Unmanned Air-traffic Management (UTM): Formalization, a Prototype Implementation, Verification, and Performance Evaluation
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Unmanned Aircraft Systems (UAS) traffic management system (UTM) is necessary for automated safe and efficient low-altitude airspace operations. FAA has conceptualized the requirements on UTM protocols and components in the FAA's Concept of Operations for UTM report. In this paper, we explore applying rigorous formal reasoning on building and analyzing UTM protocols to (1) help provide high assurance on UTM protocols and (2) discover the strength and weaknesses of existing formal techniques. We propose the first mathematical formalization of FAA's notion of operation volumes that express aircraft intent in terms of 4D blocks of airspace and associated real-time deadlines. We present an executable prototype coordination protocol using operation volumes, involving participating aircraft and an airspace manager. Next, we show how to use an ensemble of existing simulation and formal verification tools to analyze the protocol including (1) formally proving the safe separation and liveness properties of distributed coordination with the help of proof assistants Dione and Dafny, (2) using data-driven reachability analysis with DryVR to ensure aircraft to follow operation volumes, and (3) evaluating the performance of the protocol in terms of workload and response delays with extensive simulations in ROS and Gazebo. We show that our analysis can be applied on heterogeneous aircraft models. Our experiments also delineate the trade-off between performance and workload across different strategies for generating operation volumes.
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