Luís Sebastião

Robotic ocean vehicles for marine science applications: the European ASIMOV project

The key objective of the ASIMOV project is the development and integration of advanced technological systems to achieve coordinated operation of an Autonomous Surface Craft (ASC) and an Autonomous Underwater Vehicle (AUV) while ensuring a fast communication link between the two vehicles. The ASC/AUV ensemble is being used to study the extent of shallow water hydrothermalism and to determine the patterns of community diversity at vents in the D. Joao de Castro (DJC) bank in the Azores.

Vehicle and Mission Control of the DELFIM Autonomous Surface Craft

DELFIM is an autonomous surface craft developed at ISR/IST for automatic marine data acquisition and to serve as an acoustic relay between submerged craft and a support vessel. The paper describes the navigation, guidance, and control systems of the vehicle, together with the mission control system that allows end-users to seamlessly program and run scientific missions at sea. Practical results obtained during sea tests in the Atlantic, near Azores islands, are briefly summarized and discussed.

Cooperative Control of Multiple Marine Vehicles Theoretical Challenges and Practical Issues

Abstract This paper is a brief overview of some of the theoretical and practical issues that arise in the process of developing advanced motion control systems for cooperative multiple autonomous marine vehicles (AMVs). Many of the problems addressed have been formulated in the scope of the EU GREX project, entitled Coordination and Control of Cooperating Heterogeneous Unmanned Systems in Uncertain Environments. The paper offers a concise introduction to the general problem of cooperative motion control that is well rooted in illustrative mission scenarios developed collectively by the GREX partners. This is followed by the description of a general architecture for cooperative autonomous marine vehicle control in the presence of time-varying communication topologies and communication losses. The results of simulations with the NetMar SyS (Networked Marine Systems Simulator) of ISR/IST are presented and show the efficacy of the algorithms developed for cooperative motion control. The paper concludes with a description of representative results obtained during a series of tests at sea in the Azores, in 2008.

EXtreme ecosystem studies in the deep OCEan : Technological Developments

EXOCET/D was a three-year project that started in 2004 and that was funded by the European Commission (STREP, FP6-GOCE-CT-2003-505342). The general objective of this project was to develop, implement and test specific technologies aimed at exploring, describing and quantifying biodiversity in deep-sea fragmented habitats as well as at identifying links between community structure and environmental dynamics. The MoMARETO cruise, held during the summer 2006, was the main demonstration action of EXOCET/D. After nearly 3 years of development, the project was a real success with the at sea trial and validation of 13 instrument prototypes developed for the study of deep-sea extreme habitats. These instruments were dedicated to quantitative imaging, in situ measurements, faunal sampling and in vivo experiments.

The MEDUSA class of autonomous marine vehicles and their role in EU projects

This paper describes a new class of autonomous marine vehicles named Medusa and highlights their role in a number of EU projects addressing multiple vehicle scenarios. The MEDUSA vehicles, with surface and diving versions, were designed and built at the Institute for Systems and Robotics, IST, Univ. de Lisboa, Portugal as a result of an effort aimed at affording researchers and practitioners of marine robotics tools to: i) assess the efficacy of cooperative motion control and navigation algorithms and ii) seamlessly execute scientific and commercial missions with multiple robots at sea. We first define the problem of designing the MEDUSA-class of vehicles by describing the desired functional requirements that motivated their development and then present our solution. Mechanical and electrical design considerations that relate to the requirements are explained, and the software architecture is described. This includes a brief overview of the navigation system, the main lower-level control loops which other features can build upon, and some of the higher-level algorithms for multiple-vehicle cooperative missions. We also illustrate the functionality of the mission control system, a dedicated software suite that allows operators to seamlessly program and follow the state of execution of cooperative missions involving multiple vehicles, possibly running different operations or missions in parallel. Finally, we summarize the participation of IST and the MEDUSA vehicles in a number of representative EC-funded Marine Robotics-related projects.

The use of “CARAVELA 2000®” vehicles in operational oceanography

Abstract World-wide, there has been increasing interest in the operational analysis of mesoscale ocean dynamics, which appear to hold the key for a correct description and prediction of ocean system behaviour (e.g. EuroGOOS goals). However, due to the three dimensional characteristics of the underlying phenomena, the characterisation of mesoscale ocean processes for numerical modelling and prediction purposes poses formidable challenges. This stems from the fact that the spatial and time scales of the phenomena involved span the ranges from 10km to 300km and a few days to some months, respectively. With currently available means, it is simply impossible (mainly for cost reasons) to obtain oceanographic data with the 3D space and time resolutions required for accurate large scale, high resolution, ocean modelling in a regular operational mode. Thus the urgent need to develop advanced technological systems for cost effective, automatic ocean data acquisition that will be able to accomplish with the 4D sampling requirements.

Dual accelerometer vector sensor mounted on an autonomous underwater vehicle (AUV)—Experimental results

In seismic geo-acoustic exploration, the use of ships equipped with long streamers is of major concern due to the complexity of the operations. The European project WIMUST aims to improve the efficacy of actual geo-acoustic surveys through the use of AUVs towing short streamers. A Dual Accelerometer Vector Sensor (DAVS) was developed in order to complement the streamer’s data, allowing for the reduction of their size and facilitating the operation of the WiMUST distributed configuration. Each DAVS consists of two tri-axial accelerometers and one hydrophone aligned along a vertical axis. This configuration has the ability to cancel or significantly attenuate the direct and the surface reflection paths, which are undesirable in seismic imaging. Calibration tests with the DAVS have already been performed; this paper presents experimental results on the estimation of azimuthal directions when the DAVS is in motion. Signals in the 1-2kHz band were emitted by a source deployed in a shallow pond at 1.5m depth an...

Cooperative navigation and control: The EU MORPH project

The EU MORPH project advances the use of a formation of five autonomous marine vehicles for mapping and scientific surveying of challenging, unstructured underwater environments as a means to overcome the limitations imposed by current single-vehicle based technology. We describe the test scenarios envisioned in the project and the requirements and constraints that they impose on the cooperative navigation and control systems that enable the concerted operation of the vehicle formation. We then provide a high-level description of each of the blocks that compose the final navigation and formation control architecture, developed at ISR/IST. We highlight how the systems take into account specific mission-related requirements and applications (e.g., typical trajectories employed for mapping and surveying). We describe the results of several trials at sea (involving multiple partners in the project and a group of heterogeneous vehicles) that illustrate the applicability of the MORPH concept in real operational scenarios as well as the limitations of the systems developed.