Richard C Lind

US Patent:

6216063, Apr 10, 2001

Filed:

May 6, 1998

Appl. No.:

9/074024

Inventors:

Richard C. Lind - Lancaster CA
Martin J. Brenner - Lancaster CA

Assignee:

The United States of America as represented by the Administrator of the
National Aeronautics and Space Administration - Washington DC

International Classification:

G05D 300
G06G 776

US Classification:

701 3

Abstract:

A structured singular value (. mu. ) analysis method of computing flutter margins has robust stability of a linear aeroelastic model with uncertainty operators (. DELTA. ). Flight data is used to update the uncertainty operators to accurately account for errors in the computed model and the observed range of aircraft dynamics of the aircraft under test caused by time-varying aircraft parameters, nonlinearities, and flight anomalies, such as test nonrepeatability. This. mu. -based approach computes predict flutter margins that are worst-case with respect to the modeling uncertainty for use in determining when the aircraft is approaching a flutter condition and defining an expanded safe flight envelope for the aircraft that is accepted with more confidence than traditional methods that do not update the analysis algorithm with flight data by introducing. mu. as a flutter margin parameter that presents several advantages over tracking damping trends as a measure of a tendency to instability from available flight data.