Multi-Scale and Multi-Reference Longitudinal Guidance Logic for UAS

As uncrewed aerial systems (UAS) employment slowly creeps toward urban airspace, it becomes evident that current guidance logics traditionally used become insufficient to provide the proper tracking required. Especially true of this are current longitudinal guidance logics, which focus more on altitude regulation rather than trajectory tracking. While altitude regulation may have sufficed for open airspaces this is not the case for dense urban areas which require as much maneuverability as possible. This paper presents and compares four methods of aircraft longitudinal guidance logic: L
1
-Guidance, which regulates the proportional altitude error through pitch changes,
$h$
-Guidance which incorporates error rate regulation into the proportional error, γ-Guidance, which focuses on commanding aircraft longitudinal flight path angle rather rather than aircraft pitch angle, and γ-
$h$
-Guidance, which combines a flight path angle command with the error rate feed forward. Additionally, the guidance logic can be expanded through L
N
-guidance methods to improve performance by tracking a reference area on the desired altitude rather than the single point, as seen in traditional L
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guidance logics. Flight path guidance is compared with traditional altitude error longitudinal guidance; flight path guidance is shown to have superior tracking, while altitude error guidance is shown to have superior maneuverability. Combining the two guidance logics produces a longitudinal guidance logic that provides excellent tracking with no steady state error and maneuverability that far exceeds the original flight path guidance logic.