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Publications

Publications by CRAS

2014

Navigation Performance of an Autonomous Sailing Robot

Authors
Cruz, NA; Alves, JC;

Publication
2014 OCEANS - ST. JOHN'S

Abstract
Autonomous sailing robots are a relatively new technology for oceanographic missions, targeting at long term presence in the ocean by using wind as the main source of propulsion. This paper addresses the navigation performance of FASt, an autonomous sailboat being developed in Porto, Portugal, since 2008. A series of results selected from various sea trials illustrate the accuracy of navigation and the maneuvering ability. The paper provides some quantitative performance in downwind, sidewind and upwind trajectories, with various environmental conditions. It also addresses the ability to stay within a watch circle of a few tens of meters, during the station keeping maneuver.

2014

TEC4SEA-A Modular Platform for Research, Test and Validation of Technologies Supporting a Sustainable Blue Economy

Authors
Monica, P; Martins, A; Olivier, A; Matos, A; Almeida, JM; Cruz, N; Alves, JC; Salgado, H; Pessoa, L; Jorge, P; Campos, R; Ricardo, M; Pinho, C; Silva, A; Jesus, S; Silva, E;

Publication
2014 OCEANS - ST. JOHN'S

Abstract
This paper presents the TEC4SEA research infrastructure created in Portugal to support research, development, and validation of marine technologies. It is a multidisciplinary open platform, capable of supporting research, development, and test of marine robotics, telecommunications, and sensing technologies for monitoring and operating in the ocean environment. Due to the installed research facilities and its privileged geographic location, it allows fast access to deep sea, and can support multidisciplinary research, enabling full validation and evaluation of technological solutions designed for the ocean environment. It is a vertically integrated infrastructure, in the sense that it possesses a set of skills and resources which range from pure conceptual research to field deployment missions, with strong industrial and logistic capacities in the middle tier of prototype production. TEC4SEA is open to the entire scientific and enterprise community, with a free access policy for researchers affiliated with the research units that ensure its maintenance and sustainability. The paper describes the infrastructure in detail, and discusses associated research programs, providing a strategic vision for deep sea research initiatives, within the context of both the Portuguese National Ocean Strategy and European Strategy frameworks.

2014

From Boolean algebra to processor architecture and assembly programming in one semester

Authors
Matos, JS; Alves, JC; Mendonca, HS; Araujo, AJ;

Publication
Proceedings of the 2014 29th Conference on Design of Circuits and Integrated Systems, DCIS 2014

Abstract
The paper presents the approach followed at the Faculty of Engineering of the University of Porto, to introduce design automation tools and structured design techniques in the first course on digital system design of our Integrated Master in Electrical and Computer Engineering. Digital Systems Laboratory is an introductory course on digital design, with the classical task of teaching Boolean algebra and combinational and sequential circuit design, using gates, flip-flops and medium complexity components/function blocks like counters and shift-registers. The need to cope with new curriculum requirements and modern digital design demands, motivated an extensive reformulation of the course contents and organization, leading to the introduction of the use of hardware description languages and synthesis tools, in order to implement small systems, of increasingly complex nature, on an FPGA platform. At the same time its coverage was extended to include low-level processor architecture issues, and to teach assembly programming for the MIPS processor. The paper describes how this reformulation was carried out. It presents the course contents and timeline, and discusses the main choices that were made. The paper also describes the laboratory experiments that were developed and discusses some of the challenges and results obtained so far. © 2014 IEEE.

2014

Permanent Ocean Presence With Autonomous Sailing Robots Wind-Propelled Vessels Foster Long Missions With Precise Maneuvering

Authors
Alves, JC; Cruz, NA;

Publication
SEA TECHNOLOGY

Abstract
The demand for accurate ocean sampling is continuously growing to provide a better understanding of the complex sea environment. Current economic and social activity is strongly dictated by knowledge built on data collected from thousands of sensors around the world, ranging from space-borne remote sensors to underwater devices transported by profilers. Autonomous sailboats have great potential to gather long-term data to understand multiple aspects of the ocean environment. In terms of oceanography, they can be used to study many processes occurring at the surface, like the energy exchange between the ocean and the atmosphere and how it affects the climate. They can also be a valuable tool to understand the dynamics of episodic events that evolve on a timescale of weeks or months, like harmful algae blooms or the evolution of pollution plumes. Even though these incidents can already be tracked by satellite, the ability to capture in-situ data for the full cycle can provide valuable data about the phenomena.

2014

MPL—A Mission Planning Language for Autonomous Surface Vehicles

Authors
Cabral, HMP; Alves, JC; Cruz, NA; Valente, JF; Lopes, DM;

Publication
Robotic Sailing 2013

Abstract

2014

Autonomous Tracking of a Horizontal Boundary

Authors
Cruz, NA; Matos, AC;

Publication
2014 OCEANS - ST. JOHN'S

Abstract
The ability to employ autonomous vehicles to find and track the boundary between two different water masses can increase the efficiency in waterborne data collection, by concentrating measurements in the most relevant regions and capturing detailed spacial and temporal variations. In this paper we provide a guidance mechanism to enable an autonomous vehicle to find and track the steepest gradient of a scalar field in the horizontal plane. The main innovation in our approach is the mechanism to adapt the orientation of the crossings to the local curvature of the boundary, so that the vehicle can keep tracking the gradient regardless of its horizontal orientation. As an example, we show how the algorithms can be used to find and track the boundary of a dredged navigation channel, using only altimeter measurements.

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