P. Vu et Dj. Biezad, DIRECT-LIFT DESIGN STRATEGY FOR LONGITUDINAL CONTROL OF HYPERSONIC AIRCRAFT, Journal of guidance, control, and dynamics, 17(6), 1994, pp. 1260-1266
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 de
sign technique relies on classical, successive loop closures to determ
ine the control architecture and introduces a direct-lift control stra
tegy to design dynamic compensation. This dynamic compensation constra
ins and ''washes out'' body-flap input to avoid excessive nap deflecti
on and associated heating while providing angle-of-attack control at t
he engine inlet. The final design was implemented on a generic hyperso
nic aircraft simulation at NASA Dryden and evaluated by a NASA test pi
lot familiar with the SR-71. The pilot flew tuning and altitude change
maneuvers using the implemented control law and verified the ability
to track flight path with ease and precision. Finally, evidence is pre
sented that supports a flying qualities metric for longitudinal, hyper
sonic flight based on the bandwidth of the flight-path-angle-to-stick-
frequency response.