The objective of this applied research project is to develop an unmanned underwater vehicle (UUV) capable of superior low-speed maneuverability and hover for operations in near-shore environments.
UUVs have demonstrated many capabilities in inspection, surveillance, exploration, and object detection in deep-seas, at high-speeds, and over long distances. However, the low-speed, high maneuverability operations required of many near-shore and littoral zone missions present mobility and sensing challenges that require novel solutions. In order to mitigate the threats posed to navigation in these often turbid, cluttered, and dynamic near-shore zones, development of both a reliable, near-field, underwater obstacle sensing system and a vehicle with the propulsion and control authority to operate at very low speeds is required.
Environmental awareness required of a UUV operating in near-shore environments includes the ability to detect both flow conditions and physical obstacles. Knowledge of instantaneous flow magnitude and direction is essential when operating under waves and in changing currents. Additionally, the presence of physical objects in these often cluttered areas necessitates the ability to detect and react to these features. Fish use a lateral line system of hair-like flow and pressure sensors to detect changes in the environments around them. We have studied these systems and are developing an artificial lateral line to detect pressure changes around a UUV hull for detecting flows and obstacles.
In the realm of propulsion and control for UUVs, flapping fins are an attractive alternative to thrusters for overcoming the difficulties associated with low-speed maneuverability in the presence of ocean currents and near-shore obstacles. We have taken inspiration from the pectoral fin of a particular coral reef fish, the bird wrasse, to develop a robotic fin that uses active curvature control to generate vectored thrust. We have further developed a vehicle prototype that employs these fins as the primary means of propulsion and control.
Advances in both sensing and propulsion that benefit operations in near-shore, cluttered environments will enable a variety of Navy essential missions including harbor monitoring and protection, hull inspection, and covert very shallow water and riverine operations.
Laboratory for Propulsion, Energetics, and Dynamic Systems
Naval Research Laboratory
Washington, DC 20375