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Publications

Publications by CRAS

2003

Control and localisation for the ISePorto robotic soccer team

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

Publication
PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON ADVANCED ROBOTICS 2003, VOL 1-3

Abstract
This paper describes the design and implementation status of the Control and Localisation systems of the ISePorto robotic football team for participation in Robocup Middle Size League (F2000). The objectives guiding the project were the applications and research in hybrid control and coordination systems. The system has also an educational support role. 4 special attention is made to the custom design to allow the execution of complex manoeuvres and team coordinated behaviours. The robot has different pass, shot, and manoeuvre capabilities providing high level tactical and strategic planing and coordination.

2003

Specification of multiple AUV strategies for search of freshwater oceanic sources

Authors
Silva, EP; Martins, AM; Almeida, JM; Sousa, JB; Pereira, FL;

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

Abstract
System and mission requirements for the use of Autonomous Underwater Vehicles (AUV) were defined. A requirement analysis was done having in mind the definition of search methodologies involving multiple cooperating vehicles. Control and navigation issues were addressed. Various search strategies were proposed and analyzed in terms of control, navigation and overall system requirements.

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.

2003

An Internet DGPS service for precise outdoor navigation

Authors
Soares, MG; Malheiro, B; Restivo, FJ;

Publication
ETFA 2003: IEEE CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, VOL 1, PROCEEDINGS

Abstract
The goal of the work presented in this paper is to provide mobile platforms within our campus with a GPS based data service capable of supporting precise outdoor navigation. This can be achieved by providing campus-wide access to real time Differential GPS (DGPS) data. As a result, we designed and implemented a three-tier distributed system that provides Internet data links between remote DGPS sources and the campus and a campus-wide DGPS data dissemination service. The Internet data link service is a two-tier client/server where the server-side is connected to the DGPS station and the client-side is located at the campus. The campus-wide DGPS data provider disseminates the DGPS data received at the campus via the campus Intranet and via a wireless data link. The wireless broadcast is intended for portable receivers equipped with a DGPS wireless interface and the Intranet link is provided for receivers with a DGPS serial interface. The application is expected to provide adequate support for accurate outdoor campus navigation tasks.

2003

Real time Internet DGPS service

Authors
Snares, MG; Malheiro, B; Restivo, FJ;

Publication
7TH WORLD MULTICONFERENCE ON SYSTEMICS, CYBERNETICS AND INFORMATICS, VOL IX, PROCEEDINGS: COMPUTER SCIENCE AND ENGINEERING: II

Abstract
The accuracy of the Navigation Satellite Timing and Ranging (NAVSTAR) Global Positioning System (GPS) measurements is insufficient for many outdoor navigation tasks. As a result, in the late nineties, a new methodology - the Differential GPS (DGPS) - was developed. The differential approach is based on the calculation and dissemination of the range errors of the GPS satellites received. GPS/DGPS receivers correlate the broadcasted GPS data with the DGPS corrections, granting users increased accuracy. DGPS data can be disseminated using terrestrial radio beacons, satellites and, more recently, the Internet. Our goal is to provide mobile platforms within our campus with DGPS data for precise outdoor navigation. To achieve this objective, we designed and implemented a three-tier client/server distributed system that establishes Internet links with remote DGPS sources and performs campus-wide dissemination of the obtained data. The Internet links are established between data servers connected to remote DGPS sources and the client, which is the data input module of the campus-wide DGPS data provider. The campus DGPS data provider allows the establishment of both Intranet and wireless links within the campus. This distributed system is expected to provide adequate support for accurate (submetric) outdoor navigation tasks.

2003

Contributions to time varying spectrum estimation using the instantaneous power spectrum (IPS)

Authors
Hippensteil, R; Oliveira, P;

Publication
International Conference on Acoustics, Speech, and Signal Processing

Abstract

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