Comparison of a Robust and a Flatness Based Control for a Separated Shear Flow

Closed-loop flow control is gaining more and more interest in the last few years. Whereas most of the published results are based on simulation studies, this work explores the synthesis of black-box model based closed-loop controllers for separated, wall-bounded shear flows in experiments. In this paper we compare a linear robust controller with a flatness based approach. To consider both the uncertainty of the model and the inherent time delay, the well-known flatness based controller synthesis scheme had to be extended by a robust design approach and a prediction step. The actuated backward-facing step flow is chosen as a benchmark configuration, in which the length of the separated flow region is to be controlled. This configuration can be seen as a simple representation of the situation in a burner or behind a flame holder.