Axial Permanent Magnet Research Articles

Design and Experimental Test of a self-sealing component for reciprocal motion of MR fluid based device

This research presents a novel approach to sealing components by proposing an optimized design and experimental evaluation of a magneto-rheological fluid (MRF) sealing component for reciprocal motion, with a specific focus on MR dampers. The traditional O-ring is replaced by a continuously activated MRF seal using an axial permanent magnet. The paper begins with a comprehensive overview of previous research on the application of MR fluid in sealing and presents a proposed configuration for a MRF based seal (MRF seal shortly) for reciprocal motion. Optimal design and modeling of the MRF seal are performed through finite element analysis, and a prototype is manufactured for experimental testing. The performance characteristics of the MRF seal are thoroughly investigated based on both experimental and simulated results. The study evaluates the effectiveness of the MRF seal in terms of its sealing capability and durability. The findings of this research have potential applications across various industries that require sealing components for reciprocating motion, including automotive, aerospace, and manufacturing. By embracing this innovation, these industries can achieve significant energy savings by minimizing friction and enhancing overall operational efficiency.

Design and empirical evaluation of a magneto-rheological fluid-based seal with rectangular and trapezoidal pole head

The focus of this study is on the design and experimental validation of MRF self-sealing (also known as MRF seal) utilizing permanent magnets. The MRF seal has been built to readily replace traditional seal (lip-seal) for rotation shaft sealing. Following a review of studies on MRF seals, two configurations of MRF seal featuring an axial permanent magnet and two distinct pole head forms, rectangular and trapezoidal, are presented. The two MRF seals are then subjected to a magnetic analysis using the finite element method (ANSYS APDL). The Bingham plastic model of MRF and the assumption of linear velocity profile of MRF in the sealing gap are employed to construct mathematical models of crucial seal characteristics such as maximum static working pressure and frictional torque. The seals are optimized employing the optimization toolbox integrated in the ANSYS APDL to obtain the optimal geometric dimensions of the MRF seals. Finally, prototypes of the two MRF seals are fabricated and testing work is conducted to validate and compare them with the simulated results.

A Modified Vector Jiles-Atherton Hysteresis Model for the Design of Hysteresis Devices

In this paper, a modified vector Jiles-Atherton (JA) model is proposed to simulate permanent magnet materials. Two correction coefficients related to the maximum magnetic flux density are introduced to improve the accuracy of the vector JA model in the simulation of the minor hysteresis loops. Hook-Jeeves direct search algorithm is used to identify the correction coefficients in the modified vector JA model. The hysteresis curves of an isotropic FeCrCo are measured, which show that the simulation accuracy of the modified approach is greatly improved. A single-side axial permanent magnet hysteresis damper is modeled by the finite element method (FEM) and is designed to verify the reliability of the modified model. The results of the experiment and simulation agree well, which means that the modified vector JA model has better accuracy than the basic approach in the analysis and design of hysteresis devices.

Design and characteristic analysis of dual-excitation and dual-modulation axial permanent magnetic gear

In order to solve the problems of serious axial and tangential leakage and low torque density in the magnetic circuit axial permanent magnet gear (APMG), an external regulating ring is introduced on the basis of APMG to form a dual-excitation and modulation APMG structure, namely DEM-APMG. The low speed rotor of DEM-APMG is clamped between the inner and outer magnetizing rings to generate dual-excitation field (i.e. dual excitation). At the same time, the inner and outer magnetizing rings modulate the low speed rotor dual-directionally modulation (i.e. dual modulation). The axial and tangential leakage flux of APMG can be converted into useful harmonics to increase the output torque and torque density on the basis of APMG. In this study, mathematical analysis is used to describe the air gap magnetic density and electromagnetic torque model of a DEM-APMG, which essentially describes the root cause of the increase in torque density. Using 3D finite element static and dynamic simulations, the transmission characteristics of the APMG and DEM-APMG are compared and analyzed. Results show that the maximum static torque of the DEM-APMG high-speed and low-speed rotors with the same outer diameter increase by 22.7% and 23.8%, respectively, compared with APMG, 26% and 29%, respectively, in steady-state operation, and the torque density increases by 24%. The influence of the primary structural parameters on the transmission characteristics is also investigated using the control variable method. Results show that the duty cycle of the magnet adjusting block, the axial length of the high-speed permanent magnet and the low-speed permanent magnet have the strongest effect on the torque density of the DEM-APMG. When the axial length of the high-speed permanent magnet and low-speed permanent magnet is 8mm, and the duty cycle is 0.4, the torque density can reach the optimal value of 156kNm/m3.

Design optimization of APMEC using chaos multi-objective particle swarm optimization algorithm

In order to meet the requirement that the permanent magnet eddy current coupler has larger output torque and smaller eddy current loss in actual operation, the structural parameters and operation performance of axial permanent magnet eddy current coupler (APMEC) are optimized by chaos multi-objective particle swarm optimization algorithm (CMOPSO) in this paper. The model of APMEC is established by three-dimensional finite element simulation. The central composite design (CCD) method is used to select the appropriate test point, and the response value is obtained by ANSYS finite element analysis software simulation. The second-order response surface regression model of APMEC was established according to the response value. The CMOPSO is used to optimize APMEC, and the optimal combination of structural parameters is obtained. By comparing the eddy current density distribution of APMEC before and after optimization with the finite element simulation experiment, it is verified that the optimization method is feasible to optimize the structural parameters of APMEC. The optimization results show that the efficiency of the permanent magnet eddy current coupler is more than 94%, and the energy consumption is reduced to 83% of the original energy consumption.

Analysis on reducing eddy current loss of axial motor by permanent magnet segmentation

This paper gives the causes of eddy current loss of permanent magnet in axial permanent magnet motor, and puts forward the method of reducing eddy current loss by circumferential and radial combined sectional insulation of permanent magnet. The principle analysis and analytical formula derivation of permanent magnet sectional insulation to reduce eddy current loss are carried out. Finally, Maxwell three-dimensional finite element simulation is used to verify that the circumferential and radial combined sectional insulation of permanent magnet can greatly and quickly reduce the eddy current loss of permanent magnet of axial motor.

Thermal Analysis of Axial Permanent Magnet Flywheel Machine Based on Equivalent Thermal Network Method

The axial permanent magnet magnetic bearingless flywheel machine (APM-BFM) mostly operates under the state of high-power fast charging and discharging. Due to the characteristics of high-power density per unit volume, the centralized windings have small heat dissipation area and high thermal loads, the temperature rise on APM-BFM is a very important issue. Thermal analysis is thus of particular importance particularly for modern machines since the temperature rise and distribution are significant during their running under higher electromagnetic loads commonly used nowadays. In this paper, the equivalent thermal network method is proposed to evaluate the temperature rise of the APM-BFM. The equivalent thermal network model is established based on the basic theorem of heat transfer. The thermal resistance and heat source in the machine are analyzed and calculated, and the thermal balance equation is established. The temperature rise of each node is solved, and finally the validity of the model is verified by finite element magnetic-thermal coupling simulation.

Dynamic Equivalent Magnetic Network Analysis of an Axial PM Bearingless Flywheel Machine

A nonlinear dynamic equivalent magnetic network model for an axial permanent magnet bearingless flywheel machine (APM-BFM) is proposed in this paper. The model focuses on analyzing the magnetic field changes at the air gap of the machine. According to the relative position of the stator and rotor, the magnetic circuit between the rotor and the suspension pole (the torque pole) is divided into 7 stages (8 stages), and dynamic equivalent magnetic network models are established. The local saturation coefficient is introduced to characterize the local magnetic saturation phenomenon of the rotor yoke during the rotation of the rotor. Using the proposed model and based on the obtained winding flux, the opposing electromotive forces and inductances of the suspension and torque windings of the APM-BFM are all analyzed and calculated. Finally, the validity of the proposed model is verified by finite element analysis (FEA).

Thermal Analysis Strategy for Axial Permanent Magnet Coupling Combining FEM with Lumped-Parameter Thermal Network

Thermal analysis is exceptionally important for operation safety of axial permanent magnet couplings (APMCs). Combining a finite element method (FEM) with a lumped-parameter thermal network (LPTN) is an effective yet simple thermal analysis strategy for an APMC that is developed in this paper. Also, some assumptions and key considerations are firstly given before analysis. The loss, as well as the magnetic field distribution of the conductor sheet (CS) can be accurately calculated through FEM. Then, the loss treated as source node loss is introduced into the LPTN model to obtain the temperature results of APMCs, where adjusting conductivity of the CS is a necessary and significant link to complete an iterative calculation process. Compared with experiment results, this thermal analysis strategy has good consistency. In addition, a limiting and safe slip speed can be determined based on the demagnetization temperature permanent magnet (PM).

Influence of Rotor-Pole Number on Electromagnetic Performance of Novel Double-Rotor Hybrid Excited Axial Switched-Flux Permanent-Magnet Machines for EV/HEV Applications

In this paper, a novel 6-stator-pole double-rotor hybrid excited axial switched-flux permanent magnet (DR-HEASFPM) machine is proposed for electrical vehicles. Based on 3-D finite element analysis, the influence of 10-, 11-, 13-, and 14-rotor-pole on the electromagnetic performance of DR-HEASFPM machine, including the magnetic field distribution, flux-linkage, back-EMF, flux regulation principles and capability, is comparatively investigated. The results show that the 6/10-, Ll-pole DR-HEASFPM machines exhibit higher PM flux-linkage and back-EMF. Moreover, the back-EMF of 6/11-pole machine is more sinusoidal and the flux-regulation capability is more excellent, which is suitable for wide speed-regulation application.

Design and analysis of a novel permanent magnet synchronous machine with axial assisted magnets

The paper proposes a novel permanent magnet synchronous machine (NPMSM) with one radial permanent magnet synchronous machine (RPMSM) in the center and two axial permanent magnet synchronous machines (APMSMs) on both sides. The two APMSMs take advantage of the stator end winding spaces of the RPMSM and provide additional output power without increasing the whole machine volume. The emphasis of this study is on the unique rotor structure design and its merits for producing additional output power. The 3D finite element method (FEM), coupling with the equivalent circuit method is used in the study for designing the NPMSM. And the NPMSM prototype test results match well with the calculated results.

Improvement of Tubular Permanent Magnet Machine Performance Using Dual-Segment Halbach Array

In this paper, a modification of the dual-segment permanent magnet (PM) Halbach array is investigated to improve the performance of the tubular linear machine, in terms of flux density and output power. Instead of a classical Halbach array with only radial and axial PMs, the proposed model involves the insertion of mig-magnets, which have a magnetized angle shifted from the reference magnetized angles of axial and radial PMs. This structure leads to the elimination of flux leakage and the concentration of flux linkage in middle of the coil; therefore, the output power is increased by 13.2%.

Hybrid multilevel modelling of axial permanent magnet drivers

A five-layered analytical model of axial permanent magnet drivers that considers the permanent magnet back iron, the permanent magnet array, the air gap, the copper, and the copper back iron is presented. The multilayer boundary value problem is solved and a simple torque expression represented by the Fourier series is derived. A permanent magnet array optimisation method is proposed based on this novel idea. The results achieved are compared with the results of the finite element method and measurements which confirms that our proposed analytical method is more effective.

Levitation control of an improved modular bearingless switched reluctance motor

In order to reduce coupling between torque and suspending force in conventional bearingless switched reluctance motor (BLSRM), one 12/12 hybrid-stator-pole structure BLSRM was investigated. In this structure, motor consists of two single phase motor. Biased flux is provided by axial permanent magnet, which is installed between two motor in axial direction. However, axial permanent magnet occupies axial space, which results in increased axial length and decreased critical speed. Therefore, an improved modular BLSRM is proposed in this paper. In order to reduce axial space and improve critical speed, permanent magnet is designed to install in stator yoke. To realize steady levitation during rotor rotating, one simple levitation control strategy is put forward, which is benefitted from natural decoupling between torque and suspending force. In addition, digital control system including torque and suspending force is designed by means of TMS320F28335 and experimental platform is established. Finally, the improved BLSRM can be steadily levitated in the static and rotating conditions by experimental results.

풍력발전기용 축방향 영구자석 발전기의 코깅 토크 저감을 위한 최적설계

Among the wind power generators, the axial permanent magnet generator has an advantage for increasing the power per unit volume compared to the existing radial flux generator. In this study, we calculated the cogging torque for the shapes of the permanent magnet and the stator pole in an axial permanent magnet generator, and studied the method to minimize the cogging torque. At a first step, several optimum shapes were obtained by using the response surface method. Next, the cogging torques were calculated by using finite element method and finally the optimum design was obtained to minimize the cogging torque of the generator. The analysis model was three phase 1kVA wind power generation having 24 poles and 18 slots. As a result of the optimum design, the cogging torque decreased by 7.37N․m and the EMF increased by 25.63V compared to the basic model.

Resistive torque in permanent magnet couplings operating through a conductive wall

PurposeThe purpose of this paper is to propose an analytical approach to determine the resistive torque caused by a conductive wall between the rotors of axial permanent magnet couplings. In this configuration, relative motion between the coupling rotors and the wall generates a resistive torque that is a consequence of the induced eddy currents in this barrier. Therefore, such induced resistive torque implies a reduction in the permanent magnet coupling performance, that is, its torque transmission capacity.Design/methodology/approachThe developed resistive torque analytical formulation was based on eddy-current brakes of previous studies. To validate the proposed method, tests were conducted in a prototype and results were compared with analytical ones.FindingsThe analytical method showed a good correlation with the experiment data. Furthermore, a major degradation of the coupling capability to transmit torque was found because of the conductive wall presence, enhancing the importance of predicting such phenomenon when designing these devices.Originality/valueA novel direct assessment of the resistive torque while in motion is presented in this paper. These measurements were of great importance to accurately compare the analytical and experimental data.

Application of the Thermal Fin Approximation to Modeling Voice Coil Magnetic Fields and Performance

This paper develops an approximate analytical model to describe the magnetic fluxes, forces, and armature reaction in cylindrical voice coil actuators and related electric machines. Magnetic flux is assumed to either lie in an inner region of the actuator and parallel to its axis, or in an outer region of the actuator and oriented radially. A differential reluctance model is derived for this set of assumptions, with a structure and solution set similar to those involved in extended-surface heat transfer (“fins”) and lossy transmission lines. Particular solutions for the force constant, motor constant, coil inductance, and variable-reluctance force are found for a symmetric motor with opposed axial permanent magnets on either side of an iron flux concentrator. The model results for this topology are validated using finite-element analysis and experimental measurements from a prototype.

Study on Torque Calculation for Hybrid Magnetic Coupling and Influencing Factor Analysis

Specific to a problem that the present transmission of magnetic coupling torque was subjected to restrictions of its own structure, a hybrid magnetic coupling was proposed. Then, finite element method was adopted to carry out numerical calculations for its three-dimensional magnetic field to obtain three-dimensional magnetic field distribution of radial and axial configurations. Major influencing factors of its torque, such as lengths of axial and radial air gaps, thicknesses of axial and radial permanent magnets, the number of slots in axial copper rotor, thickness of axial and radial copper rotor, etc., were analyzed. The relevant results indicated that in certain conditions of shapes, ten magnetic poles of the axial permanent magnet rotor, nine of the radial permanent magnet rotor and nine slots from the axial copper rotor were used. Correspondingly, the axial copper rotor had a thickness of 20 mm and it was 5 mm for the radial copper rotor. Moreover, the maximum torque could reach 190 N.m approximately. If lengths of axial and radial air gaps increased, the torque may go down otherwise. Within a certain scope, the torque rose in the first place and then fell with increases in the permanent magnet thickness of axial permanent magnetic rotor, the number of axial and radial magnetic poles, the number of slots in axial copper rotor, and the thickness of axial copper rotor. Additionally, the number of slots in the axial copper rotor could not be equivalent to that of magnetic poles in axial permanent magnetic rotor. However, as the permanent magnet thickness of radial permanent magnetic rotor rose, the torque went up as well.

A novel magnetic-driven tissue retraction device for minimally invasive surgery

Introduction: The purpose of this work is to design and validate an innovative magnetic-based device for tissue retraction for minimally invasive surgery.Material and methods: An intra-abdominal magnetic module is coupled with an extracorporeal system for establishing a stable attraction, and consequently a reliable tissue retraction. Once the retractor has been inserted into the abdomen, tissue retraction is not constrained by a fixed access port, thus guaranteeing a more flexible, safer and less invasive operation. The intra-abdominal unit is composed of an axial permanent magnet attached to a stainless-steel non-magnetic alligator clip by a traditional suturing thread. A miniaturized mechanism to adjust the length of the suturing thread for lengthening or shortening the distance between the tissue grasper and the internal magnetic unit is included. A multiphysics approach assured a dedicated design that thoroughly fulfills anatomical, physiological and engineering constraints.Results: System functionalities were demonstrated both in in-vitro and ex-vivo conditions, reaching good results and promising outcomes in terms of effectiveness and maneuverability. The retractor was successfully tested in an animal model, carrying out a whole retraction procedure.Conclusion: The proposed retraction system resulted to be intuitive, reliable, robust and easy to use, representing a suitable device for MIS procedures.

Electromagnetic Vibration Analysis and Measurements of Double-Sided Axial-Flux Permanent Magnet Generator With Slotless Stator

This paper examines the effects of the electromagnetic source on the vibration of a double-sided axial permanent magnet generator with a slotless stator depending on the ac and dc-load conditions. The slotless machine has no cogging torque. Most of the vibration originates from the torque ripple and axial force distributions, which result from the current load conditions. The 3-D finite element analysis results are compared with voltage, current, and torque measurements. The order tracking analysis of the vibration test data clearly demonstrates the dependence of the critical harmonics on the load conditions.