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Publications

Publications by Alfredo Martins

2009

Radar Based Collision detection developments on USV ROAZ II

Authors
Almeida, C; Franco, T; Ferreira, H; Martins, A; Santos, R; Almeida, JM; Carvalho, J; Silva, E;

Publication
OCEANS 2009 - EUROPE, VOLS 1 AND 2

Abstract
This work presents the integration of obstacle detection and analysis capabilities in a coherent and advanced C&C framework allowing mixed-mode control in unmanned surface systems. The collision avoidance work has been successfully integrated in an operational autonomous surface vehicle and demonstrated in real operational conditions. We present the collision avoidance system, the ROAZ autonomous surface vehicle and the results obtained at sea tests. Limitations of current COTS radar systems are also discussed and further research directions are proposed towards the development and integration of advanced collision avoidance systems taking in account the different requirements in unmanned surface vehicles

2009

Autonomous Bathymetry for Risk Assessment with ROAZ Robotic Surface Vehicle

Authors
Ferreira, H; Almeida, C; Martins, A; Almeida, J; Dias, N; Dias, A; Silva, E;

Publication
OCEANS 2009 - EUROPE, VOLS 1 AND 2

Abstract
The use of unmanned marine robotic vehicles in bathymetric surveys is discussed. This paper presents recent results in autonomous bathymetric missions with the ROAZ autonomous surface vehicle. In particular, robotic surface vehicles such as ROAZ provide an efficient tool in risk assessment for shallow water environments and water land interface zones as the near surf zone in marine coast. ROAZ is an ocean capable catamaran for distinct oceanographic missions, and with the goal to fill the gap were other hydrographic surveys vehicles/systems are not compiled to operate, like very shallow water rivers and marine coastline surf zones. Therefore, the use of robotic systems for risk assessment is validated through several missions performed either in river scenario (in a very shallow water conditions) and in marine coastlines.

2007

SWORDFISH: an autonomous surface vehicle for network centric operations

Authors
Ferreira, H; Martins, R; Marques, E; Pinto, J; Martins, A; Almeida, J; Sousa, J; Silva, EP;

Publication
OCEANS 2007 - EUROPE, VOLS 1-3

Abstract
The design and development of the Swordfish Autonomous Surface Vehicle (ASV) system is discussed. Swordfish is an ocean capable 4.5m long catamaran designed for network centric operations (with ocean and air going vehicles and human operators). In the basic configuration, Swordfish is both a survey vehicle and a communications node with gateways for broadband, Wi-Fi and GSM transports and underwater acoustic modems. In another configuration, Swordfish mounts a docking station for the autonomous underwater vehicle Isurus from Porto University. Swordfish has an advanced control architecture for multi-vehicle operations with mixed initiative interactions (human operators are allowed to interact with the control loops).

2008

A real time vision system for autonomous systems: Characterization during a middle size match

Authors
Silva, H; Almeida, JM; Lima, L; Martins, A; Silva, EP;

Publication
ROBOCUP 2007: ROBOT SOCCER WORLD CUP XI

Abstract
This paper propose a real-time vision framework for mobile robotics and describes the current implementation. The pipeline structure further reduces latency and allows a paralleled hardware implementation. A dedicated hardware vision sensor was developed in order to take advantage of the proposed architecture. The real-time characteristics and hardware partial implementation, coupled with low energy consumption address typical autonomous systems applications. A characterization of the implemented system in the Robocup scenario, during competition matches, is presented.

2003

Coordinated maneuver for gradient search using multiple AUVs

Authors
Martins, A; Almeida, JM; Silva, E;

Publication
OCEANS 2003 MTS/IEEE: CELEBRATING THE PAST...TEAMING TOWARD THE FUTURE

Abstract
The 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 hydrotermal 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 I 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.

1996

On the design and implementation of a control architecture for a mobile robotic system

Authors
Sousa, JB; Pereira, FL; daSilva, EP; Martins, A; Matos, A; Almeida, J; Cruz, N; Tunes, R; Cunha, S;

Publication
1996 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, PROCEEDINGS, VOLS 1-4

Abstract
In this article, we describe the analysis, design and implementation of a control architecture for a mobile platform to autonomously carry out transportation, surveillance and inspection tasks in semi-structured industrial environments. Based on a hierarchical structure composed by the Organization, Coordination and Functional levels organized linguistically and structured according to the Principle of Increasing Precision with Decreasing Intelligence, this control architecture is permits the real-time parallel execution of tasks.

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