N251-053 TITLE: Autonomous Charging and Energy Management for Large Drone Fleets

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Renewable Energy Generation and Storage;Sustainment;Trusted AI and Autonomy

OBJECTIVE: Develop a common system of energy monitoring, electrical generation, charging configurations, and autonomous behaviors for a fleet of 100+ unmanned entities (Class 1 drones and other small unmanned vehicles) to maintain their own charge cycles without human intervention for up to 1 week.

DESCRIPTION: Small drones and unmanned air/surface/ground vehicles are present in increasingly large numbers at smaller units of force (company-level and below), and the appetite for more unmanned assets continues to grow. However, their utility is presently hampered by the energy management demands that are incurred by charging cycles, a problem that is only expected to worsen as more and more unmanned systems make their way into small units. With some flight durations as short as 20 minutes, but charge cycles on the order of hours, the users are often relegated to carrying and swapping large numbers of charged batteries or waiting long periods of time without any capability during charge cycles. An innovative solution for improving the operational availability of drone fleets is to utilize the self-tending nature of intelligent autonomy to manage energy requirements on their own, with all energy management tasks relegated to the entities themselves. This will free up human teammates to focus on their own priorities and reduce or eliminate the requirement to carry and swap batteries for extended coverage.

The outcome of this SBIR topic is a set of universal standards, configurations, and equipment for autonomous power management. The required elements include:

• Deployable electrical power generator complexes that fuse traditional fuel-powered sources with non-traditional and renewable sources (solar, wind, small hydro and found fuels via Stirling engine generators) to fully exploit all charging energy sources and reduce/eliminate dependence on fuel chain logistics
• Energy management software that resides in on-board processing and monitors usage, predicts time remaining, and assumes control of the entity to direct its movement to a charging source prior to battery exhaustion
• Connector configurations that allow single charge stations to support multiple customers simultaneously
• Command and Control (C2) interfaces that alert humans to charging "break-offs" and provide an opportunity for override and an option to assign standby assets

Performance Goals include using self-charging protocols to:

• Continuously maintain fleets of up to 100 entities for periods of up to 1 week
• Utilize the full range of available energy sources to provide uninterrupted charging power without sole reliance on fossil fuel generation
• Maximize deployability by minimizing size and weight of generating station components to 2-person lift and setup

Related state-of-the-art available technologies include recent advances in small Stirling cycle electrical generators that utilize "found fuels" such as sticks, trash or any burnable material to produce useful amounts of power, along with direct-conversion (heat to electricity) technology that can be scaled up for charging purposes. Also, tactical networks and advances in Command and Control (C2) systems for coordinated operation of large numbers of unmanned assets by few or one human, and vehicle-agnostic autonomous control systems. The key attribute of the generation component is a diversity of methods that reduce or eliminate the need to transport volatile fuels from a distance for the 1-week notional period of the engagement.

The focus of technology development is on:

• The selection of and integration of diverse power generating approaches into a single component that can be transported and set up by a typical United States Marine Corps (USMC) squad-sized element. Approaches can utilize either small modules with human carry or self-transport via wheels, tracks or unmanned airlift. The technical challenges are in developing a package that produces stable charging power on demand from diverse sources while maintaining low Size, Weight, and Power (SWaP).
• The capability of a single charge source to meet the diverse needs of autonomous platforms that do not share a common battery configuration. The technical challenges are in standardizing battery configurations across an array of in-use autonomous systems, or in developing controllable charging stations that can sense the charging requirements and vary their output to match.
• The development of docking stations and charge connections that allow a variety of in-use vehicles to autonomously connect, charge, and disconnect when needed
• The development of on-board or remote autonomous charge/monitoring behaviors that continuously sense state of charge, locate charge sources, predict transit requirements, and break off mission to execute charging protocols without battery exhaustion

Performance Parameters:

• Transportable by a 13-member squad-sized element for distances of 5Km, or self-transporting
• Integrated into existing autonomous vehicles and control systems (no new vehicles)
• Two or more independent generation methods in a single package
• One week of unattended operation (exception for fueling at 6-hour intervals by 1-2 people)

PHASE I: Conduct a feasibility study utilizing existing vehicles in ONR Code 34’s current fleet of unmanned assets and ONR Code 34’s sequence of virtual and real-world experimentation to explore configuration options, interfaces, communication protocols, and autonomy software to assess options specified in the Description section. Investigate all known options that meet or exceed the minimum performance parameters suggested in the Description. Address the tradeoffs and risks in accordance with the level of innovation. Prepare a report to ONR on designs, simulations, prototype production, and a Phase II testing plan.

PHASE II: Design, develop, and produce prototype generators, hands-off automatic charger connections, and software that can support the charging requirements of up to 10 users for a period of 72 hours with no human interaction other than fueling Stirling generators at 6-hour intervals. This requirement is different from the 1-week, 100 user requirement to allow phased upscaling within the Phase II and the Phase III transition, and because servicing more users for longer periods can be accomplished by using more generators and extending fueling cycles. Develop, demonstrate, and validate the Concept of Operations (CONOPs) using ONR Code 34’s Kobol sequence of virtual and real of force-on-force unscripted simulated combat operations (4x yearly at multiple Department of Defense locations in the continental U.S.).

PHASE III DUAL USE APPLICATIONS: The final (Phase III) state of the technology is a set of rugged multi-source generators with unmanned connection capability that can operate for extended periods with limited human contact to supply the electrical needs of a large drone fleet.

The dual-use capability is for any user who operates unmanned fleets of similar size, and desires to transition to unattended charging in austere environments. Examples include law enforcement, forestry services, firefighting, humanitarian assistance, and disaster relief.

REFERENCES:

1. Moonka, Gourav; Surana, Harsh and Singh, Hemant Raj. "Study on some aspects of Stirling engine: A path to solar Stirling engines." Materials Today: Proceedings, Volume 63, 2022, pp. 737-744. ISSN 2214-7853. https://doi.org/10.1016/j.matpr.2022.05.107

(https://www.sciencedirect.com/science/article/pii/S2214785322033879)

2. Jadhav, Vinay and Bhosale, Surendra. "Battery Management System for Drones.

3. Jung, Jaewoo and Nag, Sreeja. "Automated Management of Small Unmanned Aircraft System Communications and Navigation Contingency." NASA Ames Research Center, Moffett Field, CA 94035, USA. https://aviationsystems.arc.nasa.gov/publications/2020/2020_Jung_SciTech2020.pdf

4. Hayajneh, Mohammad R. and Badawi, Abdul Rahman E. "Automatic UAV Wireless Charging over Solar Vehicle to Enable Frequent Flight Missions." Association for Computing Machinery, New York, NY, USA, 2019. ISBN 9781450372886. https://doi.org/10.1145/3365265.3365269

KEYWORDS: Stirling engine; Energy conversion; Automated management, Battery Management, Unmanned Power, Direct Conversion

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