Permanent Magnet Array Research Articles

Parametric Analysis for Performance Optimization of Line-Start Synchronous Motor with Interior Asymmetric Permanent Magnet Array Rotor Topology

Line-start synchronous motors have attracted researchers’ interest as suitable replacements of asynchronous motors due to their high efficiency, which has been provoked by strict regulations regarding applicable efficiency classes of motors in the EU market. The research becomes even more challenging as it takes into consideration the diverse rotor topologies with different magnet locations for this type of motor. The rotor configuration with an interior asymmetric permanent magnet (PM) array rotor was chosen for analysis and optimization in this paper as this specific configuration is particularly challenging in terms of placing the magnets with adequate dimensions into the existing rotor of the asynchronous motor with a squirrel cage winding, in order simultaneously to obtain good operational characteristics such as high efficiency and power factor, good overloading capability and low material consumption. Therefore, an optometric analysis is performed in order to find the best configuration of the air gap length, magnet thickness, magnet width and number of conductors per slot, along with modifications of the rotor slot. The motor outer dimensions remained unchanged compared with the starting model of the line-start motor derived from the asynchronous motor, which is a product of the company Končar. The optimized model obtained higher efficiency, power factor and overloading capability than the starting model, along with good starting and synchronization capabilities.

Dynamic and Energetic Characteristics Comparison of a Tri-Stable Vibration Absorber and Energy Harvester Using Different Permanent Magnet Arrays

In this paper, it has been demonstrated that the tri-stable energy harvesters are more efficient than the bi-stable and mono-stable harvesters in energy harvesting. The oscillators of energy harvesters can be designed as a vibration absorber to attenuate the vibration of the primary system. This paper presents a combined vibration absorber and energy harvester (VAEH) system for simultaneous vibration control and energy harvesting, and the dynamic performances of the VAEH with two magnet arrays of the same geometric parameters, but opposite polarity external magnets, are studied. The mathematical model of the tri-stable VAEH is established, by which the dynamic and energetic characteristics of the VAEH system are obtained. It is found that the potential barrier and potential well depth of the repulsive magnet array are greater than the attractive one, reducing the voltage harvesting efficiency under harmonic and impulsive excitation. Both the amplitude and frequency of excitation are crucial to the dynamic response of the VAEH system. The attractive VAEH performs better than the repulsive VAEH in vibration suppression, especially for high impulse input. From the frequency response of the system, the vibration of the primary system is shown to be magnified at certain frequencies. The magnified primary system vibration and the harvested voltage can be attenuated by increasing the VAEH damping, which is a critical parameter to balance the weight of vibration suppression and energy harvesting. The attractive VAEH designed in this paper performs better than the repulsive one in vibration suppression and energy harvesting.

Magnetic Recording Method (MRM) for Nondestructive Evaluation of Ferromagnetic Materials.

This paper proposes and experimentally investigates a novel nondestructive testing method for ferromagnetic elements monitoring, the Magnetic Recording Method (MRM). In this method, the inspected element must be magnetized in a strictly defined manner before operation. This can be achieved using an array of permanent magnets arranged to produce a quasi-sinusoidal magnetization path. The magnetic field caused by the original residual magnetization of the element is measured and stored for future reference. After the operation or loading, the magnetic field measurement is repeated. Analysis of relative changes in the magnetic field (for selected components) allows identifying applied stress. The proposed research methodology aims to provide information on the steel structure condition unambiguously and accurately. An interpretation of the results without referring to the original magnetization is also possible but could be less accurate. The method can be used as a standard technique for NDT (Non-Destructive Testing) or in structural health monitoring (SHM) systems.

A Novel Axial-Flux Dual-Stator Toothless Permanent Magnet Machine for Flywheel Energy Storage

This paper presents an alternative system called the axial-flux dual-stator toothless permanent magnet machine (AFDSTPMM) system for flywheel energy storage. This system lowers self-dissipation by producing less core loss than existing structures; a permanent magnet (PM) array is put forward to enhance the air–gap flux density of the symmetrical air gap on both sides. Moreover, its vertical stability is strengthened through the adoption of an axial-flux machine, so expensive active magnetic bearings can be replaced. The symmetry configuration of the AFDSTPMM system is shown in this paper. Then, several parts of the AFDSTPMM system are optimized thoroughly, including stator windings, number of pole pairs and the PM parameters. Further, the performance of the proposed PM array, including back-EMFs, air–gap flux density, average torque, torque ripple and over-load capacity, are compared with the Halbach PM array and spoke PM array, showing the superiority of proposed configuration. Finally, 3D simulations were made to testify for the 2D analyses.

Comparative Study of Two Degree-of-Freedom Rotary-Linear Machines With Permanent-Magnet Mover for High Dynamic Performance

This paper analyzes and evaluates various topologies of yokeless rotary-linear (RL) machine with permanent-magnet (PM) mover targeting for the achieving high dynamic performance. For the conventional yokeless RL machines, the single-stator topology features limited slot area for armature winding excited for both motions, and the coupled magnetic fields of both motions requires complex control strategy. In order to mitigate these issues, a double-stator RL machine with hybrid PMs array, which adopts the PMs with six magnetization directions, is proposed in this paper. An improved PMs array is introduced for the double-stator topology to achieve decoupled control for both motions. In addition, an analytical model of the radial flux density is derived to reveal the characteristics of the magnetic fields in different topologies. The parametric studies towards key dimensions are conducted to provide design guidelines and obtain the optimal design. Finally, the electromagnetic performances of the proposed design are compared systematically with the conventional single-stator counterparts. It is revealed that the proposed topology can enhance the performances in both motions, namely rotary and linear motions.

Optimization of distribution of permanent magnetrings for Faraday rotation spectroscopy

Faraday rotation spectroscopy (FRS) is generally used to detect the concentrations of various paramagnetic trace gases because of its high detection sensitivity, zero background noise and the ability to get rid of the interference of diamagnetic materials effectively. In most of FRS technologies, the used electromagnetic fields are produced by coils, thereby triggering off some problems such as high energy consumption and excessive heat generation. Thus the modeling and the simulation study of spatial magnetic field distribution based on the combined ring permanent magnets are carried out to establish an axially distributed homogeneous magnetic field and provide a permanent magnet-based homogeneous magnetic field along the optical axis for FRS measurement. In this simulation, the method of finite element mesh division is adopted based on basic electromagnetic relationship in Maxwell equations. By the simulation study of the magnetic field distribution of the actual Nd-Fe-B permanent magnet magnetic ring array, the physical model proves to be reliable. Basically, three methods of optimizing the permanent magnetic ring arrays. i.e. single ideal value optimization method, the multi-part single objective optimization method, and the gradient optimization method, are proposed. The single ideal value optimization method and the multiple ideal value optimization method are used to realize the optimization of magnets. However, by analyzing the two methods, it is clear that compared with the single ideal value optimization method, the multiple ideal value optimization method in which the whole region is divided into several small parts can achieve good uniformity of permanent magnet array. In this way, the third method, i.e. the gradient optimization method is used to realize the construction of a homogeneous magnetic field with a uniform central axis magnetic flux density distribution used for FRS. Finally, the standard magnetic field uniformity for measuring the quality of magnet field is suggested, and through the calculation and evaluation of the magnetic field uniformity, the optimization effects of different optimization methods are analyzed and compared with each other. And the final results about realizing a homogeneous magnetic field provide a reference for developing the FRS equipment based on permanent magnets.

Continuously Variable Valve Mechanism for Spark Ignition Engines Using Linear Actuator

In order to achieve higher performance in spark-ignition engines, it is required to control the intake and exhaust valves in stepless manner according to the engine speed. Our research group has been continuously studying the electromagnetic drive valve system using a linear actuator. In this report, we have designed a linear actuator with a dual Halbach array of permanent magnets in the stator to further increase the thrust of the linear actuator. The thrust characteristics of the proposed model were investigated using electromagnetic field analysis based on the finite element method. The analysis confirmed that the Halbach array concentrates the magnetic flux on the coil side, which generates Lorentz force.

MagTetris: A Simulator for Fast Magnetic Field and Force Calculation for Permanent Magnet Array Designs

MagTetris: A Simulator for Fast Magnetic Field and Force Calculation for Permanent Magnet Array Designs

Accurate Model and Verification of Suspended Vibration Energy Harvester Based on Complex Permanent Magnet Array

Accurate Model and Verification of Suspended Vibration Energy Harvester Based on Complex Permanent Magnet Array

Modeling and Dynamics of Magnetically Repulsive Negative Stiffness Permanent Magnetic Array for Precision Air/Magnetic Composite Vibration Isolation

To reduce the natural frequency of air isolators and realize low or ultra-low frequency air/magnetic composite vibration isolation with large payloads, a magnetically repulsive negative stiffness permanent magnetic array (MRNSPMA) is proposed. Specifically, we utilize cuboidal permanent magnets to form a spatial array that is mechanically repulsive in the horizontal direction and structurally parallel in the vertical direction. The superiority of MRNSPMA in achieving high amplitude negative stiffness is verified. Furthermore, the effects of structural parameters on vibration transmissibility under the base and force excitations are investigated with the introduction of MRNSPMA. The displacement transmissibility, the force transmissibility and the frequency corresponding to the peak transmissibility are significantly reduced, validating the promise of MRNSPMA for improving the isolation performance of cutting-edge scientific experimental systems and facilities.

Design and Optimization of a Novel HTS Flux-Modulated Linear Motor Using Halbach Permanent Magnet Arrays

For rope-less elevator applications, a novel high temperature superconducting (HTS) flux modulation linear motor (LM) using Halbach permanent magnet (PM) arrays is investigated in this paper. The flux modulation structure with iron segments can serve simultaneously and regulate the magnetic field. The HTS bulks are filled between the iron segments to further improve the flux modulation effect based on the Meissner effect. Compared with conventional counterparts, the force density of the proposed LM with HTS fillers is apparently higher. Furthermore, the mover with Halbach PM arrays is used to reduce the force ripple and increase the output force. The electromagnetic performances of the flux-modulated LM are researched by transient finite element analyses (FEA) to prove the effectiveness of the proposed structure. Finally, the parameters of the motor structural are optimized and analyzed by the combination of FEA and genetic algorithm (GA).

Design and Optimization of Halbach Permanent Magnet Array with Rectangle Section and Trapezoid Section

A novel Halbach permanent magnet array with rectangle section and trapezoid section is proposed and optimized in this paper. The analytical model of the premanent magnet segment is established based on the surface current method, which is numerically efficient and can be utilized to evaluate the magnetic field closely with the premanent magnet segment’s configurations. The analytical model of the Halbach array is acquired based on the superposition principle and coordinate transformation. The fundamental component of the magnetic flux density and the sinusoidal distortion rate are chosen as the optimization object. And the optimization is executed on the Halbach array with one specific set of dimensions by the genetic algorithm in global scale. The effectiveness of the optimization is validated by the finite element analysis. Compared to the traditional Halbach array with rectangle section, the magnetic field created by the optimized proposed Halbach array in this paper owns better performance.

Absolute radiation pressure detector using a diamagnetically levitating test mass

We have developed an absolute radiometer to measure laser power by means of radiation pressure in a closed control-loop configuration using diamagnetically levitated pyrolytic graphite as the soft spring and gravity as a contactless restoring force. Our approach takes advantage of an extremely low spring stiffness (2.95 mN/m) afforded by diamagnetic levitation above a permanent magnet array and a lock-in amplifier in the feedback loop to attain a 30 m W r m s noise. A horizontally directed laser beam impinges on a highly reflective dielectric stack mirror mounted on the levitating pyrolytic graphite shuttle. The light’s momentum displaces the shuttle, and its position is restored by tilting the magnet array with a piezoelectric actuator. The closed-loop configuration avoids the need for accurate knowledge of the system spring stiffness or environmental dependencies of the diamagnetic levitation. Absolute laser power measured is traceable to the mass of the diamagnetically levitating shuttle system, the local gravitational acceleration, and the interferometrically measured tilt angle of the magnet array. The system is demonstrated with a laser power of 2.7 W, yielding a combined relative expanded uncertainty ( k = 2 ) of 1.9%. The upper limit of measurable power is determined by the range of the piezoelectric actuator, and the minimum power is currently limited by the noise floor that is constrained by air currents.

Permanent magnet array-driven navigation of wireless millirobots inside soft tissues.

Creating wireless milliscale robots that navigate inside soft tissues of the human body for medical applications has been a challenge because of the limited onboard propulsion and powering capacity at small scale. Here, we propose around 100 permanent magnet array–based remotely propelled millirobot system that enables a cylindrical magnetic millirobot to navigate in soft tissues via continuous penetration. By creating a strong magnetic force trap with magnetic gradients on the order of 7 T/m inside a soft tissue, the robot is attracted to the center of the array even without active control. By combining the array with a motion stage and a fluoroscopic x-ray imaging system, the magnetic robot followed complex paths in an ex vivo porcine brain with extreme curvatures in sub-millimeter precision. This system enables future wireless medical millirobots that can deliver drugs; perform biopsy, hyperthermia, and cauterization; and stimulate neurons with small incisions in body tissues.

Experimental testing and validation of the dynamic model of a magneto-solid damper for vibration control

This paper focuses on characterization testing and validation of the dynamic model of a new type of high-damping density electromagnetic-based damping device (EMD) referred to as Magneto-Solid Damper (MSD) in which an eddy current damping mechanism acts in parallel with a solid friction mechanism to dissipate the input kinetic energy. The proposed MSD consists of a ferromagnetic plate, two copper plates placed on two sides of the ferromagnetic plate in parallel, and a planar array of permanent magnets (PMs) placed between the ferromagnetic plate and each of the two copper plates. The PMs arrays are attached to the ferromagnetic plate through non-magnetic friction pads. The friction force is developed between these friction pads and the ferromagnetic plate when the PMs arrays move relative to the ferromagnetic plate. The motion of the PMs arrays relative to the copper plates, on the other hand, generates the eddy current damping. A laboratory prototype of the proposed MSD has been designed and fabricated for the purpose of characterization testing. Finite element and simplified analytical models of this damper have also been developed to analyze the magnetic interaction between the PMs arrays and the ferromagnetic and copper plates. A dynamic model has been developed to characterize the force–displacement behavior of the proposed MSD. The parameters of this dynamic model are identified through a series of characterization tests on the prototype MSD under harmonic excitations of different frequencies. The identified dynamic model is validated by subjecting the prototype MSD to real ground motion records. It is concluded that that the proposed dynamic model is capable of describing the force–displacement behavior of the proposed MSD for a wide range of operating conditions.

Photothermal actuation of levitated pyrolytic graphite revised

The significant diamagnetism of pyrolytic graphite (PyG) allows it to be passively levitated above permanent magnet arrays and translated in the plane of these arrays via optical irradiation, which promotes applications in frictionless milli-scale robotics. Previous explanations for the translation effect have cited photothermal heating of levitated PyG and the thermal dependence of PyG’s magnetic susceptibility, as observed through measurements of samples at uniform temperatures. In this article, we offer a revision to the theory of photothermal actuation of levitated PyG. Through experiments and simulations, we demonstrate that the gradient of PyG’s diamagnetism with temperature—as measured for samples at uniform temperatures—is insufficient to explain the magnitude of forces required by the optically induced translation phenomenon. We hypothesize that the contrast in diamagnetism of PyG samples under asymmetric photothermal heating is at least an order of magnitude greater than that expected from measurements where the sample temperature is uniformly varied. We propose that the origin of the enhanced diamagnetic contrast under asymmetric optical irradiation is a photothermoelectric effect, which impacts the concentration of electrons in diamagnetically significant orbital states in graphite. To support this hypothesis, we take qualitative measurements, demonstrating the n-type thermoelectricity of PyG samples under optical irradiation while also characterizing the graphitic material with scanning electron microscopy/energy dispersive x-ray spectroscopy. We highlight the new understanding of the origin of the photothermal actuation through experiments using PyG samples with modified geometries that exhibit a pronounced preference in the axis of translation.

Rotational speed sensor based on the magnetoelectric effect of composite FeSiB/Pb(Zr,Ti)O3.

This paper proposes a rotational speed sensor based on the magnetoelectric coupling effect. The sensor is composed of a permanent magnet array and a magnetoelectric composite FeSiB/Pb(Zr,Ti)O3. The permanent magnet array rotates with the gear to provide a stable sinusoidal alternating magnetic field in its surrounding space, which is simulated and analyzed by using the finite element simulation software. Based on the magnetoelectric coupling effect, the composite FeSiB/Pb(Zr,Ti)O3 senses the magnetic field information and transforms it into electrical information so as to realize the rotating speed measurement. The experiments of sensing distance and linearity are carried out. The proposed sensor is compared and verified by a coil sensor. The results show that the proposed speed sensor has good linearity in the speed measured range, and the sensing distance can reach 15mm. At the same time, it can be used for low-speed measurement. This kind of speed sensor has broad application prospects in the field of rotational speed measurement.

Stability control of permanent magnet and electromagnetic hybrid Halbach array electrodynamic suspension system

Purpose The purpose of the paper is to study the stability control of permanent magnet (PM) and electromagnetic hybrid Halbach array electrodynamic suspension (EDS) system because of the poor suspension stability caused by the well-known under-damped nature of PM EDS system. The adjustment control is realized by PM and electromagnetic hybrid Halbach array, which is composed by winding active normal conductor coils on PM surface. Design/methodology/approach The three-dimensional (3-D) electromagnetic force analytical expression of PM and electromagnetic hybrid Halbach array EDS system for a nonmagnetic conductive plate is derived. And the accuracy of the derived equations is verified by a 3-D finite-element model (FEM). Basing on the 3-D levitation force expression, an acceleration feedback suspension controller is designed to suppress the vibration of PM EDS system, and the suspension stability of the system under the track and load disturbance was simulated and analyzed. Findings The 3-D electromagnetic force comparison of analytical model and FEM are in good agreement, which verifies the correctness of the analytical expression. The simulation results show that the acceleration feedback suspension controller can make the system have good suspension stability under the external disturbance. So it proved that the PM and electromagnetic hybrid Halbach array EDS system can overcome the poor suspension stability caused by the under-damped nature of PM EDS system through the designed acceleration feedback suspension controller. Originality/value This paper designed an acceleration feedback suspension controller to suppress the vibration of PM and electromagnetic hybrid Halbach array EDS system under external disturbance, basing on the derived levitation force analytical expression. And the simulation results show that the acceleration feedback suspension controller can make the system have good suspension stability under the external disturbance.

Unsteady Couette Flow Past between Two Horizontal Riga Plates with Hall and Ion Slip Effects

Riga plate is the span wise array of electrodes and permanent magnets that creates a plane surface and produced the electromagnetic hydrodynamic fluid behavior and mostly used in industrial processes with fluid flow affairs. In cases where an external application of a magnetic or electric field is required, better flow is obtained by the involvement of the Riga plate. Riga plate acts as an agent to reduce the skin friction and enhance the heat transfer phenomena. It also diminishes the turbulent effects, so that it is possible to get an efficient flow control and it increases the performance of the machine. So the numerical investigation of the unsteady Couette flow with Hall and ion-slip current effects past between two Riga plates has been studied and the numerical solutions are acquired by using explicit finite difference method and estimated results have been gained for several values of the dimensionless parameter such as pressure gradient parameter, Hall and Ion-slip parameters, modified Hartmann number, Prandtl number, and Eckert number. In this article, the importance of the modified Hartmann number on the flow profiles is immense owing to the Riga plate. The expression of skin friction and Nusselt number has been computed and the outcomes of the relevant parameters on various distributions have been sketched and presented as well as graphically.

Research on Mechanical Antenna Performance Based on Rotating Permanent Magnet Triangle Array

Traditional low-frequency antennas have larger volume and higher energy consumption. These characteristics make the traditional antennas easy to be destroyed by the enemy and expensive to maintain. In this paper, a mechanical antenna based on triangular array of rotating permanent magnets is introduced, and a prototype is made according to the proposed theoretical assumptions. Different from the traditional electric antenna, the mechanical antenna adopts the way of motor driving the permanent magnet to rotate, which realizes the miniaturization of the low-frequency transmitting antenna. In this paper, the analytical model of the rotating magnetic dipole is presented. By comparing the simulation results and the experimental data with the theoretical calculation results, it is proved that the mechanical antenna based on the rotating permanent magnet array can emit low-frequency sinusoidal electromagnetic waves, which has a broad application prospect in the Ultra-Low-Frequency/Very-Low-Frequency (ULF/VLF) communication field.