State-space model identification and feedback control of unsteady aerodynamic forces

Steven L. Brunton, Scott T.M. Dawson, Clarence W. Rowley

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Unsteady aerodynamic models are necessary to accurately simulate forces and develop feedback controllers for wings in agile motion; however, these models are often high dimensional or incompatible with modern control techniques. Recently, reduced-order unsteady aerodynamic models have been developed for a pitching and plunging airfoil by linearizing the discretized Navier-Stokes equation with lift-force output. In this work, we extend these reduced-order models to include multiple inputs (pitch, plunge, and surge) and explicit parameterization by the pitch-axis location, inspired by Theodorsen[U+05F3]s model. Next, we investigate the naïve application of system identification techniques to input-output data and the resulting pitfalls, such as unstable or inaccurate models. Finally, robust feedback controllers are constructed based on these low-dimensional state-space models for simulations of a rigid flat plate at Reynolds number 100. Various controllers are implemented for models linearized at base angles of attack α0=0°, α0=10°, and α0=20°. The resulting control laws are able to track an aggressive reference lift trajectory while attenuating sensor noise and compensating for strong nonlinearities.

Original languageEnglish (US)
Pages (from-to)253-270
Number of pages18
JournalJournal of Fluids and Structures
StatePublished - Oct 1 2014

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering


  • Eigensystem realization algorithm (ERA)
  • Observer/Kalman filter identification (OKID)
  • Reduced-order model
  • State-space realization
  • Theodorsen[U+05F3]s model
  • Unsteady aerodynamics


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