An holistic bio-inspired approach for improving the performance of unmanned underwater vehicles

There are over 750,000 marine species ranging in size from a few micrometers to dozens of meters, all of which, through the natural process of evolution, have arrived at “successful” solutions to surviving and operating in the ocean space. Many of these species have capabilities and functionality which have much in common with the engineered capabilities required for underwater vehicles e.g. propulsion/locomotion, manoeuvrability/agility and the ability & resilience to operate at depth. Indeed, in many examples, it appears the biological solutions exhibit superior performance compared to the technological alternative, yet in biology these capabilities are achieved by different and diverse means. In this research an extensive study on the capabilities of marine animals has been conducted in relation to the equivalent capability on AUVs. And the biological solutions to propulsion, agility, depth and vehicle (or animal) architecture have been focused on. This paper will present the approach adopted, some specific studies and key results from using a bio-inspired approach to improving AUV engineering capabilities. Acknowledgments This research is part of a collaborative project, “Nature in Engineering for Monitoring the Oceans” (NEMO), including the National Oceanography Centre and the University of Southampton and is funded by the Engineering and Physical Sciences Research Council (EPSRC, 2009). The authors would like to acknowledge that the data collected on AUV characteristics and capabilities has been a collaborative work with NEMO colleagues in the University of Southampton. Nomenclature s Second AUV Autonomous Underwater Vehicle BL Body Length Block Coefficient COT Cost of Transport Diameter (Subscripts as relevant) d Derived Diameter Eco (Speed) Economic (speed) FR Fineness Ratio Length Mass (Subscripts as relevant) MA Marine animal Re Reynolds Number ROV Remotely Operated Vehicle Yaw Radius kg Kilo gram U Speed (Subscripts as relevant) Volume (Subscripts as relevant) Density Density of sea water INTRODUCTION Man-kind has a long history in ocean exploration and exploitation; from early exploration with divers in Greek and Chinese cultures, c.4500 B.C., to the genesis of shipborne deep-sea research in the 17th Century by the likes of Sir James Clark Ross. In the 19th Century technological advances have seen human descents to the deepest regions of the ocean, when in 1960, Jacques Piccard and Don Walsh reached a manned decent to the deepest known place in the oceans in excess of 10km (Blidberg, 2001). The current Status of AUV Technology Improved access for deep water exploration has been facilitated by Unmanned Underwater Vehicles, initially ROVs and more recently, with increased sophistication of computers, Autonomous Vehicles. Nevertheless, there is still further demand for improved underwater capability beyond that currently possible with existing AUVs. For example, in the offshore industry there is demand for accessing and exploring deep waters for survey, inspections and maintenance. Similarly, there is high demand in the scientific community for improved deepwater capability for discovery and study of deep-water species, pharmacological sampling and environmental research. Furthermore, military and security agencies are constantly striving for improved capabilities in all aspects of underwater technology. More agile and manoeuvrable AUVs with larger operating ranges can satisfy these demands by performing desired missions with more precision and cost-efficiency. Benefiting from the collective abilities of hybrid ROVs and intervention underwater vehicles is another aim of new vehicle designs (Kermorgant & Scourzic, 2005). However, currently there are restrictions in AUV capabilities including depth capabilities, speed, manoeuvrability and power. For example, the gathered database in this research shows that only 29% of the AUV types operate deeper than 3000m, whereas the deepest waters are 8000–11000m deep. In the UK, AUTOSUB6000 is the deepest diving AUV, to a depth of 5600m (Thaindian News, 2009). Furthermore, compared to other marine vehicles, AUVs are relatively slow and have limited speed ranges, with even the fastest, e.g. “Alister” and “SeaOtter” at 4.12m/s, being below 10m/s) (AUVAC, 2010). Possible inspiration from nature Nature has been a source of inspiration for researchers and inventors over the last three millennia (Vincent, 2001) and systems found in nature are continuously evolving, with those surviving in their specific environment having superiority over those extinguished over time. The greatest part of Earth’s biodiversity, ~90% of the major groups of living species, is in the oceans (Madin, 2005) and marine animals have specifically adapted to thrive in underwater conditions (e.g. high water pressure, lack of air, etc.). Initial research in this project has identified marine animals with specific superior characteristics; e.g. high-speed or large depth range. Furthermore, examples of superior overall performance are evident; this being achieved through multi-functionality in biological systems. The Sailfish, for example can achieve a speed of over 30m/s and marine animals have been found at the extremes of the oceans’ depth. The research challenge This paper is reports on research carried-out at Newcastle University. The aim of this research is to improve the performance of AUVs by investigating novel technologies, inspired by marine animals, as well as generating bioinspired design techniques and implementation methods. To achieve this aim, two main objectives are being pursued:  Investigating bio-inspiration  Provide a greater understanding of marine biological organisms and systems for engineering application  Create a new way of thinking in engineering design  Use biological systems to improve engineering technology  Application of bio-inspiration  to applied the lessons learned from nature to improve depth, speed and manoeuvrability of AUVs (NEMO, 2011) A brief on Bio-Inspiration Considering all the potentials nature has to offer to improve engineering design techniques, one may learn from nature, using the relevant novelties while leaving the undesirable ones, in order to relate engineering requirements to biological function. This is different from mimicking nature; therefore NEMO is not aiming to build a robotic fish.