Inside Unmanned Systems

JUN-JUL 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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AIR, LAND, MARINE POWER 52 unmanned systems inside   June/July 2017 Improvements in wireless charging may enable fleets of drones and other robotic systems to re-energize without human help, opening the door to true autonomous operations. Meanwhile, scientists at the Naval Research Lab have developed a zinc- nickel battery that may be safer, cheaper and smaller than a comparable lithium-ion battery—a real boon to electric vehicles. by Charles Q. Choi Photos courtesy of WiBotic. A lthough drones are becoming more and more capable, they have one key limita- tion—power. Now researchers have de- veloped a wireless charging technique that makes it possible for drones to recharge themselves without human aid, potentially enabling the opperation of fully autonomous fleets of robots on land, air and sea. Scientists at the U.S. Navy and their colleagues also have been working on rechargeable batteries, developing a zinc-based power source that can significantly out perform lithium-ion in terms of energy, cost and safety. WiBotic A technique known as inductive charging is currently used to wirelessly recharge every- thing from electric toothbrushes and power tools to autonomous robotic vacuum cleaners and the cochlear implants that help deaf peo- POWERED UP ple hear. However, inductive charging typically can only transfer power a few millimeters, said Matt Carlson, vice president of business devel- opment at Seattle-based WiBotic. That sharply limited range is not a problem if one is just sliding an electric toothbrush into its stand. It does prove a challenge, however, when one must land a drone on a recharging pad "in exactly the same spot over and over again," Carlson said. "A gust of wind could easily blow a drone five to six centimeters off during landing." In contrast, the new technique developed by WiBotic can recharge devices at a distance of up to several centimeters, Carlson said. This can make wireless charging of unmanned vehicles practical, which in turn could enable fully autonomous op- eration of fleets of drones and other robots. "You wouldn't need to rely on human beings to swap out batteries," Carlson said. "Ours is the only system we're aware of that can provide com- pletely autonomous wireless charging for multiple different drones in a fleet, and can do the same for ground-based robotics and even aquatic systems." Although one could use automated systems to swap out batteries, "there are no moving parts in our system other than the drone it- self—everything is done electronically and very reliably," Carlson said. "The big knock against physical battery replacement is that you're adding a second robot to the mix, a whole other maintenance issue for yourself." Fine Tuning Inductive charging relies on at least two coils— one in the power transmitter, and one in the power receiver. When an electric current pass- es through the power transmitter coil it gener- ates an electromagnetic field that can transfer energy to the power receiver coil, a phenom- enon known as magnetic induction. A major reason inductive charging is typically limited in range is because electrical features of the coils used are often kept static and not matched to each other. By dynamically tuning the voltage, amperage and about 10 other fea- ZINC-SILVER BATTERIES should show greater levels of power than lithium-ion batteries and should "be of benefit for unmanned applications. Debra Rolison, head of Advanced Electrochemical Materials, Naval Research Laboratory

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