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Communications between two autonomous vehicles has been always an important challenge, especially when one of the vehicles is intended for conducting submerged navigation most of its operational time. Underwater communications become in that case the one most common and feasible way for allowing data trasfering underneath the sea surface. Considering low cost of the final vehicle as one of the main features in the concept of this project, a low power low-cost acoustic modem initially intended for environmental sensor applications has been adopted. With the purpose of increasing at maximum the energy reservoir, this modem includes among others, self-wake capabilities and directional transmission. The present work continues in the validation of this acoustic device for application in Underwater Unmanned Vehicles (UUV) in multivehicle configurations. Different solutions for solving the problems associated to the difficulty of conducting robust and reliable data transfering by using this device are presented.

[EN] Nowadays, distributed architectures are the base of many manufacturing systems. Some aspects like fault-tolerance, system validation and design process are very important in the development of these systems. In this paper we study the dependability of three different architectures of a distributed system, and we show the development of both physical and logical fault injectors and the implementation of local performance monitors. We also study the impact of checkpointing mechanisms on the system performance in a control system based on a CAN network. Finally we propose a distributed system design methodology based on codesign. (C) 1999 Elsevier Science B.V. All rights reserved., This article is sponsored by the Comisión Interministerial de Ciencia y Tecnologia under project CICYT-TAP96-1090-C04-01

AUVs are self-propelled and able to navigate at an acceptable speed, but they need an electric motor and batteries that are limited in autonomy. Multivehicle fleet deployment can provide an adequate platform for conducting long term surveillance. Unexpected event detection can be more easily conducted if a set of vehicles in idle mode are expecting the occurrence of this event. Long term and high persistence are very interesting characteristics that a collaborative fleet of different vehicles can provide. However, the problem is the high cost of such kind of vehicles. The possibility of performing adequate tasks by using low cost underwater vehicle could multiply the number of agents in the area and therefore, providing high persistence and wide survey area capabilities. This paper progresses in the definition of the requirements needed to be applied on these kind of vehicles considering the low cost of construction and operation as one of the main goals. A more technological advanced and better equipped ASV as communication and coordination station in the area in combination with a fleet of robust Low Cost AUVs in collaborative schema seems to be an interesting platform for providing good results.

The challenge of extending the autonomy in AUV deployments is one of the most important issues in oceanographic research today. The possibility of maintaining a team of AUV under deployment in a defined area of interest for a long period could provide an additional source of information [8]. All this data in combination with the measures provided by buoys and sea gliders used for slow motion and long range operations will be very valuable. A group of low cost AUV's in alternative automatic switching system navigation-charging operation, could allow a kind of continuous surveying operation. This work is the continuation of the ideas that some of the authors previously presented in the AUV 2010 conference at MBARI [8]. At this conference was proposed the great interest for researching oceanic processes on two areas near Cartagena, Spain: cape Tiñoso and the Mar Menor a shallow coastal lagoon. Both areas require a different research structure configuration because of their opposite characteristics. The Mar Menor is a shallow salty lagoon 20 miles long with 7 m of maximum depth and particular features. This lagoon seems to present a sort of oceanic behavior and can be compared with the major oceans but a minor scale. The second area considered is cape Tiñoso, a very deep area in the Mediterranean Sea where the presence of a self-break provides an interesting potential for the research of the effect of upwelling currents., This work has been partly supported by the Spanish Ministry of Education under projects number TIN2011-28435-C03-01 and CTM2011-29691-C02-01.

Cache memories can improve computer performance, but its unpredictable behaviour makes difficult to use them in hard real-time systems. Classical analysis techniques are not sufficient to accomplish schedulability analysis, and new hardware resources or complex analysis algorithms are needed. This work presents a comprehensive method to obtain predictability on the use of caches in real-time systems using an EDF scheduler. Reaching a predictable cache, schedulability analysis can be accomplished in a simple way through conventional algorithms.