In this study, the intrinsic mechanism of aerodynamic effects on the motion stability of a high-speed maglev system was investigated. The concept of a critical speed for maglev vehicles considering the aerodynamic eff...In this study, the intrinsic mechanism of aerodynamic effects on the motion stability of a high-speed maglev system was investigated. The concept of a critical speed for maglev vehicles considering the aerodynamic effect is proposed. The study was carried out based on a single magnetic suspension system, which is convenient for proposing relevant concepts and obtaining explicit expressions. This study shows that the motion stability of the suspension system is closely related to the vehicle speed when aerodynamic effects are considered. With increases of the vehicle speed, the stability behavior of the system changes. At a certain vehicle speed,the stability of the system reaches a critical state, followed by instability. The speed corresponding to the critical state is the critical speed. Analysis reveals that when the system reaches the critical state, it takes two forms, with two critical speeds, and thus two expressions for the critical speed are obtained. The conditions of the existence of the critical speed were determined, and the effects of the control parameters and the lift coefficient on the critical speed were analyzed by numerical analysis. The results show that the first critical speed appears when the aerodynamic force is upward,and the second critical speed appears when the aerodynamic force is downward. Moreover, both critical speeds decrease with the increase of the lift coefficient.展开更多
The multi-block high-temperature superconducting （HTS） maglev system has more complicated dynamic characteristics than the single-block HTS maglev system. To study its vibration characteristics, we designed a maglev...The multi-block high-temperature superconducting （HTS） maglev system has more complicated dynamic characteristics than the single-block HTS maglev system. To study its vibration characteristics, we designed a maglev measurement system. The system responses at the excitation frequencies of 2, 3 and 15 Hz were examined. Results show that the responses under excitation frequencies of 2 and 3 Hz include a 6 Hz component, which means that the maglev system is a critical nonlinear system. Moreover, the 6 Hz component is much stronger than the 2 Hz or 3 Hz components in the response spectra. There is the interaction between excitation and response. Under an excitation frequency of 15 Hz, intensified low-frequency perturbations were observed.展开更多
This paper studies the propellant and levitation forces of a prototype maglev system where the propellant forces are provided by a linear motor system. For this purpose, the mathematical model and method using finite ...This paper studies the propellant and levitation forces of a prototype maglev system where the propellant forces are provided by a linear motor system. For this purpose, the mathematical model and method using finite element method coupled to external circuit model is developed. The details of the propellant and levitation forces for a prototype maglev system under different operating conditions are investigated, and some directions are given for practical engineering applications.展开更多
This paper presents a control strategy for maglev system based on the sliding mode controller with auto-tuning law. The designed adaptive controller will replace the conventional sliding mode control (SMC) to eliminat...This paper presents a control strategy for maglev system based on the sliding mode controller with auto-tuning law. The designed adaptive controller will replace the conventional sliding mode control (SMC) to eliminate the chattering resulting from the SMC. The stability of maglev system is ensured based on the Lyapunov theory. Simulation results verify the effectiveness of the proposed method. In addition, the advantages of the proposed controller are indicated in comparison with a traditional sliding mode controller.展开更多
A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state ...A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state of the medium and low speed maglev coupled system by the additional deformation of the maglev track.This study investigated the dynamic properties of the coupled vibration system affected by the subgrade settlement.First,a theoretical coupled vibration model of a maglev train-track-ground girder system with uneven subgrade settlement was proposed and verified.Then,the effect mechanism of the coupled system caused by the uneven subgrade settlement was explored.Finally,settlement types and subgrade support voiding were examined.The analysis showed that the uneven subgrade settlement considerably increased the dynamic responses of the levitation control system and maglev vehicle while having a minor influence on those of the track-ground girder.The influence of a single ground girder settling was the strongest,and adjacent sides’settling of two ground girders was the weakest for the vibration of a maglev train.An extremely large uneven settlement exceeding 6 mm led to active levitation control system instability.The subgrade support voiding enlarged the vehicle-induced vibration of the track ground girder.展开更多
Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can b...Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can be well characterized based on various stochastic excitations.A three-dimensional refined spatial random vibration analysis model of high-speed maglev train-bridge coupled system is established in this paper,in which multi-source uncertainty excitation can be considered simultaneously,and the probability density evolution method(PDEM)is adopted to reveal the system-specific uncertainty dynamic characteristic.The motion equation of the maglev vehicle model is composed of multi-rigid bodies with a total 210-degrees of freedom for each vehicle,and a refined electromagnetic force-air gap model is used to account for the interaction and coupling effect between the moving train and track beam bridges,which are directly established by using finite element method.The model is proven to be applicable by comparing with Monte Carlo simulation.By applying the proposed stochastic framework to the high maglev line,the random dynamic responses of maglev vehicles running on the bridges are studied for running safety and stability assessment.Moreover,the effects of track irregularity wavelength range under different amplitude and running speeds on the coupled system are investigated.The results show that the augmentation of train speed will move backward the sensitive wavelength interval,and track irregularity amplitude influences the response remarkably in the sensitive interval.展开更多
High-speed maglev trains(HSMTs)can run at high running speeds due to their unique design.The pressure waves that these trains generate while passing each other are therefore very intense,and can even have safety impli...High-speed maglev trains(HSMTs)can run at high running speeds due to their unique design.The pressure waves that these trains generate while passing each other are therefore very intense,and can even have safety implications.In order to reduce the transient impact of such waves,the standard k-ε turbulence model is used in this work to assess the effect of railway spacing on the aerodynamic loads,pressure and surrounding flow field of 600 km/h maglev trains passing each other in open air.The sliding mesh technique is used to determine the relative motion between the considered trains.The results show that the surface pressure is approximately linearly correlated with the square of the speed while the amplitude of the pressure wave on the train surface,side force,and rolling moment all have negative exponential relationships with the railway spacing.展开更多
Currently,the design of high-temperature superconducting(HTS)maglev trains adopts a U-shaped track operation mode,and the height of the side track significantly impacts the train’s aerodynamic characteristics.In this...Currently,the design of high-temperature superconducting(HTS)maglev trains adopts a U-shaped track operation mode,and the height of the side track significantly impacts the train’s aerodynamic characteristics.In this study,we used computational fluid dynamics(CFD)methods,based on the 3D Reynolds-averaged Navier-Stokes(RANS)method and shear stress transport(SST)k-ωturbulence model,to deeply investigate the effects of the presence or absence of a U-shaped track and different side track heights(800,880,and 960 mm)on the pressure distribution,velocity distribution,and flow field structure of HTS maglev trains at a speed of 400 km/h under crosswinds.The numerical methods were verified using a scaled ICE-2 model wind tunnel test.First,the aerodynamic characteristics of the train under different wind direction angles with and without side tracks were studied.We found that the aerodynamic performance of the train is the most adverse when the wind direction angle is 90°.The presence of a U-shaped track can effectively reduce the lateral force,lift,and yawing moment of the train.The aerodynamic performance of the first suspension bogie at the bottom,which is the worst,will also be effectively improved.Next,the aerodynamic effects of different side track heights on the HTS maglev train were studied.An increase in side track height will reduce the lift and lateral force of the train,while the increase in drag is relatively small.Under the premise of ensuring passengers can conveniently alight,we found that a U-shaped track with a side track height of 960 mm has the best aerodynamic performance.The research findings offer a valuable reference for the engineering application and design of the track structure of HTS maglev train systems.展开更多
High-speed maglev trains represent a key direction for the future development of rail transportation.As operating speeds increase,they face increasingly severe aerodynamic challenges.The streamlined aerodynamic shape ...High-speed maglev trains represent a key direction for the future development of rail transportation.As operating speeds increase,they face increasingly severe aerodynamic challenges.The streamlined aerodynamic shape of a maglev train is a critical factor influencing its aerodynamic performance,and optimizing its length plays a significant role in improving the overall aerodynamic characteristics of the train.In this study,a numerical simulation model of a high-speed maglev train was established based on computational fluid dynamics(CFD)to investigate the effects of streamline length on the aerodynamic performance of the train operating on an open track.The results show that the length of the streamlined section has a pronounced impact on aerodynamic performance.When the streamline length increases from 8.3 to 14.3 m,the aerodynamic drag of the head and tail cars decreases by 16.2%and 32.1%,respectively,with reductions observed in both frictions drag and pressure drag-the latter showing the most significant decrease in the tail car.Moreover,the extended streamline length effectively suppresses flow separation on the train body surface.The intensity of the positive pressure region on the upper surface of the head car streamlined section is reduced,directly leading to a 38.2%reduction in lift.This research provides a theoretical basis for the parametric design of aerodynamic shapes for high-speed maglev trains and offers guidance and recommendations for drag and lift reduction optimization.展开更多
A high-speed train travelling from the open air into a narrow tunnel will cause the“sonic boom”at tunnel exit.When the maglev train’s speed reaches 600 km/h,the train-tunnel aerodynamic effect is intensified,so a n...A high-speed train travelling from the open air into a narrow tunnel will cause the“sonic boom”at tunnel exit.When the maglev train’s speed reaches 600 km/h,the train-tunnel aerodynamic effect is intensified,so a new mitigation method is urgently expected to be explored.This study proposed a novel asymptotic linear method(ALM)for micro pressure wave(MPW)mitigation to achieve a constant gradient of initial c ompression waves(ICWs),via a study with various open ratios on hoods.The properties of ICWs and MPWs under various open ratios of hoods were analyzed.The results show that as the open ratio increases,the MPW amplitude at the tunnel exit initially decreases before rising.At the open ratio of 2.28%,the slope of the ICW curve is linearly coincident with a supposed straight line in the ALM,which further reduces the MPW amplitude by 26.9%at 20 m and 20.0%at 50 m from the exit,as compared to the unvented hood.Therefore,the proposed method effectively mitigates MPW and quickly determines the upper limit of alleviation for the MPW amplitude at a fixed train-tunnel operation condition.All achievements provide a ne w potential measure for the adaptive design of tunnel hoods.展开更多
A disturbance decoupled fault diagnosis strategy is proposed.This disturbance decoupled fault diagnosis is both robust to disturbances and sensitive to sensor faults of magnetic levitation control system.First,a robus...A disturbance decoupled fault diagnosis strategy is proposed.This disturbance decoupled fault diagnosis is both robust to disturbances and sensitive to sensor faults of magnetic levitation control system.First,a robust controller based on a novel disturbance observer is devised to improve the disturbance attenuation ability,which greatly enhances the robustness of the system.Second,a fault reconstruction technique with adaptive method is presented,along with a strict verification for guaranteeing the robustness of fault.This fault reconstruction technique provides an accurate sensor fault reconstruction.From the results of simulation and experiments conducted on the CMS-04 maglev train,the integrated strategy is robust to model uncertainties of the system and the fault reconstruction algorithm is able to reconstruct the dynamic uncertain faults.展开更多
In order to explore the precise dynamic response of the maglev train and verify the validity of proposed controller,a maglev guideway-electromagnet-air spring-cabin coupled model is developed in the first step.Based o...In order to explore the precise dynamic response of the maglev train and verify the validity of proposed controller,a maglev guideway-electromagnet-air spring-cabin coupled model is developed in the first step.Based on the coupled model,the stresses of the modules are analyzed,and it is pointed out that the inherent nonlinearity,the inner coupling,misalignments between the sensors and actuators,and external disturbances are the main issues that should be considered for the maglev engineering.Furthermore,a feedback linearization controller based on the mathematical model of a maglev module is derived,in which the nonlinearity,coupling and misalignments are taken into account.Then,to attenuate the effect of external disturbances,a disturbance observer is proposed and the dynamics of the estimation error is analyzed using the input-to-state stability theory.It shows that the error is negligible under a low-frequency disturbance.However,at the high-frequency range,the error is unacceptable and the disturbances can not be compensated in time,which lead to over designed fluctuations of levitation gap,even a clash between the upper surface of electromagnet and lower surface of guideway.To solve this problem,a novel nonlinear acceleration feedback is put forward to enhancing the attenuation ability of fast varying disturbances.Finally,numerical comparisons show that the proposed controller outperforms the traditional feedback linearization controller and maintains good robustness under disturbances.展开更多
The dynamic interaction between maglev vehicle and three-span continuous guideway is discussed. With the consideration of control system, the dynamic interaction model has been developed. Numerical simulation has been...The dynamic interaction between maglev vehicle and three-span continuous guideway is discussed. With the consideration of control system, the dynamic interaction model has been developed. Numerical simulation has been performed to study dynamic characteristics of the guideway. The results show that bending rigidity, vehicle speed, span ratio and primary frequency all have important influences on the dynamic characteristics of the guideway and there is no distinct trend towards resonance vibration when fl/（v/l） equals 1.0. The definite way is to control impact coefficient and acceleration of the guideway. The conclusions can serve the design of high-speed maglev three-span continuous guideway.展开更多
The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train col...The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train collision with track.To study the dynamic response of the train and the viaduct when the levitation magnet control loop failure occurs,a high-speed maglev train-viaduct coupling model,which includes a maglev controller fitted by measured force-gap data and considers the actual structure of train and viaduct,is established.Then the accuracy and effectiveness of the established approach are validated by comparing the computed dynamic responses and frequencies with the measurement results.After that,the dynamic responses of maglev train and viaduct are discussed under normal operation and control loop failures,and the most disadvantageous combination of control loop failures is obtained.The results show that when a single control loop fails,it only has a great influence on the failed electromagnet,and the maglev response of adjacent electromagnets has no obvious change and no collision occurs.But there is a risk of rail collisions when the dual control loop fails.展开更多
High-speed maglev trains will play an important role in the high-speed transportation system in the near future.However,under the conditions of strong magnetic fields and continuous operation,the actuators of the high...High-speed maglev trains will play an important role in the high-speed transportation system in the near future.However,under the conditions of strong magnetic fields and continuous operation,the actuators of the high-speed maglev train suspension system are prone to lose partial effectiveness,which makes the suspension control problem challenging.In addition,most existing fault-tolerant control(FTC)methods for suspension systems require linearization around the equilibrium points during the controller design or stability analysis.Therefore,from a practical perspective,this study presents a novel nonlinear FTC strategy with adaptive compensation for high-speed maglev train suspension systems.First,a nonlinear dynamic model of the suspension system based on join-structure is established and the actuator failures are described.Then,a nonlinear fault-tolerant suspension control law with an adaptive update law is designed to achieve stable suspension against partial actuator failure.The Lyapunov theory and extended Barbalat lemma are utilized to rigorously prove the closed-loop asymptotic stability even if there is partial actuator failure,without any approximation to the original nonlinear dynamics.Finally,hardware experimental results are included to demonstrate the effectiveness of the proposed approach.展开更多
A novel maglev transportation system was proposed for large travel range ultra precision motion.The system consists of a levitation subsystem and a propulsion subsystem.During the propulsion subsystem driving the movi...A novel maglev transportation system was proposed for large travel range ultra precision motion.The system consists of a levitation subsystem and a propulsion subsystem.During the propulsion subsystem driving the moving platform along the guideway,the levitation subsystem uses six pairs of electromagnets to steadily suspend the moving platform over the guideway.The model of the levitation system,which is a typical nonlinear multi-input multi-output coupling system and has many inner nonlinear coupling characteristics,was deduced.For testifying the model,the levitation mechanism was firstly controlled by proportional-integral-differential(PID) control,and then a lot of input-output data were collected for model parameter identification.The least-square parameter identification method was used.The identification results prove that the model is feasible and suitable for the real system.展开更多
The self-excited vibration problems of maglev vehicle-bridge interaction system were addressed, which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the...The self-excited vibration problems of maglev vehicle-bridge interaction system were addressed, which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, the coupled model containing the quintessential parts was built, and the mechanism of self-excited vibration was explained in terms of energy transmission from levitation system to bridge. Then, the influences of the parameters of the widely used integral-type proportion and derivation(PD) controller and the delay of signals on the stability of the interaction system were analyzed. The result shows that the integral-type PD control is a nonoptimal approach to solve the self-excited vibration completely. Furthermore, the differential-type PD controller can guarantee the passivity of levitation system at full band. However, the differentiation of levitation gap should be filtered by a low-pass filter due to noise of gap differentiation. The analysis indicates that a well tuned low-pass filter can still keep the coupled system stable.展开更多
The steel turnout is one of the key components in the medium–low-speed maglev line system.However,the vehicle under active control is prone to vehicle–turnout coupled vibration,and thus,it is necessary to identify t...The steel turnout is one of the key components in the medium–low-speed maglev line system.However,the vehicle under active control is prone to vehicle–turnout coupled vibration,and thus,it is necessary to identify the vibration characteristics of this coupled system through field tests.To this end,dynamic performance tests were conducted on a vehicle–turnout coupled system in a medium–low-speed maglev test line.Firstly,the dynamic response data of the coupled system under various operating conditions were obtained.Then,the natural vibration characteristics of the turnout were analysed using the free attenuation method and the finite element method,indicating a good agreement between the simulation results and the measured results;the acceleration response characteristics of the coupled system were analysed in detail,and the ride quality of the vehicle was assessed by Sperling index.Finally,the frequency distribution characteristics of the coupled system were discussed.All these test results could provide references for model validation and optimized design of medium–low-speed maglev transport systems.展开更多
The dynamic interaction between moving vehicles and two-span continuous guideway was discussed. With the consideration of the magnetic levitation system, the maglev vehicle/guideway dynamic interaction model was devel...The dynamic interaction between moving vehicles and two-span continuous guideway was discussed. With the consideration of the magnetic levitation system, the maglev vehicle/guideway dynamic interaction model was developed. Numerical simulation was performed to understand dynamic characteristics of the guideway used in practice. The results show that vehicle speed, span length and primary frequency of the guideway have an important influence on the dynamic responses of the guideway and there is no distinct trend towards resonance vibration when fl equals 1.0. The definite way is to control the impact coefficient and acceleration of the guideway. The conclusions can serve the design of high speed maglev guideway.展开更多
基金supported by the National Key Research and Development Program of China(Grant 2016YFB1200602)the National Natural Science Foundation of China (Grants 11672306, 51490673)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant XDB22020101)the National Basic Research Program (973 Program) of China (Grant 2014CB046801)the State Key Laboratory of Hydraulic Engineering Simulation and Safety (Tianjin University)
文摘In this study, the intrinsic mechanism of aerodynamic effects on the motion stability of a high-speed maglev system was investigated. The concept of a critical speed for maglev vehicles considering the aerodynamic effect is proposed. The study was carried out based on a single magnetic suspension system, which is convenient for proposing relevant concepts and obtaining explicit expressions. This study shows that the motion stability of the suspension system is closely related to the vehicle speed when aerodynamic effects are considered. With increases of the vehicle speed, the stability behavior of the system changes. At a certain vehicle speed,the stability of the system reaches a critical state, followed by instability. The speed corresponding to the critical state is the critical speed. Analysis reveals that when the system reaches the critical state, it takes two forms, with two critical speeds, and thus two expressions for the critical speed are obtained. The conditions of the existence of the critical speed were determined, and the effects of the control parameters and the lift coefficient on the critical speed were analyzed by numerical analysis. The results show that the first critical speed appears when the aerodynamic force is upward,and the second critical speed appears when the aerodynamic force is downward. Moreover, both critical speeds decrease with the increase of the lift coefficient.
基金supported by the PCSIRT of the Ministry of Education of China (No. IRT0751)the National High Technology Research and Development Program of China (863 Program: No. 2007AA03Z203)+2 种基金the National Natural Science Foundation of China (Nos.50588201 and 50872116)the Research Fund for the Doctoral Program of Higher Education of China (No.SRFDP200806130023)the Fundamental Research Funds for the Central Universities (Nos. SWJTU09BR152, SWJTU09ZT24 and SWJTU11CX073)
文摘The multi-block high-temperature superconducting （HTS） maglev system has more complicated dynamic characteristics than the single-block HTS maglev system. To study its vibration characteristics, we designed a maglev measurement system. The system responses at the excitation frequencies of 2, 3 and 15 Hz were examined. Results show that the responses under excitation frequencies of 2 and 3 Hz include a 6 Hz component, which means that the maglev system is a critical nonlinear system. Moreover, the 6 Hz component is much stronger than the 2 Hz or 3 Hz components in the response spectra. There is the interaction between excitation and response. Under an excitation frequency of 15 Hz, intensified low-frequency perturbations were observed.
文摘This paper studies the propellant and levitation forces of a prototype maglev system where the propellant forces are provided by a linear motor system. For this purpose, the mathematical model and method using finite element method coupled to external circuit model is developed. The details of the propellant and levitation forces for a prototype maglev system under different operating conditions are investigated, and some directions are given for practical engineering applications.
文摘This paper presents a control strategy for maglev system based on the sliding mode controller with auto-tuning law. The designed adaptive controller will replace the conventional sliding mode control (SMC) to eliminate the chattering resulting from the SMC. The stability of maglev system is ensured based on the Lyapunov theory. Simulation results verify the effectiveness of the proposed method. In addition, the advantages of the proposed controller are indicated in comparison with a traditional sliding mode controller.
基金National Natural Science Foundation of China under Grant Nos.52478467and 52108417Guangdong Basic and Applied Basic Research Foundation under Grant No.2024A1515012569the Natural Science Basic Research Program of Shaanxi under Grant No.2021JQ-101。
文摘A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state of the medium and low speed maglev coupled system by the additional deformation of the maglev track.This study investigated the dynamic properties of the coupled vibration system affected by the subgrade settlement.First,a theoretical coupled vibration model of a maglev train-track-ground girder system with uneven subgrade settlement was proposed and verified.Then,the effect mechanism of the coupled system caused by the uneven subgrade settlement was explored.Finally,settlement types and subgrade support voiding were examined.The analysis showed that the uneven subgrade settlement considerably increased the dynamic responses of the levitation control system and maglev vehicle while having a minor influence on those of the track-ground girder.The influence of a single ground girder settling was the strongest,and adjacent sides’settling of two ground girders was the weakest for the vibration of a maglev train.An extremely large uneven settlement exceeding 6 mm led to active levitation control system instability.The subgrade support voiding enlarged the vehicle-induced vibration of the track ground girder.
基金Project(2023YFB4302500)supported by the National Key R&D Program of ChinaProject(52078485)supported by the National Natural Science Foundation of ChinaProjects(2021-Major-16,2021-Special-08)supported by the Science and Technology Research and Development Program Project of China Railway Group Limited。
文摘Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can be well characterized based on various stochastic excitations.A three-dimensional refined spatial random vibration analysis model of high-speed maglev train-bridge coupled system is established in this paper,in which multi-source uncertainty excitation can be considered simultaneously,and the probability density evolution method(PDEM)is adopted to reveal the system-specific uncertainty dynamic characteristic.The motion equation of the maglev vehicle model is composed of multi-rigid bodies with a total 210-degrees of freedom for each vehicle,and a refined electromagnetic force-air gap model is used to account for the interaction and coupling effect between the moving train and track beam bridges,which are directly established by using finite element method.The model is proven to be applicable by comparing with Monte Carlo simulation.By applying the proposed stochastic framework to the high maglev line,the random dynamic responses of maglev vehicles running on the bridges are studied for running safety and stability assessment.Moreover,the effects of track irregularity wavelength range under different amplitude and running speeds on the coupled system are investigated.The results show that the augmentation of train speed will move backward the sensitive wavelength interval,and track irregularity amplitude influences the response remarkably in the sensitive interval.
基金supported by the National Natural Science Foundation of China(12372049)Fundamental Research Funds for the Central Universities(2682023ZTPY036)Research and Development Project of JDD For HTS Maglev Transportation System(JDDKYCF2024002).
文摘High-speed maglev trains(HSMTs)can run at high running speeds due to their unique design.The pressure waves that these trains generate while passing each other are therefore very intense,and can even have safety implications.In order to reduce the transient impact of such waves,the standard k-ε turbulence model is used in this work to assess the effect of railway spacing on the aerodynamic loads,pressure and surrounding flow field of 600 km/h maglev trains passing each other in open air.The sliding mesh technique is used to determine the relative motion between the considered trains.The results show that the surface pressure is approximately linearly correlated with the square of the speed while the amplitude of the pressure wave on the train surface,side force,and rolling moment all have negative exponential relationships with the railway spacing.
基金supported by the National Natural Science Foundation of China(No.U23A20681)the S&T Program of Hebei Province,China(No.23567602H).
文摘Currently,the design of high-temperature superconducting(HTS)maglev trains adopts a U-shaped track operation mode,and the height of the side track significantly impacts the train’s aerodynamic characteristics.In this study,we used computational fluid dynamics(CFD)methods,based on the 3D Reynolds-averaged Navier-Stokes(RANS)method and shear stress transport(SST)k-ωturbulence model,to deeply investigate the effects of the presence or absence of a U-shaped track and different side track heights(800,880,and 960 mm)on the pressure distribution,velocity distribution,and flow field structure of HTS maglev trains at a speed of 400 km/h under crosswinds.The numerical methods were verified using a scaled ICE-2 model wind tunnel test.First,the aerodynamic characteristics of the train under different wind direction angles with and without side tracks were studied.We found that the aerodynamic performance of the train is the most adverse when the wind direction angle is 90°.The presence of a U-shaped track can effectively reduce the lateral force,lift,and yawing moment of the train.The aerodynamic performance of the first suspension bogie at the bottom,which is the worst,will also be effectively improved.Next,the aerodynamic effects of different side track heights on the HTS maglev train were studied.An increase in side track height will reduce the lift and lateral force of the train,while the increase in drag is relatively small.Under the premise of ensuring passengers can conveniently alight,we found that a U-shaped track with a side track height of 960 mm has the best aerodynamic performance.The research findings offer a valuable reference for the engineering application and design of the track structure of HTS maglev train systems.
基金funded by Research and Development Project of JDD For HTS Maglev Transportation System(NO.JDDKYCF2024002)ChinaNational Railway Group Science and Technology Program grant(K2024T005).
文摘High-speed maglev trains represent a key direction for the future development of rail transportation.As operating speeds increase,they face increasingly severe aerodynamic challenges.The streamlined aerodynamic shape of a maglev train is a critical factor influencing its aerodynamic performance,and optimizing its length plays a significant role in improving the overall aerodynamic characteristics of the train.In this study,a numerical simulation model of a high-speed maglev train was established based on computational fluid dynamics(CFD)to investigate the effects of streamline length on the aerodynamic performance of the train operating on an open track.The results show that the length of the streamlined section has a pronounced impact on aerodynamic performance.When the streamline length increases from 8.3 to 14.3 m,the aerodynamic drag of the head and tail cars decreases by 16.2%and 32.1%,respectively,with reductions observed in both frictions drag and pressure drag-the latter showing the most significant decrease in the tail car.Moreover,the extended streamline length effectively suppresses flow separation on the train body surface.The intensity of the positive pressure region on the upper surface of the head car streamlined section is reduced,directly leading to a 38.2%reduction in lift.This research provides a theoretical basis for the parametric design of aerodynamic shapes for high-speed maglev trains and offers guidance and recommendations for drag and lift reduction optimization.
基金Project(24A0006)supported by the Key Project of Scientific Research Fund of Hunan Provincial Department of Education,ChinaProject(2024JJ5430)supported by the Natural Science Foundation of Hunan Province,ChinaProjects(2024JK2045,2023RC3061)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘A high-speed train travelling from the open air into a narrow tunnel will cause the“sonic boom”at tunnel exit.When the maglev train’s speed reaches 600 km/h,the train-tunnel aerodynamic effect is intensified,so a new mitigation method is urgently expected to be explored.This study proposed a novel asymptotic linear method(ALM)for micro pressure wave(MPW)mitigation to achieve a constant gradient of initial c ompression waves(ICWs),via a study with various open ratios on hoods.The properties of ICWs and MPWs under various open ratios of hoods were analyzed.The results show that as the open ratio increases,the MPW amplitude at the tunnel exit initially decreases before rising.At the open ratio of 2.28%,the slope of the ICW curve is linearly coincident with a supposed straight line in the ALM,which further reduces the MPW amplitude by 26.9%at 20 m and 20.0%at 50 m from the exit,as compared to the unvented hood.Therefore,the proposed method effectively mitigates MPW and quickly determines the upper limit of alleviation for the MPW amplitude at a fixed train-tunnel operation condition.All achievements provide a ne w potential measure for the adaptive design of tunnel hoods.
基金Project(11202230)supported by the National Natural Science Foundation of China
文摘A disturbance decoupled fault diagnosis strategy is proposed.This disturbance decoupled fault diagnosis is both robust to disturbances and sensitive to sensor faults of magnetic levitation control system.First,a robust controller based on a novel disturbance observer is devised to improve the disturbance attenuation ability,which greatly enhances the robustness of the system.Second,a fault reconstruction technique with adaptive method is presented,along with a strict verification for guaranteeing the robustness of fault.This fault reconstruction technique provides an accurate sensor fault reconstruction.From the results of simulation and experiments conducted on the CMS-04 maglev train,the integrated strategy is robust to model uncertainties of the system and the fault reconstruction algorithm is able to reconstruct the dynamic uncertain faults.
基金Project(60404003)supported by the National Natural Science Foundation of China
文摘In order to explore the precise dynamic response of the maglev train and verify the validity of proposed controller,a maglev guideway-electromagnet-air spring-cabin coupled model is developed in the first step.Based on the coupled model,the stresses of the modules are analyzed,and it is pointed out that the inherent nonlinearity,the inner coupling,misalignments between the sensors and actuators,and external disturbances are the main issues that should be considered for the maglev engineering.Furthermore,a feedback linearization controller based on the mathematical model of a maglev module is derived,in which the nonlinearity,coupling and misalignments are taken into account.Then,to attenuate the effect of external disturbances,a disturbance observer is proposed and the dynamics of the estimation error is analyzed using the input-to-state stability theory.It shows that the error is negligible under a low-frequency disturbance.However,at the high-frequency range,the error is unacceptable and the disturbances can not be compensated in time,which lead to over designed fluctuations of levitation gap,even a clash between the upper surface of electromagnet and lower surface of guideway.To solve this problem,a novel nonlinear acceleration feedback is put forward to enhancing the attenuation ability of fast varying disturbances.Finally,numerical comparisons show that the proposed controller outperforms the traditional feedback linearization controller and maintains good robustness under disturbances.
基金Project (No. 2005AA505440) supported by the Hi-Tech Researchand Development Program (863) of China
文摘The dynamic interaction between maglev vehicle and three-span continuous guideway is discussed. With the consideration of control system, the dynamic interaction model has been developed. Numerical simulation has been performed to study dynamic characteristics of the guideway. The results show that bending rigidity, vehicle speed, span ratio and primary frequency all have important influences on the dynamic characteristics of the guideway and there is no distinct trend towards resonance vibration when fl/（v/l） equals 1.0. The definite way is to control impact coefficient and acceleration of the guideway. The conclusions can serve the design of high-speed maglev three-span continuous guideway.
基金Project(2021zzts0775) supported by the Independent Exploration and Innovation Project for Graduate Students of Central South University,ChinaProject(2021JJ30053) supported by the Hunan Natural Science Foundation,China。
文摘The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train collision with track.To study the dynamic response of the train and the viaduct when the levitation magnet control loop failure occurs,a high-speed maglev train-viaduct coupling model,which includes a maglev controller fitted by measured force-gap data and considers the actual structure of train and viaduct,is established.Then the accuracy and effectiveness of the established approach are validated by comparing the computed dynamic responses and frequencies with the measurement results.After that,the dynamic responses of maglev train and viaduct are discussed under normal operation and control loop failures,and the most disadvantageous combination of control loop failures is obtained.The results show that when a single control loop fails,it only has a great influence on the failed electromagnet,and the maglev response of adjacent electromagnets has no obvious change and no collision occurs.But there is a risk of rail collisions when the dual control loop fails.
基金supported by the National Natural Science Foundation of China(Nos.52272374 and 52072269)the Shanghai Soft Science Research Project(No.22692194800)the Fundamental Research Funds for the Central Universities,China.
文摘High-speed maglev trains will play an important role in the high-speed transportation system in the near future.However,under the conditions of strong magnetic fields and continuous operation,the actuators of the high-speed maglev train suspension system are prone to lose partial effectiveness,which makes the suspension control problem challenging.In addition,most existing fault-tolerant control(FTC)methods for suspension systems require linearization around the equilibrium points during the controller design or stability analysis.Therefore,from a practical perspective,this study presents a novel nonlinear FTC strategy with adaptive compensation for high-speed maglev train suspension systems.First,a nonlinear dynamic model of the suspension system based on join-structure is established and the actuator failures are described.Then,a nonlinear fault-tolerant suspension control law with an adaptive update law is designed to achieve stable suspension against partial actuator failure.The Lyapunov theory and extended Barbalat lemma are utilized to rigorously prove the closed-loop asymptotic stability even if there is partial actuator failure,without any approximation to the original nonlinear dynamics.Finally,hardware experimental results are included to demonstrate the effectiveness of the proposed approach.
基金Projects(50735007,51005253) supported by the National Natural Science Foundation of ChinaProject(2007AA04Z344) supported by the National High-Tech Research and Development Program of China
文摘A novel maglev transportation system was proposed for large travel range ultra precision motion.The system consists of a levitation subsystem and a propulsion subsystem.During the propulsion subsystem driving the moving platform along the guideway,the levitation subsystem uses six pairs of electromagnets to steadily suspend the moving platform over the guideway.The model of the levitation system,which is a typical nonlinear multi-input multi-output coupling system and has many inner nonlinear coupling characteristics,was deduced.For testifying the model,the levitation mechanism was firstly controlled by proportional-integral-differential(PID) control,and then a lot of input-output data were collected for model parameter identification.The least-square parameter identification method was used.The identification results prove that the model is feasible and suitable for the real system.
基金Projects(60404003,11202230)supported by the National Natural Science Foundation of China
文摘The self-excited vibration problems of maglev vehicle-bridge interaction system were addressed, which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, the coupled model containing the quintessential parts was built, and the mechanism of self-excited vibration was explained in terms of energy transmission from levitation system to bridge. Then, the influences of the parameters of the widely used integral-type proportion and derivation(PD) controller and the delay of signals on the stability of the interaction system were analyzed. The result shows that the integral-type PD control is a nonoptimal approach to solve the self-excited vibration completely. Furthermore, the differential-type PD controller can guarantee the passivity of levitation system at full band. However, the differentiation of levitation gap should be filtered by a low-pass filter due to noise of gap differentiation. The analysis indicates that a well tuned low-pass filter can still keep the coupled system stable.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51875483)the Independently Funded Research Project of State Key Laboratory of Traction Power(Grant Nos.2020TPL-T01 and 2020TPL-T04).
文摘The steel turnout is one of the key components in the medium–low-speed maglev line system.However,the vehicle under active control is prone to vehicle–turnout coupled vibration,and thus,it is necessary to identify the vibration characteristics of this coupled system through field tests.To this end,dynamic performance tests were conducted on a vehicle–turnout coupled system in a medium–low-speed maglev test line.Firstly,the dynamic response data of the coupled system under various operating conditions were obtained.Then,the natural vibration characteristics of the turnout were analysed using the free attenuation method and the finite element method,indicating a good agreement between the simulation results and the measured results;the acceleration response characteristics of the coupled system were analysed in detail,and the ride quality of the vehicle was assessed by Sperling index.Finally,the frequency distribution characteristics of the coupled system were discussed.All these test results could provide references for model validation and optimized design of medium–low-speed maglev transport systems.
基金The National High Technology Research and Development Program(863)of China(No.863CF-G0403-01)
文摘The dynamic interaction between moving vehicles and two-span continuous guideway was discussed. With the consideration of the magnetic levitation system, the maglev vehicle/guideway dynamic interaction model was developed. Numerical simulation was performed to understand dynamic characteristics of the guideway used in practice. The results show that vehicle speed, span length and primary frequency of the guideway have an important influence on the dynamic responses of the guideway and there is no distinct trend towards resonance vibration when fl equals 1.0. The definite way is to control the impact coefficient and acceleration of the guideway. The conclusions can serve the design of high speed maglev guideway.
