CHAOS CONTROL USING A GENERALIZED EXTENDED TIME-DELAYED FEEDBACK METHOD: APPLICATION TO A NONLINEAR PENDULUM
Chaos Control; Nonlinear Dynamics; Pendulum; ETDF
Chaos exhibits a wealth of periodic patterns exploited by chaos control through small perturbations, stabilizing one of its countless trajectories. This work aims to explore a generalization of the ETDF method to stabilize UPOs. This generalization involves considering the complete matrix gain K, instead of the conventional scalar gain approach. A nonlinear pendulum was chosen as the system for applying the method. Three UPOs, with periodicities 1, 2 and 3, were selected to evaluate the control strategy. The controller gains were evaluated by determining stability through the largest Lyapunov exponent. The matrix term K12 consistently increased system instability across all evaluated cases, leading to its exclusion for control purposes. Cases involving two parameters with K11 and K22, as well as K21 and K22, and the three-parameter case comprising K11, K21 and K22 were considered. All combinations considered revealed a broader region of stability for the system when compared to the scalar-base approach, but generally with similar magnitudes for the Lyapunov exponent. The actuation of the controller and the corresponding energy consumption were compared for each stabilization scenario. The possibility of migration between the selected UPOs was also evaluated. The results showed good flexibility when using the matrix K, prioritizing the system's needs, whether with smaller actuations or energy consumption. In the control implementations without K21, it was possible to transition between all orbits according to the control rule, whereas in those that considered this parameter, the stabilization of the period-1 UPO was not achieved.