Permanent Magnetic Levitation Research Articles

Halbach structure parameter optimization by Maxwell tensor method for PML in manned hybrid maglev

This paper presents an optimization of the Halbach structure parameters for the permanent magnetic levitation (PML) component in manned hybrid maglev system using Maxwell tensor method. The focus is on enhancing the levitation force and reducing the lateral stiffness, which are important for improving the system’s load capacity and lateral stability. Based on the analysis of the magnetic flux density formula as presented by Halbach (1985), seven structural parameters were reduced to four independent variables. The Maxwell tensor formulation enabled the derivation of analytical expressions for the levitation force and stiffness, leading to identification of parametier conbinations that maximize magneitc properties. Contour plots were constructed to visually demonstrate the impact of parameter variations on magnetic characteristics, including magnetic flux density, levitation force, and lateral stiffness. Ultimately, a series of optimization cases for structural parameters were proposed in accordance with the design requirements of the manned hybrid Maglev system, and these cases were comprehensively evaluated through contour plot analysis. Furthermore, the finite element software FEMM was utilized to model and validate the optimal cases, thereby confirming the effectiveness of the analytical expressions for magnetic properties and the optimization strategy. This research not only provides theoretical support for the design of PML components but also offers new insights into the optimization of magnetic characteristics for hybrid maglev systems.

Vibration Characterization of Permanent Magnet Levitation Vehicle System Based on Permanent Magnetic Track Relationships

Vibration Characterization of Permanent Magnet Levitation Vehicle System Based on Permanent Magnetic Track Relationships

Study on the effect of permanent magnet guideway surface defect on the mechanical properties of multi-surface high-temperature superconducting permanent magnet levitation system with halbach-type guideway

Study on the effect of permanent magnet guideway surface defect on the mechanical properties of multi-surface high-temperature superconducting permanent magnet levitation system with halbach-type guideway

Concise magnetic force model for Halbach-type magnet arrays and its application in permanent magnetic guideway optimization

In maglev trains, a permanent magnetic guideway (PMG) is an indispensable component that influences their levitation stability. PMG generates the magnetic repulsion force in permanent magnetic levitation and provides the pinning force via coupling with bulk superconductors in superconducting magnetic levitation. Typically, they are arranged in a Halbach array to enhance the magnetic force. However, the spatial inhomogeneous feature of magnetic field makes magnetic force acquisition of the double-sided Halbach array extremely difficult. For accurate magnetic force acquisition, this study proposes a concise analytical magnetic force model and elucidates upon its field behavior. Based on this, a finite element method (FEM) model was developed and verified. The experimental results demonstrated that the Halbach-type PMG’s field distribution was effectively reproduced. Subsequently, the accuracy of the was obtained via comparison with the FEM. The calculation results revealed that the increase in the levitation force tends to be saturated as more magnets are used. For a feasible PMG configuration in terms of high levitation force and low lateral force, the structural parameters were optimized using the multi-objective particle swarm optimization (MOSPO) algorithm combined with the identified magnetic force formulas. The results and findings of this study have significant implications for the design optimization of guideway configurations that heavily rely on permanent magnets.

Realization Mechanism and Development of Permanent Magnetic Levitation: A Review

Realization Mechanism and Development of Permanent Magnetic Levitation: A Review

Simulation and experimental research on electromagnetic radiation from suspended permanent magnetic levitation train

With the continuous development and innovation in the field of global magnetic levitation technology, the suspended permanent magnet maglev rail transit system has emerged. At present, no mature relevant technical standard references are available in the world. To study the electromagnetic radiation problem of the permanent magnet maglev train system, we use the finite element method to simulate and analyze the Halbach array track of different combinations of suspension modules, and the six-channel high-precision magnetic field test system is used to test and compare the actual engineering magnetic fields. The results show that the permanent magnet magnetic suspension rail transit system can shield the magnetic energy of the suspension module in the rail beam to reduce the influence of electromagnetic radiation. With the increase in suspension height between the rail and vehicle magnets, the generated magnetic field intensity exhibits a significantly weakening trend. The magnetic field energy of the permanent magnet maglev train is maintained at the centimeter level. Combined with the actual project, the passengers on the train and pedestrians, and residents along the red rail are not affected by the magnetic field intensity of the permanent magnet. This paper provides a theoretical basis for resolving people’s concerns about the electromagnetic radiation of maglev trains, and provides important theoretical support for the development of maglev rail transit.

Research of permanent magnetic levitation system: Analysis, control strategy design, and experiment

Aiming to realize levitation for a novel permanent magnetic levitation system, this paper proposes a double control strategy. The coupled dynamic model with two subsystems was established at first. According to the analysis of stable levitation, four joint control strategies of air gap length and rotation angle were designed. Then, the controller parameters tuning was implemented utilizing the improved PSO (particle swarm optimization) algorithm with non-linear inertia weight. At last, step response simulations and experiments were carried out to compare the performance of the proposed four control strategies. Results demonstrate the validity of PSO using for tuning proportional-integral-derivative (PID) parameters. In addition, the parallel double PD controller and cascade double PD controller both have better dynamic performance but more significant steady-state error. When using PID control for the air gap, the error could be eliminated. Compared with the parallel PID-PD control strategy, the cascade control is competitive in terms of 0.03 s rising time, 4.3 s settling time, and 24% peak overshoot.

Design, Build, and Evaluation of an AC Loss Measurement Rig for High-Speed Superconducting Bearings

Friction and heat generated in conventional bearings impose a limit on maximum design speed in electrical machines. Superconducting bearings offer the potential for low loss, simplified, and passively stable bearings that can overcome the speed limit and operate at high loads. Although such bearings are contactless and seem to be loss free, AC loss mainly caused by magnetic field inhomogeneity gradually slows down the rotating body. This loss, whose mechanism has not been fully explored, is measured through spin-down tests where the rotational speed of the spinning rotor is measured as a function of time. However, there are some challenges in performing a reliable spin-down test. In this paper, we discuss these challenges as well as the engineering of an experimental test rig that enables us to spin-up, release, and recapture the levitated permanent magnet. We also discuss the specifications of the driving mechanism including the self-aligning coupling, which accommodates permanent magnets of different sizes. Initial test results at 6600 rpm are discussed and further technical improvements to the test rig suggested. This rig will be used as a key tool to explore the AC loss mechanism and inform the design of bearings for high-speed superconducting machines.

Magnetic force characteristics enhancement by a novel permanent magnetic levitation (PML) analysis method for hybrid maglev

The hybrid maglev system taking advantage of better carrying capacity in permanent magnetic levitation (PML) and self-stability in superconducting magnetic levitation (SML) has been put forward. PML and SML can share the same magnet rail, which is arranged in Halbach arrays to concentrate the magnetic field on the working region and save magnet materials. Recently, the manned hybrid maglev prototype has been built in Chengdu, China. In this paper, we focus on the PML part, in which the characteristics of the levitation force and the lateral force were studied since they are key factors for load capacity and stability. The research was carried out with both analytic expressions and finite element method. With the relationship between magnetic force and lateral displacement, the recommended maximum lateral displacement was proposed. In addition, considering the end effect of Halbach array, an optimization PML model was designed, which can not only improve the levitation force but also reduce the lateral force. The study offers a reference for the further design and optimization on the PML or the hybrid maglev system involving it.

2-D and 3-D Analytical Calculation of the Magnetic Field and Levitation Force Between Two Halbach Permanent Magnet Arrays

As we know, the analytical calculation of magnetic field and magnetic force has important guiding significance for the optimal design of the size and structure of a magnet. At present, the magnetic field and magnetic force between two permanent magnet (PM) monomers have been described by effective analytical models. However, the magnetic field strength and magnetic force generated by two PM monomers are limited and cannot meet the requirements of a PM levitation system with high magnetic field strength and large levitation force. To this end, this article establishes analytical calculation models of magnetic field and levitation force between two Halbach PM arrays. First, on the basis of Ampere molecular circulation hypothesis, the 2-D analytical model of magnetic field was established based on the surface current method; on the basis of magnetic charge theory, the 3-D analytical model of magnetic field was established based on the magnetic charge method. Second, based on the analytical models of magnetic field, the 2-D and 3-D analytic models of levitation force were derived by virtual work method, respectively. Numerically, the results of two analytical models of magnetic field and two analytical models of levitation force have been compared to verify the accuracy of the models. At the same time, the 2-D and 3-D finite element simulation models of magnetic field and levitation force were established, respectively, and the accuracy of the analytical models were verified again. The results show that the analytical models established in this article is effective and can be used to guide the design and optimization of the magnet composed of two Halbach arrays.

Characteristics of cross stiffness with different physical and geometrical parameters in a high-temperature superconductor levitation system

Cross stiffness is usually defined as a change in the vertical force when the levitating body moves a small lateral displacement in a high-temperature superconductor (HTS) magnetic levitation system. In most of the existing research reports, the improvement of the levitation stiffness is usually focused on the radial (lateral) and axial (vertical) stiffnesses. The cross stiffness should be studied carefully because it can be used to analyze the stability and dynamical properties of the HTS levitations. In this paper, the quantitative properties of the cross stiffness have been investigated by a numerical method. The variations of the cross stiffness at different lateral positions are analyzed for some physical and geometrical parameters, cooling conditions and movement history of a levitated permanent magnet. The reasons for the characteristics of the cross stiffness can be obtained by the vertical force–lateral displacement curves with some minor loops under different parameters and cooling conditions.

Optimization on Size of Halbach Array Permanent Magnets for Magnetic Levitation System for Permanent Magnet Maglev Train

A permanent magnet suspension (PMS) magnetic levitation (Maglev) system consisted of magnetic rail magnets and carriage magnets are investigated for PMS Maglev vehicle. The characteristics of magnetic flux line and magnetic flux density distribution in the suspension gap region are analyzed by using finite element method. The results show that the Halbach Array stack structure generates strong sinusoidal periodic magnetic field in the suspension gap region. The size of Halbach Array permanent magnets stacked structure model was simulated and optimized, and the optimal size factor was obtained. In addition, a levitation force model describing the relationship between magnetic levitation force, permanent magnet size and levitation height was established by molecular current method. The correctness of the levitation force model is evaluated. Finite element simulation and experiment verify the validity of the levitation force model. The results show that the optimized Halbach Array permanent magnets can generate large suspension force and good stability, which is of great significance to improve the utilization rate of permanent magnet materials and save costs, and is conducive to the further development of permanent magnet maglev train. The study is useful for analysis and design optimization of maglev train.

Theoretical model and experiment of the hybrid Maglev vehicle employing high temperature superconducting magnetic levitation and permanent magnetic levitation

The Maglev vehicle, widely considered as a promising transportation type, has distinct characteristics, such as high speed, environmental protection, non-contact operation and distributed load and so on. According to the principle of magnetic levitation technology, it can be divided into four types: Permanent magnet levitation (PML), electromagnetic levitation (EML), electrodynamic levitation (EDL) and superconducting magnetic levitation (SML). Among four Maglev technologies, both the SML with high temperature superconducting (HTS) bulks and the PML with conventional permanent magnets belong to the passive levitation mechanisms, and both of them need permanent magnet track. Due to the strong magnetic properties of permanent magnet materials, the load capacity of the PML can reach 3−6 t/m, but requires additional guidance controls, while the SML with the unique HTS flux-pinning effect can realize self-stable levitation with little active control. Therefore, considering the different levitation characteristics of the SML and the PML above the permanent magnet track, their potential hybrid application can achieve a larger load capacity and a bigger levitation gap at the same time. In the paper, a new SML-PML hybrid Maglev method and the corresponding theoretical models are proposed. Firstly, simulation models of the PML module and the SML module were built by finite element software. The simulation results show the different levitation performances of the two Maglev components. As to the SML module, it vertically behaves as the levitation force within the levitation height of 10−15 mm, and always achieves passive stable along the lateral direction. As to the PML module, the levitation force is relatively bigger at the calculated height of 20−60 mm, but the lateral force increases as the levitation height decrease and increases with the lateral displacement. It implies that the SML guidance capability should cover the PML lateral force at first. Hence, according to the Earnshaw theorem, the load capacity in typical working cases of the hybrid Maglev system was predicted from the simulation data. Considering the further lateral stability and the comprehensive levitation force utilization, the optimal passive stable working range and the lateral reversible range were discussed, which provide the theoretical basis for the design of the hybrid Maglev vehicle prototype. Then, based on the real magnet tracks of the HTS Maglev ring test line, the “Super-Maglev”, in our group, a new manned hybrid Maglev vehicle prototype employing the PML and the SML modules was manufactured for carrying one passenger. In the designed two-layer Maglev frame, the linear bearings composed of the linear guide rails and the sliders are employed for vertical decoupling to guarantee the position difference of the SML and PML modules. At the same time, the lateral coupling keeps rigid since the lateral unbalance is covered by the SML module. This easy and feasible mechanical coupling way enhances the matching complementarity of the lateral recoverability of the two Maglev components. Compared with the “Super-Maglev” performance under the same working condition, the load capacity of the hybrid Maglev vehicle was increased by 17% and the cost input was lower compared with the price of one single on-board HTS bulk. Finally, static loading experiments and dynamic characteristics tests verified that the hybrid Maglev vehicle has the advantages of strong load capacity, simple structure and low cost. This work provides a new technical scheme for future Maglev transportation applications.

Analysis of Quasi-Zero Power Characteristic for a Permanent Magnetic Levitation System with a Variable Flux Path Control Mechanism

This article focuses on the analysis of the quasi-zero power characteristic for a permanent magnetic levitation system with a variable flux path control mechanism. The system mainly consists of a disk permanent magnet, a pair of yokes, and a rotary actuator. The permanent magnet magnetized diametrically is rotated by the actuator, which can achieve the control of the levitation force by changing the flux. Unlike the electromagnetic system, the input to the actuator is used to maintain the rotation angle corresponding to the equilibrium position, not to directly produce a magnetic force. Therefore, the proposed system possesses a lower power consumption. Analysis of mechanism, current model, and different levitation control strategies are presented in this article. With the variable air gap length control and the constant air gap length control, the permanent magnetic levitation system performs well in levitation with quasi-zero power in loading experiments. The constant air gap control is demonstrated to possess higher safety when the levitation mass is changed, which has the potential for magnetic levitation transportation.

Study on bilateral permanent magnetic levitation elevator

A two-side permanent magnetic levitation elevator is designed, and the traction motor is a two-side short primary long secondary permanent magnet linear synchronous motor. The structure of bilateral permanent magnetic levitation elevator is designed, and the operating principle is analyzed. The control system of the permanent magnetic levitation elevator is studied. It is concluded that the amount of winding and permanent magnet is less, the manufacturing cost is lower, and it has good controllability.

A micro-force measurement system based on high-temperature superconducting magnetic levitation

A thrust stand based on high-temperature superconducting (HTS) magnetic levitation technology capable of measuring the micro-thrust in two methods is presented in this paper. The stand mainly consists of a superconducting array, a permanent magnetic levitation platform, refrigerating devices, optical measuring devices, calibration devices and a data acquisition system. HTS magnetic levitation technology was used to provide a platform for micro-force measurements due to its low-friction and high-load-bearing characteristics. The measurements are divided into a direct method and an indirect method according to the principles. The direct method is required to measure the angular displacement of the platform and convert it into thrust with proper calibration. The indirect method, on the other hand, is required to measure the angular velocity to calculate the thrust according to the angular momentum theorem. Experiments indicate that, although the hysteresis loss of the HTS levitation system is unavoidable and may affect the accuracy of the system, it can be reduced effectively by multiple calibrations. The calibration results illustrate excellent repeatability and linearity. A propeller thruster is used to verify the performance of the stand. Four sets of micro-force with different propeller speeds were tested. The relative error between results from both methods at each speed was 11.48%, 18.11%, 22.73% and 21.00%. The direct method is more accurate and has fewer sources of uncertainty. It presents a new approach for measuring micro-thrust.

Dynamic Characteristics of the Manned Hybrid Maglev Vehicle Employing Permanent Magnetic Levitation (PML) and Superconducting Magnetic Levitation (SML)

A manned hybrid maglev vehicle employing permanent magnetic levitation (PML) and superconducting magnetic levitation (SML) was developed. It is mainly composed of a PML part, an SML part, and a maglev frame. The PML part with a repulsive force is designed to support the main load and the SML part with pinning forces is used to guarantee the lateral stability. The maglev frame is designed to support the vehicle body and connect the two maglev components. In previous studies, the sufficient levitation and guidance forces have been verified. In actual operation process, the dynamic characteristics are closely related to the stationarity, the comfortability, and the security of the maglev vehicle. Hence, the research on the dynamic characteristics of the maglev vehicle above the magnetic rails is required to ensure its safe operation. Measurements on vibration acceleration of the hybrid vehicle were conducted under different conditions, including different loads and different pulse excitations. Experimental results show that the dynamic behaviors are quite different between the vertical and lateral directions. In the vertical direction, by using linear bearings, the SML part and PML part are independent with two different natural frequencies and express passive stable characteristic on vibration acceleration curves. While in the lateral direction, the hybrid maglev vehicle has only one natural frequency, which decreases as the load onboard increases due to the decreasing levitation height of the PML part. These results help us to have an insight into the hybrid maglev vehicle employed SML and PML, and prove evidence for the following promotion and optimization.

A Loss Separation Method of a High-Speed Magnetic Levitated PMSM Based on Drag System Experiment Without Torque Meter

Varieties of loss should be optimized to be as little as possible for the stability of the permanent magnet in a high-speed magnetic levitated permanent magnet synchronous motor (HSMLPMSM) rotor and ensure the high efficiency and low temperature of the motor. First, this paper analyzes loss distribution in a motor, whose power and rated speed are 100 kW and 32 000 r/min, by a calculation method. Then, separation of losses of the HSMLPMSM is implemented based on a drag system without torque meter accounting for its particularity of high-power and high-speed level. In all kinds of losses, core loss and coil loss can be separated by a traditional calculation method with related parameters being tested. Besides, windage loss and magnetic bearing loss can be obtained by a deceleration test. Resulting from power balance equations deduced by the relationship of the drag system's power input and output, eddy current loss of the rotor can be separated, compared to its finite-element analysis results and analytical results. In the end, with thermal-electromagnetic coupled analysis, loss separation results are validated via temperature rise experiment indirectly.

A Manned Hybrid Maglev Vehicle Applying Permanent Magnetic Levitation (PML) and Superconducting Magnetic Levitation (SML)

To enhance maglev competitiveness in passive stability and simple structure, a manned hybrid maglev vehicle applying permanent magnetic levitation (PML) and superconducting magnetic levitation (SML) was developed. The vehicle is mainly composed of a maglev frame, a PML part, and an SML part. The maglev frame was employed to connect the PML and SML parts. Based on the magnetic rail of our high temperature superconducting maglev test line of the “Super-Maglev,” the onboard levitation components are bespoke to match the magnetic rails. The PML part is assembled to the maglev frame by vertical linear sliders, and is able to move freely in the vertical direction for appropriate heavy load. The driving method is linear induction motor whose primaries are installed between two rails, interacting with the induction plate mounted on the SML part. The rated load is designed as 375 kg and achieved for one passenger at 15 mm field cooling height. Measurements of its mechanical property were performed under static loads. Results display that the manned hybrid maglev vehicle possesses good advantages of load ability and passive stability at the same time. The work explores a new feasible combination of the PML and the SML for maglev applications.

A robust adaptive flux observer for a class of electromechanical systems

ABSTRACT The problem of designing a flux observer for magnetic field electromechanical systems from noise corrupted measurements of currents and voltages is addressed in this paper. Imposing a constraint on the systems magnetic energy function, which allows us to construct an algebraic relation between fluxes and measured voltages and currents that is independent of the mechanical coordinates, we identify a class of systems for which a globally convergent adaptive observer can be designed. A new adaptive observer design technique that effectively exploits the aforementioned algebraic relation is proposed and successfully applied to the practically important examples of permanent magnet synchronous motors and magnetic levitation systems.