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Nonlinear programming extensions to rational function approximation methods for unsteady aerodynamic forcesThe approximation of unsteady generalized aerodynamic forces in the equations of motion of a flexible aircraft are discussed. Two methods of formulating these approximations are extended to include the same flexibility in constraining the approximations and the same methodology in optimizing nonlinear parameters as another currently used extended least-squares method. Optimal selection of nonlinear parameters is made in each of the three methods by use of the same nonlinear, nongradient optimizer. The objective of the nonlinear optimization is to obtain rational approximations to the unsteady aerodynamics whose state-space realization is lower order than that required when no optimization of the nonlinear terms is performed. The free linear parameters are determined using the least-squares matrix techniques of a Lagrange multiplier formulation of an objective function which incorporates selected linear equality constraints. State-space mathematical models resulting from different approaches are described and results are presented that show comparative evaluations from application of each of the extended methods to a numerical example.
Document ID
19880015239
Acquisition Source
Legacy CDMS
Document Type
Technical Publication (TP)
Authors
Tiffany, Sherwood H. (NASA Langley Research Center Hampton, VA, United States)
Adams, William M., Jr. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 5, 2013
Publication Date
July 1, 1988
Subject Category
Aircraft Design, Testing And Performance
Report/Patent Number
NAS 1.60:2776
L-16205
NASA-TP-2776
Accession Number
88N24623
Funding Number(s)
PROJECT: RTOP 505-63-21-04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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