Bistable phase synchronization and chaos in a system of coupled van der Pol-Duffing oscillators

Analysis of numerical solutions for a system of two van der Pol-Duffing osc illators with nonlinear coupling showed that there exist chaotic switchings (occurring at irregular time intervals) between two oscillatory regimes di ffering by nearly time-constant phase shifts between the coupled subsystems . The analysis includes the investigation of bifurcations of the periodic m otions corresponding to synchronization of two subsystems, finding stabilit y regions of synchronization regimes and scenarios of the transitions to ch aos.