Theoretical model and experiment of the hybrid Maglev vehicle employing high temperature superconducting magnetic levitation and permanent magnetic levitation

Abstract

The Maglev vehicle, widely considered as a promising transportation type, has distinct characteristics, such as high speed, environmental protection, non-contact operation and distributed load and so on. According to the principle of magnetic levitation technology, it can be divided into four types: Permanent magnet levitation (PML), electromagnetic levitation (EML), electrodynamic levitation (EDL) and superconducting magnetic levitation (SML). Among four Maglev technologies, both the SML with high temperature superconducting (HTS) bulks and the PML with conventional permanent magnets belong to the passive levitation mechanisms, and both of them need permanent magnet track. Due to the strong magnetic properties of permanent magnet materials, the load capacity of the PML can reach 3-6 t/m, but requires additional guidance controls, while the SML with the unique HTS flux-pinning effect can realize self-stable levitation with little active control. Therefore, considering the different levitation characteristics of the SML and the PML above the permanent magnet track, their potential hybrid application can achieve a larger load capacity and a bigger levitation gap at the same time. In the paper, a new SML-PML hybrid Maglev method and the corresponding theoretical models are proposed. Firstly, simulation models of the PML module and the SML module were built by finite element software. The simulation results show the different levitation performances of the two Maglev components. As to the SML module, it vertically behaves as the levitation force within the levitation height of 10-15 mm, and always achieves passive stable along the lateral direction. As to the PML module, the levitation force is relatively bigger at the calculated height of 20-60 mm, but the lateral force increases as the levitation height decrease and increases with the lateral displacement. It implies that the SML guidance capability should cover the PML lateral force at first. Hence, according to the Earnshaw theorem, the load capacity in typical working cases of the hybrid Maglev system was predicted from the simulation data. Considering the further lateral stability and the comprehensive levitation force utilization, the optimal passive stable working range and the lateral reversible range were discussed, which provide the theoretical basis for the design of the hybrid Maglev vehicle prototype. Then, based on the real magnet tracks of the HTS Maglev ring test line, the “Super-Maglev”, in our group, a new manned hybrid Maglev vehicle prototype employing the PML and the SML modules was manufactured for carrying one passenger. In the designed two-layer Maglev frame, the linear bearings composed of the linear guide rails and the sliders are employed for vertical decoupling to guarantee the position difference of the SML and PML modules. At the same time, the lateral coupling keeps rigid since the lateral unbalance is covered by the SML module. This easy and feasible mechanical coupling way enhances the matching complementarity of the lateral recoverability of the two Maglev components. Compared with the “Super-Maglev” performance under the same working condition, the load capacity of the hybrid Maglev vehicle was increased by 17% and the cost input was lower compared with the price of one single on-board HTS bulk. Finally, static loading experiments and dynamic characteristics tests verified that the hybrid Maglev vehicle has the advantages of strong load capacity, simple structure and low cost. This work provides a new technical scheme for future Maglev transportation applications.