Passive Magnetic Bearings Research Articles

Hyperloop New Mode of Transportation

Today conventional mode of transportation is rail, road, water, and air. These modes of transport are relatively slow and expensive or a combination of relatively slow and expensive. Hyper loop is latest mode of transportation which is fast and inexpensive to change the pattern of transportation. Similar to Linux, hyper loop is also open and unique design concept. By bringing this concept to reality, it will help people to travel from one city to another city in a very small time and also at a low cost. The hyper loop capsule would accelerate with the help of linear electric motor and traverse through the tube at a high speed. By using passive magnetic levitation or air bearing, capsule will run above their track. Hyper loop consists of a low-pressure tube with capsules that are travelled at low and high speed throughout the length of the tube. The capsules are supported with the help of cushion of air. To accelerate the capsules the magnetic linear accelerator is fitted at various stations on the hyperloop tube. To enter and exit the passengers the passage may be left either at the end of the tube or branches along the tube length. Let's see how the hyperloop change mode of transportation.

Modeling and analysis of a novel 6-DOF magnetic levitation system with experimental verification

To improve the uniformity of magnetic flux and increase the stroke of the magnetic levitation system, this paper designs a novel 6-DOF magnetic levitation system and proposes an improved novel Halbach array. First, a repulsive passive magnetic bearing is utilized to provide levitation force, leading to a noticeable reduction in levitation power consumption. Then, a magnetic circuit model for the magnetic levitation system is established, and the improved novel Halbach array is optimized based on this model. Next, the stable levitation model and measurement model for the system are established, and the magnetic field distribution and magnetic bearing stiffness are analyzed. Results indicated an increase of 0.1[Formula: see text]T in the maximum magnetic flux density, accompanied by an improvement in the uniformity of magnetic flux. Additionally, there is an enhancement of 10% in magnetic bearing stiffness. Finally, a prototype of the system is constructed, and the stable levitation simulation and experiment of the actuator are conducted with this system. The maximum levitation absolute displacement error obtained by simulation is about 655[Formula: see text]nm, and the experimental results exhibited a maximum levitation absolute displacement error of approximately 750 nm for the system, confirming the effectiveness of the proposed modeling method.

Comparative study of passive magnetic bearing using four ring magnets: a critical review

Researchers on reducing energy losses caused by friction in small-scale wind turbines. This is crucial because a significant amount of energy is wasted due to friction in the main roller bearing. In order to overcome this, the concept of levitation has gained popularity. Levitation is achieved by employing the repelling forces between two opposing poles of a permanent magnet (PM), significantly reducing friction between the turbine stator and rotor. As a result, the overall energy production of the turbine increases. The use of passive permanent magnet bearings has several disadvantages, such as limited load-bearing capacity and rigidity. To address these limitations, we conducted numerical studies on four different configurations in order to enhance load-bearing capacity and stiffness. The results showed that the radial configuration outperformed the axial-type configuration in terms of stiffness and load-bearing capabilities in all four arrangements. Furthermore, it was revealed that radial passive magnetic bearings with adequate air gaps are not only more efficient but also less expensive than employing iron cores at the rear and between ring magnets for small-scale wind turbines.

Nonlinear dynamics of a horizontal rotor with asymmetric magnetic supports

In this paper, a horizontal rotor with passive anisotropic asymmetric magnetic bearings nonlinear model is developed. The model is based on the experimental evidence of an educational demonstrator, a powerful benchmark which highlights features of rotordynamics systems. An experimental setup is developed using laser sensors to track the displacements of the rotor and tachometer to record the rotor angular speed. Several test campaigns are performed with different initial conditions to characterise the educational demonstrator. The first test campaign is oriented to identify the system structural properties, while the second one is focused on the nonlinearity identification. The rotor modelling is divided into three stages with progressive increase in complexity, starting from the overall linear structural behaviour to the nonlinear subharmonic resonance phenomenon. The model is developed with a generalised approach suitable for a wide range of operating conditions and rotor configurations. Progressively, the developed rotor models are compared to highlight their limitations and advantages. Finally, rotor trajectory analysis and time–frequency analysis are used in the numerical-to-experimental comparison.

Axial Stiffness Augmentation by Adding Superconductor Bulks or Limiting Permanent Magnet Rings to a Horizontal Axis Zero-Field Cooled High-Tc Radial Passive Superconducting Bearing

This paper analyzes the viability of different solutions to passively augment the axial stiffness of a horizontal axis radial levitation passive magnetic bearing (PMB) with a previously studied topology. The zero-field cooling (ZFC) of high-temperature superconductor (HTS) bulks promotes higher magnetic impulsion and levitation forces and lower electromagnetic losses than those with field-cooling (FC) but, on the other hand, the guiding stability is much lower than those with FC. Because of stability reasons, FC was adopted in most superconducting maglev systems. The trend of this research group has been to develop a horizontal axis HTS ZFC radial levitation PMB presenting notable levitation forces with reduced electromagnetic losses, defined by a topology that creates guiding stability. Previous work has shown that optimizing the bearing geometry to maximize magnetic guidance forces might not be enough to guarantee the axial stiffness required for many applications. First, the extent to which guidance forces are augmented by increasing the number of HTS bulks in the stator is evaluated. Then, the axial stiffness augmentation by passively adding two limiting permanent magnet (PM) rings is evaluated. The results show that the axial stiffness is highly augmented by adding limiting PM rings with no significant additional investment. This change enables the use of the studied ZFC superconducting PMB in high-precision axial stability applications, such as precision gyroscopes, horizontal axis propellers, and turbines.

5-axes Levitation of a Rotor by Active Magnetic Bearings Employing Direct Output Feedback Control

In recent years the application of active magnetic bearings (AMB), as supporting element as well as vibration controller for rotors, has attracted considerable attention from researchers. In this work an attempt has been made for the complete levitation of a rotor weighing 4 kg, supported on two radial active magnetic bearings and two axial passive magnetic bearings (PMB) resulting in 5-axes levitation. The active bearings working in the mode of attraction make the system inherently unstable. Herein, a direct output feedback control scheme based on proportional and derivative of position signal has been employed to achieve stability. The active magnetic bearings consist of electromagnetic actuators, proximity probes for position measurement, feedback controller and current feedback type power amplifier. The passive bearings consisting of axially magnetized circular permanent magnets work in the mode of repulsion. The design of the electromagnetic actuator has been carried out considering load carrying capacity of the AMB, core loss and the resistive loss in the coil, so that the temperature rise in the core as well as in the coil is within allowable limit. Design of the feedback controller is based on direct output feedback control scheme, which makes the controller design easier and implementation of the controller hardware becomes simpler. The feedback controller parameters have been selected appropriately to generate required stiffness and damping in the AMBs for stable levitation of the rotor. The rotor has been driven up to a speed of 2000 rpm.

Research on Electromagnetic System of Large Capacity Energy Storage Flywheel

A large capacity and high power flywheel energy storage system (FESS) is developed and applied to wind farms, focusing on the high efficiency design of the important electromagnetic components of the FESS, such as motor/generator, radial magnetic bearing (RMB) and axial magnetic bearing (AMB). Firstly, a axial flux permanent magnet synchronous machine (AFPMSM) based on soft magnetic composite material (SMC) is designed. Then, considering the structure of FESS and machine, a permanent magnet biased radial magnetic bearing (PMRMB) and a HALBACH axial passive magnetic bearing (PMB) is proposed which have the advantages of low power consumption and large bearing capacity, then the analyses are carried out according to the load capacity requirements. Finally, the flywheel prototype is fabricated and tested. The experimental results verify the relevant theoretical analysis, and finally can achieve stable and reliable operation.

Temperature properties of passive magnetic bearing

The practical interest in passive magnetic bearings is due to the fact that they are not subject to wear and have insignificant dissipative energy losses. However, when the magnets are heated during operation, a reversible and irreversible decrease in the residual magnetization occurs and, consequently, the force of interaction between them changes. The thermal properties of passive magnetic bearings are adversely affected by the large demagnetizing fields from the coupled magnets. To predict the performance of passive magnetic bearings with regard to external temperature, an assessment of temperature changes in the bearing capacity of bearings with optimally shaped magnets is necessary. The optimum magnets were considered to be those with sizes, whose interaction force, reduced to a single volume of magnetic material, was the maximum. A magnetic system of two cylindrical magnets with equal radii and heights located coaxially or with some radial displacement was considered. The studies were carried out on cylindrical magnets made of SmCo5 alloy, capable of maintaining magnetically hard properties at temperatures up to 250°C. It was confirmed that irreversible changes in the magnetic force for bearings with optimally sized magnets are close to each other. The destabilizing (radial) magnetic force at small radial displacements of one of the magnets also irreversibly decreased. A temperature of 250°C defines the upper limit of the temperature range for the normal operation of magnetic bearings with SmCo5 magnets. It was found that as a result of the action of a demagnetizing field on magnets during heating, they develop a significant inhomogeneity of magnetization over the volume. After demagnetization of the magnets kept at a temperature of 260 °C, the force of their interaction reaches only 85 - 90% of the original, which is associated with microstructural changes in the magnets. Theoretically and experimentally, the numerical values of the temperature coefficients of changes in the bearing capacity and stiffness of bearings are determined.

Comparison of Acoustic Noise and Vibration in Ball-Bearing-Supported Motors and One-Axis Actively Positioned Single-Drive Bearingless Motor With Two Radial Permanent-Magnet Passive Magnetic Bearings

This study experimentally investigates the acoustic noise, vibration, and power consumption in a one-degree-of-freedom actively positioned single-drive bearingless motor, which has radial passive magnetic bearings (RPMBs) and compared to an identical stator part and rotor shaft with radial mechanical ball bearings. For the experiment, three test motors were set up: (a) a bearingless motor with two RPMB, (b) a motor with two ball bearings without an axial preload, and (c) a motor with two ball bearings with an axial preload. Motor (a) under test had one-axis active positioning and the radial movements were supported by RPMB made of cylindrical permanent magnets. Conversely, in motors (b) and (c), the radial and axial movements were supported by ball bearings, and there was no production of active axial force. The experimental results confirmed that the levels of acoustic noise, stator vibration, and input power consumption were significantly lower in motor (a) than those in motors (b) and (c). In the analysis section, dynamic models of the bearingless motor with RPMB and motor with ball bearings were designed and simulated using MATLAB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\backslash$</tex-math></inline-formula> Simulink. The low radial stiffness in RPMB was found to contribute to acoustic noise and vibration reductions. Thus, this article presents an example of a one-degree-of-freedom actively positioned bearingless motor with RPMB that realizes reductions of acoustic noise, stator vibration, and input power consumption.

Experimental Verification of Passive Axial Electrodynamic Suspension in a Bearingless Motor

This article investigates a bearingless motor with passive electrodynamic axial suspension. The axial suspension force is generated by a specific coil configuration called a figure-eight coil. Radial directions and tilting angles are stabilized by passive permanent magnet bearings. Since axial electrodynamic force increases with rotational speed, it must overcome a certain minimum threshold speed to compensate for the rotor weight and the unstable axial force caused by the permanent magnet bearing. Theoretical equations are derived for the braking torque caused by the suspension current and for the steady-state axial equilibrium position at constant rotational speed. A method based on the braking torque equation is proposed for correcting the mismatch between the magnetic center of the bearingless motor and the middle point of the axial clearance. This method sets the middle point between upper and lower touchdown positions in the same place where the motor current is minimum during passive axial suspension. Axial suspension is confirmed in the experiment with a noncontact laser sensor.

A novel magnetically levitated tip/tilt motion platform

This paper presents the mechatronic system design and control of a tip/tilt motion platform with a magnetically levitated mover tailored for dynamic rotational scanning operation. It employs a Lorentz force-based actuation system with five degrees of freedom and four spherical Halbach arrays on a fully passive mover. The system includes highly integrated optical proximity sensors for sensing the mover position in all degrees of freedom and a passive magnetic bearing for restraining the non-actuated degree of freedom. The actuation system enables a mechanical angular range of ±1° in both axes, with first structural modes of the 3D printed mover occurring at 1 kHz. A control system is designed for the five actively controlled degrees of freedom for obtaining a robustly stable and precise motion system. The resulting closed-loop system has a bandwidth of 200 Hz in the rotational and 100 Hz in the translational degrees of freedom and a small positioning uncertainty of 0.02% of the full motion range.

Novel Magnetic Suspension Platform with Three Types of Magnetic Bearings for Mass Transfer

For ultra-precision, large stroke, and high start/stop acceleration, a novel magnetic suspension platform with three types of magnetic bearings is proposed. The structure and working principle of the novel platform are introduced. The passive magnetic bearings are used to compensate for the weight of the actuator. The repulsive force of the passive magnetic bearing model is established and analyzed. The Lorentz force-type magnetic bearings are used to provide driving force and rotational torque in the XY-plane. The driving force model and rotational torque model are established. The electromagnetic suspension bearing is used to provide driving force in the Z-axis and rotational torque along the X-axis and Y-axis. A novel Halbach magnetic array is designed to improve the magnetic flux density in the air gap. The finite element method is used to validate the force model, torque model, and magnetic flux density in the air gap. The results show that the maximum force of the passive magnetic bearing is 79 N, and the rotational torque stiffness is 35 N/A in the XY-plane and 78 N/A along the Z-axis. The driving force stiffness is 91 N/A in the XY-plane and 45 N/A along Z-axis.

Numerical and Experimental Analysis for a Magnetic Levitation System in a Hemocompatibility Assessment Platform.

Development of pediatric left ventricular assist devices (LVADs) has lagged behind that of adult LVADs, primarily due to the size and hemocompatibility constraints of pediatric anatomy. To quantify sources of blood trauma during LVAD development, we proposed a hemocompatibility assessment platform (HAP) that can evaluate the hemocompatibility of individual components of LVADs. To eliminate the hemolysis induced by the HAP itself, we incorporated passive magnetic (PM) bearings to suspend the rotor radially and an active magnetic bearing (AMB) to control the axial position. In this study, we numerically evaluated AMB forces of 2 geometries and validated the model by comparing its predictions with experimental results. The magnetic forces generated by the AMB were evaluated by increasing the rotor-stator gap from 0.1 mm to 0.5 mm with a 0.1 mm increment and by varying the coil current from -2 A to 2 A with a 1 A increment. The average error of the numerical models was 8.8% and 7.0% for the two geometries, respectively. Higher errors were found at smaller (<0.2mm) rotor-stator gaps. For both biasing ring sizes, the AMB exhibits high magnetic stiffness from -1 A to 1 A, though it saturates for currents of -2 A and 2 A. This region of high current stiffness was identified as the optimal control region. In future work, this function will be used to tune a control algorithm to modulate current supplied to the AMB, ultimately stabilizing the rotor axially. Clinical Relevance- This work furthers the development of a hemocompatibility assessment platform that will enhance and accelerate the development of adult and pediatric LVADs.

Dynamics of a Circulatory Support Pump Rotor Adjusted for Radial Forces of a Passive Magnetic Bearing Set

Dynamics of a Circulatory Support Pump Rotor Adjusted for Radial Forces of a Passive Magnetic Bearing Set

A Review of Superconducting Magnetic Bearings and Their Application

Magnetic bearings are being researched for high-speed applications, such as flywheel energy storage devices, to eliminate friction losses. As per Earnshaw's theorem, stable levitation cannot be achieved for a static passive magnetic bearing system. Fully passive stable levitation can be achieved with the help of superconducting magnetic bearings (SMB). This article provides an in-depth review of the modeling, analysis, and development of SMB. The different SMB configurations are highlighted, together with essential methodologies for estimating and improving their performance. The advancements in mathematical models used and the optimization of bearing characteristics are thoroughly discussed. Further, key developments in the application of SMB in flywheel energy storage systems are also reviewed.

Magnetic Static Force Evaluation of Active Magnetic Bearing for a Hemocompatibility Assessment Device: Numerical and Experimental Approach

<h3>Purpose</h3> Development of pediatric left ventricular assist devices (LVADs) has severely lagged behind that of adult LVADs, primarily due to the size and hemocompatibility constraints of pediatric anatomy. To quantify sources of blood trauma within a device, we proposed a hemocompatibility assessment platform (HAP) that can evaluate the hemocompatibility of individual components of LVADs. To eliminate the hemolysis induced by the HAP itself, we incorporated passive magnetic bearings to suspend the rotor radially and an active magnetic bearing (AMB) to control the axial position. In this study, we evaluated AMB forces of 2 geometries and validated the model by comparing its predictions with experimental results. <h3>Methods</h3> The AMB comprises a stator with an electromagnetic coil and a rotor with a permanent magnet (PM) ring (1 mm and 2 mm thickness). The AMB numerical model was established in COMSOL 5.5 using the finite-element method. The magnetic forces generated by the AMB were evaluated by increasing the rotor-stator gap from 0.1 mm to 0.5 mm with a 0.1 mm increment and by varying the coil current from -2 A to 2 A with a 1 A increment. AMB force data was collected experimentally by a precision force transducer on an XYZ-micrometer-driven stage. <h3>Results</h3> The average error of the numerical models was 8.8% and 7.0% for 1 mm and 2 mm thick PM rings, respectively. Higher errors were seen at small (<0.2 mm) rotor-stator gaps. The change in magnetic force due to electrical current, or magnetic stiffness, is greater in the thicker PM ring. For both PM ring sizes, the AMB exhibits high magnetic stiffness from -1 A to 1 A, though it saturates for currents of -2 A and 2 A. This region of high current stiffness was identified as the optimal control region. <h3>Conclusion</h3> AMB force generation was characterized as a function of current and gap, both experimentally and numerically. In future work, this function will be used to tune a control algorithm to modulate current supplied to the AMB, ultimately stabilizing the rotor axially. Additionally, if design specifications such as PM ring thickness or material change, the numerical model can be used to quickly generate a new function for the AMB control algorithm.

A conical passive magnetic bearing with constant stiffness

A nested conical passive magnetic bearing is presented. The bearing consists of a nested conical rotor inside a conical stator, i.e. two coaxial tilted rings of permanent magnets, both with a rectangular cross section. Varying the cone or tilt angle of the rotor and stator we determine the rotor radius that provides the highest force for three different magnetization cases. For this optimal rotor radius, we show that the bearing with the highest volume normalized force also has the highest stiffness, and furthermore often also the highest varying stiffness with axial displacement. Finally, we show that a conical bearings with a tilt angle of 60^circ has an almost constant stiffness and a linearly varying force with axial displacement, making it ideal as a bearing.

Loss Estimation and Thermal Analysis of a Magnetic Levitation Reaction Flywheel with PMB and AMB for Satellite Application

The magnetic levitation reaction flywheel (MLRW) is a novel actuator of spacecraft attitude control because of its significant advantages, including lack of friction and active suppression of vibration. However, in a vacuum environment, the poor heat dissipation conditions make it more sensitive to various losses and rises in temperature. Therefore, increasing temperature is the key issue for components used in space. In this study, the losses of the three kinds of heat-generating areas in the MLRW, namely, the passive magnetic bearing (PMB), the active magnetic bearing (AMB) and brushless DC motor (BLDCM), were analyzed and calculated. Based on the electromagnetic field theory, the loss model of PMB was proposed. Based on the finite element method (FEM) and Bertotti model, the loss power of the AMB and the BLDCM was obtained. The calculated loss values were brought into the FEM to calculate the temperature field distribution of the MLRW system. Then, the key factors affecting the heat dissipation of the flywheel were obtained by combining thermal network analysis with the temperature field distribution. Finally, a prototype was fabricated. The maximum estimated and experimental temperatures were 34.8 °C and 36.8 °C, respectively, both at the BLDCM stator. The maximum error was 5.4%, which validates the calculated model.

An Overview on Electrodynamic Bearings

In electrodynamics, the levitation ensues when there is a relative motion between a stator and a conductor owing to which high eddy currents are induced. The repulsive forces generated by eddy currents are large enough to carry the moving body passively without violating Earnshaw&#x2019;s criterion. Electrodynamic bearings (EDB) use this technique to levitate the rotor in axial or radial degrees of freedom. The present article reviews the literature on electrodynamic passive magnetic bearings to provide an in-depth examination of EDB modeling, analysis, and development. Different types of EDB configurations are highlighted, along with improvements in their technology. In addition, essential advancements in mathematical modeling, finite element techniques, and experiments used to determine the bearing characteristics in terms of accuracy are highlighted. Furthermore, critical developments in rotordynamic analysis in terms of high-speed application have been reviewed. Finally, advances in the application of EDB are discussed.

Dynamic Modeling and Experimental Validations of Passing Through Critical Speeds by High Acceleration in One-Axis Actively Positioned Bearingless Motors

One-axis actively positioned bearingless motors have been studied for industry applications such as pumps and cooling fans. In particular, single-drive bearingless motors have a great advantage of a simple regulation system. Only one three-phase inverter is required for generating torque and active axial force by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis currents. On the other hand, radial and tilting motions of the rotor shaft are passively stabilized by passive magnetic bearings. These passive force and torque are just spring force. Inherently, damping force and torque are not generated. As a result, the rotor vibrations in the radial and tilting directions are considerably high at resonant frequencies. In this article, a valuable strategy is proposed to pass through the critical speed by high angular acceleration with a fan blade. The dynamic modeling of the radial and tilting motions is proposed and simulated to find out the possibility to pass through the critical speed. In the experiment, it is demonstrated that a prototype machine of the one-axis actively positioned bearingless motor can successfully pass through the critical speed without touch-down.