Robust Aeroservoelastic Stability Analysis


This course will introduce the concept of robustness to the study of flutter and aeroservoelasticity. The models that are traditionally used for stability analysis are augmented with uncertainties to reflect potential errors and unmodeled dynamics. The mu method is developed to directly account for these uncertainties. The resulting robust stability margin is a worst-case measure of the smallest flutter speed for the system as effected by any of the uncertainty values. This course demonstrates the procedure for formulating a model in the mu framework and computing the associated robust stability margin. Furthermore, the course discusses methods to compute uncertainties in the models based on flight data analysis. Several applications from recent flight tests are presented for which the mu method was used to compute robust aeroservoelastic stability margins.

Key Topics:

  • State-space modeling of flutter and aeroservoelasticity
  • Considering uncertainty in open-loop and closed-loop models
  • Using flight data to identify models and associated uncertainty
  • Computing robust flutter margins

Who Should Attend:

This course is intended for engineers interested in aeroservoelasticity and flutter. The course will be of particular value to anyone interested in flight test program in which flutter is a concern. The students are assumed to be familiar with basic structural dynamics but not robust stability theory. The material is at a level for graduate students and practicing engineers.

Course Information:

Type of Course: Instructor-Led Short Course
Course Level: Fundamentals/Intermediate
Course Length: 2 days
AIAA CEU's available: Yes


I. Introduction
a. Why robustness is important to consider
b. Why aeroservoelasticity is different from flutter

II. Robust Stability Theory
a. Small gain theorem
b. Mu analysis

III. Modeling
a. Structural dynamics and unsteady aerodynamics
b. Closed-loop aeroservoelasticity
c. Instability mechanisms

IV. Aeroservoelastic Models in the mu Framework
a. State-space realization of models
b. Finding worst-case perturbation
c. Match-point flutter and aeroservoelastic stability margins

V. Robust Models with Uncertainty
a. Parametric and dynamic uncertainties
b. Effects and relevance of different types of uncertainties
c. Adding uncertainty to a model

VI. Analyzing Flight Data
a. Incorporating data into a model
b. Model validation
c. Utilizing parameter estimation and identification methodologies

VII. Robust Flutter Margins
a. Computing nominal and robust flutter margins
b. Computational algorithms
c. Flutterometer

VIII. Applications
a. Robust flutter analysis of the Aerostructures Test Wing
b. Robust flutter analysis of the F/A-18 SRA
c. Robust aeroservoelastic analysis of the F/A-18 HARV



Rick Lind is an Associate Professor in the Department of Mechanical and Aerospace Engineering at the University of Florida. He has specializes in aeroservoelastic technologies, including biologically-inspired concepts, for a range of flight vehicles.

Martin Brenner is a Research Engineer at NASA Dryden Flight Research Center. He has extensive experience at flight testing of dozens of experimental aircraft including the Active Aeroelastic Wing.


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