Search

This paper deals with equivalent 2-D finite-element (FE) models of permanent magnet lead screw (PMLS), to accurately predict the thrust force. Due to the helical-shape permanent magnets (PMs), the magnetic fields of PMLS are typically 3-D and non-symmetric. However, the PMLS is approximately symmetric in some cases and an equivalent 2-D axis-symmetric FE model is developed instead of 3-D models. The problem lies in that no evaluation about the accuracy and applicability of the 2-D axis-symmetric FE model was offered in previous literature. In this paper, the 2-D axis-symmetric FE model is derived based on the concept of equivalent current sheets of PMs. The limitations of the existing 2-D axis-symmetric FE model are clarified, and a novel equivalent 2-D torque FE model is then proposed to predict thrust force with the gear ratio when the 2-D axis-symmetric FE model is not appropriate. It is shown that the choice of equivalent 2-D FE model depends on the lead angle of PMLS, 2-D axis-symmetric FE model is applicable in the range of (0°, 15°), and 2-D torque FE model is preferred in the range of (65°, 90°). [ABSTRACT FROM AUTHOR]

In this paper, two novel double-sided hybrid-excitation flux-reversal linear motors (DSHEFRLM) with the surface (S-) and interior (I-) permanent-magnet(PM) arrangements are proposed and comparatively investigated. The proposed motors feature an asymmetrical double-sided primary configuration which enables the armature and field excitations to be placed separately. Through 2-D finite-element method (FEM), two motor structures with different slot/pole combinations are optimized, and then, the magnetic fields and electromagnetic performances are calculated, including inductances, no-load flux linkage, thrust characteristics, and PM demagnetization capability. By comparison, it is found that S-DSHEFRLMs show larger thrust density while I-DSHEFRLMs exhibit superior flux-adjusting capability. Finally, these predicted results are validated by 3-D FEM. [ABSTRACT FROM AUTHOR]

This paper describes the numerical and experimental validation of a novel non-contact dc electromagnetic propulsion concept. In the proposed approach, a propulsion coil carrying a dc current is surrounded by a dc transversal multipole field created inside of a launch tube. The interaction between the transversal dc magnetic field and a dc propulsion coil results in the generation of axial (thrust) force with no need of sliding contacts. This paper describes a numerical assessment of the field-current-force interactions based on both analytical calculations and finite elements, and the corresponding validation experiments. The experiments demonstrate the generation of contactless axial (thrust) force in a dc launch coil using a dc transversal multipole field, and provide a benchmark for the model-based prediction of the field-current-force interactions. Partial magnetic shielding of the propulsion coil is used to selectively attenuate the magnetic field experienced by the thrust coil in a way that a net thrust force is achieved. Experimental measurements confirmed that it is indeed possible to generate contact-free thrust force on a dc propulsion coil using a dc multipole magnetic field, and the measured values of thrust force are in good agreement with the corresponding predictions. [ABSTRACT FROM PUBLISHER]

In this paper, a 3-D multiphysics finite-element study of microelectromechanical systems (MEMS) reed magnetic sensors is presented. This paper employs several governing equations to simulate the MEMS reed sensors, calculate their magnetostatic body force, and track the resultant mechanical displacements. The MEMS beams used are trilayer gold/Ni/gold, and the sensing ranges of the sensors are in milli-Tesla. The results in this paper point to an optimal sensor design, which is then fabricated and verified by the experimental tests. This paper presents a general performance map of the MEMS reed sensors, illustrating their performance under various field conditions. Several sensor devices are fabricated and tested, with the measured data showing good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

In this paper, the design and development of a double-sided air-cored tubular generator (DSTG) is presented. The characteristics of air-cored slot-less structures are investigated in terms of power density and efficiency. This is highly desirable for small- and medium-sized renewable energy conversion systems. In this paper, an analytical tool based on the magnetic vector potential method is built in order to achieve a fast but accurate method by which the machine is analyzed. The analytical model is validated by finite-element (FE) analysis. Further design improvements based on the analytical and FE models are then suggested in order to enhance the performance of the DSTG. The final design of the DSTG is validated by the test results from a developed prototype of the DSTG. [ABSTRACT FROM AUTHOR]

This paper presents the characteristic analysis and experiment of pitching moment in a high-precision permanent-magnet linear synchronous motor. The pitching moment is analyzed according to suggested strategy; therefore, analytical solutions for magnetic fields generated by PMs are derived based on the analytical magnetic field calculation in terms of a 2-D polar coordinate system. The analytical solution of each subdomain (PM, air gap, slot, slot opening, and end region) is derived, and the field solution is obtained by applying the boundary and interface conditions between the subdomains. The magnetic force is determined based on the magnetic field analysis results. Finally, the predictions are compared with the measured data to confirm the validity of the analysis methods presented in this paper. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to propose an efficient and unique reluctance network (RN) model for all translator displacements of a linear hybrid motor. This model has to consider several translator positions to analyze the linear motor performances. The proposed RN model takes into account the magnetic characteristic and the flux leakage. Consequently, the proposed model gives precise results of the electromagnetic characteristic. The RN model considers an interesting solution to deal quickly with an optimization task of a large number of constraints and parameters. The developed model is coupled with sequential quadrating programming method for an optimization process of the linear machine. The obtained results confirm the efficiency of this method for modeling and optimization of the linear machine. [ABSTRACT FROM AUTHOR]

This paper presents the studies on an induction planar actuator. The device uses the same principles as a linear induction motor, where the interaction between a traveling magnetic field and a conducting surface produces eddy current, which leads to the generation of a linear force. However, the planar actuator has traveling magnetic fields in two perpendicular directions, and a combination of these can produce planar movement in any direction on a planar surface. This movement, combined with an inherent normal force between the planar actuator and a magnetic surface over which it moves, provides the adhesive force to allow the utilization of this actuator in a system for inspecting steel surfaces. Theoretical and numerical results are obtained and compared with results from a prototype. These results verify the operation of the actuator and validate the device with application potential. [ABSTRACT FROM AUTHOR]

This paper presents a synthesis of analytical calculations of magnetic parameters (field, force, torque, stiffness) in cylindrical magnets and coils. By using the equivalence between the amperian current model and the coulombian model of a magnet, we show that a thin coil or a cylindrical magnet axially magnetized have the same mathematical model. Consequently, we present first the analytical expressions of the magnetic field produced by either a thin coil or a ring permanent magnet whose polarization is axial, thus completing similar calculations already published in the scientific literature. Then, this paper deals with the analytical calculation of the force and the stiffness between thin coils or ring permanent magnets axially magnetized. Such configurations can also be modeled with the same mathematical approach. Finally, this paper presents an analytical model of the mutual inductance between two thin coils in air. Throughout this paper, we emphasize why the equivalence between the coulombian and the amperian current models is useful for studying thin coils or ring permanent magnets. All our analytical expressions are based on elliptic integrals but do not require further numerical treatments. These expressions can be implemented in Mathematica or Matlab and are available online. All our models have been compared to previous analytical and semianalytical models. In addition, these models have been compared to the finite-element method. The computational cost of our analytical model is very low, and we find a very good agreement between our analytical model and the other approaches presented in this paper. [ABSTRACT FROM AUTHOR]

The detection of force with higher resolution than observed in humans (~1 mN) is of great interest for emerging technologies, especially surgical robots, since this level of resolution could allow these devices to operate in extremely sensitive environments without harming these. In this paper, we present a force sensor fabricated with a miniaturized footprint (9 mm2), based on the detection of the magnetic field generated by magnetized flexible pillars over a giant magnetoresistive sensor. When these flexible pillars deflect due to external loads, the stray field emitted by these will change, thus varying the GMR sensor resistance. A sensor with an array of five pillars with 200~\mu \textm diameter and 1 mm height was fabricated, achieving a 0 to 26 mN measurement range and capable of detecting a minimum force feature of 630~\mu \textN . A simulation model to predict the distribution of magnetic field generated by the flexible pillars on the sensitive area of the GMR sensor in function of the applied force was developed and validated against the experimental results reported in this paper. The sensor was finally tested as a texture classification system, with the ability of differentiating between four distinct surfaces varying between 0 and 162~\mu \textm root mean square surface roughness. [ABSTRACT FROM AUTHOR]

In this paper, a permanent magnet (PM) slotless tubular linear generator based on magnet field analysis model is presented for wave energy conversion. To improve air flux density and efficiency of the generator, two improved Halbach PM Arrays (T-PM structure and claw-PM structure) applied in the slotless linear generator is proposed and compared with Halbach PM Arrays. Combined with axisymmetric dimensional finite-element method (FEM), no-load electromagnetic performance is analyzed. Finally, due to test and analysis model results of prototype concordant with the FEM results, the generator model and the analysis method are correct. [ABSTRACT FROM AUTHOR]

Linear magnetic-field modulated (LMFM) motor exhibits high thrust force by effectively employing the magnetic-field modulation effect. In this paper, a new mover separated LMFM (MS-LMFM) motor is proposed, which successfully alleviates the space confliction between permanent magnets (PMs) and windings in the existing LMFM motor. The structure and the operation principle of the existing and proposed motor are described, and the major design parameters are optimized for maximum thrust force. Moreover, electromagnetic performances of both motors are compared by finite-element method. Theoretical and simulation analysis shows that the proposed motor can exhibit enhanced force performance than the existing one under fixed copper loss. Simultaneously, reduced iron and PM losses can also be obtained by proposed motor. Finally, a 3-D modeling MS-LMFM motor is built for a global observation of motor structure and further verification of the 2-D analysis. [ABSTRACT FROM AUTHOR]

In this paper, one novel heteropolar radial hybrid magnetic bearing (HRHMB) is proposed for flywheel energy storage system. First, its structure and working principle are introduced in detail. Then, its fundamental equations are derived based on magnetic circuit model, such as displacement stiffness, current stiffness, and load capacity. Furthermore, its suspension performance and magnetic coupling are analyzed based on the 2-D finite-element analysis. Finally, the comparison of main performance indexes between the proposed HRHMB and conventional one under the same constraints is made. It indicates that the displacement stiffness can be reduced by the novel structure. In addition, the rotor core loss of the novel HRHMB is just 22.53 W, which is only 41.6% of the conventional eight-pole HRHMB with the same load capacity. [ABSTRACT FROM AUTHOR]

Magnetic levitation positioning systems (MLPSs) are of great interest in high-precision applications in vacuum. In this paper, a linear magnetic bearing with rhombus magnet array (RMA-LMB) for MLPS is proposed. With the RMA, the proposed RMA-LMB possesses advantages of excellent force uniformity, high force density, and good manufacturability. First, the basic structure and operating principle of the proposed RMA-LMB are presented. Second, the expressions of magnetic field, static force and torque, and dynamic force and torque are obtained by an equivalent current model. Third, the 3-D finite-element analysis (3-D FEA) is employed to investigate the RMA-LMB, and the magnetic field distribution, the static force and torque, as well as the dynamic force and torque are analyzed. Finally, a prototype is constructed, and experiments show a good agreement with the FEA results. [ABSTRACT FROM AUTHOR]

A two-body buoys power generation system using the field-modulated tubular linear permanent magnet generator (FM-TLPMG) is proposed for direct-drive wave energy conversion in this paper. The traditional linear generator has disadvantages of large weight and low-power density caused by the slow speed of ocean wave. The FM-TLPMG can overcome these disadvantages in some extent through accelerating the speed of the traveling magnetic field. In order to design a suitable FM-TLPMG for the direct-drive wave energy conversion in a short time, ocean wave theory is applied to analyze hydrodynamic problems of the two-body buoys and calculate the operating velocity of FM-TLPMG in the sea. A 2-D analytical model for FM-TLPMG design is presented to obtain the electromagnetic field distribution by solving the Laplace and Poisson equations for each region. The analytical result has been compared with the finite-element analysis and shows its validation for the design. [ABSTRACT FROM AUTHOR]

Inductively coupled power transfer (ICPT) technology realizes energy transfer across relatively large air gap with magnetic coupling. However, the flexibility of traditional ICPT system is limited because only one-degree freedom is allowed. This paper proposes the design, simulation, and implementation of a novel multi-degree of freedom power pickup mechanism for ICPT system, which can receive power at arbitrary angle in space. The pickup mechanism is designed of regular tetrahedron structure, and the pickup coils are fixed on its six edges. An optimal winding strategy of the six coils is proposed to increase the output power capacity through theoretical analysis and Maxwell simulation. The experimental results show that the pickup mechanism has a good power pickup capacity, and system efficiency is relatively high at any angle of the pickup mechanism. [ABSTRACT FROM AUTHOR]

This paper examines the contributions of different actuator parts to the magnetic force. The method is to decompose the magnetic field into components according to the current density and magnetization in distinct parts, and to interpret all the magnetic forces by means of these components. This enables isolation and quantification of the magnetic forces between any actuator parts. The approach is demonstrated with practical design problems to explain how different actuator parts contribute to the magnetic force. [ABSTRACT FROM AUTHOR]

The magnetic susceptibility of pyrolytic graphite (PyG) is temperature dependent. Under an external magnetic field, a levitated PyG sample with a localized temperature change experiences unequal diamagnetic forces. In this paper, we present a study of the macroscale optomechanical displacement of a levitated PyG sample by using a laser source to locally increase the temperature. Dynamic finite-element method simulations show that a localized increase in the sample temperature, simulating a laser source, decreases the diamagnetic force in that local area, leading to the displacement of the PyG sample in the plane of the permanent magnet array. Experimental setups built using different laser sources and samples confirm the range of applicability of the actuation phenomenon to different conditions. An additional setup without moving parts reduced the likelihood by which airflow could have caused the displacement, as we suspect happened in the previous studies. [ABSTRACT FROM AUTHOR]

This paper presents the analytical solution of levitation problem for both magnetically anisotropic and conductive balls. The magnetic field exerts eddy currents in magnetic and conductive balls. The forces, both Lorentz (of eddy current) and material (caused by inhomogeneity of reluctivity), lead to the levitation of the ball. The electromagnetic field is determined by means of variable separation method. The forces, both Lorentz and material acting upon the ball, are calculated. Power losses are calculated twice by means of Joule volume integral and Poynting surface integral. The total force is evaluated three times by Maxwell, coenergy, and Lorentz methods. Levitation force and power losses versus frequency are presented. Asymptotic relations for levitation force and power losses are derived. The comparison to levitating disk at the same volume is presented. [ABSTRACT FROM AUTHOR]

This paper concerns a coupled analysis of the stray magnetic field and the external housing vibration of a synchronous machine to detect rotor short-circuit faults. Indeed, in addition to the possibility to measure these parameters with non-invasive equipment, these two measures depend on the air-gap flux density that is directly impacted by the short circuits of any nature. Hence, correlating these two quantities, it is achievable to confirm or discard an eventual motor fault. This method allows both to develop an analysis of non-invasive manner and to establish the magnetic state of a synchronous generator in normal operation. The experimental survey of stray magnetic field and housing vibration spectrum is shown as a promising alternative at low cost and easy to implement and to determine, for instance, rotor turn-to-turn winding faults. Faulty and healthy signatures are drawn from the measured spectra to determine a degree of healthy state of the synchronous machine. [ABSTRACT FROM PUBLISHER]

This paper proposes a new measuring system and an improved model for magnetostriction characteristics of a highly grain-oriented electric steel sheet (HGO-ESS) whose magnetic domains are bigger in size and higher in the degree of alignment than those of a grain-oriented one. The measured data of anisotropic magnetostriction characteristics of the HGO-ESS, through an improved model that has its theoretical basis on the mechanical elasticity, are included in the finite-element analysis of magnetostriction force of a power transformer. The effectiveness of the measuring system and improved magnetostriction model is validated by comparing with the experimentally measured results over a 30 MVA power transformer model. [ABSTRACT FROM AUTHOR]

This paper deals with a redesign of a magnetic wheel for a self-acting robot. The target of the redesign is both increase of the attracting force necessary for carrying of the robot and lowering of the mass of the wheel. For obtaining the most accurate results, three calculation techniques were used. The analytical solution shows conversion of the real geometry between the wheels on the surface to a fictional constant gap and allows getting the total attracting force under some simplification. The numerical linear model respects the dimensions of the wheel exactly, and both linear and non-linear solutions of the situation are compared. [ABSTRACT FROM AUTHOR]

The viscosity of a magnetorheological fluid (MRF) changes with the magnetic field; however, the behavior of magnetic particles in an MRF under the application of a magnetic field has not been fully clarified. In our previous work, we proposed a real-time observation system in which the torque is simultaneously measured. Textured poles concentrated on a magnetic field, increasing the transfer of torque. In this paper, the behavior of magnetic particles, such as the formation, fracture, and sliding of clusters, in the presence of textured poles as well as the transfer of torque was investigated by in situ observation using our torque measurement system. With increasing depth of the pole texture, the magnetic-field gradient increased, the magnetic field at the edges of the texture increased, the clusters became concentrated in a narrower region, and the maximum torque increased. These results are expected to lead to the design of more efficient torque transfer devices using MRFs. [ABSTRACT FROM AUTHOR]

This paper proposes a novel linear–rotary permanent-magnet actuator (LRPMA) with interlaced poles, which has the merit of using only 50% of the neodymium–iron–boron permanent magnets when compared with those used in traditional Halbach structure. By assuming the stator is slotless, the magnetic field distribution of the LRPMA is initially analyzed using the magnetic scalar potential in the Cartesian coordinate system. A method for calculating the relative permeance by Schwarz–Christoffel transformation (SCT) is subsequently deduced to analyze the magnetic field in detail and predict the cogging force/torque of LRPMA very accurately. The analytical linear cogging force and rotary cogging torque are derived and verified for the design optimization of the actuator. The 3-D finite-element method is used to verify the correctness and effectiveness of the proposed SCT. [ABSTRACT FROM AUTHOR]

In this paper, the nanoparticles are ferromagnetic and have charge density on the surface, and the magnetic force is coupled with the Lorentz force. To investigate the distribution of magnetic force exerted on a unit cell with different volume fraction, the nodal force method and homogenization method are applied. Lorentz force on the electric double layers of different size particles are analyzed using both 2-D and 3-D models. The calculated results show that 2-D analysis is sufficient for the analyzed nanoparticles. The proposed electromagnetic forces analysis method can be coupled to fluid and temperature analysis of nanofluid. [ABSTRACT FROM AUTHOR]

During the operation of an elevator emergency stop device, the elevator cage decelerates significantly. Some passengers have been injured in emergency stoppages because they were subjected to a large impact force from the elevator emergency-stop device. Therefore, we focused on the passengers’ safety in elevators and proposed an emergency-stop device with a spring and a magnetorheological fluid damper that enables the damping coefficient to be varied continuously by controlling the magnetic field. In this paper, based on the International Standard and the guide for elevators, we evaluate the performance of three types of emergency stop device, namely, the conventional mechanical emergency-stop device, a stop device with a controller designed for a full complement, and a stop device with a revised controller. [ABSTRACT FROM AUTHOR]

In this paper, we presented a novel miniature shaftless motor using the impact drive mechanism (IDM) that takes advantage of the friction and the inertia force to achieve the self-propelling motion. The proposed motor uses two U-shaped iron–gallium alloy (Galfenol) rods as the driving elements. Besides Galfenol, the motor consists of one permanent magnet that provides a bias magnetic field within Galfenol. This bias magnetic field helps the motor to generate the swing motion that can amplify the inertia force of the IDM motor. By controlling swing directions of two motor arms through the driving current, the consistent rotation of the motor is accomplished. The experimental result indicates that the proposed motor is able to achieve an angular velocity of 12.74°/s at 230 Hz. Because of the unique design of the motor, the motor can achieve a linear movement, and the result is briefly reported. The objective of future work is to realize an in-plane three-degree-of-freedom motor that can follow a designated trajectory. [ABSTRACT FROM AUTHOR]

This paper proposes a combined numerical and analytical approach for magnetic vibration analysis of a new dc-excited multitoothed switched reluctance (MSR) machine. First, the machine design is artfully to incorporate the dc-excited winding into the MSR topology, hence breeding a new flux controllable, high-torque, low-torque ripple, and doubly salient magnetless machine. Then, the finite-element-method is used to calculate the machine force and torque. A series of analytical equations are formulated to calculate the magnetic vibration parameters of the proposed machine. The analysis process and the corresponding results are given to verify the validity of the proposed approach for magnetic vibration analysis of the new machine. [ABSTRACT FROM AUTHOR]

A novel transverse-flux permanent magnet linear motor (TFPMLM) named as double-sided double-excited one is proposed in this paper. First, the operational principle and structural advantages of the TFPMLM are presented. Then, the 3-D magnetic circuit structure of the TFPMLM is simplified equivalently into a 2-D one in order that Schwarz–Christoffel (SC) mapping method can be adopted to analyze the motor’s magnetic field and characteristics. Then, the air-gap flux density distribution, back voltage and force waveforms when at no-load and at load are calculated by the SC mapping method and 3-D finite-element method, respectively, for a prototype linear motor, The results from the two methods coincide much better with each other. At last, influences of magnet shape on the cogging force are studied by the SC method. [ABSTRACT FROM AUTHOR]

The high-temperature superconductor (HTS) machines are more attractive due to the advantages of high power density and efficiency. This paper introduces a new HTS electromagnetic screw (HTS-EMS) that is developed for artificial heart. Two helical-shaped slots are introduced to the translator; the key to the HTS-EMS is that the HTS coils carrying dc currents are placed in the helical-shaped slots. The permanent-magnet array is placed in the rotor. Due to the high current density of the HTS coil, the power density of the HTS-EMS can be improved effectively. The electromagnetic performance of the HTS-EMS is analyzed, including the flux, thrust force, as well as torque. The proposed HTS-EMS is evaluated compared with the existing magnetic screw using time-stepping finite-element method, verifying the advantages of the proposed structure. [ABSTRACT FROM AUTHOR]

This paper presents a wireless active finger rehabilitation method controlled magnetic forces within a three-axis coil system. The three-axis coils enhanced degree of freedom in hand positioning. The developed system includes three magnets for controlling one finger within the coil, thus, providing external force to the finger without the use of a complex mechanical structure. The proposed method is simple in configuration and operates wirelessly by magnetic interaction. The system generates three magnetic forces for flexion and extension of the finger. The proposed method can be used regardless of the position of the hand in the system. The combined influence of the three magnetic forces used to generate flexion and extension of the finger was verified through experimental analysis. [ABSTRACT FROM AUTHOR]

To solve the problem caused by the heavily axial gravity load of the rotor and main shaft of the vertical hydraulic generators, a superconducting induction magnetic levitation device is proposed in this paper. AC superconducting windings are implemented to increase the levitation force. The inductive eddy magnetic field acts back on the primary field, and the levitation force and rotation torque will be produced between the primary and the secondary. A multistage primary is implemented to eliminate the rotation torque and enhance the levitation force. 3-D finite element method (FEM) is used to analyze the proposed device. In addition, the ac loss power is analyzed and estimated. The levitation force and rotation torque are deprived and analyzed under different conditions. Simulation results show that the proposed levitation device is well-suited for the de-load application of hydraulic turbo-generators. [ABSTRACT FROM AUTHOR]

This paper presents electromagnetic modeling and analysis of the detent force in a permanent magnet linear synchronous machine (PMLSM) according to auxiliary teeth configuration. Analytical solutions for magnetic fields generated by PMs are derived based on the Maxwell equation in terms of a 2-D Cartesian coordinate system. The magnetic vector potential of each subdomain (PM, air-gap, slot, and end region) is derived, and the field solution is obtained by applying the boundary and interface conditions between the subdomains. Based on the analytical solution, the magnetic force is derived by using the Maxwell stress tensor. All the analytical results were extensively validated using nonlinear finite-element analysis and experimental results. Using the proposed method, we investigated the influence of the machine parameters on the detent force. Therefore, the proposed method can be very useful in the initial design and optimization process of PMLSM for detent force analysis. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency wireless power transfer (WPT) and force transfer system for a micro-robot is proposed. Two-coil systems are employed to power the micro-robot. The two-coil parts are ac and dc, and each consists of an external source and a load coil inside the micro-robot. In the ac coil part, the external source coil generates a time-varying magnetic field that is received by the ac load coil in the micro-robot as electrical energy. In the dc coil part, the external source coil is used as an electromagnet, which is used to generate propulsion force for the micro-robot. Through the proposed system, both the efficiency of electrical energy transfer and the generation of propulsion force can be significantly improved. The feasibility of the proposed approach was verified through simulation and experimentation results. [ABSTRACT FROM AUTHOR]

This paper develops an approximate analytical model to describe the magnetic fluxes, forces, and armature reaction in cylindrical voice coil actuators and related electric machines. Magnetic flux is assumed to either lie in an inner region of the actuator and parallel to its axis, or in an outer region of the actuator and oriented radially. A differential reluctance model is derived for this set of assumptions, with a structure and solution set similar to those involved in extended-surface heat transfer (“fins”) and lossy transmission lines. Particular solutions for the force constant, motor constant, coil inductance, and variable-reluctance force are found for a symmetric motor with opposed axial permanent magnets on either side of an iron flux concentrator. The model results for this topology are validated using finite-element analysis and experimental measurements from a prototype. [ABSTRACT FROM AUTHOR]

This paper deals with finding the optimal ratio of height and length of single-sided linear induction motors using the finite-element method (FEM) for magnetic-field analysis coupled with optimal design methodology. For effective analysis, the FEM is conducted in time harmonic field, which provides steady-state performance with the fundamental components of voltage and current. The ratio of height to length providing the required output power is obtained by response surface methodology and optimal values are presented by the variation in output power. When output power is small, the ratio is high and as the power increases, the ratio shows a converged value. Considering the general application of linear motors, usage of a small ratio can be limiting, however, the shape ratio for the maximum thrust can be identified. [ABSTRACT FROM AUTHOR]

In this paper, we focused on the diamagnetism of grease oil for pivot bearings in hard disk drives (HDDs) and investigated the effect of a magnetic field on oil vapors. We vaporized the grease oil and compared the amounts of oil adsorbed on disk surfaces through two slits—one with magnets and the other without—in a preliminary experiment. As a result, we confirmed that it is possible to reduce the amount of oil adsorbed on a disk surface with the aid of a magnetic field. Based on the preliminary experiment, the grease oil vapor from the pivot bearing unit of HDDs was compared with regard to a narrow slit and clearance with and without the magnetic field gradient of permanent magnets. The amount of oil vapor was decreased by the magnetic field gradient, and the reduction ratio depended on the environmental temperature. The amount of oil vapor from the actual pivot bearing unit could be reduced by the ring magnet around the pivot unit. Finally, our results suggested the possibility of a gas seal generated by the magnetic field gradient for the pivot bearing unit in HDDs. [ABSTRACT FROM PUBLISHER]

A novel direct drive 6-degree-of-freedom (DOF) planar levitating synchronous motor has been developed that is comprised of multiple 1-D magnet arrays attached to a moving stage and multiple stationary 1-D coils built as a printed circuit board (https://www.youtube.com/watch?v=-r4Tv7GbB8o). Together these make up a set of four 2-DOF Lorentz force motors that actuate the moving stage in 6-DOF over a large planar range. This motor topology allows scalability with minimal increase in controller and drive complexity as well as direct drive actuation of a single mover body without intervening bearing elements, making it ideal for a variety of industrial automation and manufacturing applications. For high performance applications that require rapid high-precision motion, a linear, position independent force characteristic is desired to minimize the controller effort and reduce the intrinsic force disturbances, which adversely affect positioning accuracy. In the presented planar levitating synchronous motor, the primary source of force disturbance is the interaction between higher order spatial harmonics of the magnetic field of the mover and the commutated excitation current in the stationary coils. This paper presents analysis and experiment results of a novel method of reducing force ripple associated with permanent magnet planar levitating synchronous motors through the design of appropriately split and spaced magnet arrays. This method internally cancels out specific force harmonics within each 2-DOF motor, without adding controller complexity or resorting to higher order magnet arrays. Experimental results demonstrate force ripple reduction from 1.1% without magnet array splitting to 0.12% with magnet array splitting. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a microrobot powered by wireless power transfer (WPT) system which can generate propulsion force and torque as well as electrical energy to perform complex missions. The magnetic field and the induced current from the WPT coils can be utilized into the propulsion force and the Lorentz force for implementing rotational movement. The generated propulsion force and the torque are verified by 3-D finite-element simulations and experimental measurements. [ABSTRACT FROM AUTHOR]

This paper proposes to determine the radial forces in bearingless permanent magnet motor topology. We consider normal and tangential components of the magnetic field in the air gap. Their harmonic components and their evolution versus current and rotor position are considered. This allows establishing the semianalytical expressions of the radial forces considering different field sources. Their precision has been verified using a full finite element model and statistic analysis. The advantage of this semianalytical model lies in the swiftness of the different force components evaluation and consequently the reduction of CPU time. [ABSTRACT FROM PUBLISHER]

This paper mainly investigates the shear performance of a metal foam magnetorheological (MR) fluid damper. As for the damper, MR fluids are stored in metal foam in the action of magnetic field, MR fluids are drawn out from the metal foam, and then fill the shear gap, thus producing the MR effect. Based on previous research, as a sample, the metal foam nickel (Ni) is applied to store MR fluids, and the metal foam Ni MR fluid damper is designed and manufactured. A test rig, including the metal foam MR fluid damper, dc motor with speed controller, force sensor with amplifier, and DAQ card and PC with LabVIEW software, is built to study the shear performance. The effects of excitation current and shear rate on damping force are analyzed. Besides, considering the influence of different currents on magnetic field, a series of magnetic field simulations on the damper are carried out in ANSYS FEM software. The results show that the excitation current is the key factor to damping force of the damper; with the increasing of the current, the damping force will increase. However, once the current is above 1.5 A, the increment is no longer obvious. Besides, damping force will decrease with the share rate increasing. [ABSTRACT FROM AUTHOR]

Magnetic fluid is a new functional material for optical sensors. The microstructure will be changed with various applied magnetic fields. In this paper, the molecular dynamics method based on rod-like particle was first used to simulate the microscopic movements of magnetic nanoparticles in magnetic fluid with the volume fraction of 1%. Simulation results showed that magnetic nanoparticles could aggregate to form a new type of magnetic fluid photonic crystal when the applied magnetic field intensity exceeded 180 Oe. Then, the tunability of the magnetic fluid photonic crystal was studied. It was found that the average diameter of magnetic columns would decrease when the applied magnetic field intensity was increased from 180 to 320 Oe. Furthermore, based on the simulation results, optical property of the magnetic fluid photonic crystal was studied. When the direction of the incident light was parallel to the direction of the applied magnetic field, the transmissivity would increase from 0.5944 to 0.6475, whereas when the direction of the incident light was perpendicular to the direction of the applied magnetic field, the two photonic bandgaps of transverse electric mode and TM mode all moved to higher frequency, and the two bandwidths decreased about 17% and 87%, respectively. Through the above research studies, it was proved that the magnetic fluid photonic crystal processed the magnetic tunability and would be used as a novel magnetic field sensor in the future. [ABSTRACT FROM AUTHOR]

Magnetic-geared motors have been attracting attention as a type of low-speed and high-torque motor. The maximum torque is, however, limited by the maximum transmission torque between the rotors. This paper proposes a magnetic-geared motor with field windings which can increase and decrease the maximum transmission torque. Its N–T curve is then calculated and compared with a magnetic-geared motor without field windings. The characteristics are determined using finite element analysis. [ABSTRACT FROM AUTHOR]

In this paper, we derive a quantitative model for the manipulation of superparamagnetic particles by superposition of a homogeneous magnetic field and magnetic field gradients. Our results show that by this combination, the magnitude as well as the sign of the force on a magnetic particle can be controlled. By quantitatively modeling the magnetic force on a representative superparamagnetic particle, we find that for a common lab-on-chip scenario large repulsive forces can be achieved by adding a homogeneous field perpendicular to the plane of the chip. This offers new perspectives for the on-chip manipulation of magnetic particles. As a first example, in-plane positioning of particles with an accuracy of \(\sim 1 \mu \) m is experimentally demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents fluid manipulation using multiscale spiral-type magnetic machines with magnetic wireless operations. Magnetic spiral-type or helical machines have been widely used for biomedical applications. We considered two applications in the spiral-type magnetic machine: microfluid control (micromixer and micropump) and application for a pediatric blood pump. We investigated micropumping and mixing abilities by using the magnetic spiral machine ( \(\Phi ~1.25\) mm \(\times 10\) mm) in a silicone oil with a kinetic viscosity of 5 mm \(^{2}\) /s. In addition, we confirmed the ability to apply these to a pediatric blood pump based on large machine ( \(\Phi ~18\) mm \(\times 35\) mm). The pump produced a flow rate of 1 to 3.5 L/min with a pressure rise of 40–60 mmHg. [ABSTRACT FROM AUTHOR]

This paper investigates a kind of cylindrical linear single-axis actuator that is used in the magnetic levitation stage to provide fine movement. The magnetic flux density distribution due to the permanent magnet is determined using the surface charge method, and the magnitude of force generated by the actuator is calculated using the Lorentz force equation. Both of them can be solved by numerical integration. The results are verified by measurements. The magnetic force components are fitted as an analytical style that can be used in the real-time controlling of this actuator for the magnetic levitation stage. [ABSTRACT FROM PUBLISHER]

Targeted drug delivery using magnetic nanoparticles (MNPs) is a new therapeutic method and is being improved continually. However, recent improvements have focused mainly on the introduction and synthesis of special drugs and there are still limitations getting a drug to desired locations in the body, primarily owing to the small size of nanoparticles and the difficulty of controlling their movement in the body. This paper introduces a new electromagnetic actuation system for guiding MNPs in blood vessels. This system uses six electromagnets powered by currents that can generate a high-gradient magnetic field in the desired direction. A differential current coil (DCC) approach is used to calculate the current applied to each coil. Due to properties of the DCC approach, it is possible to use soft iron cores at the centers of the coils to amplify and concentrate the magnetic field in the desired region and generate a stronger magnetic force than the existing coil systems. To evaluate the performance of the actuation system, a model that guided nanoscale magnetic particles inside special channels was studied using commercial software. To improve the efficiency of the electromagnets for MNP guidance, the structural parameters of the cores and coils were chosen based on the simulation results to get the largest magnetic force in the region of interest, which was set as size of the mouse brain. The proposed actuation system is very compact and less expensive than previous systems. Furthermore, the simulation results demonstrated that the actuation system can generate adequate magnetophoretic forces for nanoparticle steering in a Y-shaped vascular model and can be potentially used as a propulsion tool for MNP guidance in blood vessels. [ABSTRACT FROM PUBLISHER]

We present a method to seamlessly self-assemble, disassemble, transport, and reconstruct ordered 2-D structures of fluid-borne microspheres on a surface using an array of magnetic zigzag wire traps. Competition between and control over: 1) the trapping forces of underlying magnetic patterns; 2) magnetic dipole repulsion; and 3) Brownian motion gives rise to reproducible cluster structures. Weak external magnetic fields (<175~Oe) tune the spacing between particles and enable the assembled structures to be remotely manipulated and reassembled on the platform. This method could be used in biological and photonic applications by utilizing the microspheres, for example, as carriers of host biomolecules or as linkers to fluorescent emitters. [ABSTRACT FROM AUTHOR]

Structural vibrations in modern buildings have been increasing concerns. If not properly controlled, they would give rise to serviceability problems and disturbances to occupants. The permanent magnet (PM) linear actuator-based active vibration mitigation strategy exhibits excellent dynamic performances on elimination of vibrations with complex modes, and has great potential. This paper describes modeling, design optimization, and numerical and experimental verifications of a PM linear actuator for structural vibration mitigation applications. Analytical expressions for prediction of the actuator performance are derived, and the linear actuator is then designed in optimization within a specific set of volumetric and thermal constraints in order to maximize the product of efficiency and power factor. It is shown that the proposed analytical model has provided a computationally efficient tool for design optimization, and the Halbach ratio and actuator width have significant impacts on the performance of the PM linear actuator. The results are validated by finite-element computations, and further verified by experimental measurements on a prototype actuator. [ABSTRACT FROM AUTHOR]

This paper develops a novel magnetomotive forces (mmfs) distribution model along the transverse direction for the 3-D analysis of linear induction motor, and it investigates the influence of a laterally asymmetric cap-secondary on the thrust, vertical force, lateral force, and efficiency in a prototype single-sided linear induction motor for linear metro. First, the mmf distribution model and its working conditions are defined, and the model is transferred into a mathematical model. Second, the air-gap flux and secondary eddy current in a prototype linear motor with a cap-secondary are obtained by a 3-D space harmonic analytical method. Third, the thrust, vertical force, lateral force, and efficiency of the test motor are analyzed with various lateral deflection, and the power factor in secondary is also presented. Finally, these results are experimentally verified by measurements on the test rig of the linear motor, and the comprehensive effect on the operating performance can be accurately calculated by the mmf model. [ABSTRACT FROM PUBLISHER]