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11,000 Meter HROV Development Program and itsRelation to Oceanographic and Commercial Undersea Use

February 2006Andy Bowen, Dr. Dana Yoerger, (Woods Hole Oceanographic Institution), Dr. Louis

Whitcomb (Johns Hopkins University), Ms. Barbara Fletcher (SPAWAR/SSC)

The Hybrid Remotely Operated Vehicle (HROV) programhas drawn from and incorporated cutting edge technologiesfrom across the academic, commercial, and militarycommunities. The unique capabilities required by theHROV system are driving the innovative use anddevelopment of relevant technologies such as advancedmaterials, energy storage, imaging and lighting technology,micro-fiber communications, low power manipulativesystems, and autonomous underwater vehicle control.

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Materials• First use of high performance ceramics for full ocean

depth floatation.Discussion:HROV will be the first project to exploit highstrength ceramic technology for full ocean depthfloatation, building on over 30 years of Navy andcommercial development. Weight savings to beachieved are approximately 40% over the moretraditional syntactic foam material, allowing thesystemto achieve significantly lighterweight andsmaller size. The HROV project has significantlycontributed to the exposure of this technologywhich is likely to have a positive impact to manyoceanographic and commercial projects requiringfloatation. The vendor (DeepSea Power and LightInc.) is now marketing the ceramic spheres to theoceanographic and commercial oil and gas industryas an alternative to syntactic foam. Lower densityfloatation has the profound benefit of allowingsystems to achieve significantly lighter weights andsmaller sizes. For example, an AUV that is smallerand lighter can travel further underwater.

• First use of high performance ceramics for full oceandepth pressure proof enclosures.

Discussion:The traditional solution for deep ocean pressureresistant enclosures to protect electrical componentsfrom the environment is to use titanium. Thismaterial has high specific strength for its weight and

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is generally impervious to corrosion, yet theresultant weights are prohibitive for full oceandepths. Here too, the HROV project will exploithigh performance ceramic materials, with aresultant 60% weight savings over titanium. Thelighter enclosures will reduce the need for floatation(ROVs and AUVs require neutral buoyancy to dotheir jobs), thus resulting in smaller and ultimatelylower cost vehicles with enhanced performance.The development and demonstration of thesesystems for HROV provide new resources for boththe oceanographic and commercial ROV/AUVcommunities.

Energy StorageDiscussion:

The HROV will require a large amount of on-boardbatteries. The batteries must be economical, easy tooperate and maintain, provide high energy density,and must be safe for conventional shipping. Basedon WHOI’s success with battery packs for theAutonomous Benthic Explorer (ABE) and othersimilar projects, lithium-ion rechargeable batterieswere selected. While these batteries are ubiquitousfor small-scale applications such as cell phones andlaptop computers, packs of the size we need forHROV are not commercially available.

To solve this problem, we have chosen to use smallcells like those found inside laptop computer batterypacks. These cells are economical, very consistent,

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and reliable as they are produced in very largenumbers. However, we need to combine over 2000of these small cells to provide the energy needed forHROV.

Our packs will be built up from subpacks of12 cells connected in parallel. Thesesubpacks can be tested extensively, allowingthe HROV packs to be shipped byconventional means.

For both charge and discharge, the packswill be managed by innovative WHOI-designed battery management electronics.With such a large collection of cells, cellscan become imbalanced over repeatedcharge and discharge cycles. Our balancingcircuit keeps all subpacks at even levels onboth charge and discharge, maintaining fullpack capacity automatically.

Our approach could be easily scaled tosupport either larger or smaller vehicles.

Extensive safety analysis methodology isbeing developed and we expect the results ofthis work to apply to future applications forAUVs and other battery powered systems.

Imaging and Lighting Technology• Development of LED based lighting

Discussion: HROV will rely upon newlydeveloped LED lighting in order to meet severalsystem requirements, including strobing

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capability, pressure tolerance, and low relativepower consumption. While these capabilities arerequirements for HROV, they will also be highlyadvantageous in other oceanographicapplications. All remote and human operatedvehicles will benefit from the availability of lowprofile pressure tolerant lighting. The ability tostrobe lighting at the duty rate of imaging sensorsshould offer energy savings in many applications,and the monochromatic ability of LED's, whencoupled with appropriate sensors, should extendthe imaging ability of autonomous vehicles andsubsea installations.

• Advanced ImagingDiscussion:The pursuit of an imaging sensor that can fillboth still and motion imaging needs forunderwater applications has been ongoing foryears. HROV has strong needs for such a sensor,given its power and space constraints. Whenintegrated with advanced LED lighting, theavailability of a single multi-purpose sensor willbe of great benefit to any space or powerconstrained subsea system

Micro-Fiber TetherDiscussion:One of the most innovative technologies for theHROV project is use of a very small diameter fiberoptic tether. Use of this tether is critical to achievingthe goal of a lightweightand inexpensive system for

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use at extreme depths, yet with real-timecommunications. Adapting a system developed forthe Mk 48 ADCAP torpedo (ARL Penn State), theHROV is pioneering the use of small diameter micro-fiber. This capability lends itself well to otherapplications, where real time communication isrequired, but space and weight are limited. It is likelythat such micro-fiber tethers will be adapted to otherapplications. For example, a micro-fiber tether couldbe a critical technology enabling real-time explorationof under ice environments, rapid deployment of smalllightweight vehicles, and a “strap-on” means toprovide real-time communication with autonomous orhuman occupied vehicles.

Low Power Manipulative SystemsDiscussion:HROV will emphasize efficient use of power in allareas, including manipulation of instrumentation andsamples. For this project a hydraulic manipulator hasbeen chosen as a reasonable compromise betweendevelopment risk, weight, cost and performance. Akey to this system will be the development of ahydraulic power unit, coupled with a suitable controlsystem, intended to minimize electrical powerconsumption. While it is quite possible such a systemmay not be suitable for a fully autonomous samplingvehicle, it is likely that certain parts of the HROVmanipulation system will provide valuable lessons forfuture vehicle developments.

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Hybrid Vehicle ControlDiscussion:From a control systems perspective, the HROV projectwill require a combination of the characteristics of anROV such as Jason II and an autonomous vehicle suchas ABE. When in ROV mode, the vehicle will becontrolled by a human pilot using joystick control aswell as a variety of supervisory control modes likethose demonstrated in Jason II (closed-loop hover,automatic trackline following, automatic bottom-following) while allowing the pilot to observe andmanage on-board sensors, sampling equipment, andmanipulators. In AUV mode, the control system willenable preprogrammed surveys as well as adaptivesurvey schemes. Also, when in ROV mode, thevehicle will automatically branch to a pre-plannedAUV mission should the micro-fiber cable loseconnectivity.

The Jason II control system has already been ported toseveral other scientific ROVs (URI’s Hercules andSOC’s ISIS), where it has proven to be effective,reliable, and extensible. The Jason2 control systemwill serve as the base for the HROV control system,which will be extended to include the autonomousfeatures required for AUV mode and for recoveryfrom the loss of the micro-fiber cable. Many of theseautonomous processes will be based on successfulresults from ABE. It is further expected that theHROV control system will prove to be an incremental

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step forward to AUV mission planning and thusreduce the dependence on highly.

Light Weight Deployable VehiclesDiscussion:System operating cost is often driven size and weight.HROV will introduce new technologies thatdramatically reduce weight of a subsea vehicle (e.g.lighting and ceramics). Such vehicles will be lessexpensive to ship and mobilize and although they maynot be ultimately as capable as either a humanoccupied submersible or remotely operated vehicle(such as Jason II), the reduced staffing requirementswill drive operating costs down for certain operations.The reduce size of both the vehicle and surfacehandling system will enable deployment of HROVand its derivatives to take place from smaller vessels.