The biggest hurdle for unmanned aerial vehicles to clear in order to gain Federal Aviation Administration approval for use in the national airspace is development of systems to prevent them from crashing into each other and, even more important, into manned aircraft. And the key challenge in developing such a “sense-and-avoid” system has been developing technology that can reliably detect the presence – and the course – of other aircraft and to engineer it into a package small enough and light enough for UAVs.
Researchers at the University of Denver’s Unmanned Systems Research Institute may have the answer. The group has developed a phased-array radar system that weighs only 12 ounces and is small enough to fit in the palm of one’s hand.
According to Mark Rutherford, assistant professor of computer science and deputy director of the Unmanned Systems Research Institute, the team wanted to develop a radar-based solution because radar offers several advantages over the two other technologies – optical camera-based systems and transponder systems – that have been under development for sense-and-avoid systems.
Transponder-based systems are highly reliable but only work when all the aircraft in the airspace are equipped with transponders. “There may be government regulations in this country that say that everything has to have a transponder, but in some cases a transponder would cost more than the whole vehicle,” Rutherford said. “We’re not sure that we want to plan on the fact that everything out there is going to have a transponder on it.”
Camera-based systems may detect other aircraft regardless of the equipment they carry, but their effectiveness is affected by atmospheric conditions. “Radar works in nighttime, and it works regardless of the lighting conditions and in weather conditions where you don’t have good visibility,” Rutherford said.
Despite radar’s advantages, Rutherford said, “we couldn’t find anything that was designed specifically for very small vehicles. And most vertical takeoff and landing vehicles are really limited in payload, so we wanted something that would work in that context.”
The team built everything from scratch except the antenna – digital signal processor, circuit boards and the software. “In our field tests we were able to detect and identify targets of the size roughly equivalent to UAV at about 100 meters or 300 feet,” Rutherford noted, and added that the team is continuing to work on increasing the range of the unit.
The technology was licensed in April to Integrated Robotics Imaging Systems in Kenai, Alaska, which will be testing it on its Infotron IT180, a French-made, dual-rotor unmanned platform.
At 31 pounds and with a 71-inch rotor diameter, the Infotron device is larger than many UAVs. But John Parker, president of Integrated Robotics, said he plans to further reduce the size and weight of the system, making it feasible for a wider array of smaller UAVs. “When I’m done it will be about 4 ounces,” Parker promised. “I’m going to be refining it and changing it and either adding claims to the existing patent or patenting the changes that we make.”
According to Parker, new phased arrays are available that don’t require a servo device to move the radar. “Instead of having the sensors driven, they are actually applied to a dome – to a “radome” – and they have overlapping fields of view so you don’t have to have a servo driving them back and forth,” Parker said. “So they can continuously scan the sky ahead.”
Parker says he’s also receiving interest from the general aviation sector. “Other small radars that are being used in general aviation are in the $15,000 range,” Parker explained. “We think we’re going to be in a very good position at around $7,300 to $7,500. That’s why general aviation is interested in this.”
“I see this industry changing rapidly the next 24 months,” Parker said. “I think you’ll see the commercialization begin to occur. It’s already happening.”