Abstract. In the present paper the influence of the excitation frequency (v) and the forcing amplitude (e) on the chaotic behaviour of the system governed by equation When e = 0, a > 0, I > 0 we have the classical Van der Pol equation which represents a self-excited oscillator with the amplitude a. = 2/ .j;;; and frequency w. Our discussion was focused upon variation of the excitation frequency v and the forcing amplitude e. The bifurcation diagrams for acquiring the overview of equation (0.1) and the Liapunov exponent method will be used [3,4,5,6,9]. For a concrete case, the parameter regions in which either periodic or chaotic motions exist were shown. In two preceding cases, the first case, when v is control parameter, it changes suddenly from periodic motion to chaotic motion , corresponding to llopf bifurcation. In the second case, it is the double-period process a nd leads to chaotic motion. Chaotic attractors illustrate the complexity of the motion of the system under consideration.
SUMMARY OF THE CASE OF SMALL PARAMETERSFirst, we recall briefly some known results of deterministic motions in (0.1) for the case of smallness of the coefficients. It is supposed that v is close to the natural frequency w, namely: v2 = w2 + c:6. , (1.1) here 6. is a detuning parameter and c is a small positive one. Applying to (0.1) the asymptotic method [2] and using the amplitude and phase variables (a,()) given by we have