Impact of viscoelastic coupling on the synchronization of symmetric and asymmetric self-sustained oscillators

We investigate a system of two viscoelastically coupled, modified Van der Pol oscillators to compare their synchronization properties due to elastic and viscoelastic coupling. We show that viscoelastic coupling leads to in-phase synchronization while elastic coupling favours anti-phase synchronization. To study the impact of symmetry and nonlinearity, the restoring forces in the Van der Pol oscillators are extended to include nonlinear and asymmetric components. If the asymmetry, or rather the nonlinearity, of the restoring forces exceeds a certain threshold, only in-phase synchronized motion is found to be stable. Another important finding is that chaotic solutions can only be found if the restoring forces are asymmetric and the coupling incorporates viscosity. (paper)