Permanent Magnet Configuration Research Articles

Reconfigurable spin-wave properties in two-dimensional magnonic crystals formed of diamond and triangular shaped nanomagnets

Two-dimensional ferromagnetic nanodot structures exhibit intriguing magnetization dynamics and hold promise for future magnonic devices. In this study, we present a comparative experimental investigation into the reconfigurable magnetization dynamics of non-ellipsoidal diamond and triangular-shaped nanodot structures, employing broadband ferromagnetic resonance spectroscopy. Our findings reveal substantial variations in the spin wave (SW) spectra of these structures under different bias field strengths (H) and angles (φ). Notably, the diamond nanodot structure exhibits a variation from nearly symmetric W-shaped dispersion to a skewed dispersion and subsequent transition to a discontinuous dispersion with subtle variation in bias field angle. On the other hand, in the triangular nanodot array a SW mode anti-crossing appears at φ = 15° which is starkly modified with the increase in φ to 30°. By analyzing the static magnetic configurations, we unveil the nature of the SW spectra in these two shapes. We reinforce our observations with simulated spatial power and phase maps. This study underscores the critical impact of dot shape and inversion symmetry on SW dynamical response, highlighting the significance of selecting appropriate structures and bias field strength and orientation for required functionalities. The remarkable tunability demonstrated by the magnonic crystals underscores their potential suitability for future magnonic devices.

Stochastic evaluation of quasi-zero stiffness magnetic spring using a reluctance-corrected analytical model

—In state of the art high-precision motion systems, which utilize magnetic levitation, a quasi-zero stiffness gravity compensation is one of the essentials to improve dynamic performance, eliminate position dependency and thus simplify controller design. Special configurations of permanent magnets, such as Halbach magnet arrays, can realize magnetic levitation as a form of magnetic spring. However, unlike conventional permanent magnet machines with large stiffness, the quasi-zero stiffness magnetic spring requires higher modeling accuracy for force estimation, which is affected by the nonlinear reluctance effect of permanent magnets. In this study, we propose an accurate magnetic modeling method for the quasi-zero stiffness magnetic spring. By correcting the reluctance effect of magnets, the proposed magnetic model achieves superior accuracy estimating levitation force and stiffness to the conventional surface current model. Using the reluctance-corrected magnetic model, tolerance analysis was performed to identify dominant geometric parameters affecting the uncertainty of the Halbach array magnetic spring performance. A Monte-Carlo simulation was used to estimate the overall tolerance of magnetic forces and stiffness. The experimental results fit in the tolerances.

Design Optimisation Approach of an Outer Rotor Multiphase PM Actuator for Multirotor Aerial Vehicle Applications

The electric urban air mobility sector has gained significant attraction in public debates, particularly with the proliferation of announcements demonstrating new aerial vehicles and the infrastructure that goes with them. In this context, the development of new methodologies for the design and sizing of actuation systems, ensuring high performances of these aerial vehicles, remains an important task in this process. This will allow for better integration within this transport sector. In this paper, a robust design optimisation approach of multiphase fault-tolerant (FT) outer rotor (OR) permanent magnets (PM) for multirotor aerial vehicle applications is proposed. In order to show the effectiveness and the robustness of the proposed design methodology, the number of stator winding phases, with a fractional slot concentrated winding (FSCW) configuration, as well as the PM configuration are considered as variables. Thus, four cases for the number of phases are considered, namely 3, 5, 6 and 7 phases, where for each number of phases case, the PM takes 3 configurations, namely surface PM, interior V-shape PM and interior spoke PM. First, a pre-sizing step is carried out, consisting of selecting the optimal combinations slot/pole, designing the multiphase FSCW layout, and estimating the electric motor (EM) geometry using analytical computations to obtain a preliminary validation of the design specifications. Second, constrained multiobjective optimisation is considered in order to optimise the EM performances, such as motor efficiency and weight, under constraints where the FEMM/Matlab based Finite Element Analysis (FEA) tool is used to perform this optimisation. Finally, results analysis and performance comparisons of different EM configurations are carried out in order to assess the design parameters, such as phases number, PM position, and harmonic currents in the EM design and consequently to select the best configuration for the considered application.

Design and Optimization of Halbach Magnetic Gear

This article proposes a new structure to enhance the torque and torque density of permanent magnet gears. The outer magnet is designed with a dual-layer permanent magnet configuration, where the first layer adopts a Halbach array, and the other layer utilizes a conventional radial magnetization structure. With the optimization objectives defined as maximum torque and torque density, and guided by parameter sensitivity, optimization analysis was conducted using response surface method and multi-objective genetic algorithm. The optimized parameters were determined, and finite element simulations were performed to validate the optimization results. The result indicate a 22.22% increase in torque and a 27.42% increase in torque density compared to the previous the traditional magnet gear. The performance of the proposed new structure of magnetic gear has shown significant improvement.

Slot-pole structure investigation for radial flux permanent magnet generator

Recently, Radial Flux Permanent Magnet Generator (RF-PMG) has been applied in various applications of generator. The configuration of the radial flux permanent magnet is the magnetic rotor arranged in a circle rotation while the inner core attached to the rotor’s center. However, various sizes and structure of RF-PMG can produce different output power levels, cogging torque and generator’s flux regulation capability. By investigating the output voltage and cogging torque value, this paper showed the suitable slot-pole combinations that can influence the output performance of the generator by using 2D-Finite Element Analysis. This investigation shows the comparison of the slot-pole that resulting the least cogging torque value and high output voltage, 0.1739Nm and 180.81V respectively. Hence, 36slots-30poles indicates as the best slot-pole combinations.

Effect of Permanent Magnet Structure on Working Characteristics of LSPMSM 3000 rpm

Reducing the cost of electricity to improve production efficiency is one of the urgent tasks. Nowadays, the rapid development of Neodymium rare earth (NdFeB) permanent magnet technology has promoted the creation of high-efficiency motors to replace low-efficiency induction motors to save electricity. One of them is a line-start permanent magnet synchronous motor (LSPMSM). The permanent magnet configuration significantly affects the operating characteristics of the LSPMSM, such as working current characteristics, pulsating torque, working efficiency, and starting speed. The content of the article focuses on investigating and evaluating some permanent magnet configurations affecting the working characteristics of the LSPMSM based on the finite element method through Ansys/Maxwell software. The research results are suggested for the design and manufacture of LSPMSM used in mining to save electricity.

Zero-Field Spin Waves in YIG Nanowaveguides.

Spin-wave-based transmission and processing of information is a promising emerging nanotechnology that can help overcome limitations of traditional electronics based on the transfer of electrical charge. Among the most important challenges for this technology is the implementation of spin-wave devices that can operate without the need for an external bias magnetic field. Here we experimentally demonstrate that this can be achieved using submicrometer wide spin-wave waveguides fabricated from ultrathin films of a low-loss magnetic insulator, yttrium iron garnet (YIG). We show that these waveguides exhibit a highly stable single-domain static magnetic configuration at zero field and support long-range propagation of spin waves with gigahertz frequencies. The experimental results are supported by micromagnetic simulations, which additionally provide information for the optimization of zero-field guiding structures. Our findings create the basis for the development of energy-efficient zero-field spin-wave devices and circuits.

Optimization of NdFeB Permanent Magnets Configuration for Spinal Cord Drug Delivery

Magnetic drug delivery is an effective method to decrease the side effects of traditional drug delivery methods. To enhance the efficiency of magnetic nanoparticle transport, a precise and cost-effective magnetic system is required. In this research, different arrangements of NdFeB magnets for drug delivery in human spinal cord were presented and then compared. Assummed magnetic nanoparticles are injected into the cerebrospinal fluid (CSF) and focused on the disease site with external magnets. The effects of these magnets on nanoparticles have been investigated. The results show that the arrangement of sharp magnets has a more accurate performance in delivering nanoparticles to the damage site than other arrangements. The designed magnetic system can improve the accuracy of drug delivery in the spinal cord compared to previous methods.

Design and comparison of electro-permanent magnetic field sources for magnetocaloric heat pumps

We present the results of a comprehensive study of the design, numerical analyses and experimental validation of various electro-permanent magnetic structures that can be used in magnetocaloric refrigeration. Most magnetic field sources currently used in conceptual magnetic cooling devices require moving parts, which produce noise, vibrations and require maintenance. Furthermore, the operating frequency of such magnetic structures is relatively low and limited by aspects of the mechanical construction. Unlike any magnetic structure currently used in a magnetocaloric refrigeration device, the presented structure consists of a hybrid assembly of an electromagnet and a permanent magnet. We report on how different configurations of permanent magnets and the windings of electromagnets, including the air gaps, affect the energy efficiency, the input power and the total mass of the magnetic field source. Some guidelines for future research and the development of electro-permanent magnetic field sources for magnetocaloric refrigeration and heat pumps are presented, supported by information on how such structures can enable higher operating frequencies that could increase the compactness of future magnetocaloric devices.

Enhanced heat transfer analysis of hybrid nanofluid over a Riga plate: Incorporating Lorentz forces and entropy generation

The Riga plate, comprising a configuration of electrodes and permanent magnets, can induce a wall-parallel Lorentz force through external electric and magnetic fields, enabling effective control of fluid flow. This paper focuses on studying the flow characteristics of Al2O3-Cu/water hybrid nanofluid past a Riga plate in the presence of strong suction. The mathematical model incorporates a two-phase approach to describe the behavior of the nanofluid, while considering the Grinberg-term to account for the wall parallel Lorentz force generated by the Riga plate. Several influential factors such as entropy generation, viscous dissipation, heat flux, thermal radiation, slippage, and convective boundary conditions of temperature are considered in our investigation. Entropy generation within thermodynamic systems contributes to energy losses resulting from various factors, including frictional forces, viscosity, and chemical reactions. Minimizing entropy generation is crucial to enhancing system performance. To address the research problem, we utilize dimensionless parameters and assume strong suction to simplify the governing partial differential equations. The dimensionless model is subsequently solved numerically using the Adams-Bashforth technique. Additionally, a comprehensive graphical analysis is conducted to examine the impact of various dimensionless parameters on the flow fields. This study highlights the importance of controlling fluid flow using the Riga plate in the presence of suction and investigates the behavior of a specific nanofluid under these conditions. The results provide valuable insights into the influence of key parameters on the flow characteristics. We conclude that effective utilization of the Riga plate can lead to significant enhancements in fluid flow control. Moreover, the study contributes to reducing energy losses through minimizing entropy generation. The novelty of this work lies in its comprehensive approach, considering multiple influential factors and employing a two-phase model for the nanofluid. Additionally, the inclusion of the Grinberg-term to account for the wall parallel Lorentz force adds to the uniqueness of the study. This research expands upon previous efforts in the literature by providing a more comprehensive analysis of the fluid flow control using the Riga plate, incorporating a broader range of factors, and presenting a numerical solution approach.

Investigating the magnetic field outside small accelerator magnet analogs via experiment, simulation, and theory

Particle accelerators use powerful and complex magnetic fields to turn, shape, and eventually collide beams of near-light-speed particles, yet the fundamental magnetic principles behind the accelerator magnets can be understood by undergraduate students. In this paper, we use small-scale accelerator magnet analogs in a multi-faceted, low-cost exploration of the magnetic field exterior to accelerator magnets. These fields are best understood using the multipole expansion of the field. If we assume that the magnetic field is created by ideal magnetic dipoles, we can derive a theoretical model that shows that each accelerator magnet configuration is dominated by a single multipole moment and obeys B∝1/rl+2, where l is the multipole order (with l=1,2,3, and 4 for the dipole, quadrupole, octopole, and hexadecapole moments, respectively). Using commercially available NdFeB magnets and the magnetic field sensor inside a smartphone, we experimentally verify the power-law dependence of the accelerator magnet configurations. Finally, we use the open-source Python library Magpylib to simulate the magnetic field of the permanent magnet configurations, showing good agreement among theory, experiment, and simulation.

Parameter-topology hybrid optimization of electric motor with multiple permanent magnets

A hybrid optimization method that combines parameter optimization (PO) with topology optimization (TO) is proposed for the design of a permanent magnet (PM) motor. The PM shape, configuration, and flux barrier topology were simultaneously optimized using the proposed method. The conventional hybrid method that deals with a single PM is effectively extended to deal with multiple PMs parameterized by several geometrical parameters. The use of this extension makes it possible to search for the optimal rotor structure of the multiple-PM motor, which is widely used in electric vehicles. The results obtained by the proposed method are shown superior over those obtained by conventional method. The rotor structure with double-U shaped PMs with small flux barriers near the airgap was obtained by the optimization.

Effect of permanent magnets in optimized arrangement for levitation support on vibration characteristics of levitated flexible steel plate

In the production line of thin steel plates, contact conveyance by rollers causes deterioration in the surface quality of the plates. To solve this problem, our research group has been continuously investigating the optimal placement of permanent magnets in hybrid magnetic levitation systems. In this study, when a thin steel sheet was magnetically levitated, the effect of the horizontal electromagnet position on the gap between the steel sheet and the permanent magnet was investigated through a permanent magnet configuration optimized using a genetic algorithm.

Particle-in-Cell Simulations for the Improvement of the Target Erosion Uniformity by the Permanent Magnet Configuration of DC Magnetron Sputtering Systems

Improving the target erosion uniformity in a commercial direct current (DC) magnetron sputtering system is a crucial issue in terms of process management as well as enhancing the properties of the deposited film. Especially, nonuniform target erosion was reported when the magnetic flux density gradient existed. A two-dimensional (2D) and a three-dimensional (3D) parallelized particle-in-cell (PIC) simulation were performed to investigate relationships between magnetic fields and the target erosion profile. The 2D PIC simulation presents the correlation between the heating mechanism and the spatial density profiles under various magnet conditions. In addition, the 3D PIC simulation shows the different plasma characteristics depending on the azimuthal asymmetry of the magnets and the mechanism of the mutual competition of the E × B drift and the grad-B drift for the change in the electron density uniformity.

Versatile magnetic configuration for the control and manipulation of superparamagnetic nanoparticles

The control and manipulation of superparamagnetic nanoparticles (SP-MNP) is a significant challenge and has become increasingly important in various fields, especially in biomedical research. Yet, most of applications rely on relatively large nanoparticles, 50 nm or higher, mainly due to the fact that the magnetic control of smaller MNPs is often hampered by the thermally induced Brownian motion. Here we present a magnetic device able to manipulate remotely in microfluidic environment SP-MNPs smaller than 10 nm. The device is based on a specifically tailored configuration of movable permanent magnets. The experiments performed in 500 µm capillary have shown the ability to concentrate the SP-MNPs into regions characterized by different shapes and sizes ranging from 100 to 200 µm. The results are explained by straightforward calculations and comparison between magnetic and thermal energies. We provide then a comprehensive description of the magnetic field intensity and its spatial distribution for the confinement and motion of magnetic nanoparticles for a wide range of sizes. We believe this description could be used to establish accurate and quantitative magnetic protocols not only for biomedical applications, but also for environment, food, security, and other areas.

Research on the torque performance for two multi-pole bilayer magnetorheological fluid couplings

This paper studies on the permanent magnets configuration on the transmission torque of the multi-pole bilayer magnetorheological (MR) coupling. Based on the electromagnetic field theory, the magnetic circuit models of traditional permanent magnet array (TPMA) and Halbach permanent magnet array (HPMA) are established, and the magnetic flux density within the MR fluid working gaps has been derived in order to evaluate the merits of the designed MR coupling. A 3D FE magnetic-fluid analysis has been necessary following the initial conceptual analysis, in order to study the influence of key parameters on the transmission torque. The results show that the transmission torque of the MR coupling with Halbach permanent magnet array is 33.45% higher than that of the ordinary permanent magnet array, with a same structure size. For the MR coupling with Halbach permanent magnet array, the unilateral magnetic focusing effect is better with the increase of the residual flux density of the secondary magnetic pole as well as the radial length of magnetic pole. And the single side magnetic focusing effect is the best when the main magnetic pole is 15°. The influence of the magnetic pole angle on the transmission torque has been further studied.

En route to next-generation nerve repair: static passive magnetostimulation modulates neurite outgrowth

Objective. Regeneration of damaged nerves is required for recovery following nervous system injury. While neural cell behavior may be modified by neuromodulation techniques, the impact of static direct current (DC) magnetic stimulation remains unclear. Approach. This study quantifies the effects of DC magnetostimulation on primary neuronal outgrowth in vitro. The extension of neurites of dorsal root ganglia (DRG) subjected to two different low-strength (mT) static magnetic flux configurations was investigated. Main results. After 3 d of 1 h in-plane (IP) magnetic field stimulation, a 62.5% increase in neurite outgrowth area was seen relative to unstimulated controls. The combined action of in-plane + out-of-plane (IP + OOP) magnetic field application produced a directional outgrowth bias parallel to the IP field direction. At the same time, the diverse magnetic field conditions produced no changes in two soluble neurotrophic factors, nerve growth factor and brain-derived neurotrophic factor, released from resident glia. Significance. These results demonstrate the potential for DC magnetostimulation to enhance neuronal regrowth and improve clinical outcomes.

Magnetorheological behavior of thermoplastic elastomeric honeycomb structures fabricated by additive manufacturing

3D printing of magnetorheological elastomers (MREs) can potentially create versatile and complex mechanical structures with reversible stiffening properties. Several additive manufacturing (AM) methods, like direct printing and stereolithography (SLA), have been used to achieve magnetic thermoset and elastomer composite structures. For the first time, we demonstrate the use of MREs based on thermoplastic elastomers (TPE) in AM and we investigate their magnetorheological (MR) effect when used in lightweight honeycomb designs. Due to the low shore hardness of TPE, a screw extruder-based printing head is employed to print disk-shaped samples with honeycomb patterns at infill percentages varying from 15% to 50%. In order to compare the MR effect of disks with varying honeycomb infills through a compression method, we investigated the effect of different testing configurations. We observe that different permanent magnet configurations, as it has been used in literature so far, create an additional effect on the measured MR effect of the MRE samples. To eradicate this effect, a test setup with an unpaired permanent magnet configuration is proposed. MRE structures with an infill density of 20% showed, at 1% deformation range, the highest MR effect, almost four times as high as 100% infilled samples. MRE structures with an infill density between 30% and 50% showed a lower MR effect than at 20%, but were still higher than at 100%. We observe in simulations that the magnetic flux density of 100% infilled samples was higher at the edges of the samples and lower at the center. For samples with honeycomb infill, the magnetic flux density was higher at the outer rim of the samples and edges of the walls within the sample, which causes a higher MR effect. Our work demonstrates that the MR effect can be tuned by designing a MRE structure with a honeycomb infill. The honeycomb infill results in lightweight MREs with improved MR effect useful for various downstream applications that require reversible strong stiffening while remaining comparatively lightweight.

Magnetic Forces by Permanent Magnets to Manipulate Magnetoresponsive Particles in Drug-Targeting Applications.

This study presents preliminary computational and experimental findings on two alternative permanent magnet configurations helpful for magnetic drug administration in vivo. A numerical simulation and a direct experimental measurement of the magnetic induction on the magnet system's surface were used to map the magnetic field. In addition, the ferrite-type (grade Y35) and permanent neodymium magnets (grade N52) to produce powerful magnetic forces were also examined analytically and quantitatively. Ansys-Maxwell software and Finite Element Method Magnetism (FEMM) version 4.2 were used for all numerical computations in the current investigation. For both magnets, the generated magnetic fields were comparatively studied for targeting Fe particles having a diameter of 6 μm. The following findings were drawn from the present investigation: (i) the particle deposition on the vessel wall is greatly influenced by the intensity of the magnetic field, the magnet type, the magnet size, and the magnetic characteristics of the micro-sized magnetic particles (MSMPs); (ii) ferrite-type magnets might be employed to deliver magnetoresponsive particles to a target location, even if they are less powerful than neodymium magnets; and (iii) the results from the Computational Fluid Dynamics( CFD) models agree well with the measured magnetic field induction, magnetic field strength, and their fluctuation with the distance from the magnet surface.

Permanent-Magnet Optimization for Stellarators as Sparse Regression

A common scientific inverse problem is the placement of magnets that produce a desired magnetic field inside a prescribed volume. This is a key component of stellarator design, and recently permanent magnets have been proposed as a potentially useful tool for magnetic field shaping. Here, we take a closer look at possible objective functions for permanent magnet optimization, reformulate the problem as sparse regression, and propose an algorithm that can efficiently solve many convex and nonconvex variants. The algorithm generates sparse solutions that are independent of the initial guess, explicitly enforces maximum strengths for the permanent magnets, and accurately produces the desired magnetic field. The algorithm is flexible, and our implementation is open-source and computationally fast. We conclude with two new permanent magnet configurations for the NCSX and MUSE stellarators. Our methodology can be additionally applied for effectively solving permanent magnet optimizations in other scientific fields, as well as for solving quite general high-dimensional, constrained, sparse regression problems, even if a binary solution is required.