G. Veruggio

Modeling and identification of open-frame variable configuration unmanned underwater vehicles

A lumped parameter model of open-frame unmanned underwater vehicles (UUVs) including the effects of propeller-hull and propeller-propeller interactions is presented. The identification of the model parameters consists of a least squares method using only on-board sensor data without requiring any towing tank tests. The identification scheme is based on separate tests for the estimation of drag and thruster installation coefficients, taking into account propeller-hull and propeller-propeller effects first and inertia parameters subsequently. The scheme has been experimentally implemented on ROMEO, the latest UUV developed by CNR-IAN. Experimental results show both the effectiveness of the proposed method and the relevance of the propeller-hull and propeller-propeller interactions that are usually neglected in standard UUV models.

Sampling sea surfaces with SESAMO: an autonomous craft for the study of sea-air interactions

This paper presents the system design, sea trials and Antartic exploitation of the SESAMO platform. The SESAMO (sea surface autonomous modular unit) prototype robot was especially designed to collect data and samples for the study of the sea-air interface. At sea, operations showed that a relatively simple robot could satisfactorily work in a natural, outdoor environment, dramatically facilitating the job of the human operator. To achieve high quality sampling of the surface microlayer, however, requires a large amount of time, leading to significant demands on logistics resources, mainly in terms of operating time of the support vessel.

Fault detection of actuator faults in unmanned underwater vehicles

Abstract A fault-diagnostic system for unmanned underwater vehicles has been designed and tested in real operating conditions. Actuator faults have been considered, relying on approximate models of the vehicles’ dynamics. Fault detection and diagnosis is accomplished by evaluating any significant change in the behaviour of the vehicle. This task is performed by a bank of estimators: a filter is implemented for each actuator fault type, including the no-fault case. The estimators used are extended Kalman filters (EKF), due to the presence of nonlinearities in the dynamic models. Experimental results are reported, to demonstrate the effectiveness of the proposed approach.

Bottom-following for remotely operated vehicles

Abstract This paper addresses the problem of designing high precision bottom followers for remotely operated vehicles. In the framework of hierarchical control architectures able to uncouple the robot’s kinematics (guidance) and dynamics (velocity control), the task of bottom-following is accomplished by suitable guidance task functions, which enable the system to handle unmodelled, i.e. not measured or estimated, kinematics interactions between the robot and the operating environment. In order to increase the bottom followers’ reliability, the paper discusses possible techniques for modeling and handling the environmental and measurement uncertainty in the estimate of the local interactions between the vehicle and the operating environment, i.e. altitude and bottom slope. In particular, according to at-sea operational experience, the problem of managing dropouts due to erroneous tracking of multi-path echoes by the ROV altimeters) is addressed. Results of a large set of pool trials carried out with the Romeo ROV are reported and discussed.

Variable-configuration UUVs for marine science applications

In this article, after a brief overview of trends in underwater unmanned vehicle (UUV) design and applications, results in developing an automatic guidance and control system for Romeo are presented. Attention is focused on the design, development, and testing in the operating conditions of a bottom and ice-canopy following system and on the development of methodologies for the at-field identification of the vehicle dynamics in order to guarantee high motion-control performance, even in the presence of variations in the vehicle configuration. In particular, the system performance in the proximity of the coast, where there is only a very shallow column of free water between the ice-pack and the sea-bed, is discussed.

Application of LS and EKF techniques to the identification of underwater vehicles

The modelling and identification of an open-frame underwater vehicle for marine applications is considered. The goal of this work is to demonstrate that modelling and identification of small underwater vehicles is feasible at low cost: the identification has been accomplished using only standard on-board devices. First, the selection of a model for such vehicles is discussed, as well as a suitable identification method. The parameters of the selected model are identified in two steps: based on least squares (LS) and extended Kalman filter (EKF) techniques. The results of the identification applied to experimental data are presented and discussed.

Active sonar-based bottom-following for unmanned underwater vehicles

Abstract The problem of high-precision bottom-following in the proximity of the seabed for open-frame unmanned underwater vehicles (UUVs) is addressed in this paper. The suggested approach consists of the integration of a guidance and control system with an active multi-hypothesis extended Kalman filter, able to estimate the motion of the vehicle with respect to the bottom profile. The guidance module is based on the definition of a suitable Lyapunov function associated with the bottom-following task, while the motion controller is a conventional autopilot, performing autoheading, autodepth, and autospeed. The motion of the vehicle is estimated from range and bearing measurements supplied by a high-frequency pencil-beam profiling sonar. Moreover, a general-purpose sensor-based guidance and control system for advanced UUVs, able to manage active sensing-based guidance and motion estimation modules, is presented. An application of the proposed architecture to execute high-precision bottom-following using Romeo, a prototype UUV, developed by the Robotics Dept. of the Istituto Automazione Navale, is described. Experimental results of tests, conducted in a high-diving pool with the vehicle equipped with a sonar profiler, are presented.

Guidance of unmanned underwater vehicles: experimental results

This paper addresses the problem of guidance of unmanned underwater vehicles (UUVs). In the framework of a two layered hierarchical architecture decoupling the system dynamics and kinematics, two guidance laws for approaching a target with the desired orientation and following an environmental feature have been designed with Lyapunov-based techniques. Suitable acoustic-based estimators of the corresponding operational variables have been designed and integrated with the guidance and control system. Experimental results of pool trials of a prototype UUV executing free-space maneuvering and wall-following tasks are reported and discussed.

ROBY goes to Antarctica

The IX Italian Expedition 1993-94 of PNRA (Programma Nazionale di Ricerche in Antartide) included the first experimental campaign in Antarctica in the field of underwater robotics. It can be described as a pilot mission to better define the role of this technology in the future of Antarctic exploration. The work plan was as follows: to test and develop the CPR-IAN test-bed prototype called ROBY; to verify requirements and constraints of the SARA (Sottomarino Autonomo Robotizzato Antartica), an advanced Antarctic AUV currently being designed by a consortium including CNR, ENEA, Tecnomare and others; and to help scientists collect oceanographic data. The results were satisfactory both from the technical and scientific points of view. Roby worked well in all renditions and no electrical or mechanical problems arose from either the low temperatures or rough treatment involved in such harsh working conditions. Eighteen dives were performed at a maximum depth of 150 metres for a total underwater working time of 20 hours. Most of the marine environments of Terra Nova Bay were explored and documented in the form of video and data; the work met with a favourable response from marine biologists and oceanographers, who will use the collected data for their studies.<<ETX>>

Design and Exploitation of an Autonomous Surface Vessel for the Study of Sea-Air Interactions

The design, development, sea trials and exploitation of the SESAMO (SEa Surface Autonomous MOdular unit) platform, an autonomous surface vessel for the study and characterization of the air-sea interface, are presented. The SESAMO prototype robot, developed by the robotics group of CNR-ISSIA, Genova branch, in strict cooperation with the scientific end-users in the framework of a project of the Italian National Program of Research in Antarctica (PNRA), was able to sample the sea surface microlayer and immediate sub-surface. After satisfactory basic at field trials of the navigation, guidance and control (NGC) and sampling systems, the robotised catamaran was exploited by the scientific end-users for water sample collection in the area of Terra Nova Bay, Ross Sea, Antarctica, in the framework of the PNRA project Chemical contamination.