Higher speed is the eternal goal of rail transit, and maglev is an important development direction of rail transit in the future. High temperature superconducting (HTS) maglev has the potential for high-speed application because of its non-friction, self-stabilization and no inherent magnetic resistance in the forward direction. Different from the low-speed operation, the HTS maglev system may face new problems in high-speed application. Therefore, it is necessary to study the dynamic response of HTS maglev at high speed. At present, the influence of various factors on HTS maglev system under high-speed operation cannot be accurately considered only by simulations of dynamics software. It is an important research method to build a test platform to measure the dynamic response of HTS maglev system at high speed. By using this method, the test results which are close to the actual application of HTS maglev can be obtained more accurately. In this paper, the HTS maglev high-speed test-platform in Southwest Jiaotong University is introduced and the preliminary results of static and high-speed tests are presented. These results will provide guidance for subsequent tests and provide experience accumulation for the high-speed application of HTS maglev.

High-temperature superconducting (HTS) maglev, owning to the capability of passive stabilization, is potentially promising for high-speed transportation. The guidance force of bulk HTS materials above a permanent magnetic guideway has a nonlinear response due to the hysteresis effect. As a kind of rail transit, when the vehicle runs along the track, the curve and other disturbances will cause vibrations to the vehicle system. These physical factors will pose dynamic loads on the components, reducing structural reliability as well as affecting the ride comfort. The lateral motion, as an important part of the vehicle system dynamics, needs to be studied in the pursuit of HTS maglev realization. In this paper, we first measured the guidance forces of HTS bulks under different motion conditions, and analyzed the relationship between the lateral displacement, the movement velocity and the guidance force. Then, a mathematical model was built based on these experimental data. The key feature of this mathematical model is that it can describe the hysteresis characteristic of the guidance force. Based on this model, we investigated the lateral motion stability of the HTS levitation system, and found three singular points, one stable focus point, and two unstable saddle points. Lastly, a phase portrait was proposed to indicate the safe working region of the HTS maglev vehicle where the vehicle can automatically return to its equilibrium position. These experimental and simulation results are important to clarify the lateral motion stability under external disturbance or shock, and provide a reference basis for the design of levitation systems.

Free vibration of the high temperature superconducting (HTS) Maglev vehicle model has been investigated after an impulse force over the permanent magnet guideway. The impulse force was used to simulate the external disturbances on the HTS Maglev vehicle so as to study its vibration characteristics. In the experiments, the free vibration curves of time dependence of acceleration and frequency dependence of displacement were measured. It was found that the free vibration curves were some damped free vibration curves which seemed to decrease exponentially. Applying the impulse response curves to the dynamic equation of the HTS Maglev vehicle model, the stiffness and the damping coefficient were evaluated. The relationships between field cooling height (FCH) and the stiffness and damping coefficient were investigated. A 30 mm FCH has been proposed for the good dynamic stiffness and damping coefficient so that the unnecessary vibration of the HTS Maglev vehicle model can be eliminated automatically. The dynamic results are helpful to the further design of the HTS Maglev transport system for high-speed application.

In order to design high temperature superconducting (HTS) maglev launch system, three NdFeB permanent magnetic guideways (PMGs) are investigated and compared for the better levitation forces and guidance forces. The laboratory-scale HTS maglev launch system was designed and developed successfully in the Applied Superconductivity Laboratory (ASCLab), Southwest Jiaotong University, China. The cooling process of the melt-textured YBaCuO bulk superconductors is made in a big low temperature tube, which is connected with PMG. The method merit is to eliminate fluctuation of liquid nitrogen in the operation test. The longitudinal slopes of the PM guideway are designed with 0-30 degree from the horizontal, and transverse slopes is designed with 15 degree from the horizontal. The HTS maglev launch system is carried out an experiment in the laboratory. Test results indicate design validity of the HTS maglev launch system.

High-temperature superconducting (HTS) maglev has great potential in the field of high-speed transportation due to its capability for passive stabilization. The levitation force between the bulk HTSs and the permanent magnet guideway is a significant parameter relating to operational safety and comfort. This force has an obvious hysteresis nonlinear characteristic, which can be represented by nonlinear stiffness and damping. The stiffness and the damping are functions of vertical displacement and velocity, respectively. The vibration velocity of a HTS maglev vehicle can at times exceed 100 mm s⁻¹, but the existing levitation force test methods are almost quasi-static. These methods are unable to accurately measure the damping characteristic of the maglev system. In this paper, a viscoelasticity model is introduced to describe the dynamic force. The parameters in the model are identified using the least square method based on the vibration response of the HTS maglev system. Meanwhile, the effectiveness of the model and identification method are tested by numerical simulations. The hysteresis loops derived from the motion theory coincide with the practical ones. Finally, the method is applied to identify the parameters of hysteresis nonlinear levitation force in a previous experiment with dampers. Based on the established hysteretic model, the dynamic characteristics of the HTS maglev system can be well presented.