Search Results (8)

With the continuous development of maglev transportation technology, medium–low-speed maglev trains have been widely implemented in many countries. However, due to the limitations of existing specifications, the stiffness limit values of the large-span main girders used in medium–low-speed maglev trains have not been unified. To address this issue, this study takes a specific bridge on a dedicated maglev line as an example and uses self-developed software to model the vehicle–bridge dynamic system. The natural vibration characteristics and vehicle–bridge coupling vibration response of the bridge are calculated and analyzed. Based on this, the influence of pier top stiffness on the dynamic characteristics of a typical medium–low-speed maglev train–bridge system under different working conditions is investigated, with a focus on the lateral line stiffness at the pier top. The results show that vehicle speed has no significant effect on the lateral displacement of the main girder, the lateral displacement of the pier top, the lateral acceleration of the pier top, and the transverse and longitudinal angles of the beam end, and no obvious regularity is observed. However, in the double-track operating condition, the vertical deflection of the main girder is significantly higher than that in the single-track operating condition. As the lateral linear stiffness at the pier top increases, the fundamental frequency of the bridge’s lateral bending vibration gradually increases, while the fundamental frequency of longitudinal floating gradually decreases. The lateral displacements, including those of the main girder, pier top, and beam ends, all decrease, whereas the lateral and vertical vibration accelerations of the main girder and the train are less affected by the lateral stiffness at the pier top. Full article

The propulsion system is a critical component of medium–low-speed maglev trains and the single-sided linear induction motor (SLIM) has been adopted to generate thrust. However, the SLIM operates periodically in maglev trains. The temperature of the secondary plate of the SLIM rises significantly due to eddy currents when the train enters and leaves the station, where large slip occurs. Subsequently, the temperature decreases through natural cooling during the shift interval time. This periodic operating condition is rarely addressed in the existing literature and warrants attention, as the temperature accumulates over successive periods, potentially resulting in thermal damage and thrust variation. Furthermore, the conductivity of plate varies significantly in the process, which affects the losses and thrust, requiring a coupled analysis. To investigate the temperature variation patterns, this paper proposes a coupled model integrating the lumped parameter thermal network (LPTN) and the equivalent circuit (EC) of the SLIM. Given the unique structure of the F-shaped rail, the LPTN mesh is well designed to account for the skin effect. Three experiments and a finite element method (FEM)-based analysis were conducted to validate the proposed model. Finally, optimizations were performed with respect to different shift interval time, plate materials, and carriage numbers. The impact of temperature on thrust is also discussed. The results indicate that the minimum shift interval time and maximum carriage number are 70.7 s and 9, respectively, with thrust increasing by 22.0% and 22.0%. Furthermore, the use of copper as the plate material can reduce the maximum temperature by 22.01% while decreasing propulsion thrust by 26.1%. Full article

To ensure safety and passenger comfort, for the medium- and low-speed Maglev transportation system, very strict control standards were developed and set into action. The relevant high costs were therefore not conducive to the promotion of this advanced mode of transportation. Moving from the above described situation, field tests were carried out at the Maglev test line located in Shanghai Lin’gang. The dynamic response of the Maglev system was studied under the influence of beams of the supporting frame with a varying stiffness and under different environmental (in terms of temperature) effects. The collected data showed that the system can guarantee good stability under relatively unfavorable ambient conditions so that the effect of temperature on the dynamic response of the system lies within an acceptable range. Full article

When a medium–low-speed (MLS) maglev train is braking, part of its regenerative braking (RB) power consumption may cause a significant rise in the positive rail (PR) voltage. For RB energy re-utilization, an RB energy feedback system (RBEFS) is a promising application, but there is still no specific research in the field of MLS maglev trains. From this perspective, this article focuses on identifying the PR voltage rise behavior and investigating the application of an RBEFS on the over-voltage inhibition. Some development trends of the MLS maglev train, including the DC 3 kV traction grid system and the speed being raised to 160~200 km/h, are also considered in the analyzed scenarios. At first, a modeling scheme of a detailed vehicle–grid electrical power model with the RBEFS is established. On this basis, the PR voltage rise characteristics are analyzed with consideration of three pivotal influencing factors: RB power, PR impedance and supply voltage level. Subsequently, to stabilize the PR voltage fluctuations, the influence rules of the RBEFS on the voltage rise and the mutual transient voltage influences under the operating status switching for multiple vehicles running on the same power supply section are analyzed. Full article

In order to reduce the impact of noise on the environment and reduce the dissipation of useless energy of traction motors, this study analyzed the noise of a traction motor by detecting the vibration acceleration of the suspension frame. Field tests were conducted to measure the traction noise and suspension frame vibration in a commercially operational medium- and low-speed maglev train. The tests showed that as the train accelerates, the sound pressure grows overall, but the increase becomes smaller at each test speed. The speed of the maglev train is closely correlated with the vibrations of the suspension frame in lateral/vertical directions. The dominant frequency of traction motor noise is basically consistent with that of suspension frame vibration acceleration, showing that the suspension frame vibration is the main reason for high-frequency noise in the operation of low–medium-speed maglev trains. Full article

As a new mode of transportation, maglev train has a broad prospect. As one of the key technologies of maglev train, suspension control technology has been a hot research field. Maglev train has the characteristics of complex system modeling, strong nonlinear model, unstable open-loop system, and complex and changeable working conditions. To date, the widely used method is still the design of PID controller based on linearized maglev model. However, with the passage of time, its shortcomings become increasingly clear. To achieve better control effect, an adaptive sliding mode control method based on linear extended state observer (LESO) is proposed in this paper, which not only improves the response speed of the system, but also improves the robustness and anti-interference ability of the system, and greatly reduces the impact of external disturbances on the suspension stability. First, the dynamic model of the system is established, the control characteristics of the system are analyzed, and the design method of current loop is proposed to reduce the order of the system model. Then, the traditional sliding mode control based on reaching law is designed for the reduced order system, and the performance and shortcomings of the controller are analyzed. Aiming at the defects of traditional sliding mode control, a sliding mode controller based on linear extended state observer is designed. The total disturbance and unmodeled part of the system are estimated in real time by LESO and eliminated in sliding mode control. It can be proved that the designed controller can ensure the stability of the closed-loop system, the system state can converge asymptotically in the neighborhood near the expected value, and has a very fast convergence speed. At the same time, the system has strong robustness to noise and external disturbances. Finally, the effectiveness of the proposed controller is verified by simulation and experiment. Full article

The suspension system of the EMS (Electro-Magnetic Suspension) medium-and-low-speed maglev train is affected by the eddy current effect when the train is in motion. This is a crucial problem related to the improvement of train operation speed. In this article, this phenomenon is analyzed and the method of suppressing the eddy current effect is put forward. Firstly, theoretical analysis and experimental verification are carried out. It is worth mentioning that the experimental data, which thoroughly show how the suspension current changes with the maglev train speed under the influence of the eddy current effect, are collected and published for the first time, which strongly confirms the accuracy of the theoretical analysis. Secondly, an improved scheme to suppress the influence of the eddy current effect is proposed from the perspective of the rail structure for the first time and simulation results verify the effectiveness of the improved scheme. This research makes important progress on the improvement of the rail used in the maglev train. Full article

The levitation stability of maglev trains is determined by the interaction of vehicle-bridge dynamic characteristics. The state change of vehicle and track beam will affect the dynamic performance of maglev trains. In order to study the levitation characteristics of maglev trains, a coupled vehicle-bridge dynamic model based on an elastic beam was established to study the influence of beam stiffness and vehicle load on the dynamic performance of the maglev system. In the form of numerical simulation, the time-domain characteristics of key characteristic variables, such as levitation gap and vertical deflection of track beam, under different working conditions of stiffness and load were analyzed. The simulation shows that the levitation system can smoothly converge to the stable value under each working condition, which indicates the rationality of the field test. Based on the Shanghai Lingang medium-and-low-speed maglev test line, the maglev test was carried out, and the time-domain and frequency-domain characteristics of the above key variables were analyzed based on the measured data. The results show that the fluctuation of the levitation gap was affected by load and stiffness, and the law was consistent with the simulation results. The increase in load or the decrease in beam stiffness would lead to an increase in vertical deflection and vibration of the track beam. However, the train could still maintain good levitation performance under the above extreme conditions, which verified the reliability of the levitation system and the correctness of the simulation model. The conclusion of this paper can provide a reference for the design of the levitation system and track line of medium-and-low-speed maglev train. Full article