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This paper proposes an all-in-one system for hyperloop that conducts propulsion, levitation, and guidance. Currently demand on high-speed long-distance transportation is increasing, so that hyperloop is getting attention and studied hard globally. Hyperloop is a new innovative transportation in which a levitated subsonic speed train travels through a vacuum cylindrical tube. Hyperloop needs functions of propulsion, levitation, and guidance for its service, and many devices are necessary for those functions. In the tube, a constrained space, many devices make the entire system complicated, and the size of the vehicle and tube are increased. Therefore, the costs of maintenance, manufacture, and construction are increased and control of each device becomes very difficult. But a non-symmetric double-sided linear induction motor (NSDLIM), the subject of this paper, is an all-in-one system that could conduct all functions. In this paper, the concept of NSDLIM was introduced and its possibility was suggested. Requirements of NSDLIM were investigated considering very high acceleration, velocity, and low air pressure. An NSDLIM model was designed and analyzed by using the finite-element method. Then, NSDLIM parameters that affect performance were investigated and adjusted to improve performance. The derived model performance was shown, and its possibility was considered. [ABSTRACT FROM AUTHOR]

Rotary-linear switched reluctance motors (RLSRMs) have been introduced to realize simultaneous rotary and linear motions in one structure. This paper proposes the modeling of RLSRM in two manners: analytical and finite-element methods. In the first approach, a model is proposed based on position-wise functions which describe the governing equations of the motor. The derived equations are utilized in a block diagram to comprise the model. In the second approach, static FEA is utilized to improve the former model by obtaining the inductance profile of the motor. The models separate the rotary motion from the linear motion in order to calculate the torque and force. The analytical model is faster than the FEA-based model because of the independency to FEA. However, it is less accurate. The FEA-based model needs prior static FEA and considers the fringing and saturation effects more accurately. The FEA-based model is computationally more efficient than the 3-D transient FEA. The motor’s performance parameters obtained via the models versus the 3-D transient FEA as well as the experimental test results indicate the accuracy and efficiency of the proposed models. [ABSTRACT FROM AUTHOR]

The isolation bandwidth of zero stiffness permanent magnet bearing (ZSPMB) is limited by the stiffness variation near the zero stiffness point. This paper proposes an accurate and effective modeling technique to analyze and optimize the stiffness of ZSPMB in working range. Since the stiffness of ZSPMB is very sensitive to modeling errors, the variable current model of the permanent magnet is first derived considering magnetic permeability, the influences of which on the magnetic field and force are attributed to the reluctance effect in this paper. Then, the force exerted between permanent magnets (PMs) is equivalently decomposed into Lorentz force and reluctance force. Based on the Biot–Savart law and elliptic integral, the magnetic field of rings with axial, radial magnetizations and the equivalent Lorentz force (ELF) of typical ZSPMB topologies are calculated analytically. The equivalent reluctance force (ERF) is subsequently obtained by combining the finite element method. Compared with the ELF, the ERF is about one order of magnitude smaller and in the opposite direction and it causes the stiffness-displacement curve to drift and deflect. Finally, a Halbach ZSPMB is optimized with the ELF model, and then the ERF is suppressed by fine-tuning the structural size. The finite element analysis results show that the stiffness variation in the working range is effectively reduced, and the validity of the proposed hybrid analytical-finite element model modeling technique is verified. [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 proposes a novel permanent magnet planar motor with moving multilayer orthogonal overlapping windings. This novel motor topology can achieve a five-degrees-of-freedom drive using two sets of $x$ -direction windings and two sets of $y$ -direction windings in a coreless configuration. The orthogonal multilayer construction guarantees a high utilization of the magnetic field and realizes decoupling between the $x$ -direction thrust and the $y$ -direction thrust. The topology and operating principle of the planar motor are introduced in this paper. The analytical modeling of the motor is established based on the equivalent current method, and the expressions of forces are derived. The force characteristics of the two-layer and three-layer winding topologies are compared, and the design guidelines of a planar motor are proposed. The analytical and 3-D finite-element model results are validated with the experimental results of a tested prototype. [ABSTRACT FROM AUTHOR]

This paper presents an improved magnetic circuit (MC) model considering the leakage, cross coupling, and saturation effects for the performance analysis of an integrated 3 degrees of freedom magnetic bearing (3-DOF MB). Compared with the conventional MC model, this paper analyzes the permanent-magnet bias field, radial and axial control current fields together. By using this improved MC model, it reveals the cross-coupling effect between radial and axial directions in such an integrated 3-DOF MB. The stiffnesses of radial force are significantly influenced by the axial control current, while the stiffnesses of the axial force are independent of the radial control current. Its accuracy is verified by the 3-D finite-element method. [ABSTRACT FROM AUTHOR]

This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison with PM-type lead screw is given. In addition to this, the theoretical analysis to support the use of a 2-D finite element model to analyze the 3-D magnetic-type lead screw is given, which has not been well covered in the existing literature. [ABSTRACT FROM AUTHOR]

This paper presents a study on the braking effect of the electromagnetic forces produced by eddy currents induced in nonmagnetic materials. The purpose of this paper analyzes the behavior of a moving device within ducts when a constant magnetic field is applied on its inner surface, causing induction of eddy currents in pipeline walls, and verifies how the interaction effects of these currents with the field that induced them might be significant on the device movement. [ABSTRACT FROM AUTHOR]

This paper focuses on the performance analysis of linear flux-switching permanent magnet (LFSPM) motor. The analysis of electrical machines is mostly done by finite element method (FEM) and analytical method. However, it is time-consuming to determine the effects of the design parameters on the motor performance with FEM. It is also difficult to utilize the analytical technique for the intricate structure of LFSPM motor. In this paper, the response surface methodology in conjunction with FEM is proposed to analyze the LFSPM motor efficiently. As a demonstration, the influence of design parameters on the motor net thrust force is analyzed with the proposed method. Analysis of variance and comparison between the fitted response and results obtained from FEM all confirm the validity of the proposed method. [ABSTRACT FROM AUTHOR]

With an increased mobility, hard disk drives (HDDs) now use ramp load/unload technology, and multiple disks are used to increase the data capacity. This can result in contact between the ramp and the disks, which negatively affects the slider dynamics under operational shock conditions. There are several types of ramp–disk contact, such as simultaneous, successive, and single contact, and these depend on the distance between the ramp and each disk in a multi-disk HDD. This paper examines the effect of ramp–disk contact on the slider dynamics using a transient shock analysis. The ramp–disk contact affects the head stack assembly bending mode and slider dynamics. The effect of irregular gaps between the disks and adjacent ramp on the slider dynamics is analyzed with the ramp–disk contact force. The simulation shows that the gap irregularity between the ramp and each disk should be as small as possible to improve the stability of the slider dynamics. [ABSTRACT FROM AUTHOR]

A novel electrodynamic suspension device using an asymmetrical double-sided Halbach array is proposed in this paper. A 3-D analytical model describing the eddy current field and the electromagnetic force is established via the second-order vector potential formulation. The validity of the analytical model is verified by both finite-element simulations and an experiment. The configuration of the proposed suspension device is optimized exploiting a dynamic kriging surrogate model assisted by a multi-objective genetic algorithm. The multi-objective optimization is performed utilizing the 3-D analytical model. [ABSTRACT FROM AUTHOR]

The aim of this paper is, first, to extend the application of the hybrid analytical modeling (HAM) approach for the analysis of tubular linear machines (TLPM), something that has never been reported yet in the scientific literature. The HAM consists of a strong coupling between the reluctance network and the Fourier series solution of magnetic scalar potential. In order to assess the merits and capabilities of the HAM, it is applied to the study of the cogging force in linear machines and compared with finite element analyses (FEA). The cogging force is a global quantity, which is very sensitive to magnetic field computation accuracy and constitutes, therefore, a good measure of the accuracy of the HAM as compared with FEA. The HAM should require less computation time as compared with FEA, and is then more suitable for predesign stage. Three different structures are analyzed: a flat linear machine, a TLPM with internal mobile armature, and, finally, a TLPM with external mobile armature. The analyses are conducted, considering the effect of magnetic saturation. [ABSTRACT FROM PUBLISHER]

An exact analytical model of a surface-mounted bearingless permanent-magnet synchronous motor (BPMSM) with rotor eccentricity by a perturbation method is proposed in this paper and its computational accuracy is verified by the finite-element method. Considering the rotor eccentricity, a compensation control system is implemented based on the mathematical model of levitation force by applying a coefficient of the rotor eccentricity calculated by the exact analytical method (EAM). The experimental results suggest the improvements of the dynamic and the static performances of the stable suspension state for the surface-mounted BPMSM and the feasibility and effectiveness of the EAM. [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]

In this paper the concept of magnetic rolling resistance (MRR) is introduced. The MRR is particularly useful when trying to characterize maglev devices that operate with a slip. Approaches to minimize the MRR for an electrodynamic wheel magnetic suspension device are discussed. MRR is calculated from the power losses and it is shown that by using MRR a direct performance comparison with existing modes of transportation can be made. The MRR for a number of different maglev designs is calculated. [ABSTRACT FROM PUBLISHER]

The goal of this contribution is to show the capabilities of relatively fast computation techniques which can be advantageously used in design optimization procedures of electrical machines. The computation of cogging torque, for rotating machines, and force, for linear machines, being very sensitive to the accuracy of used models, its estimation is then used as an indicator for the efficacy and correctness of these techniques. A finite-element (FE) model will be used as a reference model. The first technique is based on a reluctance network (RN) generated from a mesh of studied structure. The second technique consists of coupling RNs obtained from a mesh of some parts of studied structure and an analytical model of magnetic field in other parts. These techniques are used for the modeling of a linear tubular flux-switching permanent magnet (LTFSPM) machine. LTFSPM machines are relatively complicated to model, and their modeling using these two techniques has never been reported yet in the scientific literature. The two models are both validated by comparisons with FE analyses. [ABSTRACT FROM AUTHOR]

Novel multi-tooth linear variable flux reluctance machines (LVFRMs) are proposed in this paper. First, the topologies and feasible primary-/secondary-pole combinations of single- and multi-tooth LVFRMs with six primary poles are introduced. Based on the analytical analysis of permeance model, the maximum average force can be obtained when the dc field and ac armature copper losses are equal. Moreover, four small teeth per primary pole ($n = 4$) LVFRM exhibits the largest average force. Furthermore, the electromagnetic performances of single- and four-tooth LVFRMs with $N_{s} = nN_{p} + 1$ are comparatively studied using the 2-D finite-element analysis (FEA). It is shown that 6/25 primary-/secondary-pole four-tooth LVFRM can provide higher force capability and lower force ripple than that of 6/7 primary-/secondary-pole single-tooth LVFRM at relatively low copper loss. Similar to single-tooth LVFRMs, four-tooth LVFRMs with $N_{s} = nN_{p} \pm 1$ exhibit more sinusoidal back electromotive force, larger thrust force and lower force ripple than those with $N_{s} = nN_{p} \pm 2$. Finally, the 3-D model of 6/25 primary-/secondary-pole four-tooth LVFRM is investigated to validate the 2-D FEA predicted results. [ABSTRACT FROM AUTHOR]

This paper is concerned with the analytical calculation of the interaction force between two permanent magnets (PMs) under relative rotation by means of the surface charge method, taking into account the non-unity relative permeability of the PMs. This model combines high accuracy and short calculation time. As the considered PM configuration is a free-space, unbounded problem, the results from the surface charge method are compared with its numerical counterpart, the boundary element method. The analytical expressions were validated by means of the measurement results obtained from a 3-D printed test setup. [ABSTRACT FROM PUBLISHER]

An analytical model could be very useful in the design and analysis of electromagnetic devices. In this paper, a nonlinear analytical model of a hybrid-excitation double-sided linear eddy-current brake is presented. The nonlinear analytical model takes into account leakage flux, higher harmonics, core saturation, and the actual path of eddy currents in the secondary conductor. Therefore, as compared with the conventional analytical model, the accuracy of the nonlinear analytical model is observably improved. Finally, the finite element analysis is employed to confirm the validity of the nonlinear analytical model. [ABSTRACT FROM AUTHOR]

This paper analyzed thrust characteristics by considering the step-skew method and permanent magnet (PM) overhang in a linear synchronous motor. Although the PM overhang increases the thrust, it also influences the air-gap flux density distribution in the stacking direction, and thus, each step length should be adjusted according to the existence and length of the PM overhang. 3-D finite element analysis is used to calculate the magnetic field and the thrust characteristics are compared each other. The analysis results show that the stacking length of both ends of the step should be reduced to get lower detent force and thrust ripples, and higher generated thrust as the PM overhang is increased. [ABSTRACT FROM PUBLISHER]

This paper proposes a permanent magnet (PM) biased axial magnetic bearing (MB) with multiple air gaps. However, the inherent complex structure makes finite-element analysis (FEA) very time-consuming. For the sake of simplifying the analysis, an equivalent magnetic circuit model together with the conformal mapping method and Laplace’s equation is developed. The conformal mapping method is employed to obtain the flux distributions in rectangular air gaps by accounting fringing effect, while the Laplace’s equation is used to predict the leakage flux surrounding PM rings. The developed analytical model is validated by FEA. Consequently, the design parameters in the axial MB are analytically determined. [ABSTRACT FROM AUTHOR]

In this paper, a novel parallel magnetic path hybrid excitation linear eddy current brake is presented. The parallel magnetic path scheme is adopted in the proposed eddy current brake. Flux lines of permanent magnets are opposite to the ones from the excitation windings, which have the effect of mitigating the saturation of the primary teeth. This allows the brake to be fed with more intense currents improving the braking force. The structure and the working principle are introduced. The analytical model of the hybrid excitation linear eddy current brake is built based on the magnetic circuit method and the layer theory approach. The relationship between the force characteristics and the design parameters are analyzed. The finite element analysis is employed to confirm the validity of the analysis and compare it with the experimental results obtained from the prototype of hybrid excitation linear eddy current brake. [ABSTRACT FROM AUTHOR]

The magnetic bearing’s (MB) performance is determined by its electromagnetic and mechanical parameters, which should be optimized to meet the working requirements. Many optimal methods of MB have been only focused on a single objective, which may be limited to a small amount of aspects, while other important ones are ignored. A multiobjective optimization (MOO) model to design the MB considered for a better comprehensive property is proposed in this paper. After modeling the equivalent circuit model whose simplification has been clarified by finite element method, we provide the constraints and optimal objectives in the shape of analytical expression. First, every single objective is solved to get utilization by complex method, then, a novel concept of utilization vector is proposed to calculate the weighting coefficients to resolve the MOO problem, by chaotic local search particle swarm optimization with the constraints as penalty functions. MOO design methods are applied for one type of two-degree-of-freedom hybrid MB, and this method could obtain a better balanced overall result, improving the levitated force and decreasing flux density in the air gap. [ABSTRACT FROM AUTHOR]

A nonlinear equivalent magnetic network (EMN) model is proposed for a linear permanent magnet vernier (LPMV) machine. The meshing method is employed to solve the problem of the modeling of complex flux paths in stator teeth tips. Especially, an end-region model based on the electromagnetic principle is developed to consider the longitudinal end effect of the LPMV machine. The key contribution of this paper is to present a faster and simpler approach to separate the detent force (end force component and cogging force component) than finite-element analysis (FEA). Besides, taking the iron saturation and air-gap flux leakage into account, the proposed model is used to predict the electromagnetic performances of the LPMV machine, such as air-gap flux density, back-electromotive force, cogging force, and thrust force. Finally, through comparisons among the FEA simulations, experimental measurements and EMN analyses, the accuracy and effectiveness of the proposed model are verified. [ABSTRACT FROM PUBLISHER]

This paper analyzes the design variations of an electromagnetic linear actuator with a divided coil excitation system, such as the colenoid system, using the equivalent magnetic circuit (EMC) method. First, the magnitude and direction of magnetic flux for each pole can be obtained using the EMC method, while the magnetic flux density for each pole is calculated using the superposition principle. To make the magnetic flux density uniform at each pole, the pole width is adjusted by the iteration method. The generated clamping force of the optimized model with EMC has almost the same force characteristics as the optimization results based on the finite-element analysis. By the proposed EMC method, the characteristics of the electromagnetic linear actuator with variations in the slot width and current are investigated. An electromagnetic linear actuator is also developed to produce a clamping force of 35 kN, and the experimental results show that it can be used to hold a workpiece firmly instead of using a hydraulic cylinder in a chucking system. [ABSTRACT FROM AUTHOR]

This paper studies an auxiliary poles technique that is used to reduce the end effect detent force for permanent magnet linear synchronous motor (PMLSM). Based on the lateral force method, the analytical model of the end effect detent force is built. The expressions of the optimal position and the optimal width for the auxiliary poles are derived. Through the use of finite-element calculations, the influence of the position, width, and height of the auxiliary poles on the end effect detent force is obtained. In addition, the detent force characteristics for five PMLSMs with typical slot–pole combinations after adopting the auxiliary poles are analyzed. The inhibitory effect of the auxiliary poles on the end effect detent force is separated from the slot effect detent force using harmonic analysis. The simulation results of the optimal auxiliary poles positions match the analytical expressions well, which proves the correctness of the analytical model. Finally, a prototype of the PMLSM with auxiliary poles, which has a better structure strength and eliminates the installation error, is manufactured and tested. [ABSTRACT FROM AUTHOR]

This paper describes the configuration of a permanent magnet linear actuator for biometric applications and explains the basics of the methodology used to evaluate the actuator thrust. The methodology, based on analytical expressions of the magnet flux linkage, enables a fast and accurate evaluation of the axial force and can apply to any set of coaxial coils. The formulations are used to optimize the actuator configuration, in order to improve the thrust uniformity along the mover stroke, some technological design fulfilling some technological design constraints. Introducing an auxiliary set of coaxial coils, the optimization procedure enables a remarkable uniformity improvement. The results are verified by finite-element analyses, and the measurements performed on a prototype confirm the effectiveness of the design procedure. [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]

In the ultra-precision system, the multi-axis servo system is composed of air-core monopole linear motors (AMLM) for achieving nanopositioning. In the AMLM system, the thrust varies according to the changes of the relative position of motor's primary and secondary. In this paper, the concept of thrust stiffness is proposed in order to illustrate the phenomenon of varieties of thrust according to changes in position. By using the surface charge model, the air-gap magnetic flux density of AMLM is predicted. Based on this prediction, the whole winding's thrust, including straight and corner segments of winding, is calculated. Then, this winding thrust model is simplified to replace the original complicated analytical model. The accuracy of the simplified model is verified by the corresponding experimental tests. Thus, the thrust stiffness simplification model can be used in the feedforward compensation model in the control system of AMLM and efficiently decrease the calculation time of DSP. [ABSTRACT FROM AUTHOR]

In the nanopositioning system, a damping force is generated by eddy current in the cooling plate and it is a disturbing force for this system. In this paper, a new method is introduced to suppress eddy current by offsetting back EMF. In order to offset back EMF, several slits have been incorporated in the cooling plate, which can help with regulating the series order in every region. Based on the electromagnetic theory, the analytical model of new cooling plate is established. The analytical model and eddy current suppression effect of the new cooling plate are proven by experiment: 17% reduction in the damping force significantly help with reducing the thrust fluctuation, with less than 4% analytical error. [ABSTRACT FROM AUTHOR]

This paper presents novel overlapping ironless windings for permanent magnet planar motors, which have high winding factors and make full use of the magnetic field of the magnet array in the planar motor. A simple analytical model of the planar motors is developed and validated by finite-element method first. Then the winding factors of the ironless windings are derived and used to simplify the analytical model. Furthermore, the design rules of the ironless windings for the planar motor are obtained from the analytical model with winding factors and the ironless windings are optimized for maximum steepness of the planar motor. Compared with the nonoverlapping ironless windings, the novel overlapping ironless windings have a much (up to 25%) larger force with the same copper loss and nearly the same size when the coils of the windings have a large length/width ratio. [ABSTRACT FROM PUBLISHER]

This paper deals with the dynamic characteristics of a linear induction motor (LIM) in terms of acceleration times and jerk conditions. We employed Matlab Simulink for conducting simulations of the dynamic modeling of LIM operated by a space vector pulse width modulation inverter. From the simulation results, the maximum load conditions and minimum acceleration times to guarantee passengers' safety were determined. Further, the electromagnetic field theory was employed to derive equivalent circuit parameters, and the results were validated by the finite element method. The analysis model was applied to a magnetic levitation vehicle for providing electromagnetic propulsion force, and its dynamic characteristics were analyzed to predict its operating performance; moreover, experimental results were employed to demonstrate the validity. We believe that the proposed prediction technique for the operating characteristics of LIMs can contribute to improving passengers' safety and riding quality. [ABSTRACT FROM AUTHOR]

The stationary discontinuous armatures that are used in permanent magnet linear synchronous motors (PM-LSMs) have been proposed as a driving source for transportation systems. However, the stationary discontinuous armature PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the armature. For this reason, the high alteration of the outlet edge cogging force produced between the armature's core and the mover's permanent magnet when a mover passes the boundary between the armature's installation part and non-installation part has been indicated as a problem. Therefore, we have examined the outlet edge cogging force by installing the stair-shaped auxiliary teeth at the armature's outlet edge in order to minimize the outlet edge cogging force generated when the armature is arranged discontinuously. This paper presents the results of 2-D numerical analysis by FEM of the cogging force exerted by the outlet edge. [ABSTRACT FROM AUTHOR]

To investigate the noise reduction for an electrical machine, coupled magnetic field and mechanical analyses should be carried out. In this paper, the method of modeling the laminated core using a homogeneous core model with equivalent anisotropic parameters considering the laminated structure in the coupled magnetic field and mechanical analyses is proposed and the effect of the laminated structure on the coupled analysis is investigated. The distributions of the flux densities, nodal forces by electromagnetism and magnetostriction, and displacements corresponding to these forces of the real laminated iron core model, the solid core model neglecting the laminated structure and the homogeneous core model considering the laminated structure are obtained and compared. It is shown that the laminated structure cannot be neglected in both the magnetic field and mechanical analyses and the displacement distribution obtained from the homogeneous model is in good agreement with the real model. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the eddy current losses in permanent magnets of surface mounted magnet synchronous machines. An original analytical method based on the magnetodynamic problem of a conductive ring is introduced and the obtained results are compared with the ones given by 3-D FEM analysis. The analytical model considers the effect of the width on the magnet loss. The axial effect is considered through a correction coefficient. The comparison includes the induced current density, the instantaneous losses, the impact of the circumferential segmentation, and the effect of the frequency on the magnet losses. By focusing on the importance of the skin effect and the magnetic reaction due to the magnet currents, the analytical model provides an accurate determination of the magnet eddy current losses. [ABSTRACT FROM AUTHOR]

An objective in the design of high performance machinery is to minimize weight so magnetic bearings are often designed to operate slightly lower than their magnetic material saturation. Further weight reduction in the bearings requires operation in the nonlinear portion of the B\-H curve. This necessitates a more sophisticated analysis at the bearing and rotordynamic system levels during the design stage. This paper addresses this problem in a unique manner by developing a fully nonlinear homopolar magnetic bearing model. The nonlinear dynamics of a permanent magnet-biased homopolar magnetic bearing (PMB HoMB) system with a flexible rotor is analyzed. Nonlinear effects due to power amplifier voltage and current saturation and position dependent reluctances are also included in the model. A new curve fit model of the B\-H curve is shown to have significantly better agreement with the measured counterpart than conventional piecewise linear. The modified Langmuir method, with a novel correction terms for the weak flux region, is used to form an analytical model of the experimental magnetization curve of Hiperco 50. High static and dynamic loads applied to the rotor force the magnetic bearing to operate in a flux saturated state. The response of the heavily loaded 4-DOF rotor-bearing system shows that limit cycle stability can be achieved due to the magnetic flux saturation or current saturation in the amplifier. The stable limit cycle prevents the linear model instability, creating what is experimentally observed as a “virtual catcher bearing.” To the authors' knowledge this is the first explanation of this commonly observed phenomenon. [ABSTRACT FROM PUBLISHER]

An analytical output force model is proposed for noncontact Lorentz force actuators (NLFAs), which are used for positioning and vibration isolation control of space sensitive loads that require an extremely quiet environment. A biaxial NLFA is presented. The actuator mainly consists of a closed magnetic circuit and a novel biaxial exciting circuit board developed by printed circuit board technology. The closed magnetic circuit consists of a C-type yoke and two permanent magnets and is simplified by the magnetic image method. A model of the spatial magnetic flux density in the air gap of the simplified closed magnetic circuit model is derived by the Ampere molecular current hypothesis and the Biot–Savart law. Finally, an analytical output force model of the actuator is obtained by calculating the magnetic flux densities and forces at selected finite points by considering the winding of the coils. The influences of the key dimensional parameters of the actuator on the output forces and their variations are studied using the derived analytical model. To verify the derived analytical model, a measurement setup is established based on an electronic scale. The experimental results show that the forces calculated by the proposed analytical model agree with the experimental values very well, and the deviation between the results is less than 4% when a rated force of 3 N is produced. Moreover, the relation between the number of selected points and computing time and the relation between the number of selected points and the extra calculation deviation, which are important for real-time control, are discussed. The proposed analytical model can help to improve the design efficiency and output force control of this kind of actuator. [ABSTRACT FROM AUTHOR]

This paper considers analytical and numerical techniques to model the magnetic field distribution in a tubular actuator with skewed permanent magnets (PMs). A fast 3-D analytical model based on Fourier analysis is developed for calculation of the various field components resulting from the skewed PMs for various skewing topologies. This techniques provides means for validating the assumptions of 2.5-D multilayer methods. Furthermore, a 2.5-D analytical multilayer model is derived for calculation of the cogging force due to the slot openings including skewed PMs. The analytical methods are validated by means of 3-D finite element analysis. [ABSTRACT FROM PUBLISHER]

The touch-down test is widely used to calibrate the flying-height (FH) of sliders by gently contacting the disk with the thermal protrusion of thermal FH control (TFC) sliders. However, the dynamic instability of TFC slider during the touch-down process may significantly affect the contact detection and the FH calibration, and therefore, hinders further reduction of the FH of TFC sliders. This paper highlights the nonlinear dynamics perspectives on the instability of TFC sliders during the touch-down process. A single-DOF (degree-of-freedom) and a 2-DOF nonlinear dynamics models were developed respectively to quantitatively study instability of TFC sliders at the near contact regime and to explain the nonlinear dynamic behaviors of TFC sliders at touch-down. The simulation results from the nonlinear analytical models reveal that the existence of multiple equilibriums and the self-excited vibrations of the slider-air bearing system are the main reasons for the instability and bouncing of TFC sliders during touch-down process. [ABSTRACT FROM AUTHOR]

We derive an analytical formula for the Lorentz force and torque between 1-D linear current elements in arbitrary relative positions explicitly without remaining integral. A circuit is represented as the links of linear elements, and the force and torque on an element are represented as equivalent nodal forces on either side of it. We then treat the circuit as a link mechanism. Furthermore, we consider the singularity that appears in connected elements in a single circuit due to zero distance and avoid it using an approximation with a small radius. This singularity treatment makes the formula applicable even for calculation of the partial force from the entire circuit. Since the formula does not require numerical integration, it can reduce computation time. The accuracy of the approximation is also evaluated by comparing our calculations with the existing experimental results in the literature and numerical integrations. [ABSTRACT FROM AUTHOR]

The detent force in long-stator linear motor is caused by open longitudinal ends of permanent magnet mover, which differs from rotary motor and short-armature counterparts. First, the modeling of end magnetic field is established, and then the nonuniformity of magnetic field between edge and middle magnets is analyzed. Based on the corrected factors of air-gap magnetic field calculation, a general mathematical expression of the detent force by energy method and Fourier transform is developed. Finally, a novel method by unequal pole-arc coefficients of edge and middle magnets is proposed, and the optimized pole-arc coefficients combinations are obtained. The effectiveness of the proposed method is verified by finite-element results. [ABSTRACT FROM AUTHOR]

Reduction of vibration noise of propulsion motor, which is the main excitation source of ships, is of great significance for improving the acoustic stealth performance of ships. An established motor feet vibration transfer path analysis (TPA) model is used to determine the primary excitation source and transfer path. Hammering method is used to test the transfer function of the path and collect the response of reference and target points in the operation conditions. The TPA is carried out based on the experiment to identify the equivalent exciting force and to calculate the path contribution amount. The results show that in the frequency range of 1–1000 Hz, the vibration acceleration-level error of the synthetic response and the measured response is <3 dB, and hence the model is accurate and reliable. Recognized equivalent excitation force can be used for the simulation of excitation load. Contribution analysis results indicate the direction for structural improvements that have practical value. [ABSTRACT FROM AUTHOR]

To improve the production qualities of a steel mill, in-mold electromagnetic stirrers (M-EMS) are generally implemented at the continuous casting process to provide the desired stirring forces to remove those undesired inclusions and bubbles during the metal solidification. As the system is mainly operated by interaction of induced eddy currents and composite traveling electromagnetic fields in the molten metal, inputs of stator currents and structures of M-EMS will dominate the entire system performance. Assisted by three-dimensional (3-D) finite-element analysis (FEA) and flux path modeling refinements, a compact analytical model with sufficient accuracy that can adequately predict the time-averaged performance of the M-EMS system at various structure- and material-compositions will be devised. From these confirmed operational indices, a convenient assessment tool for on-site operation and maintenance of the M-EMS at the metal industry has been successfully established. [ABSTRACT FROM PUBLISHER]