Date of Award

6-1996

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Brett Ridgely, PhD

Abstract

Systems which vary significantly over an operating envelope, such as fighter aircraft, generally cannot be controlled by a single linear time-invariant controller. As a result, gain-scheduling methods are employed to design control laws which can provide the desired performance. This thesis examines a relatively new approach to gain-scheduling, in which the varying controller is designed from the outset to guarantee robust performance, thereby avoiding the disadvantages of point designs. Specifically, the parameter-varying (LPV) aircraft model is linearized using linear fractional transformations (LFT's), and the resulting control problem is characterized as the solution to a set of four linear matrix inequalities (LMI's). The supporting theory is reviewed and two pitch-rate controllers are designed; one for the full longitudinal aircraft model, and another for the short period model. It is found that, even though the varying controllers are quite conservative, they can guarantee better robust performance over a large portion of an operating envelope when compared to time-invariant u-synthesis controllers.

AFIT Designator

AFIT-GAE-ENY-96J-1

DTIC Accession Number

ADA308905

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