  We investigate in this paper the superharmonic and subharmonic resonances of
forced modified Rayleigh-Duffing oscillator. We analyse this equation by the
method of multiple scales and we obtain superharmonic, subharmonic resonances
order-two and order-three and primary resonance. We obtain also regions where
steady-state subharmonic responses exist. We also use the amplitude-frequency
curve for demonstrate the effect of various parameters on the response of the
system. Finally, we focus our attention on chaotic motion of this oscillator by
simulation. We obtain that this oscillator is chaotic for certains values for
natural and excitation frequency but chaotic motion is not the same in
subharmonic and superharmonic cases.
