Experimental Study of Suppressing a Parametric Resonance in a HTSC Levitation System by a Horizontal Pendulum

This research deals with the experimental investigation of reduction in the amplitude of nonlinear oscillation in a high-Tc superconducting magnetic levitation system by using a vibration absorber. High-Tc superconducting levitation systems have very low damping and stable levitation without control. In such low-damped systems, complicated phenomena of dynamics can be easily generated by nonlinearity of the magnetic force. Our previous research showed that if the frequency of vertical excitation is in the neighborhood of double the natural frequency in the horizontal direction, horizontal oscillation can occur parametrically through nonlinear coupling between vertical motion and horizontal motion. This research investigates an effect of a vibration absorber on the parametrically excited horizontal oscillation of the levitated body. We performed experiments on a symmetric rigid bar, levitated by the electromagnetic force between superconductors fixed on the base, and magnets fixed at both ends of the bar. A simple damped horizontal pendulum is attached to the main system as a vibration absorber, so that it is linearly coupled with the main system. Through these experiments, it has been confirmed that this kind of a vibration absorber is useful for reducing the amplitude of a parametric resonance in a high-Tc superconducting levitation system.