Identification based generation of self-excited oscillations for underactuated mechanical systems via two-relay algorithm

A tool for generating a self-excited oscillations for underactuated mechanical systems by means of a variable structure controller is proposed. The design procedure allows to find the explicit expressions of the controller gain parameters in terms of the desired frequency and amplitude through describing function (DF) method. Necessary conditions for orbital asymptotic stability of linear systems are derived via a modification of the Loeb criteria. The identification and compensation method yields an exact linearization of the original nonlinear system avoiding imperfections on oscillations characteristics. Performance issue of a self-excited system, applied to a Furuta pendulum, is illustrated by simulations.