The double pendulum, a simple system of classical mechanics, is widely studied as an example of, and testbed for, chaotic dynamics. In [1], Maiti et al. study a generalization of the simple double pendulum with equal point-masses at equal lengths, to a rotating double pendulum, fixed to a coordinate system uniformly rotating about the vertical. In this paper, we study a considerable generalization of the double pendulum, constructed from physical pendula, and ask what equilibrium configurations exist for the system across a comparatively large parameters space, as well as what bifurcations occur in those equilibria.Elimination algorithms are employed to reduce systems of polynomial equations, which allows for equilibria to be visualized, and also to demonstrate which models within the parameter space exhibit bifurcation. We find the DixonEDF algorithm for the Dixon resultant [2], written in the computer algebra system (CAS) Fermat [3], to be capable to complete the computation for the challenging system of equations that represents bifurcation, while attempts with other algorithms were terminated after several hours.
I. INTRODUCTIONThis work is concerning a system of classical physics, namely a rotating double pendulum (RDP).Here, 'rotating' is used to indicate a double pendulum that is made to rotate about a vertical axis with a constant angular velocity ω a . A double pendulum has two joints or pivots, and we take the vertical axis of this rotation to pass through the inner, stationary pivot. Additionally, our consideration is of a physical double pendulum, constructed from two 3-dimensional rigid bodies.Thus the physics depends on many dimensional parameters: masses, lengths, ω a , the strength of gravity, and principal moments of inertia -13 in total. However, only 6 dimensionless parameters are required to describe the dynamics of the system.