The old saying, "birds
of a feather, flock together," can now be applied to a couple of
small uninhabited aerial vehicles (UAVs) flown in a NASA research
experiment using principles derived from studies of fish and bird
motions to simultaneously guide them around obstacles.
Engineers and technicians from NASA's Ames Research Center,
Moffett Field, Calif., and Dryden Flight Research Center, Edwards,
Calif., recently conducted flight tests over a 'virtual' forest
fire to evaluate new flight-control software that will allow UAVs
the ability to autonomously react to obstacles as they fly
pre-programmed missions. The tests were conducted over a remote
area of Edwards Air Force Base, Calif., to investigate cooperative
flight strategies for airborne monitoring and surveillance of
natural disasters and for atmospheric sampling.
"We developed and flight tested several novel approaches for
providing assistance to wildfire suppression crews using a team of
two small UAVs," said Ames' John Melton, principal investigator for
the Networked UAV Teaming Experiment. "The aircraft were flown
using a combination of rules from nature and robotics to
cooperatively transit and search a virtual forest fire."
The NASA researchers borrowed a mathematical tool devised by
Hollywood movie makers to map and mimic the choreography used by
swarms of birds and fish as they wheel and turn without striking
one another. These in turn guided the inexpensive robotic UAVs
around obstacles such as simulated smoke plumes. Called the boid
algorithm, this tool separates the activities of individual birds
or fish into three categories: heading matching, where the animals
all try to keep the same direction; flocking, where the animals
move to come into proximity to one another; and collision
avoidance, in which the birds or fish maneuver to keep from running
into each other.
Jason Clark, research algorithm developer at NASA Dryden, said
the boid algorithm has been adapted to direct remotely operated
UAVs to fly within predetermined proximity to each other, while
avoiding collisions and maneuvering around phantom objects
digitally placed in their flight paths. Though still in its
infancy, this emerging software technology promises to one day
enable swarms of UAVs to conduct aerial searches and participate
cooperatively in activities such as firefighting.
For the tests, NASA used the Piccolo autopilot system and global
positioning system (GPS) transmitters to enable a pair of RnR
Products APV-3 UAVs to maneuver responsively in relation to each
other. With the two 12-foot wingspan UAVs, the NASA researchers
proved the concepts inherent in the boid algorithm. Neither
aircraft communicated with the other directly, but sent and
received signals with a central computer station on the ground that
directed both airplanes to maneuver as needed.
In one test, the software automatically developed individual
flight plans and transmitted them to each aircraft. After passing
their first few waypoints, one of the UAVs was commanded to begin
orbiting over the virtual fire. The remaining search points were
then transmitted to the second aircraft, which incorporated these
points into its flight plan and completed the mission.
"This technology may one day enable swarms of aircraft to move
safely from one area to another as a flock or group," said Melton.
"A number of UAVs could be flown 'stacked' in a vertical column
with instruments to collect air samples on future science missions
or help ground personnel monitor forest fires and other natural
disasters," he added.
NASA's Aeronautics Research Mission Directorate is supporting a
variety of technology development projects for remotely or
autonomously controlled high-altitude, long-endurance UAV aircraft.
Such UAVs have the potential to serve as platforms for a wide
variety of earth science, surveillance, communications relay and
disaster-mitigation missions, especially in circumstances where
flying a manned aircraft is dangerous. The Networked UAV Teaming
Experiment was sponsored by the Directorate's Aeronautics Systems
Analysis Project.