Chaotic motion of a nonhomogeneous torsional pendulum

In this paper, the nonlinear oscillations of a nonhomogeneous torsional pendulum are investigated. Chaotic motions are shown to exist in both damped systems with two-well potential and undamped systems with one-well or two-well potential. Autocorrelations of the Poincare mappings of the motion are presented and shown to be another useful tool to judge whether the system is chaotic. The total energy of the torsional pendulum is explored as well and it is conjectured that the irregularity of the total energy is probably one of the important factors which cause chaos. Lyapunov exponents are used as an indication of chaos in this paper. For systems with two-well potential, the phase-plane trajectories are found to stay in one well if the motion is regular, but jump from one well to another if the motion is chaotic. Making the initial conditions near the local minimum of the two-well potential is proved to be successful in preventing chaos from happening in the undamped systems.