Disturbance rejection tube model predictive levitation control of maglev trains

Magnetic levitation control technology plays a significant role in maglev trains.Designing a controller for the levitation system is challenging due to the strong nonlinearity,open-loop instability,and the need for fast response and security.In this paper,we propose a Disturbance-Observe-based Tube Model Predictive Levitation Control(DO-TMPLC)scheme combined with a feedback linearization strategy for the levitation system.The proposed strategy incorporates state constraints and control input constraints,i.e.,the air gap,the vertical velocity,and the current applied to the coil.A feedback linearization strategy is used to cancel the nonlinearity of the tracking error system.Then,a disturbance observer is implemented to actively compensate for disturbances while a TMPLC controller is employed to alleviate the remaining disturbances.Furthermore,we analyze the recursive feasibility and input-to-state stability of the closed-loop system.The simulation results indicate the efficacy of the proposed control strategy.

Aerodynamic Features of High-Speed Maglev Trains with Different Marshaling Lengths Running on a Viaduct under Crosswinds

The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.

Communication simulation of on-board diagnosis network in high-speed Maglev trains

The on-board diagnosis network is the nervous system of high-speed Maglev trains, connecting all controller sensors, and corresponding devices to realize the information acquisition and control. In order to study the on-board diagnosis network＇s security and reliability, a simulation model for the on-board diagnosis network of high-speed Maglev trains with the optimal network engineering tool （OPNET） was built to analyze the network＇s performance, such as response error and bit error rate on the network load, throughput, and node-state response. The simulation model was verified with an actual on-board diagnosis network structure. The results show that the model results obtained are in good agreement with actual system performance and can be used to achieve actual communication network optimization and control algorithms.

Aerodynamic simulation of evacuated tube maglev trains with different streamlined designs

Based on the Navier-Stokes （N-S） equations of incompressible viscous fluids and the standard k-ε turbu- lence model with assumptions of steady state and two dimensional conditions, a simulation of the aerodynamic drag on a maglev train in an evacuated tube was made with ANSYS/FLOTRAN software under different vacuum pressures, blockage ratios, and shapes of train head and tail. The pressure flow fields of the evacuated tube maglev train under different vacuum pressures were analyzed, and then compared under the same blockage ratio condition. The results show that the environmental pressure of 1 000 Pa in the tube is the best to achieve the effect of aerodynamic drag reduction, and there are no obvious differences in the aerodynamic drag reduction among different streamline head shapes. Overall, the blunt-shape tail and the blockage ratio of 0.25 are more efficient for drag reduction of the train at the tube pressure of 1 000 Pa.

How Maglev Trains Work

上海磁悬浮列车专线西起上海地铁2号线的龙阳路站,东至上海浦东国际机场,专线全长29.863公里,是世界第一条商业运营的磁悬浮专线。这列当今世界上最酷的列车按其时速,14分钟内能在上海市区和浦东机场之间打个来回。置身其中,您将亲身体验到这架“陆地客机”所带来的奇异感受。通过阅读本文,你将对磁悬浮列车的工作原理有一个清晰的认识。

A study on aerodynamic noise characteristics of a high-speed maglev train with a speed of 600 km/h

Purpose–This study aims to explore the formation mechanism of aerodynamic noise of a high-speed maglev train and understand the characteristics of dipole and quadrupole sound sources of the maglev train at different speed levels.Design/methodology/approach–Based on large eddy simulation(LES)method and Kirchhoff–Ffowcs Williams and Hawkings(K-FWH)equations,the characteristics of dipole and quadrupole sound sources of maglev trains at different speed levels were simulated and analyzed by constructing reasonable penetrable integral surface.Findings–The spatial disturbance resulting from the separation of the boundary layer in the streamlined area of the tail car is the source of aerodynamic sound of the maglev train.The dipole sources of the train are mainly distributed around the radio terminals of the head and tail cars of the maglev train,the bottom of the arms of the streamlined parts of the head and tail cars and the nose tip area of the streamlined part of the tail car,and the quadrupole sources are mainly distributed in the wake area.When the train runs at three speed levels of 400,500 and 600 km$h1,respectively,the radiated energy of quadrupole source is 62.4%,63.3%and 71.7%,respectively,which exceeds that of dipole sources.Originality/value–This study can help understand the aerodynamic noise characteristics generated by the high-speed maglev train and provide a reference for the optimization design of its aerodynamic shape.

The approach to calculate the aerodynamic drag of maglev train in the evacuated tube

In order to study the relationships between the aerodynamic drag of maglev and other factors in the evacuated tube, the formula of aerodynamic drag was deduced based on the basic equations of aerodynamics and then the calculated result was confirmed at a low speed on an experimental system developed by Superconductivity and New Energy R＆D Center of South Jiaotong University. With regard to this system a high temperature superconducting magnetic levitation vehicle was motivated by a linear induction motor （LIM） fixed on the permanent magnetic guideway. When the vehicle reached an expected speed, the LIM was stopped. Then the damped speed was recorded and used to calculate the experimental drag. The two results show the approximately same relationship between the aerodynamic drag on the maglev and the other factors such as the pressure in the tube, the velocity of the maglev and the blockage ratio. Thus, the pressure, the velocity, and the blockage ratio are viewed as the three important factors that contribute to the energy loss in the evacuated tube transportation.

Numerical Analysis of the Rotational Magnetic Springs for EDS Maglev Train

Different from the traditional railway trains,the combined levitation and guidance EDS maglev train is more likely to rotate after being disturbed.Therefore,the rotational electromagnetic stiffnesses are significant operating parameters for the train.In this paper,the different effects of each translational offset generated in the rotational motion on the corresponding rotational electromagnetic stiffnesses in the EDS maglev train are analyzed and calculated.Firstly,a three-dimensional model of the maglev train is established.Then,based on the space harmonic method and the equivalent circuit of the levitation and guidance circuits,the formulas of rolling,pitching and yawing stiffness are presented.Finally,by comparing with the three-dimensional finite element simulation results,the key translational displacements in the rotational motion which has a great impact on the stiffness are obtained.Hence,the three-dimensional analytical formula can be simplified and the computation can be reduced.In addition,the accuracy of the calculation results is verified by comparing with the experimental data of Yamanashi test line.

Multi-objective aerodynamic optimization design of high-speed maglev train nose

Purpose–The nose length is the key design parameter affecting the aerodynamic performance of high-speed maglev train,and the horizontal profile has a significant impact on the aerodynamic lift of the leading and trailing cars Hence,the study analyzes aerodynamic parameters with multi-objective optimization design.Design/methodology/approach–The nose of normal temperature and normal conduction high-speed maglev train is divided into streamlined part and equipment cabin according to its geometric characteristics.Then the modified vehicle modeling function(VMF)parameterization method and surface discretization method are adopted for the parametric design of the nose.For the 12 key design parameters extracted,combined with computational fluid dynamics(CFD),support vector machine(SVR)model and multi-objective particle swarm optimization(MPSO)algorithm,the multi-objective aerodynamic optimization design of highspeed maglev train nose and the sensitivity analysis of design parameters are carried out with aerodynamic drag coefficient of the whole vehicle and the aerodynamic lift coefficient of the trailing car as the optimization objectives and the aerodynamic lift coefficient of the leading car as the constraint.The engineering improvement and wind tunnel test verification of the optimized shape are done.Findings–Results show that the parametric design method can use less design parameters to describe the nose shape of high-speed maglev train.The prediction accuracy of the SVR model with the reduced amount of calculation and improved optimization efficiency meets the design requirements.Originality/value–Compared with the original shape,the aerodynamic drag coefficient of the whole vehicle is reduced by 19.2%,and the aerodynamic lift coefficients of the leading and trailing cars are reduced by 24.8 and 51.3%,respectively,after adopting the optimized shape modified according to engineering design requirements.

SIMULATION STUDY OF AERODYNAMIC FORCE FOR HIGH-SPEED MAGNETICALLY-LEVITATED TRAINS

Based on Reynolds average Navier-Storkes equations of viscous incompressible fluid and k-ε two equations turbulent model, the aerodynamic forces of high-speed magnetically-levitated （maglev） trains in transverse and longitudinal wind are investigated by finite volume method. Near 80 calculation cases for 2D transverse wind fields and 20 cases for 3D longitudinal wind fields are analyzed. The aerodynamic side force, yawing, drag, lift and pitching moment for different types of maglev trains and a wheel/rail train are compared under the different wind speeds. The types of maglev train models for 2D transverse wind analysis included electromagnetic suspension （EMS） type train, electrodynamic suspension （EDS） type train, EMS type train with shelter wind wall in one side or two sides of guideway and the walls, which are in different height or/and different distances from train body. The situation of maglev train running on viaduct is also analyzed. For 3D longitudinal wind field analysis, the model with different sizes of air clearances beneath maglev train is examined for the different speeds. Calculation result shows that： ① Different transverse effects are shown in different types of maglev trains. ② The shelter wind wall can fairly decrease the transverse effect on the maglev trains. ③ When the shelter wall height is 2 m, there is minimum side force on the train. When the shelter wall height is 2.5 m, there is minimum yawing moment on the train. ④ When the distance between inside surfaces of the walls and center of guideway is 4.0 m, there is minimum transverse influence on the train. ⑤ The size of air clearance beneath train body has a small influence on aerodynamic drag of the train, but has a fairly large effect on aerodynamic lift and pitching moment of the train. ⑥ The calculating lift and pitching moment for maglev train models are minus values.

A nonlinear control method for the electromagnetic suspension system of the maglev train

To deal with the inherent nonlinearity and open-loop instability of the electromagnetic suspension（EMS） system,a new nonlinear control method is proposed.The simulation results show that,for a PID controller,the over-shoot of the system response to an airgap step disturbance is about 3 mm,and the transient time is 6 s;however,for the proposed nonlinear controller,there is no overshoot and transient time within 2 s.The proposed method has a faster response and stronger robustness.With a designed bi-DSP suspension controller,this nonlinear control method was implemented on the Shanghai Urban Maglev Test Line（SUMTL） to validate its effectiveness and feasibility.

Aerodynamic shape optimization of an urban maglev train

With rapid development of urban rail transit,maglev trains,benefiting from its comfortable,energy-saving and environmentally friendly merits,have gradually entered people's horizons.In this paper,aiming at improving the aerodynamic performance of an urban maglev train,the aerodynamic optimization design has been performed.An improved two-point infill criterion has been adopted to construct the cross-validated Kriging model.Meanwhile,the multi-objective genetic algorithm and complex three-dimensional geometric parametrization method have been used,to optimize the streamlined head of the train.Several optimal shapes have been obtained.Results reveal that the optimization strategy used in this paper is sufficiently accurate and time-efficient for the optimization of the urban maglev train,and can be applied in practical engineering.Compared to the prototype of the train,optimal shape benefits from higher lift of the leading car and smaller drag of the whole train.Sensitivity analysis reveals that the length and height of the streamlined head have a great influence on the aerodynamic performance of the train,and strong nonlinear relationships exist between these design variables and aerodynamic performance.The conclusions drawn in this study offer the chance to derive critical reference values for the optimization of the aerodynamic characteristics of urban maglev trains.

Study on the effect of dimple position on drag reduction of high-speed maglev train

Transient numerical simulations were carried out by placing dimples at the top,sides and bottoms of the tail car streamline area of a high-speed maglev train.The results of an improved delayed detached eddy simulation turbulence model using three-dimensional compressible Navier-Stokes and shear-stress transport K-Omega double equations were compared to the results of a wind tunnel test to verify the numerical simulation accuracy,within 5%of the ground truth,which is an acceptable precision range.The results show that dimples arranged on the streamline area atop the train tail car affected the locations at which the airflow at the top and bottom of the train met and weakened the strength of the wake.The aerodynamic drag and lift coefficient decreased by 3.40%and 4.27%,respectively.When the dimples were arranged on the streamline area at the sides or bottoms of the train tail car,they had little effect on the top of the tail car,so they did not destroy the balance of the airflow at the top and bottom.They also had little influence on the development of wake topology.Therefore,the aerodynamic drag and lift of the train changed little.

The Effect of Concave Size on the Aerodynamics of a Maglev Train

Inspired by shark’s skin in nature,a non-smooth surface could be an ideal model for changing the flow characteristics of fluids on the object surface.To analyze the effect of a non-smooth surface with concaves on the maglev train aerodynamic performances and to investigate how the concave size affects the aerodynamic forces and flow structure of a maglev train,four 1/10th scaled maglev train models are simulated using an Improved Delayed Detached Eddy Simulation(IDDES)method.The numerical strategy used in this study is verified by comparison with the wind tunnel test results,and the comparison shows that the difference was in a reasonable range.The results demonstrate that the concaves could effectively reduce the tail car pressure drag,thus reducing the total drag,and that the smaller the concave size was,the better the drag reduction effect would be.The change in the lift with the concave size was more significant than that of the drag,and the tail car lift of R1(0.0012H),R2(0.0024H),and R3(0.0036H)train models was 30.1%,43.0%,and 44.5%less than that of the prototype,respectively.In addition,different flow topologies of the wake are analyzed.The width and height of the vortex core of the counter-rotating vortices tended to decrease with the concave size.Thus,from the point of view of ensuring the operating safety of a maglev train,a non-smooth surface with small-size concaves is recommended.

Unsteady aerodynamic performance of a maglev train:the effect of the ground condition

The effect of ground condition on unsteady aerodynamic performance of a maglev train was numerically investigated with an IDDES(Improved Delayed Detached Eddy Simulation) method. The accuracy of the numerical method has been validated by wind tunnelexperiments. The flow structure, slipstream and aerodynamic force around the train under stationary and moving ground conditionswere compared. Track and ground play a leading role in the influence of wake vortex structure;the flow structure around the trainis more complex under the stationary ground boundary condition. Near the nose point of the head and tail vehicles, the peak valueof the slipstream under the condition of moving ground is slightly higher than that under stationary ground. In the wake area, theeffect of themain vortex structure on both sides of the tail vehicle and the trackmakes the vortex structure in the wake area strongerthan that under moving ground, the slipstream peak is larger and the locus thereof is further forward. In the horizontal direction, thevortex desorption energy near the nose tip of the train is higher on stationary ground, while the vortex desorption energy far fromthe nose tip of the train is higher on moving ground. Compared with the static ground boundary condition, the resistance coefficientof the head and tail of a maglev train increases by 3.45% and 3.31% respectively under the moving ground boundary condition. Thelift coefficient decreases by 157.78% and 5.13%, respectively.

System dynamics in structural strength and vibration fatigue life assessment of the swing bar for high‐speed maglev train

High‐speed maglev trains are subjected to severe dynamic loads,thus posing a failure hazard.It is necessary to account for the vehicle dynamics to improve the structural strength and fatigue life assessment approach under harsh routes and super high‐speed grades.As the most critical load‐carrying part between the vehicle body and levitation frames,the swing bar was taken as an example to demonstrate the significance of vehicle dynamics to integrate classical structural strength and fatigue life with the service conditions.A multiphysics‐coupled dynamic model of an alpha improvement scheme for an electromagnetic suspension maglev train capable of 600 km/h was established to investigate the complex dynamic loads and fatigue spectra.Using this model,the structural strength and fatigue life of the wrought swing bars were investigated.Results show only a slight effect on the structural strength and fatigue life of swing bars by the super high‐speed grades.The nonaxial bending moments caused by the uncompensated relative displacement between the vehicle body and bolsters are identified as the decisive factors.The minimum safety factor of the structural strength for wrought swing bars is 1.33,while the minimum fatigue life is 34 years.Both match the design requirements but are not conservative enough.Therefore,further verification and optimization are recommended to improve the design of swing bars.