Keywords: 
• 分数阶 /
• Chua系统 /
• 负参数空间 /
• 混沌电路

Abstract: Because of simple schematic structure and complex dynamical behaviors, the Chua's system is considered as a paradigm for chaos research. Despite a great many of studies relating to the Chua's system, most of them focus on its positive parameter space. This is explained by the fact that the implementation of the Chua's circuit with negative parameters needs resistors, inductances and/or capacitors with negative values, and thus leads to physical impossibility. In order to extend the parameter space of the Chua's system to its negative side, where all system parameters are negative, an equivalent realization of the Chua's circuit is developed with off-the-shelf electronic components by an electronic analogy method. Recently, the research of fractional-order chaotic systems has received considerable interest. However, the theoretical and experimental studies of the fractional-order Chua's system with negative parameters are still lacking. In this study, we set up a model of the fractional-order Chua's system in negative parameter space. The stability of all equilibrium points is investigated with the fractional-order stability theory. Based on the Grünwald-Letnikov derivative, the dynamical behaviors dependent on the control parameter and the fractional orders are investigated by standard nonlinear analysis techniques including phase portraits, the largest Lyapunov exponents, and bifurcation diagrams. In order to further verify the dynamic behaviors of the fractional-order Chua's system with negative parameters, an experimental implementation of the Chua's circuit with negative parameters based on an electronic analogy is performed with off-the-shelf electronic components such as operational amplifiers, resistors and capacitors. The experimental tests are conducted on the resulting circuit. A period-doubling bifurcation route to chaos is successfully observed and some typical phase diagrams are captured by an oscilloscope, which are well consistent with theoretical analyses and numerical simulations. The numerical simulations and the experimental results show that the fractional-order Chua's system in negative parameter space can still exhibit rich dynamical behaviors. But it is worth noting that the classical double-scroll chaotic attractor emerging in a conventional Chua's system cannot be found in this system. This work focuses mainly on the dynamical behaviors of the fractional-order Chua's system with negative parameters, which was not reported previously. Thus the research results of this study will further enrich the dynamical behaviors of the Chua's system, and play a positive role in promoting the chaos-based applications of the Chua's system. Meanwhile, the results obtained in this work lead to the conjecture that there remain some unknown and striking behaviors in the Chua's system with negative parameters, which need further revealing.