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Publications

Publications by CRAS

2009

Dilatometer for characterization of thermal expansion of ceramic samples

Authors
Rocha, JG; Correia, V; Martins, M; Cabral, JM;

Publication
IECON: 2009 35TH ANNUAL CONFERENCE OF IEEE INDUSTRIAL ELECTRONICS, VOLS 1-6

Abstract
This article describe the design, fabrication steps and experimental results of a dilatometer that will be used to characterize ceramic samples in terms of thermal expansion. The basic idea is to heat a 25 mm ceramic sample up to 1000 degrees C and register its dimension variations during the rising and the falling of the temperature. The device prototype consists in a master-slave structure since there are two control units: the high-level one (master) and a low-level one (slave). The high-level control unit will be responsible for supporting the user interface, exchanging and processing the necessary information between the user and the low-level control unit. The low-level control unit main component is a microcontroller. It is responsible for acquiring data from the strain and temperature sensors and controlling the temperature of the samples. The experimental results show that the prototype is appropriate for dilatometry essays once the maximum error was 0.037% of full-scale.

2008

FASt - An autonomous sailing platform for oceanographic missions

Authors
Alves, JC; Cruz, NA;

Publication
OCEANS 2008, VOLS 1-4

Abstract
Sailing has been for long times the only means of ship propulsion at sea. Although the performance of a sailing vessel is well below the present power driven ships, either in terms of navigation speed and predictability, wind energy is absolutely renewable, clean and free. Unmanned autonomous sailing boats may exhibit a virtually unlimited autonomy and be able to perform unassisted missions at sea for long periods of time. Promising applications include oceanographic and weather data collecting, surveillance and even military applications. The Microtransat competition, launched in Europe in 2006, has been a key initiative to promote the development of robotic unmanned sailing boats. Various regattas have taken place across Europe and the ultimate challenge will be a transatlantic race. This paper presents an autonomous sailing boat developed at the University of Porto, Portugal, with emphasis on the hardware and software computing infrastructure. This platform is capable of carrying a few kilograms of sensing equipment that can be hooked to the boat's main computer, also providing support for short and long range data communications.

2008

Autonomous sailboats: an emerging technology for ocean sampling and surveillance

Authors
Cruz, NA; Alves, JC;

Publication
OCEANS 2008, VOLS 1-4

Abstract
Autonomous sailboats are robotic vessels that use wind energy for propulsion and control the sails and rudders without human intervention. The use of autonomous sailboats for ocean sampling has been tentatively proposed before, but there have been minor efforts towards the development and deployment of actual prototypes, due to a number of technical limitations and significant risks of operation. Currently, most of the limitations have been surpassed, with the availability of extremely low power electronics, flexible computational systems, reliable communication devices and high performance renewable power sources. At the same time, some of the major risks have been mitigated, allowing this emerging technology to become an effective tool for a wide range of applications in real scenarios. We illustrate some of these scenarios and we describe the status of the current efforts being made to develop operational prototypes.

2008

A project driven digital design course using FPGAs

Authors
Araujo, AJ; Alves, JC;

Publication
19th EAEEIE (European Association for Education in Electrical and Information Engineering) Annual Conference - Formal Proceedings

Abstract
This paper presents a project based teaching experience in an advanced digital systems design course with emphasis on design methodologies and laboratory assignments. Projects are the core of the practised teaching methodology and are structured in a pedagogical format according to the course programme. The use of the FPGA technology as the most suitable implementation technology for digital design teaching purposes is discussed. The course structure, oriented to the development of real working digital systems, challenges the students and increases their motivation. This way, the learning process is improved and the classes are more productive. A laboratory development infrastructure based on a FPGA device, used to implement a real-time video processing system, is presented. Examples of laboratory projects implemented with this infrastructure in a recent course edition are also presented. © 2008 IEEE.

2008

A reconfigurable computing system for an autonomous sailboat

Authors
Alves, JC; Ramos, TM; Cruz, NA;

Publication
OGAI Journal (Oesterreichische Gesellschaft fuer Artificial Intelligence)

Abstract
This paper presents the computing infrastructure used in an autonomous unmanned small-scale sailboat. The system is based on a FPGA and includes custom designed interfaces for the various sensors and actuators used in the sailboat. The central processing unit is a 32-bit 50 MHz RISC microprocessor implemented as a soft IP core in the FPGA. The computing system runs uClinux, a simplified version of the popular Linux operating system. The usage of a reconfigurable platform enables a quick reconfiguration of the logic circuit implemented in the FPGA, facilitating the development stage and allowing a dynamic switch among different implementations, according to the navigation requirements and environmental conditions.

2008

A custom processor for a TDMA solver in a CFD application

Authors
Oliveira, F; Santos, CS; Castro, FA; Alves, JC;

Publication
RECONFIGURABLE COMPUTING: ARCHITECTURES, TOOLS AND APPLICATIONS

Abstract
This paper presents a custom processor designed to execute a time consuming function in a CFD application. The selected function implements the method TDMA (Tri-Diagonal Matrix Algorithm) for solving a tri-diagonal system of equations. The custom processor was implemented in a commercial PCI prototyping board based on Virtex4LX FPGAs and uses a dedicated memory cache system, address generators and a deep pipelined floating-point datapath. Running at 100MHz and assuming the input data already in the cache memories, the system reaches a throughput greater than 1.4GFLOPS.

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