This model is described in the xrk handout. It is essentially a forced oscillator with nonlinear damping. The model equations are as follows.
where , a, b, , and A are positive constants and and are constants that can take any value.
The dynamics of this model can be very rich. To help focus your investigation, I suggest fixing the parameter values , , a=3, b=0, and A = 1. Varying the two remaining parameters close to the values and should give you lots of interesting behavior.