High-speed (supersonic or hypersonic) atmospheric flight vehicles are typic
ally characterized by a significant degree of interaction between the highl
y elastic airframe and the propulsion system. To achieve adequate stability
and performance requirements, robust, integrated multivariable control law
s will be required. But to apply robust control analysis or synthesis techn
iques such as structured-singular-value techniques (mu) or quantitative fee
dback theory, the uncertainty in the plant dynamics must be characterized i
n special ways. Furthermore, certain assumptions regarding the uncertaintie
s present are frequently made in the application of these techniques. The f
ocus of this research is the development of uncertainty models for this cla
ss of flight vehicle that are derived from the physics of the system, yet a
re compatible with the cited control synthesis techniques. The potential so
urces of uncertainty for this class of vehicle are discussed, and three for
ms of uncertainty models are developed: real parameter, unstructured, and s
tructured. We are especially interested in how the usual sources of uncerta
inty manifest themselves in this context. It will be shown that for this cl
ass of vehicle care is required in making the usual assumptions regarding t
he uncertainty. It is also shown that the flexible degrees of freedom must
be considered in the flight-control synthesis for this class of vehicle.