Guideway Irregularities Research Articles

Vibration separation method for permanent magnet guideway irregularity measurement

High-temperature superconducting (HTS) pinning maglev has the potential to achieve high operational speed while having a low maintenance cost, attracting a lot of attention. The HTS pinning maglev system realizes the levitation of the vehicle through the flux pinning characteristics between the high-temperature superconducting bulk and the magnetic field of the permanent magnet guideway (PMG). Thus, the profile of the magnetic field of the PMG can significantly affect the levitation status of the vehicle, which makes the PMG irregularity become one of the main excitation sources of the system. The magnetic induction intensity on the surface of the PMG can be used to characterize the PMG irregularity, but the non-contact dynamic measurement may produce large errors by the vibration of the measurement system during the process. In order to evaluate the PMG irregularity, the vibration component needs to be separated from the overall signal. In this paper, through the synchronous measurement of the Hall sensor and accelerometer, the vibration separation method of the PMG irregularity measurement is simplified to the optimal filter estimation. The particle swarm optimization (PSO) algorithm is used to calculate the parameters of the optimal filter based on the correlation coefficient criterion. The effectiveness of the proposed method is verified by the test. The separated signal is more accurate in both time domain and frequency domain for the characterization of PMG irregularity.

Stochastic optimization of levitation control system for maglev vehicles subjected to random guideway irregularity

The dynamic performance of maglev vehicle-bridge coupled systems subjected to random guideway irregularity, especially the levitation stability of the running vehicle subsystem, is a critical issue affecting the safe operation and the comfort riding of maglev railways. This study is devoted to stochastic optimization of the levitation control system considering the coupled vibration of maglev vehicle and bridge under the random guideway irregularity. To alleviate the computational burden in the stochastic optimization process, the explicit expressions of the critical responses of the maglev vehicle-bridge coupled systems and the sensitivities of critical responses with respect to the feedback gains of the proportional-integral-derivative (PID) levitation controller are respectively constructed in terms of the guideway irregularity by virtue of the dimension-reduced formulation capability of the explicit time-domain method (ETDM), enabling stochastic dynamic analysis and stochastic sensitivity analysis to be executed at high efficiency. The stochastic optimization problem is formulated as the minimization of the standard deviation of the air gap variation with the constraint on the standard deviation of the current variation, and the optimal values of the PID gains are searched by the gradient-based method of moving asymptotes (MMA), in which the statistical moments and moment sensitivities of the critical responses required in the optimization process are obtained by ETDM. A numerical example with a 2-degree-of-freedom maglev vehicle moving on a multi-span simply-supported bridge is used to demonstrate the efficacy of ETDM for the stochastic analysis of maglev vehicle-bridge coupled systems under guideway irregularity. An engineering example involving a 3-car maglev train traversing a multi-span simply-supported bridge is further presented to show the effectiveness of the ETDM-based approach for the stochastic optimization of large-scale engineering problems. The levitation stability of the maglev train under the action of random guideway irregularity is considerably improved with the use of optimal feedback gains.

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

Vertical Dynamic Response Analysis of HTS Maglev Vehicle Excited by a Designed Coreless-Typed PMLSM

High-temperature superconducting (HTS) pinning maglev has the potential for high-speed application because of its advantages of passive self-stabilization, energy conservation, environmental protection, and no inherent magnetic resistance along the forward direction. The HTS pinning maglev can realize non-contact levitation and guidance. Permanent magnet linear synchronous motor (PMLSM) is suitable for HTS pinning maglev to realize non-contact drive. However, in addition to the longitudinal driving force for the HTS pinning maglev train, the PMLSM also produces the normal force which will cause additional excitation on the maglev train and affect its levitation height and vertical dynamic response. In this paper, a coreless-typed PMLSM is designed for HTS pinning maglev driving system, and the driving force and normal force characteristics of the motor under different air gaps are calculated. Then, a vertical dynamic model of the HTS pinning maglev vehicle is established. The vertical dynamic response of the HTS pinning maglev vehicle excited by the normal force of PMLSM and permanent magnet guideway (PMG) irregularity is simulated and analyzed. This work can provide a reference for the study of the electromechanical coupling effect between the HTS pinning maglev levitation system and linear motor driving system.

Dynamic Response Analysis of High-Speed Maglev-Guideway System

PurposeMaglev train travel is an efficient, modern and unconventional mode of transportation of passengers that has many advantages over the conventional railway transportation. In practice, maglev trains are primarily used for city transportation and connection with the airports. They often travel on elevated guideway bridges. This paper is concerned with developing a computationally efficient and accurate numerical method for the dynamic response of a maglev train traversing an “infinitely” long multi-span guideway bridge.MethodsThis study is based on numerical analysis in the time domain. Each guideway span is modelled as a simply supported beam with rotational springs connecting to the adjacent spans. The maglev vehicle is modelled by employing the multi-body system. The vehicle and the guideway are coupled via the electromagnetic force. In the numerical analysis, a computational scheme in conjunction with the MEM is proposed for the global time-domain simulations.ResultsThe accuracy of the proposed computational model is validated by comparison with available data for a maglev test line in the literature. Thereafter, parametric studies are conducted to examine the effects of train speed, stiffness of the suspension system and the coupling connection between adjacent guideway beams, and guideway irregularity on the dynamic response of the train. Results show that a stiffer guideway coupling connection helps to reduce the vertical acceleration of the car body and the vertical displacement of the guideway for the parameters considered in the study.ConclusionsThe computational model presented in this study in conjunction with the moving element method has the advantage of computationally efficient analysis and accurate prediction of the dynamic responses of a maglev train traversing an “infinitely” long multi-span guideway bridge over the conventional finite-element method, especially when the train is travelling at high speeds. The method can be extended to further consider more complex and practical cases.

Stochastic resonance analysis of a coupled high-speed maglev vehicle-bridge coupled system under bounded noise

Coupled oscillations typically occur in maglev vehicle-bridge coupled systems excited by bounded noise caused by guideway irregularities. The paper employed Hamilton equations to derive the corresponding canonical transformation equations and determined the critical stable regions for two kinds of resonances using the largest Lyapunov exponents. The results show that the critical stable region between the excitation amplitude and the resonant frequency ratio is a valley shape when the system has external resonance only. When considering both internal and external resonances, the critical stable region between the excitation amplitude and resonant frequency ratio presents a small saddle shape. Energy transfers from the first to the second oscillator under with both internal and extrinsic resonance. As the guideway irregularities’ coefficients increase, the maximum Lyapunov exponents of the two conditions change from negative to positive, which means that the system varies from a stable state to instability.

Permanent Magnet Guideway Irregularity Measurement and Characterization by Single Dewar HTS Pinning Maglev System

Permanent Magnet Guideway Irregularity Measurement and Characterization by Single Dewar HTS Pinning Maglev System

Numerical Studies of Dynamic Characteristics of a Stack-Type HTS Maglev System Based on H-Formulation

High temperature superconducting (HTS) magnetic levitation (maglev) is a promising technology for future high-speed transit systems. Superconducting magnetic bearings are made of a permanent magnet guideway and HTS bulks (bulk-type) or stacks of 2G HTS tapes (stack-type). If the dynamic behavior of bulk-type HTS maglev systems has been well reported, there is little literature about the dynamics of stack-type HTS maglev system. To fill the gap, we built here an electromagnetic-mechanical model of a stack-type bearing. We used a segregated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -formulation finite element model to account for the nonlinear resistivity. The multi-layer structure of the HTS tape is either homogenized or modeled in detail. We studied the bearing dynamic response when subjected to different time-varying external magnetic fields mimicking the guideway irregularity and the vehicle speed. The results show that the induced current in the copper layer negatively impacts the stability. By extension, since it cannot account for the copper layer, the homogenized model is not suitable for such analysis. This work contributes to finding viable measures for improving the stability of stack-type HTS maglev systems.

Measurement and Characterization Method of Permanent Magnetic Guideway Irregularity in HTS Maglev System

Measurement and Characterization Method of Permanent Magnetic Guideway Irregularity in HTS Maglev System

A numerical model to predict three-dimensional interaction dynamic of low-medium-speed maglev vehicle–guideway bridge system

This paper established a numerical model to investigate the dynamic behavior of LMS (low-medium-speed) maglev vehicle-guideway bridge coupling system. In this model, the vehicle was simulated as a 3D (3-dimensional) multi-rigid body with 45 DOFs (degree of freedoms), and the guideway bridge was built through finite element method. Two-dimensional magnet-guideway relationship was introduced, and the control strategies of active suspension control based on PID controller and passive guidance control were employed to reflect the vehicle-guideway interaction. A solution program was then developed to solve the vehicle-guideway interaction problem. Through case study, the vibration responses achieved from 3D interaction model were compared to those from corresponding 2D (2-dimensional) model. Besides, the effects of pier and guideway irregularity on dynamic responses of vehicle-guideway bridge coupling system were investigated, and the frequency responses of vehicle and guideway were also analyzed. The result shows that ignoring the pier modeling or guideway irregularity would significantly undervalue the vibration responses of maglev vehicle-guideway bridge interaction system. The frequency responses indicate that the vibrations of vehicle-guideway bridge system are significantly related to the geometric dimensions of maglev vehicle, especially the distance between two magnet units. Finally, parametric study was carried out to determine the effects of key parameters (i.e., vehicle speed and natural frequency of guideway) on guideway responses.

The Effect of Running Speed and Guideway Irregularity on the Levitation Performance of a Linear HTS Maglev Bearing

High-temperature superconducting (HTS) magnetic levitation (maglev) bearing is regarded as a promising candidate for the future high-speed transportation system as a result due to the merits of passive stabilization, low power consumption and environmental-friendliness. The dynamic characteristics are critical for its high-speed applications performance. The current research on the dynamic characteristics of linear HTS maglev bearings is limited to small-scale, approximate harmonic excitation or low-speed. In this paper, the expression of random guideway irregularity spectrum in time domain, which could describe the realistic guideway excitation in rail transportation system, was obtained by Inverse Fourier Transform method with a homemade code. Based on a strong-coupled electromagnetic-thermal-mechanical model, the dynamic characteristic of a heavy-load linear HTS maglev bearing under the excitation of random guideway irregularity with different speeds (400, 500, 600 km/h) and guideway irregularity amplitudes were studied. The results show that the influence of high speed and the temperature on the dynamic stability of linear HTS maglev bearing is quite limited, which is contrary to common concern. On the other hand, the guideway irregularity amplitude plays a great effect on the system dynamic stability. Thus cautious attention is still needed when selecting the line route and manufacturing the guideway. These conclusions could serve as a design guideline for the future high-speed application of linear HTS maglev bearing.

A Non-Iterative Integration Scheme Enriching the Solution to the Coupled Maglev Vehicle–Bridge System

A non-iterative integration scheme is presented in this study to enrich the solutions to the coupled equations of the maglev vehicle–bridge system. The proposed integration scheme is composed of two integration methods aiming at providing the solutions to equation of motion and state-space equation. First, the equation of motion of the simply supported girder bridge is transformed by the modal superposition method. Then the state-space equation is used to describe the motions of both the vehicle and the suspension control system, with the associated matrices assembled using the fully computerized approach. By adopting this integration scheme, only pure vector calculations arise in the solution process, regardless of the existence of time-dependent displacement and velocity on the right-hand sides of the two coupled equations. The proposed integration method is of the second-order accuracy with and without damping. Being equipped with adequate numerical dissipation and dispersion, the method also possesses the characteristic of little computing errors, as can be achieved through the use of different pairs of parameters. Finally, numerical simulations have been conducted to assess the influence of different feedback gains, three types of bridges with different lengths, and guideway irregularity on the maglev vehicle–bridge system.

Dynamic Performance Optimization of Electromagnetic Levitation System Considering Sensor Position

The controlled air gap of the electromagnetic levitation system of maglev train is generally 8-10mm, which makes the vehicle/guideway coupling problem prominent. In practice, it is found that the stability of the magnetic levitation system is affected by guideway irregularities, and the levitation gaps show different dynamic characteristics, which is closely related to the sensor positions. The purpose of optimization of the dynamic performance of the electromagnetic levitation system is to reduce the dynamic deviation amplitude of the levitation gaps. Firstly, a linear model of the module levitation system with guideway is proposed. On this basis, the discrete frequency excitation method is used to obtain the dynamic amplitude response of the levitation gaps at different guideway wavelengths and vehicle speeds. Then, an optimization framework based on sensor positions is proposed. Based on this framework, the optimal sensor position at different speeds is obtained. The simulation results show that the optimal scheme can effectively reduce the deviation amplitude and the difference between the two levitation gaps, thus improving the dynamic performances of the electromagnetic levitation system.

Curve Negotiation Performance of High-Temperature Superconducting Maglev Based on Guidance Force Experiments and Dynamic Simulations

High-temperature superconducting (HTS) maglev has the potential in high-speed transportation owning to its capability of passive stabilization. As an important research field of vehicle dynamics in HTS maglev area, the curve negotiation performance is in connection with the vehicles’ operational safety and comfort. This article reports the curve negotiation performance of the HTS maglev through three steps. First, the guidance force is measured to determine the safe motion range, and the range will be used as the indicator of the safety. Second, the dynamic model of HTS maglev vehicle “Super-Maglev” is established and compared with the experimental results to verify the correctness. The magnetic guideway irregularity is measured, and the measured value is used as the input of dynamic simulation. Finally, the dynamic curve negotiation characteristics of maglev vehicle are simulated. Results show the HTS maglev freight vehicle can safely pass through the curves at a certain speed without external rail superelevation. However, as a passenger vehicle, it can pass through the curve safely and smoothly when the suspension system and the superelevation are added. The curve radius of HTS maglev line, the superelevation outer rail, and the suspension parameters of maglev vehicle are also suggested in this article.

Nonlinear dynamic analysis of Maglev Vehicle Based on flexible guideway and random irregularity

Nonlinear dynamic analysis of Maglev Vehicle Based on flexible guideway and random irregularity

Dynamic Simulation of the Vehicle/Bridge Coupled System in High-Temperature Superconducting Maglev

This paper builds a six degree-of-freedom dynamic model of the high-temperature superconducting (HTS) maglev vehicle/bridge coupled system and simulates its dynamic responses in different conditions. The influences of velocity, air spring dynamics parameters, and guideway irregularity on the ride quality of vehicle are also systematically studied. Results show that the resonant frequency of the carbody acceleration is about 0.5–1.5 Hz, and the main vibration frequency of carbody is related to the periodic configuration of rigid pillars when the HTS maglev train travels over the flexible elevated-guideway. Generally, the maximum carbody acceleration is usually less than 0.3 m/s2, and the maximum elevated-guideway acceleration is also at a low level. In a word, this paper develops and computes a dynamic model of HTS maglev vehicle/bridge coupled system. It could be concluded that the HTS maglev train has great advantage in ride comfort.

Nonlinear Model Predictive Control for a Maglev Vehicle regarding Magnetic Saturation and Guideway Irregularities

In this work, a nonlinear magnet model including magnetic saturation is proposed with focus on control design for a magnetically levitated (Maglev) vehicle. It is shown that the model’s static characteristics corresponds with measurements obtained from a test bench, whereas standard models which neglect saturation fail especially for high currents. To consider the nonlinearities of the system directly in the control design, a nonlinear model predictive control scheme is used for controlling the magnet’s unstable dynamics. With focus on highspeed application, the nonlinear model predictive control algorithm is adapted to incorporate estimates of the guideway irregularities which are obtained from magnet control units located further to the front of the vehicle. The proposed control scheme offers much more flexibility in designing the controller focusing on ride comfort and gap variation, as shown by means of simulations. For these simulations guideway irregularities are applied which are derived from measurements. The necessary computations for the control law are performed in real-time.

Thermal effect on dynamic performance of high-speed maglev train/guideway system

Temperature fields and temperature deformations induced by time-varying solar radiation, shadow, and heat exchange are of great importance for the ride safety and quality of the maglev system. Accurate evaluations of their effects on the dynamic performances are necessary to avoid unexpected loss of service performance. This paper presents a numerical approach to determine temperature effects on the maglev train/guideway interaction system. Heat flux density and heat transfer coefficient of different components of a 25 m simply supported concrete guideway on Shanghai High-speed Maglev Commercial Operation Line is calculated, and an appropriate section mesh is used to consider the time-varying shadow on guideway surfaces. Based on the heat-stress coupled technology, temperature distributions and deformation fields of the guideway are then computed via Finite Element method. Combining guideway irregularities and thermal deformations as the external excitations, a numerical maglev train/guideway interaction model is proposed to analyze the temperature effect. The responses comparison including and excluding temperature effect indicates that the temperature deformation plays an important role in amplifying the response of a running maglev, and the parameter analysis results suggest that climatic and environmental factors significantly affect the temperature effects on the coupled maglev system.

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.

초전도 선형동기전동기 추진 휠-레일 고속열차의 동특성 분석

This study examined the running dynamic characteristics of a hybrid type wheel-rail high speed train, in which the propulsion method of maglev is applied. A wheel-rail high speed train propelled by a superconducting linear synchronous motor (SC-LSM) is expected to be superior to a maglev train regarding economical and interoperable aspects, still having powerful thrust force as maglev. In this paper, regarding the two methods of applying the SC-LSM to an existing wheel-rail train, to investigate the influences of SC-LSM propulsion on the dynamic characteristics of wheel-rail high speed train, the dynamic model of train including interaction between the rotor and stator of SC-LSM is established. Through the simulation using the model, the influence of the interaction between the rotor and stator of SC-LSM on stability, ride comfort and the effect of guideway irregularity are investigated.