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C-Enduro USV Developed for Offshore Long-Endurance Applications
ASV Designs Vehicle for UK NOC's LEMUSV Concept

Dan Hook

Richard Daltry

Rafael Coelho

The C-Enduro during sea trials held off Portchester, England, in December 2013.
Unmanned maritime systems offer expanding capabilities to collect large volumes of environmental data safely and cost effectively. The LEMUSV (Long Endurance Marine Unmanned Surface Vehicle) concept was born from a U.K. National Oceanography Centre (NOC) requirement for a long-endurance USV for environmental research. A target duration of three months at sea was set. A competition for funding ran under a Small Business Research Initiative (SBRI) in conjunction with the National Environment Research Council (NERC), the Technology Strategy Board (TSB) and the Defence, Science and Technology Laboratories (DSTL), resulting in Autonomous Surface Vehicles (ASV) Ltd. (Portchester, England) winning funding to design, build and commission a platform named the C-Enduro.

Throughout the development of the C-Enduro, ASV worked alongside Hyperdrive Innovation Ltd. (Cramlington, England) to develop the power management system. ASV also worked with Cranfield University, which conducted research into collision avoidance technologies.

The C-Enduro vehicle centers on a 'three pillar' energy system providing a flexible and fault tolerant solution to energy supply. Having researched and tested various energy sources, the team selected solar panels, a wind generator and a lightweight diesel generator. Detailed calculations and tests show that this selection, combined with efficient power management and command and control systems packaged in a rugged self-righting vehicle, provides the greatest likelihood of meeting the performance requirements.

This unique, environmentally friendly energy system gives C-Enduro an endurance of up to three months at sea. The robust design enables the vehicle to operate in coastal or open ocean weather conditions, currents and sea states with the ability to support up to 500 watts of payload power.

The Project
The objective of the project was to reliably deploy unmanned surface vehicles at sea for periods of up to three months in varied environmental conditions. ASV dedicated the first phase of the project to developing a numeric simulation tool to evaluate in time and space the capability of harvesting solar and wind energy. In order to further understand these challenges, a representative catamaran fitted with a solar panel, wind generator and data logger was moored in realistic conditions for a month to study the performance of these devices and evaluate the software predictions. The team also completed a full-scale towing test to validate their hull drag CFD simulations. The experiments and simulations indicated that a large solar array (10 square meters) coupled to a wind generator and a micro-diesel generator would reliably provide the required energy.

ASV worked with Hyperdrive to design and build the electrical system. The components were extensively bench tested in order to optimize the power management system and the cooling system and identify possible points of failure. Hyperdrive's expertise in the design and build of electric cars was vital to the success of the project.

The enclosed volume of the mast and the 2-meter-long pivoting keel ensure the catamaran platform is very stable and capable of self-righting, allowing operation in harsh weather conditions. In order to save weight and assure a stiff and rugged structure, the designers selected a hybrid carbon-fiber Kevlar prepreg construction. Even when fully loaded, the unit is still easily recoverable using a small trailer on a slipway or vessel crane/A-frame. To continue this article please click here.

Dan Hook is ASV's managing director, with more than 13 years of experience in the unmanned marine industry. He is a qualified naval architect and chartered engineer. Dan has a master's degree in ship science from the University of Southampton.

As ASV's technical director, Richard Daltry is a highly experienced naval architect overseeing ASV's design and control teams. He graduated from the University of Southampton with a master's degree in ship science.

Rafael Coelho is ASV's design manager, responsible for the C-Enduro's platform concept and lines. He is a qualified naval architect with a master's in hydromechanics. He has 10 years of experience in design and production of small watercraft. He is also a keen sailor.

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