  This work is devoted to the Keldysh model of flutter suppression and rigorous
approaches to its analysis. To solve the stabilization problem in the Keldysh
model we use an analog of direct Lyapunov method for differential inclusions.
The results obtained here are compared with the results of Keldysh obtained by
the method of harmonic balance (describing function method), which is an
approximate method for analyzing the existence of periodic solutions. The
limitations of the use of describing function method for the study of systems
with dry friction and stationary segment are demonstrated.
