Abstract
The thermocline is a vertical transition layer in the water column with a strong impact on marine biology, since it affects phytoplankton concentration and, hence, primary production. AUVs can play an important role in understanding this relationship, by sampling the relevant data, usually describing yo-yo patterns spanning the whole water column. In this paper we describe a reactive behavior implemented onboard a small sized AUV, to adapt depth in real time in order to maintain the vehicle in the vicinity of the thermocline and therefore increasing efficiency in the sampling process. Preliminary field tests show that the method is simple, robust and effective. © 2010 IEEE.

Abstract
This paper addresses the navigation and guidance of an AUV operating in a network of moving acoustic beacons. In this network, the vehicle position is obtained from acoustic signals exchanged between the vehicle and the beacons and is computed in a reference frame associated with the moving beacons. The paper describes the operation of the acoustic network, the mission specification and guidance system that computes the references for the vehicle controllers, and the navigation system that produces all the data required by the guidance system.

Abstract
In this paper, we present an approach to control an autonomous underwater vehicle in the vertical and the horizontal planes while pitching down or up (theta = +/-pi/2). Such a capability is explored in MARES, a small-sized, torpedo-shaped hovering AUV with four degrees of freedom. Despite the fact that roll angle is not controllable, we find a guidance law that makes the vehicle reach any point in the horizontal plane while maintaining the vehicle in the vertical position.

Abstract
This paper addresses the simultaneous localization and control of an AUV using a single acoustic beacon. To determine its horizontal position, the AUV fuses distances to the single beacon with dead reckoning data, heading and longitudinal velocity. A particle filter and an extended Kalman filter are implemented and compared in terms of performances. As this is an ill-posed problem, special guidance laws are derived so that the overall horizontal positioning error remains bounded. Besides presenting the derivation of such guidance and control laws, as well as procedures to estimate the horizontal position, we also demonstrate the performance of the proposed system by means of simulation results.

Abstract
In this paper, we discuss the design aspects and the development of the MARES AUV, a 1.5m long vehicle, weighting 32kg, designed and built at the University of Porto, Portugal. This vehicle is highly maneuverable, with the ability to move in the vertical plane, controlling pitch and vertical velocity; forward velocity can also be determined, anywhere between 0 and 2 m/s. MARES can easily integrate any new payload within reason, finding applications in a wide range or areas, such as pollution monitoring, scientific data collection, sonar mapping, underwater video or mine countermeasures.

Abstract
This paper focuses on the positioning control of of a small size autonomous surface vessel (ASV) that can be used to carry a multitude of payload systems, including acoustic devices for underwater positioning and for communications with autonomous underwater vehicles. Its main motivation is the development of highly operational systems, by replacing typically moored support infrastructures with others that can dynamically position themselves. This work covers the design of feedback control laws that assure that the underactuated surface vessel Zarco can keep its position even in the presence of water currents and wind, and without special sensors to estimate such disturbances. Experimental results showing the performance of the designed control laws are also shown.