In five years, commuting could be eased by drive-time 'eye in the sky' traffic reports coming from the 'vision' of pilotless airplanes. And growers of high value crops, such as coffee and wine grapes, using such Unmanned Aerial Vehicles (UAVs), will determine when beans are at their ripening peak and ready to harvest or apply water to stave off frost damage to vines.
Recently, military UAVs have made the headlines from Iraq and Afghanistan. Such combat missions not only included traditional pilotless-aircraft roles of surveillance and reconnaissance, but also laser-guided weapons delivery perfected in the last couple of years. Much less heralded are prospective civilian missions (see sidebar).
But while military UAVs operate over wide ranging areas in a combat zone under coordinated control, civilian vehicles will have to share the airspace with piloted aircraft, from airliners to small general aviation craft. Many of the latter are flown more or less independently under Visual Flight Rules where only filing a flight plan is required. To come up with the necessary technologies to integrate UAVs into this mix, as well as address procedural issues, the FAA (Federal Aviation Administration) is working with the UAV Technical Analysis and Applications Center (TAAC; www.psl.nmsu.edu/uav) at the New Mexico State University (Las Cruces).
'The biggest concern is routine access to civil airspace,' says Bill Gutman, TAAC technical advisor. 'The technical challenge is to provide the pilot function, other than controlling the aircraft, of safety—avoiding collisions and crashes.' To give a UAV the capability to detect, see, and avoid potential conflicts with other aircraft, engineers are taking a three-pronged approach.
One is vision-based systems, which use, for instance, a low-cost, lightweight camera with a visible-light or an infrared pixel array. Scanning the camera and image processing algorithms would determine threats. For example, comparing an image to a database of known aircraft sizes, the system's geometry algorithms could determine distance to another aircraft from the number of pixels its image subtends on the imaging array. Rate of change in image size would give relative closing velocity. Gutman says the difficulty may come in determining distance of an aircraft whose size is not known.
Radar is an active option, transmitting energy and using the reflected return to determine position. But radar uses more energy than imaging, and the transmitter and receiver weight can detract greatly from the available payload on a small UAV, adds Gutman.
Up all night: One goal of UAV development
is continuous 24-hour apperationof solar-powered aircraft using energy
storage such as fuel cells. In daytime-only tests in Hawaii last year,
this AeroVironment Pathfinder Plus surveyed coffee crops.
Lastly is a co-operative technology 'where everyone tells a central system where they are,' notes Gutman. It could be based on the Automatic Dependent Surveillance-Broadcast (ADS-B) system (see DN, 9.3.2001, p. 65) being readied for deployment in piloted civilian aircraft. Timely communication and coordination of automatic or remotely piloted evasive maneuvers will be paramount for safety in a given airspace. Again weight of system components is an issue.
To account for each method's limitations, Gutman feels the best see-and-avoid option might be a combination of two approaches, such as networking supplementing an infrared vision system that could be hampered by clouds or fog.
Another wide-ranging technical concern is FAA design requirements to certify UAVs, as with any manned airplane, to operate in the public airways. The agency is working with TAAC to draft such regulations. According to Gutman, in many ways this task is simplified by not having to certify pilot-oriented systems such as emergency oxygen.
Not only will see-and-avoid systems have to meet
requirements, but provisions are needed if a remotely piloted vehicle looses the
link to its base station or an autonomous programmed aircraft has a malfunction,
Gutman adds. Solutions to these problems could include entering a
holding-pattern orbit to reestablish a link or programming to redirect a vehicle
to a recovery airport. As a last resort, a recovery parachute can pop out for a
Out of harm's way: UAV missions might
include measuring evaporation from reservoirs to improve water management
in arid areas. Such missions require low-level flight during reduced
visibility near rugged terrain, posing danger to piloted aircraft.
A key to certifying UAVs for civil applications will be testing and validation of software, concludes Gutman. 'The appropriate equations of flight have to be captured and formulated correctly in software, then tested in a realm where they will be used—they shouldn't operate where they haven't been tested,' he says.