Disturbance gain and bandwidth margins: definitions and application to autopilot design

Deals with the notion of disturbance model uncertainty. The disturbance is modeled as the output of a first-order filter which is driven by white noise and whose bandwidth, ω_b, and H ₂-norm, K, are uncertain. An analytical expression for the steady-state output variance as a function of ω_b and K is derived. Several properties of this variance function are given and the notions of disturbance gain margin and disturbance bandwidth margin are introduced. These tools are then applied to the analysis of an altitude hold autopilot system in the presence of turbulence with uncertain turbulence scale