Multimode chaos in two coupled chaotic oscillators with hard nonlinearities

In this study, multimode chaos observed from two coupled chaotic oscillators with hard nonlinearities is investigated. At first, a simple chaotic oscillator with hard nonlinearities is realized. It is confirmed that in this chaotic oscillator the origin is always asymptotically stable and that the solution, which is excited by giving relatively large initial conditions, undergoes period-doubling bifurcations and bifurcates to chaos. Next, four different modes of oscillations are observed from two coupled chaotic oscillators with hard nonlinearities by both computer calculations and circuit experiments. One of the modes of oscillation is a nonresonant double-mode oscillation and this oscillation is stably generated even in the case that oscillation is chaotic. Namely, for this oscillation mode, chaotic oscillation and periodic oscillation can be simultaneously excited. We call this phenomena double-mode chaos. Finally, the beat frequency of the double-mode chaos is confirmed to be changed by tuning the value of the coupling capacitor