Wireless Energy Transfer to Overcome Electrical Energy Limitations to UAV Mission Effectiveness

Wireless Energy Transfer to Overcome Electrical Energy Limitations to UAV Mission Effectiveness

Given all the technological advances in unmanned systems over the last several years, electrical demands and battery life have been a limiting factor when discussing UAV mission life and overall system capabilities. Effectively managing and designing a system that is conscientious of power demands depending on sensor/payload duty cycle, as well as required times of higher than normal power regimes (i.e. takeoff and landing) where electric motors may be running outside of predetermined ranges (Hepperle, 2009). Increasing battery life using different chemical composite structures, such as lithium polymer, lithium-ion, nickel-cadmium, and nickel-hydrogen may be expensive and too heavy for a vehicle to carry and effectively execute the prescribed mission (Hepperle, 2009). 

In order to maximize vehicle efficiency in terms of airborne time and minimizing weight to increase payload/sensor capability, it may become necessary to externally power a vehicle while it is in operation. Operation of a tethered drone using a hardwire connection could prove problematic as an electrical umbilical cable could yield issues in vehicle maneuverability, and severely limit the intended flight path (Glaser, 2016). However, line of sight wireless transmissions using millimeter and microwave technology, there is a potential for a vehicle to receive constant power during regular operation so long as it remains within a predetermined area. For some of these technological innovations to become realized, a military application may enter the technical sphere first prior to incorporation into a commercial or private market. 

Every year the U.S. Combating Terrorism Technical Support Office puts out a Broad Agency Announcement (BAA), which highlights technical issues and requirements for future research areas the United States Government wishes to purchase or invest in (Nordrum, 2016). In November of 2016, the BAA requested technology research areas for the intent to wirelessly recharge drones while in flight, with a clear emphasis on meeting new demands in both its counterterrorism and counterinsurgency efforts (Nordrum, 2016). Based on this announcement, it is a strong indication that the need for increased range and flight time for unmanned vehicles is not only a technical innovation that is requested for research, but also a critical application area for the US Department of Defense, Homeland Security and possibly feed into US Military service branch requirements (Nordrum, 2016).

Despite the research request at the discretion of the DoD, commercial companies such as Facebook, and Amazon are already heavily researching methods of increasing flight time for their unmanned vehicles (Morris, 2016). Research efforts to increase the sophistication of electrical subsystems internal or external to the UAV include (but are not limited to): photovoltaics for fixed wing type UAVs, recharge stations integrated into existing structures such as telephone poles or buildings, and focused electromagnetic fields (such as microwaves) and lasers to transmit energy (Morris, 2016).

References:

Glaser, A. (2016, October 12). Wireless Charging Could Keep Drones in the Air for Much Longer. Retrieved from https://www.recode.net/2016/10/12/13257790/wireless-charging-drones-air-longer-solar-power-batteries 

Hepperle, M. (2009). Electric Flight – Potential and Limitations. German Aerospace Center: Institute of Aerodynamics and Flow Technology, STO-MP-AVT-209. Retrieved from http://www.mh-aerotools.de/company/paper_14/MP-AVT-209-09.pdf.

Morris, D. (2016, September 24). Demo Shows Drone Flying Under Wireless Power. Retrieved from Fortune Magazine, http://fortune.com/2016/09/24/drone-flies-wireless-power/

Nordrum, A. (2016, December 12). Wanted: In-flight Drone Charging, Itty-Bitty Spy Cams, and More. Retrieved from http://spectrum.ieee.org/tech-talk/aerospace/military/wanted-wearable-chemical-sensors-wireless-recharging-stations-for-drones-and-ittybitty-spy-cams