Materials First use of high performance ceramics for full ocean depth floatation. HROV will be the first project to exploit high strength ceramic tech

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1 11,000 Meter HROV Development Program and its Relation to Oceanographic and Commercial Undersea Use February 2006 Andy 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) program has drawn from and incorporated cutting edge technologies from across the academic, commercial, and military communities. The unique capabilities required by the HROV system are driving the innovative use and development of relevant technologies such as advanced materials, energy storage, imaging and lighting technology, micro-fiber communications, low power manipulative systems, and autonomous underwater vehicle control. WHOI 2/13//06

2 Materials First use of high performance ceramics for full ocean depth floatation. HROV will be the first project to exploit high strength ceramic technology for full ocean depth floatation, building on over 30 years of Navy and commercial development. Weight savings to be achieved are approximately 40% over the more traditional syntactic foam material, allowing the systemto achieve significantly lighterweight and smaller size. The HROV project has significantly contributed to the exposure of this technology which is likely to have a positive impact to many oceanographic and commercial projects requiring floatation. The vendor (DeepSea Power and Light Inc.) is now marketing the ceramic spheres to the oceanographic and commercial oil and gas industry as an alternative to syntactic foam. Lower density floatation has the profound benefit of allowing systems to achieve significantly lighter weights and smaller sizes. For example, an AUV that is smaller and lighter can travel further underwater. First use of high performance ceramics for full ocean depth pressure proof enclosures. The traditional solution for deep ocean pressure resistant enclosures to protect electrical components from the environment is to use titanium. This material has high specific strength for its weight and

3 is generally impervious to corrosion, yet the resultant weights are prohibitive for full ocean depths. Here too, the HROV project will exploit high performance ceramic materials, with a resultant 60% weight savings over titanium. The lighter enclosures will reduce the need for floatation (ROVs and AUVs require neutral buoyancy to do their jobs), thus resulting in smaller and ultimately lower cost vehicles with enhanced performance. The development and demonstration of these systems for HROV provide new resources for both the oceanographic and commercial ROV/AUV communities. Energy Storage The HROV will require a large amount of on-board batteries. The batteries must be economical, easy to operate and maintain, provide high energy density, and must be safe for conventional shipping. Based on WHOI s success with battery packs for the Autonomous Benthic Explorer (ABE) and other similar projects, lithium-ion rechargeable batteries were selected. While these batteries are ubiquitous for small-scale applications such as cell phones and laptop computers, packs of the size we need for HROV are not commercially available. To solve this problem, we have chosen to use small cells like those found inside laptop computer battery packs. These cells are economical, very consistent,

4 and reliable as they are produced in very large numbers. However, we need to combine over 2000 of these small cells to provide the energy needed for HROV. Our packs will be built up from subpacks of 12 cells connected in parallel. These subpacks can be tested extensively, allowing the HROV packs to be shipped by conventional means. For both charge and discharge, the packs will be managed by innovative WHOIdesigned battery management electronics. With such a large collection of cells, cells can become imbalanced over repeated charge and discharge cycles. Our balancing circuit keeps all subpacks at even levels on both charge and discharge, maintaining full pack capacity automatically. Our approach could be easily scaled to support either larger or smaller vehicles. Extensive safety analysis methodology is being developed and we expect the results of this work to apply to future applications for AUVs and other battery powered systems. Imaging and Lighting Technology Development of LED based lighting HROV will rely upon newly developed LED lighting in order to meet several system requirements, including strobing

5 capability, pressure tolerance, and low relative power consumption. While these capabilities are requirements for HROV, they will also be highly advantageous in other oceanographic applications. All remote and human operated vehicles will benefit from the availability of low profile pressure tolerant lighting. The ability to strobe lighting at the duty rate of imaging sensors should offer energy savings in many applications, and the monochromatic ability of LED's, when coupled with appropriate sensors, should extend the imaging ability of autonomous vehicles and subsea installations. Advanced Imaging The pursuit of an imaging sensor that can fill both still and motion imaging needs for underwater applications has been ongoing for years. HROV has strong needs for such a sensor, given its power and space constraints. When integrated with advanced LED lighting, the availability of a single multi-purpose sensor will be of great benefit to any space or power constrained subsea system Micro-Fiber Tether One of the most innovative technologies for the HROV project is use of a very small diameter fiber optic tether. Use of this tether is critical to achieving the goal of a lightweightand inexpensive system for

6 use at extreme depths, yet with real-time communications. Adapting a system developed for the Mk 48 ADCAP torpedo (ARL Penn State), the HROV is pioneering the use of small diameter microfiber. This capability lends itself well to other applications, where real time communication is required, but space and weight are limited. It is likely that such micro-fiber tethers will be adapted to other applications. For example, a micro-fiber tether could be a critical technology enabling real-time exploration of under ice environments, rapid deployment of small lightweight vehicles, and a strap-on means to provide real-time communication with autonomous or human occupied vehicles. Low Power Manipulative Systems HROV will emphasize efficient use of power in all areas, including manipulation of instrumentation and samples. For this project a hydraulic manipulator has been chosen as a reasonable compromise between development risk, weight, cost and performance. A key to this system will be the development of a hydraulic power unit, coupled with a suitable control system, intended to minimize electrical power consumption. While it is quite possible such a system may not be suitable for a fully autonomous sampling vehicle, it is likely that certain parts of the HROV manipulation system will provide valuable lessons for future vehicle developments.

7 Hybrid Vehicle Control From a control systems perspective, the HROV project will require a combination of the characteristics of an ROV such as Jason II and an autonomous vehicle such as ABE. When in ROV mode, the vehicle will be controlled by a human pilot using joystick control as well as a variety of supervisory control modes like those demonstrated in Jason II (closed-loop hover, automatic trackline following, automatic bottomfollowing) while allowing the pilot to observe and manage on-board sensors, sampling equipment, and manipulators. In AUV mode, the control system will enable preprogrammed surveys as well as adaptive survey schemes. Also, when in ROV mode, the vehicle will automatically branch to a pre-planned AUV mission should the micro-fiber cable lose connectivity. The Jason II control system has already been ported to several other scientific ROVs (URI s Hercules and SOC s ISIS), where it has proven to be effective, reliable, and extensible. The Jason2 control system will serve as the base for the HROV control system, which will be extended to include the autonomous features required for AUV mode and for recovery from the loss of the micro-fiber cable. Many of these autonomous processes will be based on successful results from ABE. It is further expected that the HROV control system will prove to be an incremental

8 step forward to AUV mission planning and thus reduce the dependence on highly. Light Weight Deployable Vehicles System operating cost is often driven size and weight. HROV will introduce new technologies that dramatically reduce weight of a subsea vehicle (e.g. lighting and ceramics). Such vehicles will be less expensive to ship and mobilize and although they may not be ultimately as capable as either a human occupied submersible or remotely operated vehicle (such as Jason II), the reduced staffing requirements will drive operating costs down for certain operations. The reduce size of both the vehicle and surface handling system will enable deployment of HROV and its derivatives to take place from smaller vessels.