Some teams don't require lots of communication
How much communication does a fleet of underwater vehicles really need to autonomously complete a given task? It is difficult to communicate underwater: the channels available for land, air, or surface vehicles (such as radio) aren’t an option, and the limited bandwidth of underwater acoustics allows for little information to be passed between vehicles.
A group of VaCAS researchers wants to answer that question with a very small number. They are developing a new class of algorithms that not only enable teams of autonomous underwater vehicles (AUVs) to cooperate as a team, but do so with as little communication as possible between vehicles.
Brian McCarter assembles a hydrophone array built by Virginia Tech students. The arrays are towed by Virginia Tech’s 475 AUVs to locate an acoustic noises.
The researchers are not just developing algorithms, but also testing and perfecting them using Virginia Tech’s own fleet of AUVs. The group recently field tested data fusion and motion control algorithms using two Virginia Tech 475 AUVs. Each AUV towed a custom hydrophone array built by Virginia Tech students that measures the relative bearing to a source of acoustic noise. The AUVs maneuvered themselves into the best positions to cooperatively identify the location of an acoustic source. During the entire mission, the AUVs exchanged only a total of seven one-way data packets.
The project is directed by Dan Stilwell of electrical and computer engineering, who is in charge of algorithm development and field trials. Wayne Neu of aerospace and ocean engineering has led tow-body development activities, and Mike Roan of mechanical engineering provided early advice on sensor specifications. The effort is funded by the Office of Naval Research.
“We are very excited that we have actually implemented these ideas on real vehicle systems,” Stilwell said.
“It is rare and very exciting for new theoretical developments such as ours to be demonstrated in the field, and to have the field trials so convincingly demonstrate the utility of the new theory!”
The Virginia Tech AUV Fleet
The 475 AUVs used for the field test are the workhorses of the Virginia Tech fleet. These are mature AUVs that support a number of research programs, according to Stilwell. “We find that by doing both — the theory and platform development — we are able to solve the more complex problems in this area,” he said.
The team is currently developing a new AUV platform. This new AUV will be capable of deploying an anchor in order to moor itself on the ocean floor and remain on station for extended periods of time. It will travel a long distance to the mooring location, and then release the anchor at a desired time and return a long distance to be recovered.
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The self-mooring AUV concept, led by Wayne Neu and Dan Stilwell, was successfully demonstrated for the Navy sponsor using a prototype vehicle based on the 475 AUV. A larger version of the AUV is being designed for deployment next year.