Inside Unmanned Systems

OCT-NOV 2017

Inside Unmanned Systems provides actionable business intelligence to decision-makers and influencers operating within the global UAS community. Features include analysis of key technologies, policy/regulatory developments and new product design.

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53 unmanned systems inside October/November 2017 ENGINEERING. PRACTICE. POLICY. Two examples of the considered scenario where two UAS fl y outside an unknown area to collect WiFi RSSI measurements for the purpose of 3-D through-wall imaging based on the proposed approach. Mostof i and her colleag ues prev iously experimented with imaging via WiFi using ground-based robots. This helped collect 2-D data. "I have background in both wire- less systems and robotics, so putting the two together was a natural thing for me to do," Mostofi said. Moving to 3-D To move to 3-D imaging, the researchers chose to work with unmanned aerial sys- tems (UAS), which can approach a target area from several angles. "Apply ing our previous approach that had worked well for 2-D imaging through walls with ground ve- hicles did not work well for 3-D imaging," Mostofi said. "This is due to the considerable increase in the number of unknowns in the 3-D case—for example, 10 times more (un- knowns) as compared to 2-D—requiring new methodologies." The scientists experimented with two com- mercial 3DR X8 octocopters that were each equipped with an off-the-shelf D-Link WiFi router. The researchers had the octocopters slowly f ly outside an enclosed square structure about 10 feet wide and 1.3 feet high with brick walls about 4 inches thick. Inside this struc- ture were various objects made of bricks. While in f light, one drone continuously transmitted a WiFi signal, while the other drone measured the power of the signal it re- ceived. The researchers designed f light paths for the drones enabling them to capture as much spatial variation in all three dimen- sions as possible while keeping the f lights efficient. "It takes the UAVs about 150 seconds to fin- ish an angle, which consists of a few routes," Mostofi said. "Each operation typically con- sists of a few angles—like, four or so. Wind and battery limitations can also affect the overall time." " WAVES AT FREQUENCIES SIMILAR TO WiFi CAN STILL MAKE IT THROUGH WALLS, AND THE RESULTING RESOLUTION CAN WORK FOR SEVERAL APPLICATIONS." Yasamin Mostofi , professor, University of California at Santa Barbara Using drones to peer through walls with WiFi poses a few challenges. "For instance, they have a limited battery life time, which can limit the operation time and can result in down times to recharge the batteries," Mostofi said. "Using multiple battery packs can help with this to reduce the downtime." POTENTIAL APPLICATIONS •  Structural Monitoring •   Surveillance/Law Enforcement •  Search and Rescue •   Archaeological Discovery ã RX–UAS TX–UAS

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