Arc-shaped Magnets Research Articles

MagTetris: A simulator for fast magnetic field and force calculation for permanent magnet array designs

In this paper, a simulator named “MagTetris” is proposed for fast magnetic field (B-field) and force calculation for permanent magnet arrays (PMAs) designs consisting of cuboid and arc-shaped magnets (approximated by cuboids) with arbitrary configurations. The proposed simulator can compute the B-field of a PMA on arbitrary observation planes and the magnetic force acting on any magnet/group of magnets. An accelerated calculation method for B-fields of PMAs is developed based on the current model of permanent magnet, which is further extended to magnetic force calculation. The proposed method and the associated codes were validated with numerical simulation and experimental results. The calculation speed of “MagTetris” is at least 500 times higher than that using finite-element method (FEM)-based software with uncompromised accuracy. Compared with a freeware in Python, Magpylib, “MagTetris” has a calculation acceleration of greater than 50% using the same language. “MagTetris” has a simple data structure, which can be easily migrated to other programming languages maintaining similar performances. This proposed simulator can accelerate a PMA design and/or allow designs with high flexibility considering the B-field and force simultaneously. It can facilitate and accelerate innovations of magnet designs to advance dedicated portable MRI in terms of compactness, weight, and performance.

Multi-Objective Optimization of an Axial Flux Permanent Magnet Brushless DC Motor with Arc-Shaped Magnets

To get a better electromagnetic performance of an axial flux permanent magnet brushless DC motor (AFPMBLDC), an AFPMBLDC with arc-shaped magnets and its multi-objective optimization design are researched. Firstly, the main design parameters of the AFPMBLDC are proposed, and the initial designs are carried out according to the given requirements. Furthermore, the pole arc coefficient, permanent magnet thickness, permanent magnet arc radius, and air-gap length are selected as optimization factors. Then, an orthogonal experiment table is established, in which the flux density, no-load back EMF, harmonic distortion rate, and output torque ripple are selected as optimization targets. The Taguchi optimization method is adopted to optimize the performance indexes and the optimal parameters are obtained. Finally, the optimized model is constructed, and some simulations are carried out to verify the optimal design. The research results have shown that the air-gap flux density of the optimized AFPMBLDC is reduced to 31.8%, the total harmonic distortion rate of no-load back EMF is less than 7.5%, and the torque ripple is reduced to 4.3%.

Design, modeling and optimization of an N-shape electromagnetic energy harvester for smart bearing of high speed train

Smart bearings have integrated sensors and processor and could monitor the real time status of the mechanical equipment. To achieve a long-term service of the smart bearing without human maintenance, the self-powering capability is of great necessity. This paper proposes an N-shape electromagnetic energy harvester (NEMEH) with cylindrical Halbach array embedded within an axle box bearing for the high speed train. The proposed electromagnetic energy harvester is radially embedded in the smart bearing, which includes arc-shaped magnets, an N-shape electric steel and coils. The arc-shaped Halbach array and the N-shape electric steel form a concentrated and closed magnetic flux path, which could improve the magnetic performance of the harvester. A magnetoelectric coupling model of the proposed harvester is derived and shows good agreement with the finite element analysis. An optimization route is performed to maximize the output power under the dimension constraint of the smart bearing. Experimental results demonstrate that the proposed theoretical model can well estimate the output of the harvester. The power generation of a prototype with optimal structure parameters could reach 4.26 W at a 1200 r min−1 rotational speed and a 2 mm air gap. It demonstrates that the developed NEMEH is capable of harvesting rotational motion energy to power the wireless sensor nodes.

Magnet pole shape design for reduction of thrust ripple of slotless permanent magnet linear synchronous motor with arc-shaped magnets considering end-effect based on analytical method

The shape of the magnet is essential to the performance of a slotless permanent magnet linear synchronous machine (PMLSM) because it is directly related to desirable machine performance. This paper presents a reduction in the thrust ripple of a PMLSM through the use of arc-shaped magnets based on electromagnetic field theory. The magnetic field solutions were obtained by considering end effect using a magnetic vector potential and two-dimensional Cartesian coordinate system. The analytical solution of each subdomain (PM, air-gap, coil, and end region) is derived, and the field solution is obtained by applying the boundary and interface conditions between the subdomains. In particular, an analytical method was derived for the instantaneous thrust and thrust ripple reduction of a PMLSM with arc-shaped magnets. In order to demonstrate the validity of the analytical results, the back electromotive force results of a finite element analysis and experiment on the manufactured prototype model were compared. The optimal point for thrust ripple minimization is suggested.

A Magnetically Actuated Drug Delivery System for Robotic Endoscopic Capsules

There is an increasing need to incorporate an actively controlled drug delivery system (DDS) into the next generation of capsule endoscopy in order to treat diseases in the gastrointestinal tract in a noninvasive way. Despite a number of attempts to magnetically actuate drug delivery mechanisms embedded in endoscopic capsules, longer operating distances and further miniaturization of on-board components are still drawbacks of such systems. In this paper, we propose an innovative magnetic system that consists of an array of magnets, which activates a DDS, based on an overly miniaturized slider–crank mechanism. We use analytical models to compare the magnetic fields generated by cylindrical and arc-shaped magnets. Our experimental results, which are in agreement with the analytical results, show that an optimally configured array of the magnets enhances the magnetic field and also the driving magnetic torque and subsequently, it imposes a high enough force on the piston of the DDS to expel a required dose of a drug out of a reservoir. We conclude that the proposed magnetic field optimization method is effective in establishing an active DDS that is designed to deliver drug profiles with accurate control of the release rate, release amount, and number of doses.

Development of NdFeB Permanent Magnet Generator

Simple permanent magnet synchronous motor has the structure of reliable operation, small size, light weight, high efficiency, flexible shape and size and other characteristics. The pole surface of the rotor core is composed of several small magnet block arrays, spacing, width, height, and the magnet block arrays of magnetic blocks relationship between modulations. This paper introduces a development of NdFeB permanent magnet generator. Rotor structure of high-strength permanent magnet synchronous generator by the central shaft, attached to the core and its outer surface two pairs of circular arc-shaped magnets. The design of structures of the key components is demonstrated and the experimental results show the good performance of the generator.

Arc-Shaping of Magnets for Reduction of Cogging Torque in Permanent-Magnet Synchronous Generators

Wind power is an important source of green power. The equipment, generators, and power systems are all determining factors of equipment efficiency. High efficiency generators of medium and small size are widely used in daily life. Cogging torque is a major issue affecting generator efficiency. This paper proposes an optimized design for permanent-magnet synchronous generators using arc-shaped magnets to reduce cogging torque. The proposed approach improves performance significantly.

Radially Anisotropic Ring/Arc-Shaped Rare-Earth Bonded Magnets Using a Self-Organization Technique

We developed a new technique using self-organization of binder that enabled the alignment of a molecular chain. By using this technique, we controlled the flexibility of Nd-Fe-B-based rigid sheet magnets, transformed them into various shapes, and succeeded in preparing radially anisotropic ring- or arc-shaped magnets. Optimizations of the consolidation process of the self-organization binder under a transverse alignment field and the transformation process into various specific shapes realized radially anisotropic magnets with 160 kJ/m/sup 3/ in (BH)/sub max/.

分子鎖配向を利用したラジアル異方性希土類ボンド磁石

Magnetic properties of radially-anisotropic ring-shaped magnets were deteriorated when their outer-diameter is decreased down. Therefore, anisotropic Nd2Fe14B bonded-magnets have not been mainly applied to small motors up to now. In order to overcome the above difficulty, we developed a new technique using self-organization of binder which enabled the alignment of molecular-chain. By using this technique, we controlled the flexibility of Nd2Fe14B /Sm2Fe17N3 rigid sheet-magnets (approximately 1 mm in thickness), transformed them into various shapes, and succeeded in preparing radially-anisotropic ring- or arc-shaped magnets. Optimizations of the solidification process of the binder under a transverse alignment-field and the transformation process into various specific shapes realized radially-anisotropic magnets with superior properties such as values of (BH)max and also magnetic stabilities. Their value of (BH)max exceeded 160 kJ/m3, even if their outer diameter is less than 25 mm.

Nd-Fe-B Thin Arc-shaped Bonded Magnets for Small DC Motors Prepared by Powder Compacting Press with Ion-implanted Punches.

Magnets prepared from Nd-Fe-B based melt-spun powder, using a powder compacting press, have not been applied to thin arc-shaped magnets for small magnet motors up to now. We developed new techniques to prepare a granular compound with epoxy resin binder and to press it into arc-shaped segments with Ti- and C-ion-implanted upper and lower punches. Using these techniques, we made thin arc-shaped rare-earth bonded magnets (maximum thickness of 0.9 mm) for small magnet motors whose output power was less than 1 W. Both high motor efficiency and high mechanical output power were obtained for magnet made by the powder compacting press, compared with magnet made by the extrusion molding.

Magnetic properties of arc-shaped Nd-Fe-B die-upset magnets

Abstract The development of arc-shaped die-upset magnets with high-energy products was investigated. An arc-shaped magnet with ( BH ) max of more than 40 MGOe and i H c of more than 15 kOe was obtained. This arc-shaped die-upset magnet exhibits an almost radial anisotropic alignment. However, the anisotropic direction is tilted about 12° from the radial direction to the middle of the circumference. This magnet exhibits a much better B g profile for voice coil motors than magnets with a conventional parallel alignment.

Ｐｒ‐Ｆｅ‐Ｂ‐Ｃｕ系圧延磁石の熱間曲げ加工性

The workability of hot bending for hot rolled Pr-Fe-B-Cu magnets was investigated. Under optimum bending conditions, Pr-Fe-B-Cu magnets are bent without cracking. The workability is improved at higher temperatures and lower strain rates. The deformation during the bending is derived from the sliding of the grain boundary. Addition of Cu enables the magnets to be worked at a higher strain rate, because of the increased wettability and grain refinement. Arc-shaped magnets were formed by die bending without deterioration of the magnetic properties. Further, radially oriented ring magnets were produced by bonding these magnets with a liquid phase at a high temperature.