Multistability and organization of periodicity in a Van der Pol-Duffing oscillator

We investigate the dynamics of a Van der Pol-Duffing forced oscillator, which is modelled by a five-parameter second order nonautonomous nonlinear ordinary differential equation. Firstly we fix three of these parameters, and investigate the dynamics of this system by varying the other two, namely the amplitude and the angular frequency of the external forcing. We also investigate the existence of different attractors, periodic, quasiperiodic, and chaotic. Finally, we investigate the occurrence of multistability in the considered Van der Pol-Duffing forced oscillator, for some fixed sets of parameters.