February 03, 2011      

Existing technologies have made unmanned ground-vehicle and IFR (instrument flight rules) airplane flight commonplace. However, at low altitudes, the presence of obstructions such as trees, mountains, and buildings has made the operation of unmanned air systems in near-earth environments more difficult. Unmanned helicopters, for example, can only fly autonomously in mapped areas known to be free of obstructions.

A new navigation and sensing solution has been developed that enables full-size, autonomous helicopters to fly at low altitude while avoiding obstacles. Jointly developed by Essington, Pa.-based Piasecki Aircraft Corp. and Carnegie Mellon University (CMU) in Pittsburgh, the new systems can also evaluate and select suitable landing sites in unmapped terrain, as well as land safely using a self-generated approach path.

Included in the Piasecki/Carnegie Mellon package is an inertial sensing and an advanced laser scanner that can look forward or down, depending on flight parameters. Paired with mapping and obstacle-avoidance software, these sensors build 3-D maps of the ground, and can locate obstacles in the aircraft’s path.

The Piasecki/Carnegie Mellon team flight-tested this navigation/sensor system, the Autonomous Helicopter Collision Avoidance & Landing Zone Selection System, in mid-June 2010 at The Boeing Co.’s Rotorcraft Systems facility in Mesa, Ariz. The system was tested utilizing an Unmanned Little Bird (ULB) helicopter test bed.

The team reported that the system’s sensor package and navigation, mapping, and collision avoidance software was repeatedly employed to safely land the ULB in cluttered environments. In each test, the navigation/sensor system had to map an unknown area where multiple obstructions of varying sizes limited possible landing sites.

During the Arizona tests, the system reliably identified level landing sites with clear approach paths that were accessible for evacuating a simulated casualty. The system’s sensors demonstrated that the system could detect 4-inch-high pallets, chain link fences, vegetation, people, and other objects that could block a potential landing site.

The laser scanner proved effective even when dust obscured the landing site, while the sensor package was also able to detect high-tension wires over desert terrain. In addition, the system detected and maneuvered around a manlift extended to a height of 60 feet while flying at a speed of more than 20 knots.

Significant Risk Reduction
According to Piasecki, these tests marked the first time a full-sized helicopter (the ULB is 10 meters long) has flown autonomously from mission take-off through navigation to a landing zone.

The primary impetus for developing this technology is to allow future unmanned helicopters to evacuate wounded soldiers from contaminated or live-fire battlefields, and to resupply forward military bases. Such low-altitude operations are where helicopters are most valuable, but also where they are most vulnerable. Autonomous operation can significantly reduce risk to pilots, either by giving a pilot aid in avoiding mishaps, or by eliminating the pilot entirely.

Usage Scenarios
The primary applications of the Autonomous Helicopter Collision Avoidance & Landing Zone Selection System are military in nature. Fully autonomous helicopter flight would give battlefield commanders more operational choices when evacuating wounded soldiers. For example, commanders often must weigh the option of delaying evacuation of wounded from a dangerous environment against sending in a substantial number of additional soldiers on a rescue mission, putting their lives at risk in the process. Autonomous, vertical-lift platforms that can navigate a complex combat environment would help minimize the number of soldiers necessary in either evacuation scenario.

The Piasecki/CMU system also holds promise for enhancing the safety of resupplying forward military bases located on the last leg of a distribution chain for supplies such as water, food, fuel, ammunition, and medical supplies. As has been amply demonstrated in Iraq and Afghanistan, once supply trucks are off the primary (often secured) roadways, land-based logistics platforms (i.e., trucks) can become easy targets for improvised explosive devices (IEDs). Using fully autonomous helicopters to distribute supplies to remote units would reduce some of the exposure of trucks and soldiers to attack.

In the civilian sector, given the lack of established standards by the Federal Aviation Administration for broad-based operations of unmanned systems in the national airspace, the technology is primarily applicable as an aid to pilots. Near-term civilian application will most likely be as sensor systems for manned helicopters, helping entities such as emergency medical services teams to avoid obstacles and select landing sites at emergency scenes.

The Future
According to Piasecki, the ULB performance of the Autonomous Helicopter Collision Avoidance & Landing Zone Selection System should scale larger craft with little problem. Work still remains, however, particularly as it relates to increasing overall system intelligence so that it can interpret more complex data sets.

The Mesa demonstration was the culmination of work sponsored by the U.S. Army’s Telemedicine and Advanced Technology Research Center (TATRC) through a Small Business Innovation Research (SBIR) program with Piasecki Aircraft and Carnegie Mellon’s Robotics Institute, supplemented with significant additional funding from Piasecki.