To reduce the vehicle/guideway-coupled vibration and improve the levitation stability of medium–low-speed maglev vehicle, a new type of levitation frame with air springs installed in the middle of the longitudinal beams is developed. This levitation frame with mid-set air spring (LFMAS) is studied comparatively with the levitation frame with end-set air spring (LFEAS) in electromagnetic levitation mode. The coupling degrees of the two kinds of frames are analysed by vertical motion equations; the energy consumptions for levitation control system to overcome the spring resistance in the whole adjustment process are calculated by the energy method; and the vibration accelerations are compared by dynamics analysis and bench test. The equations indicate that the LFMAS has a better decoupling effect and lower energy consumption than that of the LFEAS in any adjustment process. Simulation and test results show that the LFMAS can effectively reduce the vibration acceleration at a low-speed and achieve a better levitation stability in working conditions, validating that the LFMAS has a better levitation performance and adaptability to the guideway, which is attributed to the mechanical decoupling of the levitation module. It is expected that this new levitation frame will be very helpful in enhancing levitation stability and the ride index of medium–low-speed maglev vehicle.

In recent years, low and medium speed maglev (LMSM) transportation system has been greatly promoted in China to meet different social demands. Accordingly, a LMSM train using levitation frames with mid-set air springs has been developed, and it is necessary to investigate the dynamic characteristics of its train-track-bridge coupled system. First, environmental vibration tests were conducted on the bridge to study its self-vibration characteristics. Then, field tests were carried out on this coupled system within the 60 km/h speed range. Subsequently, a three-dimensional rigid-flexible coupled dynamics model of the system was developed to evaluate its dynamic behavior at higher speeds. Results show that the first-order vertical and lateral bending frequencies of the bridge are 7.32 Hz and 6.00 Hz, respectively; train speed has little effect on the vertical dynamic displacement of the track-bridge system, yet has a significant impact on the acceleration responses of the coupled system; key dynamic indicators of the bridge meet the relevant requirements; the vertical ride quality of car body is not so good as that in the lateral direction, but on the whole the train has “Good” ride quality. These results can provide a useful reference for the optimal design of LMSM transportation systems.

The levitation bogie of the TR-series maglev vehicle is redesigned by adding an intermediate buffer layer between the levitationbogie and the levitation module to improve the curve negotiation capacity of the high-speed maglev vehicle and reduce the vertical coupleddynamic effect of the vehicle and the track beam. As the existing TR08 maglev vehicle dynamic model has been verified by experiments, anew type of dynamic model of maglev vehicle is constructed by transplanting the functional module of TR08 model. The vehicle-elastic trackbeam coupled dynamic model and the vehicle-curved track dynamic model are established. Simulation analyses of the dynamic response ofvehicles and track beams show that: the curve negotiation capacity of the new-type maglev vehicle is better than that of TR08 type maglevvehicle; the resonance effect does not occur between the vehicle and the track beam; the vertical dynamic displacement of the track beammid-span decreases by 23% compared with the TR08 type; the redesigned levitation bogie structure and the track beam have less dynamicinteraction, indicating that the working environment of the electromagnet in the new maglev vehicle has been improved, which can effectivelyreduce the burden of electrical decoupling of the control system.

Train-track-bridge dynamic tests were conducted on the Shanghai Lingang Medium and Low Speed Maglev Test Line. A newly developed levitation bogie with mid-set air spring was used on the test train. The test results show that: the vertical and lateral first-order natural frequencies are 7.50 Hz and 6.00 Hz, respectively; vehicle speed has no significant effect on the vertical dynamic displacement of the bridge; within specific speed ranges, the acceleration of the test train-track-bridge system shows monotonic variation characteristics as vehicle speed changes; the lateral accelerations of the bridge, sleeper, and F-shaped rail are distributed in a wider dominant frequency band compared with the corresponding vertical accelerations; the dominant frequency bands of vibration acceleration of levitation bogie and car body are generally concentrated below 15 Hz; the vertical and lateral Sperling indexes of the test train are less than 2.5, indicating that the test train is superior in ride quality.

In order to simulate the runtime behaviour of coupler and buffer systems accurately, the dynamic model was improved by adopting the polygonal contact model. And the reliability of the friction phenomenon in flat-pin coupler’s tail and the connecting constraint between coupler heads were verified. Then the detailed model which fully considered the dynamic characteristics of middle locomotive and its adjacent wagons was incorporated into the simplified longitudinal dynamic model of combined heavy-haul train. The dynamic response of coupler and its influence on the running safety of locomotive under flat straight line emergency braking condition and long steep grade cycle braking condition were simulated respectively. According to the simulation results, the following suggestions were proposed: flat-pin coupler is more suitable for heavy-haul locomotive, but the inspection work on the friction surface of coupler tail needs to be strengthened; and the vertical anti-off stopping device should be added to avoid the occurrence of decoupling accidents.