Aurora Flight Sciences plans to demonstrate a vision-based guidance system that combines optical and sonar sensors and allows a micro air vehicle (MAV) to navigate through a cluttered urban environment.

The Panoramic Avoidance and Navigation using Optics Integrated with Sonar - Panoptis - system combines bat-inspired echolocation for obstacle detection with a phenomenon called "optic flow" for navigation, says principal investigator Jim Paduano.

Optic flow is the perceived motion of objects relative to the observer. "The eye does not recognise anything, just how quickly it passes through the field of view," he says. "Pilots use this to land an aircraft. Bees and flies only have optic flow [for vision]."

The Global Positioning System is not accurate enough to allow a MAV to fly along a city street at 15-20 knots, but optic flow relies only on relative motion. If an object is expanding, but not moving, the vehicle is heading towards it; if it is expanding and moving to the side, the MAV will pass by.

In Panoptis, developed under a U.S. Air Force Research Laboratory (AFRL) contract, optic flow allows the MAV to navigate relative to its environment. But because the wide-field optical sensor is not sensitive enough to see small objects in the vehicle's path, sonar is added to detect and "dodge" obstacles such as poles, trees or wires, says Paduano.

In Phase 1, Aurora simulated an aircraft flying through a three-dimensional urban environment using optical flow for navigation. In the two-year second phase the company will build and fly a small MAV to demonstrate Panoptis.

One configuration under consideration uses six cellphone cameras arranged to provide spherical coverage, according to Paduano. Another uses a spherical mirror, like a Christmas ornament, to show the optical flow. Aurora is working with the University of Maryland professors Sean Humbert and Tim Horiuchi in optic flow and echolocation, respectively.

The target application for Panoptis is Applied Research Associates' Nighthawk, a 1.6-pound, hand-launched MAV that stores in a 6-inch tube. But to demonstrate the prototype system, Paduano says Aurora will build its own air vehicle with a larger payload and more maneuverability.

Photo: Applied Research Associates