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Improving Coastal Operations With Unmanned Surface Vehicles
Charlie USV Overcomes Common Problems By Utilizing Dual-Communications System, Acoustic Integration, Mission Control

Gabriele Bruzzone
Research Scientist
Marco Bibuli
Massimo Caccia
Senior Researcher
Institute of Studies on Intelligent Systems for Automation
Italian National Research Council
Genoa, Italy

USVs are an emerging technology destined to play a key role in future networked systems of heterogeneous manned and unmanned air, ground and marine vehicles. Although their employment in defense applications, such as mine countermeasures and harbor and coastal protection, increased during the past years, their use in civil scenarios is still limited by the lack of international rules for the operations of unmanned vessels at sea. Nevertheless, many routine periodic surveys in shallow waters could gain dramatic benefits from the adoption of USV technology without interfering with everyday recreational and trade traffic any more than the use of conventional methodologies.

A number of scenarios require the periodic acquisition and evaluation of bathymetries and sediment distributions, such as surveys for dredging and environmental monitoring in harbors, lagoons, river deltas and swamps; for landslide monitoring, beach maintenance and ecological evaluation in coastal areas; and for monitoring of water quality and dam conditions in artificial lakes.

View of the Charlie USV with its communication system, which includes wireless LAN (left) and radio modem (right).

In addition to conventional acoustic devices (e.g., echosounder, multibeam, side scan sonar and sub-bottom profiler), USVs should be able to carry different sensors for measuring biological, chemical and geochemical parameters, fluid emissions, currents and suspended particles. Moreover, the vehicles are required to automatically follow predefined paths, typically grids, leaving them to focus attention on detected interesting points and then recovering the interrupted mission.

In this context, the Institute of Studies on Intelligent Systems for Automation, Genoa, part of the National Research Council of Italy, is concentrating research efforts and technological developments to improve the operational capabilities of the Charlie USV, a small autonomous catamaran originally designed and exploited for the sampling of the sea surface microlayer in Antarctica (Sea Technology, 2004) and then used as a testbed for robotics research on advanced guidance and cooperative control of marine craft.

Based on previous experience, research and technological efforts focused on three main issues: first, to define and assemble a reliable communication system based on inexpensive standard commercial devices; second, to design and develop a mission control system supporting online replanning and adaptive sampling; and, third, to integrate acoustic devices that support online monitoring of quality of service (QoS) and parameter setting by a remote operator. In-field evaluation of the adopted solutions was carried out during a two-week campaign last fall with the support of Breaking the Surface 2010, an international interdisciplinary field training program on marine robotics and applications held in Croatia.

Solutions to Technological Issues Facing USVs
Communication. USV communications have to support the remote supervision of vehicle operations—sending commands and receiving telemetry—as well as the real-time monitoring of the QoS of payloads to allow remote tuning of instrument parameters.

Even when operating in a protected area, safety reasons require to always have the possibility of tracking the vehicle's motion and basic state, as well as sending commands to take control of the USV in emergencies or unforeseen operating conditions.

These capabilities are for more than safety. Real-time monitoring of the scientific instrumentations' QoS and remote tuning of the parameters controlling data acquisition is fundamental in order to avoid wasting time if the sensor package is not working properly. Due to the high throughput of imaging devices and the priority of information related to basic navigation and control, an adaptive configuration of the instrumentation data link with smooth degradation of performance according to bandwidth limitations is required.

The solution adopted with the Charlie USV relies on a dual-communication system integrating a radio modem and a wireless local area network (LAN).

The idea is to guarantee safe remote supervision of USV behavior with a highly reliable radio communication system and to use the high-bandwidth, but less reliable, wireless channel for real-time observation and monitoring of the acquired data. Thus control commands, characterized by a suitable progressive code, are duplicated on both the transmission channels while a reduced safety telemetry—consisting of vehicle position, heading, speed and basic state—is sent through the radio modem. The wireless LAN handles the transmission of the full vehicle telemetry and payload data using the user datagram protocol, allowing the human operator to tune the instrument data transmission parameters according to the quality of the signal.

Mission Control. In the case of a single vehicle, mission control has to support the automatic survey of user-defined areas, enabling an intelligent system, typically the human operator, to focus attention on areas of interest detected online.

The Charlie USV path is automatically computed as a sequence of transects (straight lines) and connectors (arcs of circles) to comply with common survey practices adopting lawn-mowing strategies and to be compatible with basic motion primitives defined for unmanned marine vehicles. The result is a grid, spaced according to user requirements, with joining curvilinear paths compatible with the maneuvering capabilities of the USV. To continue this article please click here.

Gabriele Bruzzone, responsible for the robotics lab of the Institute of Studies on Intelligent Systems for Automation, contributed to the design and development of the Charlie and other USVs. He oversaw the Break the Surface 2010 campaign for the Charlie USV and has worked on numerous embedded real-time platform projects for industrial automation and robotics.

Marco Bibuli, Ph.D. in electronic and computer engineering, robotics and telecommunications, is an experienced researcher at the Institute of Studies on Intelligent Systems for Automation. He focuses on USV design and development of navigation, guidance and control algorithms, and software architectures for supervision and mission control.

Massimo Caccia is responsible for the autonomous robotic systems and control group at the Institute of Studies on Intelligent Systems for Automation. He coordinated projects on a sea surface autonomous modular unit and a multipurpose unmanned vessel for seabed monitoring. He is a foreign expert to a European Community project 'Developing the Croatian Underwater Robotics Research Potential.'

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