Cylindrical Permanent Magnet Research Articles

Derivation of a general and explicit equation for the force between identical cylindrical permanent magnets with the help of Wolfram|Alpha application

Abstract Until recently, there has been no single, explicit equation that explains how force between identical permanent magnets varies with distance over any distance. Typically, observation data is fitted using two curve segments: at large and small distances. In this work, we derive a general equation to determine the force between identical cylindrical permanent magnets at any distance with the help of the Wolfram|Alpha application to get the explicit form of an integral problem introduced by Vokoun et al (J. Magn. Magn. Mater. 321 3758–63, 2009) that appears to have no analytical solution. The resulting equation accurately fits observational data and can be used to estimate the magnetization of permanent magnets.

Research on the Motion of Few Tooth Magnetic Gears with Given Initial Angular Velocity Based on Euler Method

Abstract This paper aims to investigate the motion patterns of magnetically interacting gears with a few teeth and given initial angular velocities. Based on Ampere’s molecular current hypothesis, an equivalent current model is utilized to solve the magnetic field generated by cylindrical permanent magnets. Comsol software is employed to simulate the distribution of the magnetic field, demonstrating that the magnetic field calculated by the equivalent current model is in good agreement with the actual situation. Vector analysis, field theory, and the symmetry of the magnetic field distribution are leveraged to simplify the calculations, thereby reducing the runtime of the program. The Euler method is adopted to numerically simulate the motion of the gears. Finally, a comparison with experiments shows that the motion patterns in the experiments are essentially consistent with those in the numerical simulations. It is concluded that the ratio of magnetic field intensity to resistance torque, initial magnetic potential energy, and initial angular velocity positively correlate with the motion duration; the ratio of magnetic field intensity to resistance torque and initial magnetic potential energy positively correlate with the intensity of motion; when the initial angular velocity is excessively high, the other gear exhibits slight vibrations in its original position, and only when the initial velocity decreases to a certain value do the two gears interact significantly.

A compact and portable gamma-ray spectrometer (GRASP) for inertial confinement fusion and basic science experiments.

A compact and portable gamma-ray spectrometer has been designed to diagnose different components of the inertial confinement fusion-relevant γ-ray spectrum with energies between ∼3.7-17.9MeV. The system is designed to be as compact as possible for convenient transportation and fielding in diagnostic ports on the OMEGA laser, the National Ignition Facility, and other photon-source facilities. The system consists of a conversion foil for Compton scattering in front of four magnetic spectrometer "arms," each covering a different energy range and constructed out of cylindrical permanent magnet Halbach arrays. Monte Carlo simulations have been used to optimize and assess the performance of the conversion foil, and COSY INFINITY ion-optical simulations have been used to optimize the spectrometer magnets. The performance of the design is assessed for a simulated direct-drive γ-ray spectrum. Spanning its total γ-ray energy bandwidth and using a 1.7mm thick boron conversion foil, the system's total energy resolution and efficiency are ∼15.8%-4.5% and 5.4 × 10-7-3.7 × 10-7e-/γ, respectively, with room for improvement. Spectral γ-ray measurements will provide guidance to the inertial confinement fusion program toward achieving high-energy gain relevant to inertial fusion energy and enable new measurement capabilities for basic discovery science.

Efficient computational model of the in-flow capturing of magnetic nanoparticles by a cylindrical magnet for cancer nanomedicine.

Magnetic nanoparticles have emerged as a promising approach to improving cancer treatment. However, many nanoparticle designs fail in clinical trials due to a lack of understanding of how to overcome the in vivo transport barriers. To address this shortcoming, we develop a computational model aimed at the study of magnetic nanoparticles in vitro and in vivo. In this paper, we present an important building block for this overall goal, namely an efficient computational model of the in-flow capture of magnetic nanoparticles by a cylindrical permanent magnet in an idealized test setup. We use a continuum approach based on the Smoluchowski advection-diffusion equation, combined with a simple approach to consider the capture at an impenetrable boundary, and derive an analytical expression for the magnetic force of a cylindrical magnet of finite length on the nanoparticles. This provides a simple and numerically efficient way to study different magnet configurations and their influence on the nanoparticle distribution in three dimensions. Such an in silico model can increase insight into the underlying physics, help to design prototypes, and serve as a precursor to more complex systems in vivo and in silico.

Magnetic proximity sensor based on colossal magnetoresistance effect

Magnetic proximity sensors are widely used to determine the distance to ferromagnetic or highly conductive materials and to investigate their shape or to detect their motion. In this study, a magnetic proximity sensor incorporating a cylindrical permanent magnet and a scalar magnetic field sensor (measuring the magnitude of the field independently from its orientation) based on the phenomenon of colossal magnetoresistance in manganite films is presented. Two versions of the sensor, one with a solid cylindrical magnet and one with a hollow cylindrical magnet, were constructed and tested. A steel plate and a superconducting YBaCuO disk were used to investigate the static response. The measurements of the dynamic behavior were carried out with rotating steel and duralumin plates. The results of the static experiments and modelling showed that the output response (change of the magnetic field) of the sensor had a hyperbolic relationship with the distance between the sensor and the measured object. This change was positive for solid cylindrical magnet design and negative for hollow cylindrical magnet design when the target was steel. In contrast, the solid magnet-based sensor produced a negative signal for the superconducting material, while the hollow cylindrical magnet sensor showed a positive signal. It was found that the main features of the dynamic response of the proximity sensors can be explained by the magnetization of steel and the induction of eddy currents in duralumin. The present study demonstrates that the proposed magnetic proximity sensor can be successfully used to search for ferromagnetic objects, investigate the properties of superconductors and detect the motion of non-ferromagnetic conductive materials and can have advantages over conventional magnetic proximity sensors.

Study of Electron Energy Distribution Function, Transport Parameters and Instability Analysis of Argon Plasma confined by a Dipole Magnet

This theoretical study is to investigate production and properties of plasma confined by a dipole magnet. A cylindrical permanent magnet (N40 grade) having a surface magnetic field of nearly 1Tesla is simulated to create a dipole magnetic field. Plasma is created by electron cyclotron resonance heating. Heating is accomplished using microwaves operating in continuous mode at 2.45 GHz and electron cyclotron resonance. The investigation is performed in systems of cylindrical geometries at varying pressures (0.5 mTorr – 1.5 mTorr). The electron temperature lies in the range of 1 - 5 eV, is hotter near the magnets and follows a downstream fashion throughout the region.Electron Energy Distribution Function (EEDF) growth investigation throughout the region was done to understand the role of magnetic field confinement. The EEDF was calculated numerically from steady state Boltzmann equation, considering plasma follows druyvesteyn distribution. Followed by analysing transport parameters such as diffusion coefficient, drift velocity, mobility, and recombination rates in plasma. A comparative study for all plots gave been done with respect to pressure. The instability analysis of elastic collisional frequency with inelastic collisions, real frequency and growth factor with wave vector has been also listed in the study.

Самопроизвольное вращение магнитов, левитирующих над высокотемпературным сверхпроводником

Levitation of a cylindrical permanent magnet over a high-temperature superconductor cooled by liquid nitrogen can be accompanied by spontaneous oscillations and rotation. The reason for spontaneous rotation of the magnet is magnetization inhomogeneity induced by the temperature gradient. An experiment was carried out on the levitation of Nd–Fe–B magnets over a composite high-temperature superconductor. The experimental results confirm that the rotation frequency depends on the difference in the magnetization values in its upper and lower halves of the magnet. Methods for controlling the rotation frequency of a levitating magnet are proposed.

Modeling and control of magnetically actuated micro/milli robots position under laminar flow

The goal of this study is to model and control the position of micro- and milli-scale robots (MMRs) under laminar flow for multiscale robotic applications. A conceptual design depending on Lagrange point-based manipulation of the MMRs is proposed. The design includes a channel between two cylindrical permanent magnets that are used as the magnetic actuator. Spherical magnetic MMRs are placed in this channel with a diameter range of 0.25–1 mm. First, an analytical permanent magnet model is implemented. Following this, an adaptive mathematical model is built considering the dynamic magnetic forces on the MMRs. The position of the MMRs is analyzed for different parameters such as the channel dimension, the magnet diameter and distance, the type of the surrounding liquid, and the Re number. It is observed that there are considerable fluctuations during the positioning. Also, there is a deviation from the Lagrange point due to the significant drag forces caused by the laminar flow. To overcome these fluctuations and the deviation, an I-PD controller is implemented. Then, the position of the MMRs is analyzed with similar parameters in the presence of the controller. Results indicated that it is possible to control the MMR position at the Lagrange point by the I-PD controller, with a 14 % maximum overshoot.

Analytical Solution for Electromagnetic Performance Analysis of Permanent Magnet Synchronous Motor with a Parallel Magnetized Cylindrical Permanent Magnet

High-speed direct-drive permanent magnet synchronous motors (PMSMs), supported by elastic foil gas bearings, have broad applications, such as in microcompressors. However, some problems remain to be solved for the electrical performance analysis of PMSMs. For example, there is presently no related analytical model that can be used in rotor dynamics expression for this type of PMSM. This study aimed to establish theoretical models for electromagnetic force density and torque. The process involved both theoretical and experimental research. The analytic models of air gap magnetic density, electromagnetic force density, and electromagnetic performance were established for a PMSM with a parallel magnetized cylindrical permanent magnet. The analytic calculation was conducted, and the results of the analytic model were obtained. The analytical model of the electromagnetic torque and force can be applied in theoretical research on rotor dynamics. The model provides a theoretical basis and method for studying the influence of the electromagnetic load on rotor dynamics. A finite element simulation analysis of the electrical performance of the PMSM was carried out. An electrical performance experiment was conducted. The deviation between the experimental result and the theoretical value was less than 4%. This result indicated that the analytic models could be used in a dynamics analysis of compressors that are directly driven by a PMSM for application in engineering and industrial contexts.

Nondestructive Evaluation of Tensile Stress-loaded GFRPs Using the Magnetic Recording Method.

This paper presents the results of inspecting tensile stress-loaded GFRP (glass fiber-reinforced polymer) samples using the Magnetic Recording Method (MRM). The MRM can be utilized solely to examine ferromagnetic materials. The modification was proposed in order to examine nonmagnetic composites. Ferromagnetic strips made of low-carbon steel DC01 were bonded to the surface using an adhesive composed of epoxy resin with the addition of triethylenetetramine. The modified method's feasibility was tested on six samples made of GFRP. The research procedure consisted of three steps. In the first step, a metal strip is glued at the top surface of each sample, and an array of 100 cylindrical permanent magnets is used to record a sinusoidal magnetic pattern on the strip. The initial residual magnetization is measured in the second step, and the samples are subjected to static stress. In the third step, the residual magnetization is measured one more time. Ultimately, the measurement results from the second and third steps are compared. Generally, the applied stress causes changes in the amplitude and frequency of the sinusoidal magnetization pattern. In the case of GFRP, the frequency changes have not been used for evaluation due to minimal variations. The statistical parameters (mean, median, max, and mode) of the RMS (root mean square) value of the sinusoidal pattern were calculated and analyzed. The analysis demonstrates that the modified method is suitable for providing unequivocal and exact information on the load applied to a nonmagnetic composite material. For the presented results, the applied load can be assessed unambiguously for the samples elongated up to 0.6%.

Analytical modeling and experimental verification of a multi-DOF spherical pendulum electromagnetic energy harvester

Low-frequency vibration energy harvesting is a promising technology for providing floating buoys and small marine robots with sustainable energy from ocean waves. A spherical vibration energy harvester with multiple degrees of freedom has the advantages of good multi-directional adaptability and compact structure. However, its magnetic field distribution in three-dimension space is much more complex due to the combined effect of a series of cylindrical permanent magnets mounted on the surface of a gimbaled pendulum. The traditional finite element method is too time-consuming to perform efficient parameter design and optimization. To solve this problem, this work develops an analytical electromagnetic model for the spherical vibration energy harvester based on Biot-Savart Law. This model can be used to predict spatial magnetic flux distribution and electromotive force for given magnet and coil parameters. The accuracy and computational cost of the analytical model is verified by the comparison with the finite element method. Furthermore, the optimization of electromagnetic parameters is implemented to achieve maximum energy conversion efficiency. Finally, an optimized prototype is fabricated and tested in both laboratory and real sea. The resonant frequency and energy conversion efficiency of the prototype reaches 1.0 Hz and 25.45 %, respectively. It is shown that the experimental results are in good accordance with the analytical results.

Magnetic field model of radially magnetized cylindrical permanent magnets in a self-biased magnetic pendulum array

Self-Biased Magnetic Pendulum Array (SBMPA) is an efficient and portable transmitter in ultralow frequency (ULF). The resonance frequency of SBMPA is affected by the magnetic field of the radially magnetized cylindrical permanent magnets. In order to calculate the resonance frequency, the magnetic field model of a single radially magnetized cylindrical permanent magnet is derived based on the concept of magnetic charge. Then, the influence of the demagnetizing field and external magnetic field on the magnetization of permanent magnets is analyzed, and the magnetic field model of SBMPA is established. The results of the magnetic field model are verified through simulation. The average deviation of magnetic field intensity is determined as 0.021%; thus, the magnetic field model and simulation have consistent results. Finally, the influence of the size and distance of permanent magnets on the resonance frequency is analyzed, which could provide theoretical guidance for the dynamic analysis of SBMPA.

Three-dimensional motion control of an untethered magnetic object using three rotating permanent magnets

Magnetic motion control has been actively studied mainly for the purpose of biomedical applications. However, in many cases, many actuator magnets surround a small magnet to be moved, and they consume large electric power. In some cases, complex calculations are required to estimate the control input of the actuator magnets. This study proposes a simple method to move a small magnet to the desired positions. For this, three cylindrical permanent magnets magnetized in the radial direction were positioned as the sides of a triangle; these actuator magnets were rotated using motors. By monitoring the position of the small magnet and through simple feedback control based on the angles of the three actuator magnets, the untethered small magnet could be moved along arbitrary three-dimensional (3D) paths. The control principle was established by calculating the magnetic force and torque acting on the small magnet for some sets of actuator-magnet angles.

Positioning system design of closed-loop magnetically driven laser steering manipulator for endoscopic microsurgery

This study presents a closed-loop magnetically driven laser steering manipulator positioning system for endoscopic microsurgery. A multimagnetic field strength sensor circuit is embedded in a 16−mm diameter analog laser steering manipulator. The magnetic field distribution of a cylindrical permanent magnet in three-dimensional space is first modeled using an integral model to overcome the large error induced by the magnetic dipole model when the sensor and permanent magnet are close. The integral in the model is then decomposed using the Gauss–Legendre quadrature to improve the computational efficiency of the formulation. Moreover, five commonly used global search optimization methods are compared. Then, the algorithm with the fastest computational rate among these five algorithms, the tree-seed algorithm, is fused with the Levenberg–Marquardt algorithm, which performs well in local search, to obtain a hybrid optimization algorithm. Finally, it is demonstrated through static and dynamic experiments that the system based on the hybrid algorithm can obtain satisfactory computational errors while maintaining a high computational rate.

Theoretical and experimental study of a novel triple-magnet magnetic dynamic vibration absorber with tunable stiffness

PurposeThe existing Nonlinear Dynamic Vibration Absorbers (NLDVAs) have the disadvantages of complex structure, high cost, high installation space requirements and difficulty in miniaturization. And most of the NLDVAs have not been applied to reality. To address the above issues, a novel Triple-magnet Magnetic Dynamic Vibration Absorber (TMDVA) with tunable stiffness, only composed of triple cylindrical permanent magnets and an acrylic tube, is designed, modeled and tested in this paper.Design/methodology/approach(1) A novel TMDVA is designed. (2) Theoretical and experimental methods. (3) Equivalent dynamics model.FindingsIt is found that adjusting the magnet distance can effectively optimize the vibration reduction effect of the TMDVA under different resonance conditions. When the resonance frequency of the cantilever changes, the magnet distance of the TMDVA with a high vibration reduction effect shows an approximately linear relationship with the resonance frequency of the cantilever which is convenient for the design optimization of the TMDVA.Originality/valueBoth the simulation and experimental results prove that the TMDVA can effectively reduce the vibration of the cantilever even if the resonance frequency of the cantilever changes, which shows the strong robustness of the TMDVA. Given all that, the TMDVA has potential application value in the passive vibration reduction of engineering structures.

Computational Analysis of Semi-Analytical Modeling Techniques for a Novel PM-Based Planar Actuator

A novel type of permanent magnet planar actuator is proposed which consists of a permanent magnet mover that interacts with individually mechanically controllable permanent magnets in the stator. A state of levitation and actuation is obtained by mechanically altering the orientation of the stator magnets to control the forces and torques on the mover. To design and control the actuator, fast and accurate electromagnetic models are required. In this study, the harmonic modeling technique is applied to rotating and translating cuboidal and cylindrical permanent magnets and is compared to the equivalent charge model in terms of accuracy and computational effort. The models are compared for a finite stator topology which demonstrates that the harmonic model has a substantial computational advantage over the equivalent charge method in a non-periodic system while both models are in good agreement in terms of accuracy.

Design, Implementation and Test of a Novel Cylindrical Permanent Magnet DC Linear Motor

Electric motors that convert electrical energy into motion are one of the basic components of automation systems. In these systems, either linear or circular motion is needed. Linear motion can be obtained either from motors that generate circular motion with the help of ancillary equipment or directly by the means of a linear motor. Obtaining linear motion from motors that produce rotary motion leads to additional costs and reduced efficiency. Linear motors, on the other hand, eliminate the need for conversion mechanisms. Despite this advantage, linear motors have some disadvantages, such as length limitation and low force/current ratio. In this study, a novel Cylindrical Direct Current Linear Motor (CDCLM) with high force/current ratio and no length limitation (long stroke) has been developed. Analyses of the developed motor has been performed with an analytical method. In addition, detailed numerical analyses have been carried out in an Ansys-Maxwell environment. A prototype of the designed DC linear motor has been implemented in a laboratory environment and experimental analyses have been carried out. The results of analytical, numerical and experimental analyses have been compared.

Semi-Analytical and Experimental Investigation of the Magnetic Field Generated by a Permanent Magnet

For magnetic field calculations, cylindrical permanent magnets are often approximated as ideal, azimuthally symmetric solenoids. Despite the frequent usage of this approximation, research papers demonstrating the validity and limitations of this approach are scarcely available. In this paper, the experimentally derived magnetic field of a cylindrical permanent magnet is compared with the semi-analytically calculated magnetic field of an ideal solenoid. An experimental setup for measuring the magnetic field distribution is demonstrated and employed for gathering the data. The proposed setup allows to measure the distributions of the axial and radial components of the magnetic field surrounding the magnet. In addition, we calculated the magnetic field using the FEM method and compared it with the solution of an ideal solenoid and discussed the obtained deviation.

The development of the permanent magnet system for the ion diode isolation

The paper demonstrates the possibility of using the field of permanent magnets for the magnetic isolation of an ion diode and for the ion beam formation. To form a radial magnetic field of a given geometry, ring magnets of complex (special) shape were developed on the base of cylindrical permanent magnets. We also elaborated the design of the anode, magnet frames, and the cathode system of the ion diode. Investigations of the magnetic field parameters were carried out; and experimental data on the accelerating voltage and ion current density were obtained.

Adaptively Adjusted EKF-Based Magnet Tracking Method for Fast-Moving Object

Permanent magnet tracking (PMT) can be employed in robots and precision control due to its advantage of wireless, without optical occlusion, and simultaneous position and orientation tracking. However, existing PMT studies based on optimization algorithms are limited to stationary or low-speed motions, where the tracking accuracy rapidly decreases with the increasing magnet speed. This study presents an extended Kalman filter (EKF)-based PMT. The magnetic field distribution around the cylindrical permanent magnet is approximated with a magnetic dipole model, where a random walk model is utilized as the system motion model. The state update model of the EKF estimation is adaptively adjusted according to different magnet speeds, while the initial magnet pose is approximated by the statistical analysis of magnetometer array outputs. The proposed PMT method hence can track the object at a higher speed while ensuring an effective pose accuracy than the previous studies. The proposed method was tested in technical verification experiments and a practical application. In addition, the relationship between the magnet speed and the position accuracy is investigated. When the magnet speed reaches 40 mm/s, experimental results show that the average pose error and algorithm latency are (1.83 ± 0.25 mm, 1.296 ± 0.091°) and 0.485 ± 0.064 ms, respectively. In the robot parking experiment for charging, the pose errors are (2.85 ± 0.41mm, 1.302 ± 0.023°) when the robot speed reaches 40 mm/s. The proposed method can greatly improve tracking performance for fast-moving object is greatly improved by performing the proposed method, thereby expanding the application scenarios of PMT.