Question: Poincare Section diagram for pendulum

I am trying to draw the Poincare section diagram related pendulum problem, article is shared below. I can not understand and code gives error, can you help me to draw Poincare section Fig. 4 of attached article?7._Energy_distribution_in_intrinsically_coupled_system [moderator: URL changed to respect IP, as per Mapleprimes Terms of Use]

pendulum.mw

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