Direct-lift design strategy for longitudinal control of hypersonic aircraft

Abstract

A longitudinal control design called the G-command, alpha follow-up is described that significantly improves the lag between pitch angle and flight-path angle responses associated with hypersonic flight. The design technique relies on classical, successive loop closures to determine the control architecture and introduces a direct-lift control strategy to design dynamic compensation. This dynamic compensation constrains and "washes out" body-flap input to avoid excessive flap deflection and associated heating while providing angle-of-attack control at the engine inlet. The final design was implemented on a generic hypersonic aircraft simulation at NASA Dryden and evaluated by a NASA test pilot familiar with the SR-71. The pilot flew turning and altitude change maneuvers using the implemented control law and verified the ability to track flight path with ease and precision. Finally, evidence is presented that supports a flying qualities metric for longitudinal, hypersonic flight based on the bandwidth of the flight-path-angle-to-stick-frequency response.

A Composite Control Strategy for an Air-Breathing Hypersonic Vehicle with Wing-Rudder Deflection

“…The hypersonic vehicle in this work has a configuration with tailcontrol rudders [4] [5] [8] and a set of deflectable wings installed nearby the center of gravity [6] [9]. During the cruising period, the precision of AOA is achieved by the deflecting of tail rudders, and the maneuverable acceleration command is tracked by deflecting wings.…”