Discussion on: "Analysis of control relevant coupled nonlinear oscillatory systems"Pušenjak, Rudi (Avtor) Oblak, Maks (Avtor) van der Pol oscillatorsexternal excitationmultiple time scalesThe paper by I. D. Landau et al. presents an analysis of two structures of coupled van der Pol oscillators done by using the Krylov-Bogoliubov (K-B) averaging method. They devise the K-B method to effectively compute self-excited and externally driven oscillations, respectively on systems presumably subjected to control, where amplitudes and phases are slowly varying functions of time. After they present feedback structures of single and coupled generalized van der Pol equations, respectively, they perform the K-B analysis of these equations, which results in explanation of various regimes of self-excited and externally driven oscillations including the analysis of the combustion instability model. Although the proposed K-B methodmay be considered as a step forward in modeling self-oscillating systems, this discussion wants to show, that problems solved by the K-B method can be treated also in an alternative way. Based on the paper [1], it is obvious that coupled van der Pol oscillators, driven by an external excitation with slowly varying frequency or amplitude, can be analyzed by using Extended Lindstedt- Poincare (EL-P) method with multiple time scales.20082012-05-31 12:22:13Neznano26274sl