Stabilization of longitudinal motion of a hypersonic transport aircraft

Abstract

Hypersonic transport (HST) aircraft are the subject of much current research as the need to reduce block times on long haul flights becomes more pressing. The dynamics of such HST aircraft are strongly influenced by the close interdependence of the aerodynamic and propulsion systems. The key dynamic features of such aircraft are their dynamically unstable longitudinal motion, and extremely sluggish response in pitch attitude, which make aircraft of this type difficult to fly. This paper presents the design of an automatic flight control system which can provide the required degree of stability and the required flying qualities. The optimal feedback control law was derived from the use of linear quadratic regulator (LQR) theory, in which the state weighting matrix was calculated from known closed-loop eigenvalues which were specified by the designer to obtain the required stability and flying qualities. The effectiveness of the multivariable control law is illustrated by means of dynamic responses obtained from a simulation based upon an HST aircraft flying at Mach 8.0 at a height of 85 000 feet.

Keywords

Aircraft dynamics hypersonic flight optimal control eigenvalue assignment LQR theory.

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