Feature ArticleAssisting Micro-ROV Operators During Surveys in Fragile Environments
By David Scaradozzi
Universitá Politecnica delle Marche
Italian Institute of Technology
A 3D virtual reconstruction of an ancient shipwreck in Kolocep, Croatia, showing the Assisted Guidance System's static operational mode (top) and dynamic operational mode (bottom).
Piloting ROVs can be challenging for scientists, such as biologists or archaeologists, who do not have ROV-specific training. The need for automatic navigation, guidance and control systems that can assist operators, especially in low-level tasks, becomes a key aspect in global system realization. Researchers have recently designed and developed the Assisted Guidance System for a micro-ROV, which is part of a more complex robotic system that includes a large ROV. Within this framework, the smaller robot is employed as a mobile appendix of the larger robot, which acts as an actuated garage and supply vessel for the micro-ROV.
During operations, the two ROVs' guidance systems are decoupled. The larger robot works in station keeping or path following, either automatically or under the supervision of an expert operator, while the smaller one is controlled by an operator not specifically trained for piloting ROVs. This guidance system was deployed during a documentation campaign performed on a shipwreck near Kolocep offshore Dubrovnik, Croatia.
Architecture of the Integrated System
Underwater monitoring and documentation activities are often addressed to particular intervention areas, which need to be protected from accidental alterations caused by the activities themselves. This is the case, for instance, of sites that are part of delicate ecosystems, contain fragile archaeological findings or can be irreparably damaged by an invasive intrusion. Moreover, this kind of site could present the additional disadvantage of being difficult to reach because of its particular position or depth.
In these situations, the employment of large robotic vehicles for site investigation turns out to be a scarcely viable solution, since they may disturb, modify or damage the site. The use of a micro-ROV, however, can overcome these problems, even if it presents difficulties related to the limited performances of these vehicles. An integrated robotic system for deep intervention, consisting of two coupled ROVs of different dimensions, has been developing within LabMACS software. In such a system, a micro-ROV is tethered to a large one, which is tethered to a surface supply vessel. This configuration allows the micro-ROV to work at considerable distance from the supply vessel without the burden of a long umbilical and with the large ROV acting as its mother ship. An ultrashort baseline (USBL) acoustic system, coupled with a digital GPS (DGPS) system, is an integral part of the structure and monitors the geopositions of both vehicles.
A supervised control system can be developed to guide the large ROV, while a human operator on the vessel pilots the micro-ROV. Using position information from the acoustic system, the automatic guidance implemented by the supervisory control system maintains the large ROV in a stationary position or guides it along a predetermined path. This way, the bigger vehicle remains distant from the site, avoiding any disturbance or damage and, at the same time, allowing the micro-ROV to investigate the deeper areas due to its closer position.
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After receiving a Ph.D. in artificial intelligent systems, David Scaradozzi worked at Indesit Co. and at Inter-University Center of Integrated Systems for Marine Environment as a senior scientist. He is assistant professor at the Universitá Politecnica delle Marche. His research activities are in robotics and automation.
Giuseppe Conte received a degree in mathematics from the University of Genova in 1974. Since 1990, he has been a professor of automation at the Universitá Politecnica delle Marche. He is chairman of the International Federation of Automatic Control Technical Committee on Linear Systems and the Italy chapter of the IEEE Control System Society.
Laura Sorbi received a bachelor's degree in informatics and automation engineering in 2007 and a master's degree in industrial automation engineering in 2009 from Universitá Politecnica delle Marche. She is now a third-year Ph.D. student of life and humanoid technologies at the Italian Institute of Technology, concentrating on topics regarding underwater activities.