“…On the other side, dynamical pendulum models with 2 or 3 DOF have been studied in many research works such as (Awrejcewicz et al, 2016;Starosta et al, 2011;Starosta et al, 2012;Amer et al, 2016;Nayfeh, 2004;Awrejcewicz et al, 2013;Amer et al, 2018;Amer et al, 2019;El-Sabaa et al, 2020). The plane motion of nonlinear spring pendulum with 2DOF is investigated in (Awrejcewicz et al, 2016) for a fixed supported point under the influence of two external forces in the direction of a spring arm and its perpendicular direction.…”