Papers

A physics-based approach to flow control using system identification

Aurelien Hervé^a1, Denis Sipp^a1, Peter J. Schmid^a2 c1 and Manuel Samuelides^a3

^a1 ONERA - The French Aerospace Lab, 8 rue des Vertugardins, 92190 Meudon, France

^a2 Laboratoire d’Hydrodynamique (LadHyX), CNRS-Ecole Polytechnique, 91128 Palaiseau, France

^a3 ONERA - The French Aerospace Lab, 2 av. Edouard Belin, 31055 Toulouse, France

Abstract

Control of amplifier flows poses a great challenge, since the influence of environmental noise sources and measurement contamination is a crucial component in the design of models and the subsequent performance of the controller. A model-based approach that makes a priori assumptions on the noise characteristics often yields unsatisfactory results when the true noise environment is different from the assumed one. An alternative approach is proposed that consists of a data-based system-identification technique for modelling the flow; it avoids the model-based shortcomings by directly incorporating noise influences into an auto-regressive (ARMAX) design. This technique is applied to flow over a backward-facing step, a typical example of a noise-amplifier flow. Physical insight into the specifics of the flow is used to interpret and tailor the various terms of the auto-regressive model. The designed compensator shows an impressive performance as well as a remarkable robustness to increased noise levels and to off-design operating conditions. Owing to its reliance on only time-sequences of observable data, the proposed technique should be attractive in the design of control strategies directly from experimental data and should result in effective compensators that maintain performance in a realistic disturbance environment.

(Received April 01 2011)

(Reviewed December 09 2011)

(Accepted February 23 2012)

(Online publication June 07 2012)

Key Words:

• flow control

Correspondence:

^c1 Email address for correspondence: peter@ladhyx.polytechnique.fr