Equilibrium response of flight control systems

Abstract

The steady-state response of a controlled system is of particular importance in non-zero set point regulation, and nowhere is this of more concern than in the piloting of aircraft. Possible equilibrium states are, to a large extent, independent of the aircraft's stability and transient behavior; hence, stability and command objectives can be specified separately. Singular as well as nonsingular steady-state response may be desirable from the pilot's viewpoint, i.e. a constant command vector can imply varying state and control vectors. The flight control structure can be designed to account for this characteristic, while allowing full state or state-estimate feedback if desired. Dissimilar command vectors lead to markedly different responses in systems whose eigenvalues and eigenvectors are identical. A methodology for designing to achieve proper command response is presented, and numerical and graphical illustrations are provided for a generic lightweight fighter aircraft example.