Guidance Force Research Articles

A condition monitoring approach for the detection of defects in the primary suspension of railway vehicles

This work presents the main problems in the primary suspension of metro vehicles and a methodology to detect those using wayside systems. The primary suspension is usually based on rubber elements, which are space saving and have damping properties. However, rubber characteristics change with time, often in a different way in each element. Differences between elements can cause irregular transmission of loads to the wheels, and thus, a reduction or loss of guidance forces. The ageing of rubber can also lead to a general stiffening of the primary suspension, which increases the risk of derailment. This paper presents a wayside system that uses a few strain gauge bridges to detect those problems independently of the vehicle load and speed. Firstly, the system is developed by means of a multibody model. Secondly, a demonstrator is installed in an operating metro exploitation. Finally, the accuracy of the predictions is proven by testing some of the elements in the laboratory.

Pumping sequence effect on levitation and guidance forces of YBCO bulks for evacuated tube transportation

As a part of high temperature superconducting Maglev-evacuated tube transport (HTS Maglev-ETT), ETT technology provides a potential new solution to realize the proposition of higher ground speed transportation. In this system, due to the low pressure caused by tube evacuation, the temperature of liquid nitrogen (LN2) changes and ultimately affects the performance of HTS bulks. Considering the significant necessity to guarantee HTS Maglev-ETT operational stability and safety, this paper focuses on the levitation and guidance performance variations of YBCO bulks caused by the pumping sequence under low pressure. One working condition is to pump the air out during the field cooling stage before levitating the vehicle, defined as “evacuating and then levitating” (E-L case). The other working condition is to pump the air out after the field cooling stage when the vehicle is already levitated, defined as “levitating and then evacuating” (L-E case). Based on the superconducting maglev measurement system (SCML-01) and a self-developed ambient pressure-reducing platform, the working conditions’ effect on levitation and guidance force in the two sequences above is experimentally explored. Simultaneously, the difference between the two sequences is also discussed specifically. For a larger levitation force, the E-L case with high field cooling height (FCH) and low working height (WH) is an efficient condition; The L-E case with low FCH and low WH is suitable for a larger guidance force. In addition, the two specific conditions perform better under lower air pressure. All these conclusions are anticipated to provide a reference for practical startup procedures and future engineering design of HTS Maglev-ETT systems.

Enhancing magnetic levitation and guidance force and weight efficiency of high‐temperature superconducting maglev systems by using sliced bulk YBCO

AbstractWe aimed to enhance the magnetic force efficiency of Maglev systems without increasing total weight. For this aim, we divided YBCO bulks into three slices horizontally to utilize the YBCO‐permanent magnetic guideway (PMG) interaction surface as much as possible. We used whole YBCO above PMGs with different magnetic pole directions (PMG‐A and PMG‐B) in two lying positions of transversal and longitudinal and investigated levitation and guidance force performances. It is determined that levitation and guidance forces by using YBCO in transversal lying mode are bigger compared to the longitudinal mode. For sliced YBCO, the maximum levitation force increased by 69% and 78%, while the guidance force enhancements are determined as 212% and 91%, compared to the whole YBCO above PMG‐A and PMG‐B, respectively. The levitation and guidance force density with respect to the total mass of unit a set of slices YBCO increased by 92% and 106%, respectively, compared to the whole YBCO above PMG‐B in transversal mode. Since the higher levitation force and the lower total weight of the onboard unit are important parameters in point of the energy efficiency in Maglev and other levitation applications, the result of this study supplies useful data for the engineers and industrial partners.

Study on Electromagnetic Relationship and Dynamic Characteristics of Superconducting Electrodynamic Maglev Train on Curved Track

This study considers an electrodynamic maglev train of the MLX01 type as the research object. Equivalent circuit models of levitation/guidance were established, and forces in different directions were solved using the energy method A field-circuit-motion coupling numerical model of a single bogie and a ground coil was established. Based on the field-circuit-motion coupling model, the various electromagnetic relationship of maglev train on curved track was analyzed. The law of the electromagnetic spring coefficient and the internal mechanism under different electromagnetic parameters was explored. Considering the coupling characteristics between the electromagnetic forces, the characteristics of the levitation force and guidance force under different standard air gaps were analyzed, and a numerical fitting analysis was performed. On this basis, the laws of levitation force and guidance force with levitation displacement and guidance displacement, as well as the characteristics of drag force with operation speed under different standard air gaps, were studied. Meanwhile, the characteristics of the guidance-drag ratio and levitation-drag ratio were analyzed. A dynamic model with 20 degrees of freedom was established based on the analysis of the geometric model of the maglev train. Taking the track irregularity as the external excitation source of the bogie, the dynamic characteristics of the bogie and vehicle body under different standard air gaps and speeds were analyzed. The effects of different suspension damping and stiffness coefficients on the vibration characteristics of a vehicle body were studied. This provides important theoretical and data support for design and dynamic analysis of superconducting electrodynamic maglev trains.

Magnetic Force Performance of Hybrid Multisurface HTS Maglev System With Auxiliary Onboard PMs

The vertical levitation force, guidance force, and magnetic stiffness values, and thus the loading capacity and movement stability of high-temperature superconducting (HTS) Maglev systems, are aimed to be increased in this study by using auxiliary permanent magnets (PMs) in the onboard unit together with the multisurface HTS-permanent magnetic guideway (PMG) arrangement (hybrid multisurface arrangement). First, the magnetic levitation force, guidance force, and stiffness performances of the hybrid multisurface arrangement were investigated at different field cooling heights (FCH). Then, to compensate for the negation of instability that results from the higher repulsive force between the onboard PMs and the PMG and to obtain an optimal magnetic field medium, we have changed the vertical position of the auxiliary onboard PMs (Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PM</sub> ) to Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PM</sub> = 0, 2, and 4 mm, at the cost of a bit of adecrement in the vertical levitation force. The bigger levitation force, together with the guidance force values for FCH = 25 mm and Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PM</sub> = 0 mm, indicates that the hybrid multisurface HTS–PMG arrangements are beneficial to increasing the practical applicability of Maglev systems.

Priming locomotor training with transspinal stimulation in people with spinal cord injury: study protocol of a randomized clinical trial

BackgroundThe seemingly simple tasks of standing and walking require continuous integration of complex spinal reflex circuits between descending motor commands and ascending sensory inputs. Spinal cord injury greatly impairs standing and walking ability, but both improve with locomotor training. However, even after multiple locomotor training sessions, abnormal muscle activity and coordination persist. Thus, locomotor training alone cannot fully optimize the neuronal plasticity required to strengthen the synapses connecting the brain, spinal cord, and local circuits and potentiate neuronal activity based on need. Transcutaneous spinal cord (transspinal) stimulation alters motoneuron excitability over multiple segments by bringing motoneurons closer to threshold, a prerequisite for effectively promoting spinal locomotor network neuromodulation and strengthening neural connectivity of the injured human spinal cord. Importantly, whether concurrent treatment with transspinal stimulation and locomotor training maximizes motor recovery after spinal cord injury is unknown.MethodsForty-five individuals with chronic spinal cord injury are receiving 40 sessions of robotic gait training primed with 30 Hz transspinal stimulation at the Thoracic 10 vertebral level. Participants are randomized to receive 30 min of active or sham transspinal stimulation during standing or active transspinal stimulation while supine followed by 30 min of robotic gait training. Over the course of locomotor training, the body weight support, treadmill speed, and leg guidance force are adjusted as needed for each participant based on absence of knee buckling during the stance phase and toe dragging during the swing phase. At baseline and after completion of all therapeutic sessions, neurophysiological recordings registering corticospinal and spinal neural excitability changes along with clinical assessment measures of standing and walking, and autonomic function via questionnaires regarding bowel, bladder, and sexual function are taken.DiscussionThe results of this mechanistic randomized clinical trial will demonstrate that tonic transspinal stimulation strengthens corticomotoneuronal connectivity and dynamic neuromodulation through posture-dependent corticospinal and spinal neuroplasticity. We anticipate that this mechanistic clinical trial will greatly impact clinical practice because, in real-world clinical settings, noninvasive transspinal stimulation can be more easily and widely implemented than invasive epidural stimulation. Additionally, by applying multiple interventions to accelerate motor recovery, we are employing a treatment regimen that reflects a true clinical approach.Trial registrationClinicalTrials.gov NCT04807764. Registered on March 19, 2021.

From depression to wellbeing: How to protect the mental health of isolated people under the "dynamic clearance" of patients with COVID-19.

In 2020, COVID-19 became a global pandemic. The Chinese government's quarantine measures tend to cause anxiety, tension and depression among the quarantined people. This article constructs a differential game model of self-regulation, government guidance and social forces guidance. Then, the psychological benefits of the masses and the benefits of the whole society under the three modes are obtained, and the applicable conditions of various connection modes are compared. The research results show that: compared with social power channeling, the public under the government channeling mode can obtain more psychological benefits. However, with the increase of guidance, the difference between the psychological benefits of different ways of guidance first decreases and then tends to be stable. Under the guidance mode, the social benefits of the government decrease, and the more guidance, the smaller the social benefits. Therefore, both the government and social forces should make use of limited resources to conduct appropriate psychological counseling for the isolated population.

&lt;b&gt;Evaluation of Vibration Resistance of Levitation and Guidance Ground Coils by Electromagnetic Excitation Tests Using a Superconducting Magnet&lt;/b&gt;

During superconducting Maglev vehicles running, ground coils vibrate due to the reaction force of levitation force and guidance force. In electromagnetic excitation tests, a ground coil is vibrated under the strong magnetic field of a superconducting magnet. This paper describes an examination of test conditions based on numerical analysis, a processing method for energizing only the unit coil to be evaluated, and the electromagnetic excitation test results of the levitation and guidance coil. The vibration resistance of levitation and guidance ground coils were evaluated by electromagnetic excitation tests.

Research on Levitation and Guidance Characteristics of DSSC HTS-PMG Maglev System Integrating Upper Suspension and Down Hanging

The maglev train has great application potential in the field of high-speed transportation, which is based on high-temperature superconductor-permanent magnet guideway (HTS-PMG) maglev system. In order to break through the bottleneck of insufficient performance of the conventional upper HTS-PMG maglev system, it is of great value to explore a higher performance maglev configuration. In this article, the mechanical characteristics of the upper suspension and the down hanging type are studied through numerical simulation and experimental methods, and a new type of double-sided strongly coupled (DSSC) HTS-PMG maglev configuration is proposed based on the PMG concentrating magnetic field through the iron plate in the middle. The results show that the upper suspension and down hanging type complement each other in the characteristics of levitation force and guidance force, that is, when the levitation force (guidance force) of the upper suspension type increases (weakens) with the increase of cooling height, the hanging force (guidance force) of the down hanging type exhibits the opposite changing behavior, and vice versa. For the coupled system, within a certain levitation gap range, its levitation force and guidance force can be approximated as the linear superposition of the upper suspension and the down hanging, and the coupling degree of the system increases with the decrease of the levitation gap. Through optimization, the levitation force and guidance force are significantly improved. When the upper cooling height (UCH) and the down cooling height (DCH) are fixed at 20 and 5 mm, at the upper working height (UWH) of 15, 10, and 5 mm, the levitation force is respectively increased by 267.7, 105.7, and 46.8% compared with the upper suspension type. When the UCH is 20, 25, and 30 mm, the guidance force is, respectively, increased by 181.4, 201.2, and 188.2% at the lateral displacement ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LD</i> ) of 20 mm compared with the upper suspension type. The above research results provide a design reference for the development of higher-performance HTS-PMG maglev train.

Retracted: Characteristics Analysis of the Combined Levitation and Guidance EDS Maglev Train in the Rolling Motion

The influence of the rolling motion and the lateral motion caused by the rolling motion on electromagnetic performance of combined levitation and guidance EDS maglev train is calculated and analyzed. First, the coupling mechanism between the rolling motion and the lateral motion caused by the rolling motion is discussed in detail. Then, the mathematical model and analytic method are presented, and the formulas of levitation force, guidance force, and rolling torque are derived. By decoupling the lateral motion and the rolling motion, the coupling stiffness and equivalent rolling stiffness are obtained. Third, the variation trends of levitation force, guidance force, and rolling torque with lateral offset after rolling motion occurs are discussed, the redistributions of guidance force and rolling torque with levitation height are predicted, and the coupling stiffness and equivalent rolling stiffness at different speeds are compared. Meanwhile, the three-dimensional finite-element model is established to verify the correctness of the analytical model. Finally, the analytical results are experimentally verified.

The Validation of the Improvement Effect of Maneuverability on Power Assist System using Guidance Force of Toward the Planned Trajectory Considering Approachability

The Validation of the Improvement Effect of Maneuverability on Power Assist System using Guidance Force of Toward the Planned Trajectory Considering Approachability

Pumping Timing Effect on Levitation and Guidance Force Of Ybco Bulks for Evacuated Tube Transportation

Pumping Timing Effect on Levitation and Guidance Force Of Ybco Bulks for Evacuated Tube Transportation

Design and Analysis of Guidance Function of Permanent Magnet Electrodynamic Suspension

Inspired by the guidance principle in the electromagnetic levitation system, a new permanent magnet electrodynamic suspension (PM EDS) structure with ferromagnetic guidance track is proposed and analyzed in this paper. Considering the lack of effective guidance ability for the PM EDS system, we adopted the ferromagnetic guidance track as being mounted under the conductor plate. The guidance principle is studied and the implementation of the guidance function is also introduced, and the finite element method (FEM) is employed and its accuracy is confirmed via the PM EDS high-speed rotating experimental platform fabricated in our laboratory. The influence of longitudinal speed on the guidance force is taken into account, which shows that the guidance performance is enhanced more obviously at low speeds. Moreover, the influence of the guidance track parameters on the guidance performance is also analyzed, including the geometric parameters, section shape, installation position and material. The equivalent small-scale PM EDS system experimental prototype is carried out to validate the effectiveness of the ferromagnetic guidance. The proposed ferromagnetic guidance structure is demonstrated to improve the guidance performance of the PM EDS system effectively, which will offer a technical reference for the practical engineering application of the PM EDS system.

The Formation of a Polycentric City in Transitional China in a Three-Level Analysis Framework: The Case Study of Hangzhou

Given cities’ different development backgrounds, the spatial evolution of each city has a path-dependent development track. Understanding the characteristics of urban spatial structure evolution in contemporary China is essential for sustainable urban development. By establishing a theoretical framework comprising a macro-background, planning tool, and resource allocation, this paper takes Hangzhou as an example to analyze the evolutionary process of the polycentric spatial structure and reveal the formation characteristics of its polycentric urban spatial form. The results show that (1) its institutional background and planning tools are the driving forces behind the formation of the polycentric structure in Hangzhou, i.e., the evolution of the polycentric structure mainly relies on planning guidance and government forces rather than being market-driven. (2) Under the government-led mode of polycentric formation, urban elements, such as education, medical care, transportation, and green space, are still concentrated in the main urban center, while subcenters lack the necessary public facilities and are underdeveloped. (3) The spatial distribution of the population and nightlights also shows the trend of diminishing concentric circles with the main center at the core. Therefore, it is impossible to implement polycentric cities by decentralizing the population and industries alone. The comprehensive consideration of capital investment, production services, and the supply of life service facilities is also required. This empirical study can complement empirical evidence in order to verify the validity of polycentrism as a potential solution that can alleviate the sprawl of central urban areas.

Curve Negotiation Characteristics of the Side-Suspended High-Temperature Superconducting Maglev System

Thanks to its superb curve negotiation characteristics, the side-suspended high-temperature superconducting (SS-HTS) maglev system boasts a great potential for high-speed transportation. The SS-HTS maglev system, however, significantly differs in suspension features from the conventional maglev system because of its unique side-suspended structure. To improve suspension performance, the field-cooling technique of superconducting bulks in the SS-HTS system was investigated through a number of experiments. To fit the experimental data, the authors proposed the mathematical models of the levitation and guidance forces as well as the optimal field-cooling position. Furthermore, a dynamic model was developed for the SS-HTS maglev vehicle operating on a curve line, and the curve negotiation characteristics were simulated for the maglev vehicle. Finally, the stability of the curve negotiation for the SS-HTS system was assessed using the Sperling index. The results show that the SS-HTS maglev vehicle can pass over bends at a certain speed. The authors also recommended the suspension parameters the maglev vehicle.

Dynamic guidance performance of HTS bulk under varying external magnetic field

With the unique flux pinning characteristics, high temperature superconducting (HTS) bulk can stably levitate above the permanent magnet guideway (PMG). Moreover, owing to its advantages of environmental protection, frictionless and pollution-free, the HTS maglev has shown significant potential in high-speed rail transit. At present, HTS maglev technology is at a critical moment from laboratory research to engineering application. Among the numerous parameters related to its engineering application, the curve negotiation ability determined by the guidance performance of the HTS bulk superconductors is crucial to the safety and stability of its operation. Thus, in this paper, we experimentally investigated the dynamic guidance force of the HTS bulks under different operational conditions including different rotational speeds, maximum lateral displacement (MLD), field cooling height (FCH), and working height (WH) based on a customized HTS maglev dynamic measurement system (SCML-03). In addition, the dynamic guidance force of HTS bulk under long-time operation was studied. It is concluded that FCH, WH, and MLD are intimately associated with the dynamic guidance performance of the HTS bulk, while the rotational speed of the circular PMG has little influence on it. Namely, to improve the dynamic guidance performance of the HTS bulk, reducing the FCH and increasing the WH properly can be regarded as an effective method. Eventually, this research also verifies the long-term lateral stability of the HTS maglev system during dynamic operation.

Brain and spinal cord paired stimulation coupled with locomotor training facilitates motor output in human spinal cord injury.

Combined interventions for neuromodulation leading to neurorecovery have gained great attention by researchers to resemble clinical rehabilitation approaches. In this randomized clinical trial, we established changes in the net output of motoneurons innervating multiple leg muscles during stepping when transcranial magnetic stimulation (TMS) of the primary motor cortex was paired with transcutaneous spinal (transspinal) stimulation over the thoracolumbar region during locomotor training. TMS was delivered before (TMS-transspinal) or after (transspinal-TMS) transspinal stimulation during the stance phase of the less impaired leg. Ten individuals with chronic incomplete or complete SCI received at least 20 sessions of training. Each session consisted of 240 paired stimuli delivered over 10-min blocks for 1 h during robotic assisted step training on a motorized treadmill. Body weight support, leg guidance force and treadmill speed were adjusted based on each subject's ability to step without knee buckling or toe dragging. Most transspinal evoked potentials (TEPs) recorded before and after each intervention from ankle and knee muscles during assisted stepping were modulated in a phase-dependent pattern. Transspinal-TMS and locomotor training affected motor neuron output of knee and ankle muscles with ankle TEPs to be modulated in a phase-dependent manner. TMS-transspinal and locomotor training increased motor neuron output for knee but not for ankle muscles. Our results support that targeted brain and spinal cord stimulation alters responsiveness of neurons over multiple spinal segments in people with chronic SCI. Noninvasive stimulation of the brain and spinal cord along with locomotor training is a novel neuromodulation method that can become a promising modality for rehabilitation in humans after SCI.

Analytical Calculation and Experimental Verification of Superconducting Electrodynamic Suspension System Using Null-Flux Ground Coils

Superconducting (SC) electrodynamic suspension (EDS) has a wide application prospect due to the advantages of no active control, self-stability and large gap, especially in the ultra-high speed maglev, rocket launching, Electromagnetic Aircraft Launching System and other high speed fields. SC coils and null-flux Ground Coils which are the primary and secondary windings respectively are applied in a typical EDS system, in that the null-flux ground coils provide levitation and guidance force. The calculation of electromagnetic forces that has been extensively studied by scholars all over the world is the basis of the design and optimization of the system. However, due to the limitation of complex structure, the calculation formula is often so complicated that the results have to be obtained by means of finite element method and numerical simulation. This paper aims to derive an analytical calculation of electromagnetic forces for SC EDS system based on some reasonable assumptions. The experimental data of MLX01 on the Japanese Yamanashi testline was used to verify the calculation model of this paper. In order to get a further validation, a small EDS rotary table was built based on null-flux ground coils and permanent magnets. The results of the experiment confirms the effectiveness of the proposed analytical calculation model.

Levitation Characteristics of High-Temperature Superconducting Bulks of Different Orientations and Arrays

High-temperature superconducting (HTS) maglev has good application prospects due to its passive stability. There are a lot of researches on the levitation characteristics of a single HTS bulk in the applied magnetic field. However, the bulks are usually arranged in an array in practical applications. In addition, experiments proved that the levitation force and guidance force of the system with multiple bulks are not equal to their linear superposition. Therefore, it is interesting to further study the law of interaction between bulks quantitatively. In this paper, firstly, the method of how the bulk's inhomogeneities are described in the electromagnetic model is introduced. Secondly, the levitation and guidance force of bulks of different orientations and combinations are calculated using a three-dimensional (3D) simulation model considering the inhomogeneities. A Qualitative Rapid Analysis Method (QRAM) to predict the effect of the combinations is proposed. The accuracy of the prediction method has been verified for different working conditions. Finally, the effect of the shape of bulks on the levitation characteristics is investigated. The result shows a weak “aggregation advantage”. This paper provides some reference for the design and prediction of the levitation and guidance performance of the HTS maglev system with a combination of multiple HTS bulks.

Two-parameter bifurcations analysis of a delayed high-temperature superconducting maglev model with guidance force.

A modified high-temperature superconducting maglev model is studied in this paper, mainly considering the influence of time delay on the dynamic properties of the system. For the original model without time delay, there are periodic equilibrium points. We investigate its stability and Hopf bifurcation and study the bifurcation properties by using the center manifold theorem and the normal form theory. For the delayed model, we mainly study the co-dimension two bifurcations (Bautin and Hopf-Hopf bifurcations) of the system. Specifically, we prove the existence of Bautin bifurcation and calculate the normal form of Hopf-Hopf bifurcation through the bifurcation theory of functional differential equations. Finally, we numerically simulate the abundant dynamic phenomena of the system. The two-parameter bifurcation diagram in the delayed model is given directly. Based on this, some nontrivial phenomena of the system, such as periodic coexistence and multistability, are well presented. Compared with the original ordinary differential equation system, the introduction of time delay makes the system appear chaotic behavior, and with the increase in delay, the variation law between displacement and velocity becomes more complex, which provides further insights into the dynamics of the high-temperature superconducting maglev model.