Mechanisms of excitation and amplitude limitation of self-oscillations and auto-waves. Classification of self-oscillatory systems

Abstract

The best known mechanism of self-oscillation excitation is so called negative friction (or negative resistance). For definiteness’ sake, we shall speak about negative friction only. Such a character of friction can be achieved by means of feedback. A classical example of a system in which a similar mechanism manifests itself is a well known vacuum tube generator studied by van der Pol [Van der Pol, 1920]. The feedback, resulting in the appearance of a negative friction, is called positive feedback. Negative friction can be both linear and non-linear. The linear negative friction results in self-excitation of oscillations, i.e., in their appearance for as small initial perturbations as wished.