Abstract
This paper presents a centralized coordination scheme for multiple marine vehicles. The only requirements for proper operation of this method are the presence of bidirectional communication links with a virtual leader and bounded reference tracking errors. By relying on a, lower level, individual position tracking control, coordination is achieved by means of a centralized potential-field that uniquely defines the desired formation geometry as well as its position. The formation can be driven along a path that does not necessarily need to be predefined. Instead, a virtual leader defines the formation position at each instant of time. Furthermore, the possibility of setting stationary points over the path followed by the formation is guaranteed. The approach is illustrated in practice with autonomous surface vehicles in real environment, subjected to disturbances such as wind and waves.

Abstract
In this paper we address the problem of tracking multiple AUVs using acoustic signals. Using For this challenging scenario, we propose to use a Probability Hypothesis Density Filter and present a suitable implementation of the Sequential Monte Carlo PHD filter. It will be demonstrated that a particle filter implementation of the aforementioned filter can be used to successfully track multiple AUVs, changing in number over time, using range measurements from the vehicles to a set of acoustic beacons. Simulation results will be presented that allow to evaluate the performance of the filter.

Abstract
This paper addresses the problem of bottom following by the MARES Autonomous Underwater Vehicle, and presents derivation of a controller able to cope with the peculiarities of such problem. In specific, the main requirement for the controller is the existence of no overshoot both in the depth and pitch outputs of the system. The existence of such time-domain requirements motivates the use of Eigenstructure Assignment techniques in the formulation of the controller. Simulation results obtained with a dynamic model of the MARES AUV are presented and discussed, indicating the validity of the proposed approach.

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. © 2014 IEEE.

Abstract
The ocean and the Blue Economy are increasingly top priorities worldwide. The immense ocean territory in the planet and its huge associated economical potential is envisioned to increase the activity at the ocean in the forthcoming years. The support of these activities, and the convergence to the Internet of Things paradigm, will demand wireless and mobile communications to connect humans and systems at remote ocean areas. Currently, there is no communications solution enabling cost-effective broadband Internet access at remote ocean areas in alternative to expensive, narrowband satellite communications. This paper presents the maritime communications solution being developed in the BLUECOM+ project. The BLUECOM+ solution enables cost-effective broadband Internet access at remote ocean areas using standard wireless access technologies, e.g., GPRS/UMTS/LTE and Wi-Fi. Its novelty lies on the joint use of TV white spaces for long range radio communications, tethered balloons for lifting communications nodes high above the ocean surface, multi-hop relaying techniques for radio range extension, and standard access networks at the ocean. Simulation results prove it is possible to reach radio ranges beyond 100 km and bitrates in excess of 3 Mbit/s using a two-hop land-sea communications chain.

Abstract