US Naval Research Lab Develops Autonomous Underwater Vehicles

US Naval Research Lab (NRL) has designed and developed underwater propulsion, control and sensing solutions for littoral zone missions, Unmanned Systems Technology website reported Wednesday.

According to the report, the autonomous underwater vehicles (AUVs) were inspired by bio-mechanics of fish. The AUVs have demonstrated successful capabilities in inspection, surveillance, exploration and object detection in deep seas at high speeds and over long distances.

Results of operations in littoral zones that require low-speed and high-maneuverability present mobility and sensing have not been satisfactorily resolved.

“Expeditions in near-shore environments are complex, often proving turbid, cluttered with obstacles, and plagued with dynamically changing currents,” Jason Geder, aerospace engineer, Laboratories for Computational Physics and Fluid Dynamics at NRL was quoted as saying by UST.

“Inspired by the pectoral fins of the reef fish, bird wrasse, NRL researchers have developed an actively controlled curvature robotic fin that provides scaled down AUVs a novel low-speed propulsion system,” Jason added.

The artificial pectoral fin has been integrated into a man-portable, unmanned vehicle named the Wrasse-inspired Agile Near-shore Deformable-fin Automaton, or WANDA. Four side-mounted fins, two forward and two aft, provide all the propulsion and control necessary for the vehicle. A set of custom control algorithms uses information about the vehicle motion and surrounding environment to inform changes to the fin stroke kinematics, or fin gaits. This kind of artificial fin technology can adapt to varying flow conditions and provide the thrust control necessary for low-speed maneuvering and precise positioning.

WANDA is designed to operate at speeds in excess of two knots, or hold position in the presence of two-knot currents, giving it the propulsion and control authority needed in many harbor and other near-shore operational zones. WANDA can also successfully coordinate maneuvers to achieve waypoint navigation.

As WANDA’s fish-inspired technologies are perfected, the AUV is being prepared for payload testing. The vehicle’s modular construction enables easy integration of different mission-specific payload packages, and one such payload that will be developed and tested on WANDA starting this year is a biochemical sensing system for trace level detection of chemical signatures. This sensor system built onto a capable low-speed platform such as WANDA will enable missions in plume tracking and target localization in shallow water environments.

As the Navy’s focus on autonomy and unmanned systems intensifies, NRL’s bio-inspired research into capable propulsion and control technologies for low-speed operation in near-shore environments is helping to close a clear gap in AUV technology. An unmanned vehicle that can effectively operate in these areas, where traditional platforms experience stability and control problems, will improve performance for critical missions including harbor monitoring and protection, hull inspection, covert very shallow water operations, and riverine operations.