Measurement and Characterization Method of Permanent Magnetic Guideway Irregularity in HTS Maglev System

High-temperature superconducting (HTS) maglev has been developed rapidly in the last few decades. Due to its numerous advantages, such as self-stabilization, low energy consumption, no mechanical friction, and being environmentally friendly, researchers from all around the world have done a large amount of research to promote the engineering application of HTS maglev. The researchers have found that during the operation of HTS maglev, the primary source of external disturbance is the permanent magnetic guideway (PMG) irregularity. It is composed of geometric irregularity and magnetic field inhomogeneity. When evaluating the irregularity of the PMG used in the HTS maglev system, it is different from the traditional railway track. The difference is reflected in that not only the geometric irregularity but also the inhomogeneous distribution of magnetic field at the working height of superconductors should be considered. So far, the research on PMG irregularity is not complete. There is no track spectrum for PMG irregularity by now. The track structure and vehicle-track coupling mode of HTS maglev system are fundamentally different from that of other rail transit systems. When investigating the vehicle-track coupling dynamics of HTS maglev system, it is not accurate to substitute the track irregularity spectrum of other rail transit systems for PMG. Therefore, it is necessary to measure and characterize the irregularity of PMG. First, to measure the geometric irregularity and magnetic flux density at the position of 10 mm above PMG at the same time, an irregularity detection equipment is designed. Then, the PMG of the ring test line in Southwest Jiaotong University is measured by the equipment. According to the measured geometric irregularity, using the form of the power spectral density function of track irregularity proposed by the Chinese Academy of Railway Sciences, the PMG geometric irregularity spectrum is obtained. Next, the measured magnetic field inhomogeneity caused by the structure of PMG and the edge effect of magnets is analyzed. Subsequently, a method is proposed to convert the magnetic field inhomogeneity into equivalent geometric irregularity. Superimposing it with the actual geometric irregularity, the sample of PMG irregularity considering both geometric irregularity and magnetic field inhomogeneity can be generated. This article provides a measurement scheme and characterization method of PMG irregularity. It can also make a reference for the vehicle-track coupling dynamics analysis of HTS maglev.