Nonlinear vibration behaviors of HTS levitation system under different load-levitation ratios

Abstract

High-temperature superconducting (HTS) pinning maglev trains, with their self-stabilizing levitation and low magnetic resistance, are promising candidates for future transportation. This paper investigates the nonlinear vibration behaviors of the single levitation system of the world’s first HTS high-speed maglev train under different load-levitation ratios (LLRs). First, vertical free vibration experiments were conducted under various load conditions, obtaining response curves for stable levitation height, main vibration frequency, stiffness, and damping with various loads. Based on these results, a set of equivalent stiffness and damping parameters for different LLRs was compiled. Second, focusing on three specific LLR conditions, levitation force curves were fitted using experimental data. The system’s stability and nonlinear vibration characteristics were analyzed through theoretical, numerical, and experimental methods. The experimental results show that the stable levitation height decreases nonlinearly as the load increases and stabilizes at 10 mm under rated load conditions. The system’s natural frequency remains nearly constant, showing minimal sensitivity to load changes. Both equivalent stiffness and damping increase with load. The analysis reveals that the HTS levitation system exhibits inherent stability and can recover balance after transient disturbances. It also shows nonlinear dynamics behavior such as period-doubling bifurcation and harmonic resonance, influenced significantly by excitation frequency, amplitude, and LLRs. These phenomena are more pronounced with larger LLR. Under certain conditions, the system exhibits jump phenomena. Resonance primarily occurs in the primary and double-frequency bands. This study enhances the understanding of HTS system dynamics and provides a reference for the dynamic research of HTS pinning maglev trains.