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Publications

Publications by CRAS

2010

Reactive AUV motion for thermocline tracking

Authors
Cruz, NA; Matos, AC;

Publication
OCEANS'10 IEEE Sydney, OCEANSSYD 2010

Abstract
The thermocline is a vertical transition layer in the water column with a strong impact on marine biology, since it affects phytoplankton concentration and, hence, primary production. AUVs can play an important role in understanding this relationship, by sampling the relevant data, usually describing yo-yo patterns spanning the whole water column. In this paper we describe a reactive behavior implemented onboard a small sized AUV, to adapt depth in real time in order to maintain the vehicle in the vicinity of the thermocline and therefore increasing efficiency in the sampling process. Preliminary field tests show that the method is simple, robust and effective. © 2010 IEEE.

2010

Single Beacon Navigation: Localization and Control of the MARES AUV

Authors
Ferreira, B; Matos, A; Cruz, N;

Publication
OCEANS 2010

Abstract
This paper addresses the simultaneous localization and control of an AUV using a single acoustic beacon. To determine its horizontal position, the AUV fuses distances to the single beacon with dead reckoning data, heading and longitudinal velocity. A particle filter and an extended Kalman filter are implemented and compared in terms of performances. As this is an ill-posed problem, special guidance laws are derived so that the overall horizontal positioning error remains bounded. Besides presenting the derivation of such guidance and control laws, as well as procedures to estimate the horizontal position, we also demonstrate the performance of the proposed system by means of simulation results.

2010

Estimation Approach for AUV Navigation Using a Single Acoustic Beacon

Authors
Ferreira, B; Matos, A; Cruz, N;

Publication
SEA TECHNOLOGY

Abstract
The article presents an estimation approach for navigation of the Modular Autonomous Robot for Environment Sampling (MARES) autonomous underwater vehicle (AUV) based on the range to a single beacon deployed in the operation area. Faculty of Engineering of the University of Porto developed the MARES AUV. Typical MARES missions include environmental sampling and monitoring in which the vehicle sweeps a given area while collecting relevant data. The current localization system uses a long-baseline acoustic system based on two acoustic beacons mounted on surface buoys. Each beacon answers the AUV with an acoustic pulse after having been questioned by the AUV in the same way. The MARES AUV interprets sensor data and generates commands at a constant rate of 10 hertz. While measurements from the depth sensor and the compass are available at each time step, range measurements are performed at a lower frequency due to the speed of propagation of acoustic waves.

2010

Automatic Interface for AUV Mission Planning and Supervision

Authors
Abreu, N; Matos, A; Ramos, P; Cruz, N;

Publication
OCEANS 2010

Abstract
This paper describes an integrated application that automates the procedure for sea outfall discharges data acquisition with an Autonomous Underwater Vehicle (AUV). Since most applications for this type of technology are research related, the used software tends to be more technical, oriented for engineers. This fact, allied with the bad sea conditions usually encountered at the portuguese coast, cause the mission execution to be extremely difficult at times. Before starting operating the AUV, a wide range of operations must be completed: we need to get data to estimate plume position, calculate mission path, transfer the AUV and acoustic buoys to the water, test communications and configure a variety of systems. So clearly there is a need to develop an application that fully automates a monitoring mission, allowing the operator with little to no experience to conclude it efficiently. Ultimately, by automating the procedure, there is the possibility of expanding the use of AUV's across several fields of study since no prior knowledge about the its systems is required. In summary this guides the user through a series of tasks and provides visual and audio information.

2010

An integrated application for geostatistical analysis of sea outfall discharges based on R software

Authors
Abreu, N; Ramos, P;

Publication
OCEANS 2010

Abstract
This paper describes an integrated application that performs a geostatistical analysis of data acquired by an AUV in monitoring missions to sewage outfalls. This comes as an effort for automating the procedures of a monitoring campaign from data acquisition to data processing. This application is based on the R statistical software and uses the Gstat package for the geostatistical prediction. R is a console based application that uses software packages developed by the community. The application interfaces with R guiding the user through several steps that perform the geostatistical analysis. It was not our intention to cover all geostatistical procedures but only the ones that are needed for the data processing concerned. The major advantage of this application is that the user does not need to be familiar with methods and data structures associated with the base software, allowing the processing and analysis to be more simple, fast and efficient which is particularly important for routine monitoring. This software application also enables us to give a quicker response in case of contamination to near-by beaches.

2010

Autonomous Guided Vehicles Applied to Industrial Engineering and Management Studies

Authors
Dias, A; Dias, N; Campos, D; Ferreira, H;

Publication
PROCEEDINGS OF THE 1ST INTERNATIONAL CONFERENCE ON ROBOTICS IN EDUCATION

Abstract
This article presents a framework to an Industrial Engineering and Management Science course from School of Management and Industrial Studies using Autonomous Ground Vehicles (AGV) to supply materials to a production line as an experimental setup for the students to acquire knowledge in the production robotics area. The students must be capable to understand and put into good use several concepts that will be of utmost importance in their professional life such as critical decisions regarding the study, development and implementation of a production line. The main focus is a production line using AGVs, where the students are required to address several topics such as: sensors actuators, controllers and an high level management and optimization software. The presented framework brings to the robotics teaching community methodologies that allow students from different backgrounds, that normally don't experiment with the robotics concepts in practice due to the big gap between theory and practice, to go straight to "making" robotics. Our aim was to suppress the minimum start point level thus allowing any student to fully experience robotics with little background knowledge.

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