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On the periodic solutions of a perturbed double pendulum

2011, São Paulo J. Math. Sci.

Abstract

We provide sufficient conditions for the existence of periodic solutions of the planar perturbed double pendulum with small oscillations having equations of motion θ 1 = −2aθ 1 + aθ 2 + εF 1 (t, θ 1 ,θ 1 , θ 2 ,θ 2), θ 2 = 2aθ 1 − 2aθ 2 + εF 2 (t, θ 1 ,θ 1 , θ 2 ,θ 2), where a and ε are real parameters. The two masses of the unperturbed double pendulum are equal, and its two stems have the same length l. In fact a = g/l where g is the acceleration of the gravity. Here the parameter ε is small and the smooth functions F 1 and F 2 define the perturbation which are periodic functions in t and in resonance p:q with some of the periodic solutions of the unperturbed double pendulum, being p and q positive integers relatively prime.