Skip to Main content Skip to Navigation
Journal articles

Input-output measures for model reduction and closed-loop control: Application to global modes

Abstract : Feedback control applications for flows with a large number of degrees of freedom require the reduction of the full flow model to a system with significantly fewer degrees of freedom. This model-reduction process is accomplished by Galerkin projections using a reduction basis composed of modal structures that ideally preserve the input-output behaviour between actuators and sensors and ultimately result in a stabilized compensated system. In this study, global modes are critically assessed as to their suitability as a reduction basis, and the globally unstable, two-dimensional flow over an open cavity is used as a test case. Four criteria are introduced to select from the global spectrum the modes that are included in the reduction basis. Based on these criteria, four reduced-order models are tested by computing open-loop (transfer function) and closed-loop (stability) characteristics. Even though weak global instabilities can be suppressed, the concept of reduced-order compensators based on global modes does not demonstrate sufficient robustness to be recommended as a suitable choice for model reduction in feedback control applications. The investigation also reveals a compelling link between frequency-restricted input-output measures of open-loop behaviour and closed-loop performance, which suggests the departure from mathematically motivated H-measures for model reduction toward more physically based norms; a particular frequency-restricted input-output measure is proposed in this study which more accurately predicts the closed-loop behaviour of the reduced-order model and yields a stable compensated system with a markedly reduced number of degrees of freedom. © 2011 Cambridge University Press.
Complete list of metadata

Cited literature [20 references]  Display  Hide  Download
Contributor : Denis Roura Connect in order to contact the contributor
Submitted on : Thursday, June 5, 2014 - 8:52:15 PM
Last modification on : Tuesday, March 16, 2021 - 3:44:45 PM


Publisher files allowed on an open archive




Alexandre Barbagallo, Denis Sipp, Peter J. Schmid. Input-output measures for model reduction and closed-loop control: Application to global modes. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2011, 685, pp.23-53. ⟨10.1017/jfm.2011.271⟩. ⟨hal-00997981⟩



Record views


Files downloads