Halbach Magnet Array Research Articles

A Semi-Analytical Approach for the Optimization of High-Speed PMSM With Halbach Magnet Array

A Semi-Analytical Approach for the Optimization of High-Speed PMSM With Halbach Magnet Array

Design Considerations of High-Speed PMSM With Nonuniform Two-Segment Halbach Magnet Array

Design Considerations of High-Speed PMSM With Nonuniform Two-Segment Halbach Magnet Array

Forward modeling of single-sided magnetic resonance and evaluation of [formula omitted] fitting error based on geometric analytical method

Single-sided magnetic resonance (SSMR) offers advantages of portability and noninvasive measurement for water detection, with significant potential applications in groundwater exploration, petroleum well logging, and soil moisture monitoring. However, the inherent highly inhomogeneous static magnetic field and radiofrequency (RF) field in SSMR necessitate the utilization of the Carr–Purcell–Meiboom–Gill (CPMG) sequence measurement scheme. To accelerate forward modeling during pulse excitation, we introduce a Geometric Analysis Method (GAM) and assess T2 error using its primary parameters. The GAM involves applying spatial geometric rotations on the magnetization vector, leading to an analytical solution to the Bloch equation that disregards relaxation effects. Compared with the rotation matrix (RM) method, the GAM demonstrates high accuracy and reduces computational time by approximately 20.9%. By analyzing the primary parameters governing the magnetization vector in the analytical formula, we evaluated their impact on the transverse relaxation time (T2) obtained through fitting the SE signal. Ultimately, the forward modeling results of the CPMG sequence within the region of interest (ROI) of a single-sided Halbach magnet array are validated. The T2 fitting error increases as the primary parameters deviate from the ideal values, highlighting their significant role in the T2 fitting results. This study provides a theoretical foundation for optimizing the design of SSMR magnets and RF coils.

Enhancing unilateral EMAT performance through topological optimization of Halbach permanent Magnet arrays

A novel unilaterally excited electromagnetic acoustic transducer (EMAT) is proposed as a solution to address the challenge of weak electromagnetic ultrasonic detection signals being susceptible to interference from clutter noise signals. EMAT employs Halbach permanent magnet array (HPMA) structure and a coil designed based on Huygens superposition principle. This design enables the generation and reception of highly directive Rayleigh surface waves in aluminum plates. To enhance the operational efficiency of EMAT while maintaining a high level of directivity for surface waves, a penalty function is implemented in COMSOL Multiphysics for the topological optimization of EMAT. The objective function in this optimization process is based on covariance (COV) of the magnetic induction intensity. The research results suggest that the homogeneity of the magnetic induction intensity within the coil region is enhanced by 50 % following topological optimization compared to the original design. The energy conversion efficiency of EMAT is enhanced by 5 times compared to traditional designs. The surface wave speed was determined to be 2631 m/s when measured at a frequency of 400 kHz. The value indicates a relative error of 6.37 % in comparison to the theoretical speed. The results indicate that EMAT has the capability to generate high-directional and pure Rayleigh waves.

Study on the Influences of an Outer-Coreless-Rotor Permanent Magnet Synchronous Machine Using Halbach Magnet Array

In order to evaluate the influences of the topology design of a Halbach Magnet Array (HA) on the performance of a motor, a PMSM with an outer coreless rotor using a Halbach Magnet Array (HAORPMSM) is proposed in this article. The design parameters of the HA could be separated into dividing methods per pole, magnet thickness, and initial magnetization direction angle. The phase Back-EMF under constant mechanical speed is chosen as the index to measure the performance of the motor. To start with, different dividing methods of the HA are evaluated. After that, the influence of thickness considering the utilization of the magnet is studied. Lastly, the relationship between initial magnetization direction and motor manufacturing is represented. The results show that the HA design meets the optimized performance considering the balance of the amount of magnet usage and manufacturing when using specific HA parameters.

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.

Smart nodding duck: A hybrid Halbach electromagnetic piezoelectric self-powered sensor for smart fisheries

Wave energy harvesting plays a crucial part in promoting the sustainable development of marine fisheries. This paper presents a novel hybrid electromagnetic and piezoelectric Self-powered Sensor, known as the Smart Nodding Duck (SND). The SND consists primarily of two components: an electromagnetic generator (EMG) responsible for power generation and a piezoelectric generator (PEG) dedicated to monitoring purposes. The SND absorbs wave energy through the shell of the nodding duck, while the planetary wheel system forms a coaxial counter-rotating augmentation structure. Also, the Halbach magnetic array serves as the electromagnetic generator, simultaneously exciting the piezoelectric structure to generate voltage signals. These features enable the SND to contribute to the LSTM network modeling self-sensing system, facilitating the monitoring of sea states. To verify the power generation effect of the SND, we conducted bench tests. The results demonstrate that the electromagnetic generator achieves an average output power of 96.26mW under a wave excitation of 0.8 Hz with an amplitude of 80 mm, yielding a power density of 16 W/m3. Furthermore, the self-sensing sea state monitoring model exhibits an impressive accuracy of 99.3 %. Moreover, tank experiment verified the feasibility of the SND, further contributing to the construction of a smart marine fishery Internet of Things.

Electromagnetic vibrational energy harvester with targeted frequency-tuning capability based on magnetic levitation

Electromagnetic vibrational energy harvester with targeted frequency-tuning capability based on magnetic levitation

Improving the homogeneity of Halbach arrays by optimizing magnet combinations using a genetic algorithm.

The purpose of this study was to test the effectiveness of using a genetic algorithm to find the optimal combination of permutations of permanent magnets in a Halbach magnet array in order to achieve the best magnetic field homogeneity in this work area. The test took place on a simple Halbach magnet array of 32 cubic permanent magnets. The magnetization of these magnets was preliminary assessed. Our calculations demonstrate that it is possible to achieve homogeneity of the magnetic field within the working area comparable to that of ideal identical magnetic blocks. Therefore, our study shows that combinatorics can be used to optimize homogeneity without selecting magnetic blocks, which can significantly reduce the cost of manufacturing the final structure.

Comparative Analysis and Design Optimization of Ferrite-Based Surface PM Vernier Machines

This paper presents the results of a comprehensive investigation into the comparative analysis and design optimization of ferrite-based surface permanent magnet vernier machines (SPMVMs). While SPMVMs boast a simple mechanical structure and enhanced torque density attributed to the flux modulation effect, they suffer from a persistent challenge of low power factor. Several factors hinder the adoption of low-cost ferrite magnets in SPMVMs. First, ferrite magnets are prone to irreversible demagnetization, constraining the allowable range of magnet thickness. Second, the reduced residual magnetic flux density of ferrite magnets exacerbates the decrease in power factor and machine efficiency. Thus, achieving optimal performance in ferrite-based SPMVMs necessitates the careful selection of various design parameters. To address these issues, this study employs a surrogate-based metaheuristic optimization algorithm with adaptive sampling to identify the optimal solution. Additionally, the integration of a Halbach array is explored to further enhance the performance of the three-slot/two-pole SPMVM topology. Subsequently, two ferrite-based SPMVM baseline models—one with a conventional SPM structure and another with a Halbach magnet array—are thoroughly designed, optimized, and subjected to detailed performance analysis using the 2D finite element method.

Analytical Model of Air‐Gap Magnetic Field for Eccentric Harmonic Magnetic Gear with Halbach Array

The eccentric harmonic magnetic gear (EHMG) has the characteristics of high torque density, high transmission ratio and high efficiency. The EHMG with Halbach array has better performance than the EHMG with traditional radial magnetization. Accurate calculation of its air‐gap magnetic field is of great significance for design and optimization. Based on the boundary perturbation method, a 2D analytical model of the air‐gap magnetic field of EHMG with Halbach array is established in this paper. The eccentric air‐gap magnetic field is calculated due to the permanent magnets of the eccentric rotor and the stator acting alone, and then the air‐gap magnetic field of the EHMG is obtained according to the superposition principle. The results of the air‐gap magnetic field are compared and evaluated by the regression evaluation indexes. The analytical results are consistent with the finite element results, which verifies the validity and accuracy of the analytical model. Comparing the EHMG with Halbach array and radial magnetization, the maximum static and dynamic electromagnetic torques of EHMG with Halbach array are increased by 59.1% and 55.6% compared with the EHMG with radial magnetization, which verifies the superior performance of EHMG with Halbach array. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

An ultra-compact lightweight electromagnetic generator enhanced with Halbach magnet array and printed triphase windings

Electromagnetic generator (EMG) plays a pivotal role in in-situ power supply for low-power electronics. However, a major challenge associated with EMGs is the limited power density. To address this issue, various strategies have been proposed, including magnetic field augmentation of magnets, magnetic flux variation rate escalation at the coil, and structural miniaturization. In this study, we present an innovative ultra-compact electromagnetic generator (UL-EMG) in light weight that integrates the Halbach magnet arrays and printed circuit board (PCB) technologies. The UL-EMG incorporates a 12-layer printed triphase windings into its PCB stator, thereby upgrading both device compactness and output performance. To assess the performance of the UL-EMG, comprehensive bench tests were conducted. Interestingly, results indicate that at a low rotational speed of 200 rpm, the UL-EMG achieved a peak AC output power and power density of 54.9 mW and 1.25 kW/m3, respectively, representing a 22-fold expansion compared to conventional EMGs. Moreover, the UL-EMG exhibited exceptional output characteristics across a wide range of rotational speeds, significantly bolstering its capacity to drive various low-power electrical appliances. This study paves a novel path for heightening the power density of EMGs and highlights the promising application prospects of compact EMGs in in-situ power supply advancement.

A high-performance rotational electromagnetic energy harvester based on magnetic plucking: Design, simulation, and experiment

Harvesting rotational energy to supply low-powered electronic devices can optimize the whole power supply system layout. In this paper, we propose a high-performance rotational electromagnetic energy harvester and construct an electro-mechanical dynamic model. The harvester consists of the halbach magnet array (HMA), a radially magnetized cylindrical rotatable magnet, and a copper coil, respectively. The proposed energy harvester is tested in a rotating platform and the correctness of the mathematical model is verified by experimental results. As one of the important components of the harvester, the magnetic field characteristics of the HMA are simulated by the finite element method (FEM) and compared with other magnet arrangements. Additionally, the effect on output when the HMA is rotated individually has also been analyzed. Numerical and experimental results indicate that the rotational energy harvester also has an optimal speed, and the corresponding maximum output power decreases significantly with the increase of the distance between magnets. Numerical results indicate that the maximum power output can be obtained as 516.05 mW at 520 rpm, which is a pretty remarkable result. To verify practical application capability, a rectifier-stable circuit is constructed to light 54 LEDs in experiments.

Optimal design of transducers based on the Halbach arrays permanent magnet structure

ABSTRACT For enhancing the static magnetic field and reducing the size of torsional guided wave magnetostrictive patch transducer (MPT) with permanent magnets, a MPT with Halbach arrays is proposed. The structural parameters design of the MPT can be guided by finite element simulation. It is found that increasing the central angle of the radially magnetised magnets can increase the strength of the static magnetic field, and it can be adjusted through designing the radial size and lift-off distance of the magnets. The Halbach magnet arrays composed of circumferentially magnetised magnets with a circumferential size of 6 mm and radially magnetised magnets with a circumferential size of 4 mm are selected to experimentally compare with the alternating magnetised magnet arrays composed of magnets with a circumferential size of 10 mm. The results show that the static magnetic field strength can be increased by 54.7% using Halbach magnet arrays. The proposed MPT composed of the Halbach magnet arrays and a linear solenoid array can excite and receive T(0,1) guided wave. Compared with the alternating magnetised magnet array MPT, the guided wave signal amplitude is increased by about 70% generated and received by the MPT with the Halbach magnet arrays.

A Bicycle-Embedded Electromagnetic Harvester for Providing Energy to Low-Power Electronic Devices

Bicycles are rapidly gaining popularity as a sustainable mode of transportation around the world. Furthermore, the smart bicycle paradigm enables increased use through the Internet of Things applications (e.g., GPS tracking systems). This new paradigm introduces energy autonomy as a new challenge. The energy harvesting technology can capture the energy present in the cycling environment (e.g., kinetic or solar) to give this autonomy. The kinetic energy source is more stable and dense in this environment. There are several wheel kinetic harvesters on the market, ranging from low-complexity dynamos used to power bicycle lights to smart harvester systems that harvest kinetic energy while braking and cycling and store it for when it is needed to power sensors and other electronics loads. Perhaps the hub and the “bottle” dynamos are the most commercially successful systems because of their cost-effective design. Furthermore, the bottle generator is very inexpensive, yet it suffers from significant energy losses and is unreliable in wet weather due to mechanical friction and wheel slippage in the wheel/generator contact. This paper proposes a cost-effective bicycle harvester based on a novel kinetic-electromagnetic transducer. The proposed harvester allows for the generation and storage of harnessed kinetic energy to power low-power electronics loads when the user requires it (e.g., cell phone charging, lighting). The proposed harvester is made up of a power processing unit, a battery, and an optimized transducer based on a Halbach magnet array. An extensive full-wave electromagnetic simulation was used to evaluate the proposed transducer. Circuit simulation was also used to validate the proposed power unit. The proposed harvester generates a simulated output power of 1.17 W with a power processing unit efficiency of 45.6% under a constant bicycle velocity of 30 km/h.

A rotary magnetic separator integrating nanoparticle-assisted water purification: Simulation and laboratory validation

This work introduces a continuous flow process for the implementation of magnetic nanoadsorbents in drinking water treatment practices based on their complete recovery using a rotary separation setup with an arrangement including the use of permanent magnets. Magnetostatic analysis and computational fluid dynamics were combined to simulate the generated magnetic field of a Halbach array of magnets fixed in a PMMA disk, and the flow behavior of a Sn-based magnetic nanocomposite dispersion under the influence of the alternating field. The rotating speed and direction, the flowrate of the dispersion and the immersion level into the dispersion tank were proven to be the critical parameters to maximize capture and separation of the nanocomposite from the flowing water. To validate the efficiency of the designed setup, the corresponding magnetic separator was built and adapted as a unit in a sequence with a stirring tank which brings Cr(VI)-polluted water in contact with the nanocomposite. The experimental operation involved the use of a tin oxyhydroxide (abhurite), a phase known for its high uptake efficiency on Cr(VI), loaded with 20%wt. Fe3O4 nanoparticles which act as the magnetic carrier for the post-treatment recovery. The developed pilot unit achieved a complete water purification, for Cr(VI) concentrations up to 100 μg/L even for low contact times such as 15 min whereas the in line magnetic separator offered a total (100 %) capture of the nanocomposite providing solid-free and purified water.

Thermomagnetic convection induced in a temperature stratified state by a Halbach magnetic field

Convection induced by the permanent magnets of the linear Halbach array is numerically investigated and validated experimentally. The working fluid is a paramagnetic fluid that is weakly attracted to the magnet with temperature dependency. The fluid is filled in a rectangular enclosure and heated from the top and cooled from the bottom. The external magnetic field is applied from the top wall. Two-dimensional computations show that the Halbach magnet array can induce a strong thermomagnetic force widely in the fluid layer compared with the conventional alternate magnetic pole array. The upward flow is induced below the edges of the center magnet and then separated left and right along the top heated wall. The local Nusselt number shows a higher value and wider area than those by the conventional pole array. An experiment using the Halbach array kit is conducted and the obtained local Nusselt number profile agrees well with the computational data both qualitatively and quantitatively.

Development of a High Power Density In-Wheel Motor Using Halbach Array Magnets

In this study, a direct drive in-wheel system is proposed as a high power density system for reducing the intermediate parts, such as a speed reducer by increasing the torque. We propose a design strategy to show that multipolarization and the improvement of the gap magnetic flux density can effectively increase the power density. A Halbach array magnet rotor that combines the main electrode magnets and spoke magnets with the core is adopted as a technique for improving the gap magnetic flux density. We compare the Halbach array type rotor to the conventional SPM type rotor by using both of magnetic circuit calculation and FEM analysis. Moreover, the actual sized in-wheel motor prototype with the developed Halbach array magnet rotor is fabricated and measures the no-load induced back EMF. The measured no-load induced back EMF agrees well with the analyzed waveform.

An electromagnetic energy harvester with a half-wave rectification mechanism for military personnel

Military personnel need electronic devices and usually carry heavier batteries to meet the power consumption of electronics, which will hinder military operations. This paper proposes an electromagnetic energy harvester for converting human motion energy into electricity for military personnel. The proposed system consists of a human motion energy harvesting module and an energy storage module. The electromagnetic energy harvester using a Halbach magnet array with a half-wave rectification mechanism is proposed to harvest human motion energy for generating electricity. The half-wave rectification mechanism keeps the magnets and coils on a one-way rotation, allowing them to continue their relative motion for some time after the excitation has disappeared, thus improving the output power. Experimental results showed that the power density of the proposed electromagnetic energy harvester with a half-wave rectification mechanism could reach 190% of the power density of the electromagnetic energy harvester without a rectification mechanism at an excitation frequency of 3 Hz and an amplitude of 90°. From the experimental results, the maximum output power of the electromagnetic energy harvester with a half-wave rectification mechanism reached 39.02 mW. Experiments and application prospects confirmed the feasibility of the proposed electromagnetic energy harvester for military personnel.

Improvement of the Static and Dynamic Characteristics of Water-Lubricated Bearings With Integrated Halbach Magnet Arrays

The generation of frictional vibration and noise by water-lubricated bearings is one of the most severe problems putting at risk the safety and concealment of ships. Here, Halbach magnet arrays were integrated as the upper bush of the water-lubricated bearing with the aim of suppressing frictional vibration. Simulations and experiments were conducted and compared between the magnetic bearing and a normal rubber bearing. Effects of magnetic strength, Halbach array length, rotational speed, and external load on bearing characteristics were analyzed. The results show superior static and dynamic performances on the magnetic bearing. More specifically, attractive forces generated by Halbach magnets can reduce static pressure by nearly 37% on the bottom bush. Stiffness of magnetic bearings was calculated as smaller than for normal bearings, indicating a lower natural frequency. Shaft trajectories were observed close to the geometric center of bearing yielding less stress concentration on the bottom bush of the magnetic bearing. Finally, test rig experiments demonstrated suppressed vibrational peaks and reduced frictional vibration (more than 10 dB) on the magnetic bearing. It is also interesting to note that the magnetic bearing even shows exceptional robustness regarding fluctuations of rotating speed or external load. This study presents a new routine for overcoming the frictional vibration and noise of water-lubricated bearings.