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Real-Time Estimation of Bare-Airframe Frequency Responses from Closed-Loop Data and Multisine Inputs.

Jared A Grauer1, Matthew J Boucher2

  • 1NASA Langley Research Center, Hampton, Virginia, 23681, Research Engineer, Dynamic Systems and Control Branch, MS 308, Associate Fellow AIAA.

Journal of Guidance, Control, and Dynamics : a Publication of the American Institute of Aeronautics and Astronautics Devoted to the Technology of Dynamics and Control
|October 26, 2020
PubMed
Summary

This study introduces a new method for estimating aircraft frequency responses from flight data, even with complex control systems. The technique uses unique frequency excitations to accurately measure bare-airframe dynamics, improving flight analysis.

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Area of Science:

  • Aerospace Engineering
  • Control Systems Theory
  • System Identification

Background:

  • Estimating bare-airframe dynamics from flight test data is challenging due to feedback control and control effector mixing.
  • Existing methods may struggle to accurately isolate the airframe's inherent frequency responses in the presence of these complexities.

Purpose of the Study:

  • To develop and validate a novel method for accurately estimating multiple-input multiple-output (MIMO) bare-airframe frequency responses.
  • To address the confounding effects of feedback control and control mixing in flight test data analysis.

Main Methods:

  • Utilizing orthogonal phase-optimized multisines to simultaneously excite each input with unique harmonic frequencies.
  • Computing frequency responses as ratios of output-to-input Fourier transform data at excitation frequencies.
  • Resolving confounding effects of feedback and mixing through frequency response interpolation.

Main Results:

  • The method successfully estimated frequency responses from simulated and real flight test data.
  • Effectiveness verified on a T-2 generic transport airplane simulation with rate feedback.
  • Demonstrated on the X-56A MUTT aeroelastic airplane with both feedback control and mixing.

Conclusions:

  • The presented method provides an effective means for estimating MIMO bare-airframe frequency responses from flight data.
  • The technique can be applied in both post-flight batch analysis and real-time flight analysis.
  • Accurate estimation is achievable despite the presence of feedback control and control effector mixing.