Maglev Vehicle System Research Articles

Modeling and dynamic performance of distributed force in high-temperature superconducting pinning magnetic levitation

High-temperature superconducting (HTS) pinning magnetic levitation (maglev) systems are highly promising for future applications in rail transportation. Through the interaction between onboard HTS bulks and the permanent magnet guideway (PMG), this system generates levitation and guidance forces, known as the HTS-PMG relationship. Under practical conditions, this interaction manifests itself as a distributed force. However, past models have only considered concentrated forces. This study aims to design experiments to investigate the HTS-PMG relationship and propose a more realistic discretized lateral-vertical coupling HTS-PMG relationship to accurately reflect torques in dynamic simulations. Based on this, a dynamic model is established to analyze the Sperling index and the five-degree-of-freedom dynamic response of the HTS pinning maglev vehicle system under different HTS-PMG relationship models. The results indicate that the proposed discretized lateral-vertical coupling HTS-PMG relationship accurately characterizes the torque generated by the HTS levitator, influencing lateral, roll, pitch, and yaw motions to some extent. Compared with the concentrated force model, the discrete force model exhibits superior dynamic performance, particularly in terms of lateral dynamics and the lateral Sperling index. This study provides valuable insights into the field of HTS maglev, particularly regarding investigating HTS-PMG relationships and their impact on HTS maglev system dynamic performance.

Dynamic impact analysis of the time-delay levitation control system on maglev vehicle system after adding smith predictor

The time delay (TD) in the levitation control system significantly affects the dynamic performance of the closed-loop system in electromagnetic suspension (EMS) maglev vehicles. Excessive TD can cause levitation instability, making it essential to explore effective mitigation methods. To address this issue, a Smith Predictor (SP) is integrated into the traditional PID levitation control system. The combination of theoretical analysis and numerical simulation is employed to assess the stability of the time-delay levitation control system after the integration of the Smith Predictor. Theoretical analysis reveals that when TD exceeds a critical threshold, the levitation system becomes unstable. The addition of SP alters the root trajectory of the system characteristic equation from positive to negative, and recovers the levitation system to stable status. Assuming complete knowledge of the dynamic system, the TD compensation value in the SP becomes a key parameter that determines its performance. A minimum effective value (MEV) for TD compensation is identified, correlating with the system's stability region. Under the influence of TD, more complex systems and higher running speeds of the maglev vehicle lead to a narrower stable region and a larger MEV for TD compensation. Given the simulation parameters in this paper, with a system TD of 15 ms and a maximum vehicle speed of 160 km/h, the MEV for TD compensation in the SP should be set at 12 ms.

Levitation performance evolution of high-temperature superconducting maglev vehicle under electromagnetism-heat-force strong coupling

ABSTRACT High-temperature superconducting (HTS) maglev is considered suitable for high-speed maglev systems because of its self-stability characteristic. However, when the HTS maglev vehicle vibrates, alternating current loss occurs in the onboard superconductor due to the change in the external magnetic field. It leads to the decrease of vehicle levitation height and seriously affects the safe and stable operation of the vehicle. So, in this paper, the levitation performance evolution of HTS maglev vehicle under the electromagnetism-heat-force strong coupling model is studied. The parameter of the air spring is optimized according to the ride index and levitation height decay. The effects of random irregularity at different speeds on vehicle levitation performance are compared. The influence of periodicity geometric irregularity on the levitation performance and ride comfort of HTS maglev vehicle are studied. This paper can provide data reference for the HTS maglev vehicle system in future engineering applications.

Mortise-tenon structural design for improving initial permanent magnetic guideway irregularity in the maglev vehicle system

Mortise-tenon structural design for improving initial permanent magnetic guideway irregularity in the maglev vehicle system

Effect of levitation gap feedback time delay on the EMS maglev vehicle system dynamic response

EMS maglev train uses the active control system to maintain the levitation stability, time delay is widespread in control system. However, the existing maglev dynamics studies rarely consider the effect of time delay, so these analysis results cannot directly guide the engineering design. This paper starts from a theoretical analysis of the levitation stability of a single electromagnet levitation system to obtain the theoretical critical value for the time delay. Then the model is gradually extended to a complete vehicle model and a vehicle-girder coupling dynamics model to find the time delay engineering critical values for the complex coupling system. In order to seek ways to reduce the influence of time delay on the dynamic responses, this paper analyzes the influence regularities of the running speed and control parameters on the dynamic response under the effect of time delay. The result shows that the theoretical critical value of the time delay is equal to the ratio of the differential coefficient and proportional coefficient of the PID controller. For a complex maglev system, the engineering critical value is less than the theoretical critical value. Higher running speeds lead to time delay having a more obvious effect on the maglev system’s dynamic responses. Selecting the smaller proportional coefficient and appropriate differential coefficient for the levitation control system can expand the stability region and reduce the influence of time delay on the maglev system. This analysis is helpful and meaningful to the understanding of the EMS vehicle system stability, and helpful to explore the reason of violent coupled vibration in actual engineering.

Dynamic stability of an electromagnetic suspension maglev vehicle under steady aerodynamic load

In this study, the suspension stability of a maglev vehicle is investigated under steady aerodynamic load. The dynamics of the maglev vehicle in the vertical direction are modelled by considering aerodynamic lift and pitching moment, and this model is adopted to investigate how the aerodynamic load influences the suspension stability by analysing the critical speed by means of eigenvalue analysis and direct integration. Doing so reveals three modes of suspension failure: (i) an upward aerodynamic load or pitching moment can give rise to a dynamic instability, (ii) a downward aerodynamic load can give rise to a static instability and (iii) the electromagnet becomes locked in the guide-way because the vertical aerodynamic force borne by the electromagnet exceeds the vehicle weight borne by it, and the electromagnetic force cannot adjust the suspension gap. In essence, failure modes (i) and (ii) correspond to motion stability when the maglev vehicle system is perturbed by a small amount, whereas failure mode (iii) is similar to the electromagnet holding the track in the event of control failure, albeit by a different mechanism. Each suspension failure mode has its own critical speed, and how that speed depends on the aerodynamic coefficients and feedback control gains is determined.

Active vibration control of secondary suspension based on high-temperature superconducting maglev vehicle system

The high-temperature superconducting (HTS) magnetic levitation (maglev) vehicle system is a kind of self-stable levitation mode, which is benefited from the characteristic of flux pinning of non-ideal type II superconductor. And this novel prototype has the outstanding advantages of simple structure, reliable principle, friendly environment and so on. But in the HTS maglev vehicle system, the damping coefficients of the primary suspension are very small. The vibration of the YBCO bulks over a permanent magnet guideway (PMG) will be incurred by the fluctuant external magnetic field, which is easily transmitted to the car body to affect the running comfort. The primary goal of this paper is to apply active vibration control into two linear electromagnetic actuators on each bogie. Each electromagnetic actuator is combined with an air spring as a kind of active suspension system in secondary suspension. Initially, the primary suspension stiffness coefficient and damping coefficient of YBCO bulks are measured by experiments. And the mathematical model of HTS maglev vehicle with active actuators was built using the German track spectrum of low interference as PMG irregularity. Then, the dynamic responses of HTS maglev vehicle system were simulated with PID and Fuzzy-PID controllers used in the active actuator to verify the feasibility of the control methods, and compared with the uncontrolled system. Finally, the results of the simulation indicate that both control strategies could improve vehicle comfortable and greatly improve the stability of the system compared to the passive bogie system.

Method of Combining Theoretical Calculation With Numerical Simulation for Analyzing Effects of Parameters on the Maglev Vehicle-Bridge System

The dynamic interaction of vehicles/bridges is an important part of the research field of the Electromagnet Suspension (EMS) maglev train. However, multiple factors affect the dynamics of the coupling system, which increases the complexity of the vehicle-bridge coupling system, and makes it difficult to analyze. Herein, combining the advantages of theoretical derivation and numerical calculation, a fast and accurate analysis method of maglev vehicle and bridge system is proposed to analyze the influence of bridge and controller on the dynamics of the maglev system. This work is directed to the Changsha maglev express line, in which the mathematical equations for the vehicle- bridge system is presented. Then the influence of the parameter on the system is analyzed. Finally, the vibration experimental test system is set up, and the vibration test of the maglev vehicle bridge is tested by the test scheme, and the experimental results data are given. The test results of vibration acceleration are in good agreement with the calculation results of the proposed method, which verifies the accuracy of the model and the analysis method. Therefore, the research in this paper can provide theoretical guidance for Maglev engineering, and the analysis method in this paper can also be used in the study of other vehicles, such as the high-speed maglev train.

RBF Neural Network-Based Supervisor Control for Maglev Vehicles on an Elastic Track With Network Time Delay

When the electromagnetic suspension (EMS) type maglev vehicle is traveling over a track, the airgap must be maintained between the electromagnet and the track to prevent contact with that track. Because of the open-loop instability of the EMS system, the current must be actively controlled to maintain the target airgap. However, the maglev system suffers from the strong nonlinearity, force saturation, track flexibility, and feedback signals with network time-delay, hence making the controller design even more difficult. In this article, the minimum levitation unit of the maglev vehicle system has been established. An amplitude saturation controller (ASC), which can ensure the generation of only saturated unidirectional attractive force, is thus proposed. The stability and convergence of the closed-loop signals are proven based on the Lyapunov method. Subsequently, ASC is improved based on the radial basis function neural networks, and a neural network-based supervisor controller (NNBSC) is thus designed. The ASC plays the main role in the initial stage. As the neural network learns the control trend, it will gradually transition to the neural network controller. Simulation results are provided to illustrate the specific merit of the NNBSC. The hardware experimental results of a full-scale IoT EMS maglev train are included to validate the effectiveness and robustness of the presented control method as regards to time delay.

Levitation Performance of the Second-Generation HTS Maglev Vehicle Serving in a Ring Test Line

Based on the decades of research, the second-generation high temperature superconducting (HTS) maglev vehicle was developed for continuously running on a ring test line. In this paper, the levitation performance of the entire HTS maglev vehicle was studied. The levitation force of the entire vehicle composed of four maglev cryostats was measured in field cooling heights of 20, 30, and 40 mm. The experimental results showed that the levitation force of the HTS maglev vehicle exceeds 10 000 N at a 12 mm levitation height, which means that the vehicle can achieve a load capability of 1 t/m. In addition, the levitation height decay of the HTS maglev vehicle was studied during operating at a low speed. Some levitation height decay was found after running for a period of time. To reduce the levitation height decay, the preload method was introduced to the maglev vehicle system. It was found that the proper preload method is beneficial for reducing the levitation height decay.

Study on Electromagnetic Force Characteristics Acting on Levitation/Guidance Coils of a Superconducting Maglev Vehicle System

Superconducting Maglev has been developed as a high-speed transport system. Superconducting coils (SC coils) are installed on the vehicle, and levitation/guidance coils (LG coils) are installed on the ground. A null-flux-type electrodynamic suspension system provided by electromagnetic interaction between SC coils and LG coils serves as the levitation and guidance functions of the vehicle system. Electromagnetic forces acting on SC coils are related to levitation and guidance functions of the vehicle. These forces were studied in previous research, and characteristics of levitation and guidance forces were revealed with respect to parameters of the design of the vehicle. On the other hand, electromagnetic forces acting on LG coils also exist as action–reaction pairs with the forces acting on SC coils. The forces act on LG coils in every levitated run of the vehicle, and stress is applied on the conductor and molded resin of the LG coils. In conventional studies, the vehicle design has been decided mainly by the electromagnetic forces acting on SC coils, and not by the forces acting on LG coils. The aim of the study is to establish an improved method to design the vehicle system with the objective of not only optimization of characteristics of the vehicle, but also consideration of stress on LG coils. As a preliminary study to establish the improved method, a study by computer simulation on characteristics of electromagnetic forces acting on LG coils with respect to the parameters of the vehicle is described in this paper.

Dynamic Vibration Characteristics of HTS Levitation Systems Operating on a Permanent Magnet Guideway Test Line

With the development of high temperature superconducting (HTS) maglev stepping in a key period of test line applications, the test and analysis of the dynamic operation parameters become more and more crucial. In this paper, the dynamic operating characteristics of single-cryostat and multicryostat levitation systems were comparatively studied on a 45-m-long permanent magnet guideway test line with different working conditions. Vibration acceleration signals of three levitation systems (a single cryostat, a bogie with two cryostats, and a car with four cryostats) were measured in the running experiments. The vibration characteristics were analyzed in both time domain and frequency domain. Results show that the multicryostat levitation system has better dynamic performance of stiffness than those of the single-cryostat system. The experimental data also indicates a positive correlation between the stability of the HTS maglev vehicle and the number of the cryostat. This work is helpful to understand the essential characteristics of HTS maglev vehicle system, and will be beneficial to the future design.

Modeling and Validation of 3DOF Dynamics of Maglev Vehicle Considering Guideway

Magnetically levitated (Maglev) vehicles maintain a constant air gap between guideway and car bogie, and thereby achieves non-contact riding. Since the straightness and the flatness of the guideway directly affect the stability of levitation as well as the ride comfort, it is necessary to monitor the status of the guideway and to alert the train operators to any abnormal conditions. In order to develop a signal processing algorithm that extracts guideway irregularities from sensor data, virtual testing using a simulation model would be convenient for analyzing the exact effects of any input as long as the model describes the actual system accurately. Simulation model can also be used as an estimation model. In this paper, we develop a state-space dynamic model of a maglev vehicle system, running on the guideway that contains jumps. This model contains not only the dynamics of the vehicle, but also the descriptions of the power amplifier, the anti-aliasing filter and the sampling delay. A test rig is built for the validation of the model. The test rig consists of a small-scale maglev vehicle, tracks with artificial jumps, and various sensors measuring displacements, accelerations, and coil currents. The experimental data matches well with those from the simulation model, indicating the validity of the model.

A High-Temperature Superconducting Maglev Ring Test Line Developed in Chengdu, China

A 45-m-long high-temperature superconducting (HTS) Maglev ring test line, named “Super-Maglev,” has been successfully developed in Chengdu, China, in February 2013, 12 years after the birth of the first man-loading HTS Maglev test vehicle. The Maglev vehicle (2.2 m in length, 1.1 m in width) is designed for one passenger with a levitation height of 10–20 mm; the permanent-magnet guideway (PMG) (45 m in length, 0.77 m of track gauge) is a racetrack shape with a curve radius of 6 m; the driving is accomplished by a linear induction motor with a maximum running speed of 50 km/h. The linear motor is composed of four submotors installed at one straight section in the middle of the double PMGs, and the total length is 3 m. This second-generation HTS Maglev vehicle system is highlighted by the cost-performance and the wireless multiparameter onboard monitoring function. The current same-level load capability has been achieved over a small-section low-cost PMG whose cross-sectional area is only 3000 mm 2 . On the vehicle, parameters of levitation weight, levitation height, running speed, acceleration, lateral offset, online position, and total running distance of the vehicle are real-time monitored and displayed on the onboard tablet computer. The system component and test data are reported in detail in this paper.

Influence of radius of cylinder HTS bulk on guidance force in a maglev vehicle system

Bulk superconductors had great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFeB guideway used in the HTS maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we investigated the influence of the radius of the cylinder HTS bulk exposed to an AC magnetic field perturbation on the guidance force in the maglev vehicle system. From the results, it was found that the guidance force was stronger for the bulk with bigger radius and the guidance force decay rates of the bulks were approximately equal despite of the different radius in the maglev vehicle system. Therefore, in order to obtain higher guidance force in the maglev vehicle system, we could use the cylinder HTS bulks with the bigger radius.

VERTICAL VIBRATION CHARACTERISTICS OF A HIGH-TEMPERATURE SUPERCONDUCTING MAGLEV VEHICLE SYSTEM

The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0–100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.

Influence of Thermal Conductivity on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Bulk superconductors have great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In the vehicle system, the stable levitation can be achieved without any complex control system owed to the pinning effect of the bulks. However, the HTS bulks in the vehicle system were always exposed to the time-varying external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay characteristics of the YBCO bulk over the NdFdB guideway used in the HTS maglev vehicle system by an experiment in which the AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of thermal conductivity on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and tried to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with the lower thermal conductivity. So, we could reduce the guidance force decay of the HTS bulk exposed to the AC external magnetic field perturbation in the maglev vehicle system by improving the thermal conductance of the bulks.

Dynamic interaction analysis of actively controlled maglev vehicles and guideway girders considering nonlinear electromagnetic forces

This study intends to explore dynamic interaction behaviors between actively controlled maglev vehicle and guideway girders by considering the nonlinear forms of electromagnetic force and current exactly. For this, governing equations for the maglev vehicle with ten degrees of freedom are derived by considering the nonlinear equation of electromagnetic force, surface irregularity, and the deflection of the guideway girder. Next, equations of motion of the guideway girder, based on the mode superposition method, are obtained by applying the UTM-01 control algorithm for electromagnetic suspension to make the maglev vehicle system stable. Finally, the numerical studies under various conditions are carried out to investigate the dynamic characteristics of the maglev system based on consideration of the linear and nonlinear electromagnetic forces. From numerical simulation, it is observed that the dynamic responses between nonlinear and linear analysis make little difference in the stable region. But unstable responses in nonlinear analysis under poor conditions can sometimes be obtained because the nominal air-gap is too small to control the maglev vehicle stably. However, it is demonstrated that this unstable phenomenon can be removed by making the nominal air-gap related to electromagnetic force larger. Consequently it is judged that the nonlinear analysis method considering the nonlinear equations of electromagnetic force and current can provide more realistic solutions than the linear analysis.

Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

A Novel High Temperature Superconducting Maglev Vehicle with a Propulsion Engine

High temperature superconducting (HTS) magnetic levitation (maglev) vehicle is a fascinating transportation tool due to its unique inherent stability. In order to improve performance of present HTS maglev vehicle system, a novel HTS maglev vehicle (aero-vehicle) utilizing aerodynamic designs from modern aircraft is proposed, which is driven by an engine positioned on the top of the car body. The aerodynamic designs of the aero-vehicle include the wings and the empennage, and these new designs are used to adjust and control the pitch, roll, and yaw of the car body. To analyze the feasibility of the aero-vehicle, its characteristics are investigated in the paper. Depending on ailerons of wings, elevator and rudder of the empennage, the aero-vehicle is capable to advance safety and ride comfort of present HTS maglev vehicle.