M.S. AAI Capstone Chronicles 2024

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Background Information

Currently, there are a few approaches implemented to achieve SAA in UAVs without the use of artificial

intelligence methods. The most notable are documented by NASA and the MIT Lincoln Laboratory

(Balachandran, et al., 2018). A distributed software architecture was developed by NASA, known as the

Independent Configurable Architecture for Reliable Operations of Unmanned Systems (ICAROUS) with

the purpose of enabling safe UAV operations. This method uses a publisher-subscriber middleware to

interface between the autopilot system and the algorithms for path planning, traffic avoidance,

geofence handling, and decision making. The SAA portion of ICAROUS is handled by the Detect and

Avoid Alerting Logic for Unmanned Systems (DAIDALUS) which is a software library available under

NASA’s Open-Source Agreement. At the core of this concept is a mathematical definition describing

when two aircraft are well clear of each other based on distance and time variables, and predefined

threshold values. When these thresholds are violated, DAIDALUS provides guidance on maneuvers and

ranges to maintain or reestablish the well clear definition.

Alternatively, the Ground-Based Sense-and-Avoid (GBSAA) system was developed by the Lincoln

Laboratory in partnership with the U.S. Army Program Manager Unmanned Aircraft Systems to

specifically comply with the Federal Aviation Regulations (FARs) requirements to remain well clear of

other aircraft (MIT Lincoln Library, n.d.). The GBSAA uses 3D radars as well as Federal Aviation

Administration (FAA) radars to generate an image of the airspace and locate any aircraft that may pose a

collision threat. The radar data is processed to analyze aircraft locations and estimate the risk posed by

other aircraft to the UAV. If risks are detected, the GBSAA issues warnings and provides maneuver

guidance to the GBSAA or UAV operator. This method provides the benefit of being an open

architecture, allowing for integration with other sensors and the use of radar eliminates the need for

additional equipment on the UAV making it a suitable option for UAVs of all sizes.

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