Date of Award

6-1994

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

D. Brett Ridgely, PhD

Abstract

A general mixed H2/H∞ optimal control design with multiple H∞ constraints is developed and applied to two systems, one SISO and the other MIMO. The SISO design model is normal acceleration command following for the F- 16. This design constitutes the validation for the numerical method, for which boundaries between the H2 design and the H∞ constraints arc shown. The MIMO design consists of a longitudinal aircraft plant (short period and phugoid modes) with stable weights on the H2 and H∞ transfer functions, and is linear- time-invariant. The controller order is reduced to that of the plant augmented with the H2 weights only. The technique allows singular, proper (not necessarily strictly proper) H∞ constraints. The analytical nature of the solution and a numerical approach for finding suboptimal controllers which are as close as desired to optimal is developed. The numerical method is based on the Davidon- Fletcher-Powell algorithm and uses analytical derivatives and central differences for the first order necessary conditions. The method is applied to a MIMO aircraft longitudinal control design to simultaneously achieve Nominal Performance at the output and Robust Stability at both the input and output of the plant.

AFIT Designator

AFIT-GAE-ENY-94J-04

DTIC Accession Number

ADA280572

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