Flies, fish and the inferior olive help improve unmanned undersea design.
Navy researchers are examining work conducted jointly by the New York University Medical School and Russia’s Nizhny Novgorod State University and Institute for Applied Sciences that uses brain activity as the model for controlling movement in unmanned undersea vehicles. The advances culled from this research could support better designs for autonomous underwater vehicles that could hunt mines, deliver and retrieve sensors, track ship movement or gather plume samples.
The work is taking place at the Naval Undersea Warfare Center (NUWC), Newport, Rhode Island, with help from the Office of Naval Research (ONR), Arlington, Virginia. Techniques being explored would be used on unmanned undersea vehicles (UUVs) to solve two problems that limit their effectiveness. While current designs allow the Navy to conduct operations that might otherwise be impossible, the service is interested in improving the maneuverability and decreasing the noise of UUVs so the craft can conduct new types of missions in the future.
Dr. Thomas McKenna, program officer, division of cognitive, neural and social science and technology, department of human systems science and technology, ONR, explains that the objective of the current work is to enable precise and quiet maneuvering as well as long endurance.
To accomplish these tasks, however, requires basic research in a number of areas, and researchers are turning to biology for at least some of the answers. McKenna notes that in comparing the movements of fish and those of manmade vehicles, scientists have observed that neither has the advantage in speed when moving in one direction. However, when it comes to maneuverability and turning radius, fish are more agile than manmade vehicles by a large margin. To bring the two a little closer together, scientists have to determine both the structures that would facilitate movement and the connections to make these structures respond quickly.
McKenna explains that one facet the engineers are examining in the structures area is the high-lift principle. The principle emerged from the study of the wings of flies. The combination of the pitching and heaving motion results in enhanced lift when compared to fixed wings—up to five times higher. To improve propulsion, the researchers are exploring how to build foils in combination with motors that can mimic this superior lift.
The NUWC is working on the high-lift actuators project. The challenge is that these actuators would require a number of degrees of freedom so that the pitching and heaving could be varied among the thrusters situated on various parts of the UUV. “It’s a nonlinear control problem, and we’re taking a look at a new, very rapid and adaptive nonlinear controller based on brain circuitry,†he offers.
This nonlinear controller, called the universal control system, is based on how the cerebellum and a related structure, known as the inferior olive, work in the human body. By examining the physiology of this biological system, researchers at New York University Medical School and Nizhny Novgorod State University and Institute for Applied Sciences have built a model of chaotic oscillators.
The universal control system, which is an array of oscillators, can be divided into smaller elements, each controlling a different actuator. “We’re building the electronic hardware prototype of the system, and we’re evaluating it now to determine how good that control is compared to the conventional way of controlling actuators,†McKenna relates.
This evaluation is taking place in the form of a “little competition,†he reveals. During the next year, two scale models of UUVs that feature the high-lift foils will be built. The NUWC will work with one of the models using a series of conventional and artificial neural network controllers. Researchers at New York University will employ their brain-control circuit system to assess the effectiveness of their technology. “Once we have those results, we’ll have some idea about whether the Navy should proceed with just the high-lift foils or the high-lift foils in conjunction with the brain-based controller,†McKenna explains.
From the mechanical standpoint, the high-lift foils in the near term must be adapted to work with rotating motors. This could limit their range of motion and does not completely solve the issue of noise. But researchers are exploring solutions to this problem as well. “In the future, we’re looking at linear actuators that are like actual muscles. There are a number of efforts, about six that ONR is supporting, to build muscle-like actuators out of various compounds—in particular electro-active polymers. But they are not quite ready to be used at this scale yet,†McKenna states. Once this issue is resolved, rotating motors would not be required, and the noise would decrease tremendously, he adds.
One of the Navy’s visions in the long term would be a fleet of small UUVs equipped with communications systems and sensors that can remain in an area for some time, conducting reconnaissance and surveillance missions. The size of these vessels could be somewhere between a trout and a shark, a design feature that is limited by the power source and sensor package, he says.
As envisioned, these UUVs would be semi-autonomous. Missions would be preprogrammed into the vehicle; however, the information gathered by onboard sensors could be shared very quickly with the propulsion system, so they could adapt quickly.
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Within the sanctity and spirit of this topic - I've always wondered why anechoic tiles for subs were not made in the manner of sharkskin. It's been demonstrably proved that the barbed pattern of sharkskin assists in it's fluid mechanics...
any resident aero/fluid mechs on here care to comment??
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