Non-invasive control of synchronization region of a forced self-oscillator via a second order filter

A simple controller based on a second order active filter is proposed to extend the synchronization region of a forced weakly non-linear self-sustained oscillator. The controller stabilizes unstable periodic orbits that exist in the uncontrolled system outside the synchronization region. The control algorithm is non-invasive in the sense that it uses only small control perturbations. We present analytical and numerical results as well as an experimental demonstration.