Dynamic Behavior of HTS Levitation Pendulum Driven with a Fluctuating External Magnetic Field

In this paper, a levitation pendulum composed of high temperature superconducting (HTS) bulk and rotating permanent magnet guideway (PMG) is constructed to simulate some running states of HTS maglev train when it is running relative to the magnetic track. The dynamic characteristics of the pendulum under different levitation height, running speed and magnetic flux relaxation are studied. The pendulum is found in a quasi-periodic vibration state as it runs at a low speed but gradually evolves from quasi-periodic state to chaotic state through period-doubling bifurcation with increasing the speed. In addition to the running speed, the levitation height also has a significant impact on the dynamic characteristics of the pendulum: the larger the levitation height, the lower the running speed required for the pendulum to enter the chaotic state. What is particularly striking is that according to the spectrum analysis, the factors that cause the magnetic levitation pendulum to enter the chaotic state, besides the external field drive, the magnetic flux movement inside the superconductor is another important factor, and there is no correlation between the chaotic spectrum caused by the magnetic flux movement and the external field drive frequency.