have limited field of views, occlusions can occur, etc. In those cases, cooperative approaches with multiple tracking robots are interesting, but the different sources of uncertain information need to be considered appropriately in order to achieve better estimates. Even though there exist probabilistic filters that can estimate the position of a target dealing with incertainties, bearing-only measurements bring usually additional problems with initialization and data association. In this paper, we propose a multi-robot triangulation method with a dynamic baseline that can triangulate bearing-only measurements in a probabilistic manner to produce 3D observations. This method is combined with a decentralized stochastic filter and used to tackle those initialization and data association issues. The approach is validated with simulations and field experiments where a team of aerial and ground robots with cameras track a dynamic target.
- Uncertainty based Multi-Robot Cooperative TriangulationPublication . Dias, André; Almeida, José; Lima, Pedro; Silva, EduardoThe paper presents a multi-robot cooperative framework to estimate the 3D position of dynamic targets, based on bearing-only vision measurements. The uncertainty of the observation provided by each robot equipped with a bearing-only vision system is effectively addressed for cooperative triangulation purposes by weighing the contribution of each monocular bearing ray in a probabilistic manner. The envisioned framework is evaluated in an outdoor scenario with a team of heterogeneous robots composed of an Unmanned Ground and Aerial Vehicle.
- Coordinated Maneuver for Gradient Search Using Multiple AUV'sPublication . Martins, Alfredo; Almeida, José; Silva, EduardoThe coordinated use of multiple Autonomous Underwater Vehicles can provide important advantages for oceanographic missions. One important mission application scenario can be the search of underwater plumes such as sources of freshwater of hydrothermal vents. These plumes characterize the environment by creating a gradient field of some measurable physical quantity. An innovative integrated acoustic navigation system and coordination control maneuver for a formation of 3 AUVs and 1 surface craft to gradient search and following missions is proposed. The specific formation geometry and topology takes in account the navigation and coordination requirements. It was designed to achieve an efficient, low cost and technically feasible solution. The system can operate in 3 modes depending on formation distances. Varying pinging rates and offsets are used to communicate parameters and mode changing. No additional underwater communication systems neither acoustic transponder deployment are needed for the vehicle coordination. This way a high degree of energy efficiency and overall mission low cost and simpler logistics is achieved. The hybrid nature of the coordinating maneuver allows the formation gradient survey and following with the efficient exploitation of the environment structuring by the phenomena to be studied. The individual control laws were designed in order to minimize the inter-vehicle communication. The coordination factors are the knowledge by the vehicles of each other behavior (since all vehicles execute the same control laws) and the detection of formation distortions. These distortions are detected by the relative navigation system. The proposed approach allows the low cost implementation of a multiple AUV coordinating control for a large range of oceanographic missions.
- Hybrid Maneuver for Gradient Search with Multiple Coordinated AUVsPublication . Martins, Alfredo; Silva, Eduardo; Pereira, Fernando L.; Almeida, JoséThis work presents a hybrid maneuver for gradient search with multiple AUV's. The mission consists in following a gradient field in order to locate the source of a hydrothermal vent or underwater freshwater source. The formation gradient search exploits the environment structuring by the phenomena to be studied. The ingredients for coordination are the payload data collected by each vehicle and their knowledge of the behaviour of other vehicles and detected formation distortions.
- Distributed active traction control system applied to the RoboCup middle size leaguePublication . Almeida, José; Dias, André; Sequeira, João; Martins, Alfredo; Silva, EduardoThis work addresses the problem of traction control in mobile wheeled robots in the particular case of the RoboCup Middle Size League (MSL). The slip control problem is formulated using simple friction models for ISePorto Team robots with a differential wheel configuration. Traction was also characterized experimentally in the MSL scenario for relevant game events. This work proposes a hierarchical traction control architecture which relies in local slip detection and control at each wheel, with relevant information being relayed to a higher level responsible for global robot motion control. A dedicated one axis control embedded hardware subsystem allowing complex local control, high frequency current sensing and odometric information procession was developed. This local axis control board is integrated in a distributed system using CAN bus communications. The slipping observer was implemented in the axis control hardware nodes integrated in the ISePorto robots and was used to control and detect loss of for traction. %and to detect the ball in the kicking device. An external vision system was used to perform a qualitative analysis of the slip detection and observer performance results are presented.
- Structured Light System for Underwater Inspection OperationsPublication . Lopes, Flávio; Silva, Hugo; Almeida, José; Martins, Alfredo; Silva, EduardoIn this work we propose the development of a stereo SLS system for underwater inspection operations. We demonstrate how to perform a SLS calibration both in dry and underwater environments using two different methods. The proposed methodology is able to achieve quite accurate results, lower than 1 mm in dry environments. We also display a 3D underwater scan of a known object size, a sea scallop, where the system is able to perform a scan with a global error lower than 2% of the object size.