UUV teams, control from a biological perspective

Remote Operated Vehicles (ROVs) are used extensively for salvage operations, ocean floor surveying and numerous inspection activities that support a wide range of underwater commercial activities. In deep water (greater than 1000 ft) an ROV is the platform of choice because of the depth and endurance limitations for human divers. The key disadvantage to an ROV is the requirement for the long tether. The tether greatly inhibits the speed of the ROV, requires a ship with deck gear capable of handling this cable, and significantly restricts ship movement while deployed. Un-tethered Unmanned Underwater Vehicles (UUVs) have entered the commercial market and have demonstrated the ability to perform deep-water surveys faster and cheaper than towed vessels. With further technological advances, UUVs have the potential for supplementing and even replacing ROVs for many deep-water operations because of the cost and problems associated with the tether. One promising scenario for the near future is to use an ROV or surface ship to control multiple UUVs in a local work area. Typically in this scenario the UUVs are used to extend the sensor footprint of the ROV or surface ship. Another area of interest is the UUV team concept. A stereotypical UUV team would be a heterogeneous mix of several low-cost specific purpose vehicles, guided and supported by one or two higher cost control vessels. Because of the severe restrictions that the sub-sea environment places on communication and positioning, precision underwater navigation is difficult. Currently most precision underwater navigation relies on some sort of infrastructure such as surface ships or underwater beacons placed in known positions. Using these assets as reference-points sub-sea navigation is carried out. Some situations require that the environmental and/or commercial attributes of an area be assessed before an infrastructure exists. In order to do this the UUV team must be able to navigate to an area, carry out its task and return without any pre-existing infrastructure or step by step guidance. Given basic assumptions about the type and frequency of sensor input we present a biologically inspired, decentralized methodology for safely and efficiently moving a loose formation of UUV's to and from the task area with the goal of minimizing outside guidance.