Millimeter Wave Adaptive Power Beaming of UAVs
Abstract
The objective of this project is to investigate a far-field wireless power transfer (WPT) method to charge small to mid-size UAVs airborne during fly at distance without the need for landing to recharge. In particular, the PI will develop a millimeter wave (mmWave) remote charging scheme for battery-powered UAVs based on time-reversal adaptive power beaming technique and metamaterial receiving structures. Microwave narrow beam requires physically large aperture or antenna array which is not suitable for small UAVs on the order of a few wavelengths of microwave to achieve high gain. Millimeter waves have much smaller wavelength than microwaves and less affected by atmospheric effects than optical waves. So, power beaming of mmWave provides a better solution for far-field power transfer to charge small UAVs. Although time-reversal mirror has been studied extensively as a means of spatiotemporal focusing of acoustic or electromagnetic waves, this project will employ the time reversal (TR) technique for a different application, i.e. wireless charging of flying small UAVs at distance, employing the spatiotemporal focusing effect of the TR to improve the energy efficiency of wireless power transfer and battery lifetime. The small moving object makes it difficult to lock the beam even for a multi-rotor UAV capable of hovering, a slight drift may pull the UAV out of the beam especially when the beam is narrow. Also, even within the beam, a small drift may reduce the efficiency of power transfer. Adaptive power beaming based on the TR technique combined with tunable metamaterial surface provides a good solution to overcome this challenge. In this scheme, a pilot or training signal sent from the UAV is captured and consequently processed to adaptively apply amplitude and phase shift to each array element to direct the beam back at the UAV. The tunable meta-receiving structure can dynamically optimizes the power collection efficiency and rectify the mmWaves to charge the battery. Two types of meta-receiving structure will be designed: (1) A metamaterial superstrate on top of the conventional antenna and rectifier array; (2) Rectifier array embedded in metamaterial-receiving surface. A motion correction algorithm will also be developed to ensure constant beaming and optimize the latency. In this project, single and multiple zones will be considered. In the single zone, power will beam to a specific zone where a UAV will fly in and hover. In the second scenario, power will beam to multiple zones distributed over a broader area, so that a UAV can be constantly beamed while in operation. Compared to the first scenario, ultrafast charge in the second scenario is less demanded due to constant supply of wireless power to the battery over a longer period of time. Other parameters, such as propagation conditions, transmitting power, battery capacity, maximum range, and latency are also different for the two scenarios. These parameters and propagation models will be investigated. The goal of this project is to demonstrate the proof of concept in a short range laboratory setting at the low end millimeter wave frequency band, i.e. 26-30GHz, and show its scalability at further ranges. This project will be carried out in collaboration with the High Power Microwave Section (Code 5745) of NRL to support the NRL program, and was strongly recommended by NRL Code 5745. NRL will perform additional investigation of beaming and optimization techniques, as well as additional modeling and experimental verification towards transitioning of the proposed power beaming to operational technology. I strongly recommend funding this project.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 25, 2019
- Source ID
- N629091912049
Entities
People
- Sun K. Hong
Organizations
- Office of Naval Research
- Soongsil University
- United States Navy