Certifying a sense-and-avoid system that allows unmanned aerial systems to avert oncoming traffic is a prerequisite for full integration of unmanned aerial systems into national airspace. However, that may not be feasible in the near future, according to the agency's UAS roadmap released in 2013.
Airborne sense-and-avoid technologies are so complex that "significant progress" is not expected until the midterm, and actual fielding of a system is a long-term objective, the roadmap said. Initial
"Things would have to go very well for that. ... Seven to 10 [years] is a more realistic timeline without any major stumbling blocks," he said.
Most of the technologies needed to create sense-and-avoid systems are already mature, said
The service is working with the
According to current regulations, an aircraft operating in civil airspace must have a "see-and-avoid" capability to help it evade other planes or wildlife. A human pilot fills that role in manned planes and helicopters. With unmanned aircraft, the military employs either chase planes or ground observers to notify operators when it is in danger of a collision.
The military has been able to fly its drones freely in countries with little air traffic such as
Doing so will give the military broader global access and the ability to support missions such as disaster relief and border control, he said.
In order to see cooperative and noncooperative aircraft as well as wildlife, many sense-and-avoid systems use a mix of sensors. The traffic collision avoidance system, or T-CAS, and automatic dependent surveillance-broadcast, or ADS-B, transmit information on an aircraft's distance, altitude and velocity to others within receiving distance.
However, these systems only detect other aircraft with a corresponding transceiver or transponder. Because not all aircraft are required to carry such equipment, UAS would remain vulnerable to collisions with noncooperative aircraft. Incorporating cameras that detect both visible light and infrared, radar and light detection and ranging (LIDAR) would allow sense-and-avoid systems to see those threats.
"We then have a series of algorithms that take the data from those sensors and convert it into a situational awareness picture for both the pilot and for the computer," he said. The pilot can manually guide the aircraft out of the way, but if the operator is not able to respond in a timely manner, the system is automated to avoid collisions.
The system was created for use onboard die Global Hawk and is being retooled so that it can be installed on other large drones such as the Shadow, Predator and Reaper. The
To date, the system has flown 73 demonstration flights - most recently in
In September, the
The service plans to install ground radar for acceptance testing at the following installations:
"The money is there, we have a lot to do to get prepped for first flight," she said.
Using a ground-based sense-and-avoid system has certain advantages, particularly for the
For instance, the service's UAS fleet primarily comprises small, light aircraft, such as the 13-pound Puma and 4-pound Raven. Putting a large airborne sense-andavoid payload on such aircraft would sap their processing power and weigh them down, Kelley said.
Kelley said the
The service has not chosen what company will supply radar to each of the test sites, but the testbed uses
"We've been very careful to develop it the right way so that the cost is reduced on the backside," she said. "These radar are relatively inexpensive ... compared to other radar."
"Ultimately the goal is to tie to the airborne sense-and-avoid system that the
The military is not the only entity trying to develop a sense-and-avoid capability. The defense industry and academia are pursuing their own systems.
To build its sense-and-avoid technology, the
The algorithm can also be used with other sensors, such as ground-based radar, to give a UAS the ability to avoid wildlife and noncooperative aircraft, Semke said.
Since the project started in 2007, NDU students and faculty have refined their algorithm so that their unmanned aircraft follow the same right-of-way rules as commercial planes and civil aircraft. They have also introduced terrain avoidance capability, he said.
"What we've been working on quite a bit recently is dramatically different aircraft speeds, which is a challenging problem" because there are different strategies for efficiently avoiding an aircraft based on how fast it is going, Semke said. The lab is also working out how best to respond to rotorcraft that can move sideways.
The size and weight of sense-and-avoid equipment has dramatically changed since the program started. Initially, the lab's payload weighed 30 pounds, but that has shrunk to about four pounds and could be reduced to under a pound by using the latest equipment available on the market, Semke said.
ADS-B transceivers, which are the heaviest part of NDU's system, "started out being about 15 pounds, and now they have some that are under a pound. Our computer system and our hardware would fit inside a deck of cards."
Companies are also testing proprietary sense-and-avoid systems.
Insitu Pacific partnered with
"The sensor itself is a visual camera that detects differential movement in pixels which replicates the human eye's perception of movement. Once a pixel has been identified as a threat it sends an aural warning to the operating crew," said
During a recent flight, the system provided real time warnings to the ground control station, allowing operators to move the ScanEagle out of the way of other aircraft. Although autonomous avoidance is not a part of initial tests, the company could develop and incorporate such algorithms in the future, McDowall said in an email.
In order to convince the
Creating artificial intelligence that can mimic human decision-making processes is a major challenge, as is exercising senseand-avoid systems through test flights and simulations that put the technology through its paces, he said.
"The human brain is incredible when you're flying an aircraft. The decisions you make based upon the knowledge of all your training ... it's just hard to recreate that with artificial intelligence," he said. "The artificial intelligence community has made great strides, but ... they're not recreating the decision making of a human yet."
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