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The 3D modeling technique presented in this paper, predicts, with high accuracy, electromagnetic fields and corresponding dynamic effects in conducting regions for rotating machines with slotless windings, e.g. self-supporting windings. The presented modeling approach can be applied to a wide variety of slotless winding configurations, including skewing and/or different winding shapes. It is capable to account for induced eddy-currents in the conductive rotor parts, e.g. permanent magnet eddy-current losses, albeit not iron and winding AC losses. The specific focus of this paper is to provide the reader with the complete implementation and assumptions details of such a 3D semi-analytical approach, which allows model validations with relatively short calculation times. This model can be used to improve future design optimizations for machines with 3D slotless windings. It has been applied, in this paper, to calculate fixed parameter Faulhaber, Rhombic, and Diamond slotless PM machines to illustrate accuracy and applicability.

This paper presents a novel method to obtain fully analytical expressions of the magnetic field created by a pyramidal-frustum shaped permanent magnet. Conventional analytical tools only provide expressions for cuboidal permanent magnets and this paper extends these tools to more complex shapes. A novel analytical model for the magnetic field induced by triangular charged surfaces is combined with the field expressions for rectangular charged surfaces. This provides a fully analytical expression for the magnetic field of a pyramidal-frustum shaped permanent magnet. Field and force obtained using this model are validated with Finite Element Modeling.

This paper describes the numerical results for the dynamic behavior analysis of a thin plate vibration in magnetic field. The authors of this paper apply the full coupling method and the MMD (Modal magnetic damping) method to the magnetomechanical coupling analysis. The comparison between the results by the two methods shows almost satisfactory agreement and verifies the applicability of the MMD method. The results by the MMD method have the larger values and would give conservative evaluation in structure design in strong magnetic field. >

Analytical modeling is still a very effective manner to calculate the magnetic fields in permanent magnet devices. From these magnetic fields, device quantities, e.g. force, emf or inductance, can be calculated. This paper presents a semianalytical technique, based on a 2D Fourier series to represent the magnetic field, to describe the force components due to permanent magnets in three dimensional (3D) cylindrical structures. The Maxwell stress tensor method is selected to calculate these force components in the cylindrical coordinate system. The method is analytically evaluated by inserting the analytical expressions describing the magnetic fields. The obtained force equations avoid the use of numerical integration of the magnetic fields resulting in a fast and accurate force calculation method. An example of a 3D cylindrical structure is modeled and validated by means of a magnetostatic finite element analysis and excellent agreement is found.

Linear permanent magnet synchronous motors are often used in applications where a high accuracy is needed. This paper investigates the influence of the key design parameters on the performance of a linear actuator with vertically magnetized magnets and a magnet array with quasi-Halbach magnetization. The performance is modeled by means of analytical expressions of the three-dimensional magnetic field components and optimal design ratios and guidelines are established.

In this paper, we propose a semianalytical solution for evaluation of field distributions around a short rectangular crack in a metallic half-space excited by long current-carrying wires with arbitrary frequency. The governing Helmholtz equation is solved in three dimensions by separation of variables. The solution is obtained by developing 2-D Fourier series model and using exponential functions in the third dimension. To expand all possible field components in the metal, we first hypothesize a shielded dielectric rod waveguide where the shield enclosure lies at infinity, the surrounding dielectric (i.e., the metal) is a lossy material, and the rod dielectric is the crack opening. We then introduce hybrid modes each of which consists of two components, representing the TMy and TEy modes. The mode-matching technique is finally used to numerically solve the resultant boundary value problem. The unknown eigenvalues and field coefficients are found by searching for small singular values, using the singular value decomposition (SVD) in the resultant homogeneous linear system. The validity of our modeling technique is confirmed by comparison of our results with those obtained by measurement and finite integration code.

Moving-magnet magnetically levitated planar motors are considered for use as a wafer stage in the semiconductor lithographic industry. This puts high requirements on the accuracy and the dissipated power and cooling performance of such motors. The goal of this paper is to analyze the multi-physical behavior of three moving-magnet planar topologies using an electromagnetic model, a mechanical model, and a thermal model. This behavior is evaluated using a trajectory and performance criteria which are representative for the application. The static and dynamic behavior are evaluated.

This paper presents a novel 3-D hybrid analytical modeling method which integrates a mesh-based 3-D magnetic equivalent circuit model into 3-D Fourier modeling. This hybrid analytical modeling is capable of predicting the electromagnetic field distributions for Cartesian three-dimensional structures. A generalized approach of the hybrid modeling concept is presented. The modeling technique is applicable to a wide range of electromagnetic devices, such as linear and planar actuators. In only a fraction of the calculation times of 3-D finite element approaches, the 3-D hybrid analytical modeling calculates the magnet field distributions and forces with approximately 90% accuracy.

To improve the performance of permanent magnet (PM) machines, quasi-Halbach PM arrays are used to increase the magnetic loading in these machines. In tubular PM actuators, these arrays are often approximated using segmented magnets resulting in a 3-D magnetic field effect. This paper describes the results of this segmentation obtained from an analytical model. The influence of the number of segments on the magnetic flux density in the air gap is investigated for several actuator dimensions. Furthermore, the effect of this segmentation on the mean value of the radial component of the flux density over the circumference of the cylindrical air gap is analyzed and a 2-D definition of this effect is given. A general rule is presented as a table showing the decrease of the magnetic field as function of the design parameters.

Taking into consideration the variability specific to the nowadays nanotechnologies, the fast extraction of parametric models is a must for the present VLSI and radio-frequency (RF)-integrated-circuit (IC) design environments. The major contribution of the paper is a new, effective methodology for the extraction of parametric compact models for passive RF integrated components with field effects, valid for high-frequency broad range. The proposed numeric method is systematically based on a dual approach, which provides two complementary approximations of the exact solution. Duality is applied both to the spaces where the discrete solution is found as well as to the open boundary conditions. The adjoint field technique is applied in an original manner to the finite-integral techniques to handle the parameter variability of the extracted model. The new method needs much less computing resources for modeling than other numerical methods.

Automated electromagnetic actuator design can be achieved by means of several approaches. For example, one might consider fast, however, accuracy deficient coarse models or, in contrast, the design could be achieved exclusively by employing accurate, time expensive, fine models. The space-mapping optimization technique, with its input or output mapping based implementations, merges the advantages of the two extremes. A new algorithm variant that presents a simple structure, namely the aggressive output space-mapping, is proposed in this paper. The design problem of a tubular permanent magnet actuator is considered in order to compare the proposed algorithm with two existing techniques. Index Terms—Aggressive output space-mapping, design optimization, electromagnetic actuators, manifold-mapping, output polynomial space-mapping.

In Part I of the paper, we derive a semianalytical framework for the magnetic field calculation in the air gap of a tubular permanent-magnet (PM) actuator. We also make an extension for skewed topologies. However, the slotting effect and its related cogging force cannot be determined in a straightforward way. Therefore, in Part II, we apply the Schwarz-Christoffel (SC) conformal mapping method to one pole-pair of the tubular PM actuator. This mapping allows for field calculation in a domain where standard field solutions can be used. In this way, slotting effects can be taken into account; however, skewing cannot be implemented directly. The SC-conformal mapping method is valid only for two-dimensional Cartesian domains. We therefore apply a special transformation from the cylindrical to the Cartesian coordinate system to describe the tubular actuator as a linear actuator.

This paper presents three types of magnetostatic models of ironless planar actuators with moving magnets. The models predict the force and torque exerted on the translator of the actuator, which can be positioned in six degrees-of-freedom with respect to the stator coils. The force and torque are calculated with the Lorentz force law. The analytical and numerical models can be used for the design of large planar actuators, for the fast comparison of actuator topologies, and in the decoupling and commutation algorithm. The models have been verified with experiments

This paper describes an analytical model that includes end effects for ironless synchronous permanent-magnet planar actuators. Because of its flexibility, the model can be used to predict the performance of various permanent-magnet array and coil array topologies and commutation schemes. Moreover, since control currents have to be nonsinusoidal, it allows analysis of the motor performance without specifying a commutation scheme by directly dealing with the motor-coupling matrix that links the coil currents to the forces or accelerations acting on the translator

In high-density data storage systems, noise becomes highly correlated and data dependent as a result of media noise, channel nonlinearities, and front-end filters. In such environments, conventional timing recovery schemes will exhibit large residual timing jitter and, especially, data-dependent timing jitter. This paper presents a new data-aided timing recovery algorithm for data storage systems with data-dependent noise. We derive a maximum-likelihood timing recovery scheme based on a data-dependent Gauss-Markov model of the noise. The timing recovery algorithm incorporates data-dependent noise prediction parameters in the form of linear prediction filters and prediction error variances. Moreover, because noise can be nonstationary in practice, we propose an adaptive algorithm to estimate and track the noise prediction parameters. Simulation results, for an idealized optical storage channel incorporating a simple model of media noise, illustrate the merits of our algorithm

In this paper, a complex nonstandard finite-difference time-domain (CNS-FDTD) method is proposed in order to simulate wave propagation in lossy media. To clarify the characteristics of the method, expressions for the numerical propagation constant and the stability condition are derived. It is found that the CNS-FDTD method is much more accurate and stable than the conventional finite-difference time-domain (FDTD) method. The method is applied to the analysis of a fin ferrite electromagnetic wave absorber with a periodic structure., application/pdf

One of the still "open" issues within low-frequency magnetics is the inclusion of µr in the calculations using the magnetic charge method. In this paper a new iterative method to take the relative permeability into account is investigated. Results show that the model accurately accounts for the permeability of a magnet within 4 iterations. In part II the computational time is decreased by using a polynomial approximation of the charge density. Finally, in part III, a combination of a magnet and a soft-magnetic material is modeled.

In this paper, a measurement of the effect of the demagnetizing field and a method of reducing these disadvantages by etching both ends of the wire are studied. A magnetization reversal in magnetic wires with bistable magnetization states induces pulse voltage in a pickup coil. Amplitude of the voltage does not depend on frequency of an applied magnetic field down to zero. The magnetization switching is accompanied with a large Barkhausen jump. The twisted Vicalloy wire reveals a uniaxial magnetic anisotropy along the wire direction. A magnetization of the hard core is not normally switched in sensor applications. The symmetric output and higher voltages in Vp and Vap obtained from the etched wire are preferable for the sensor applications, which cannot be achieved from the as-prepared wire. It is suggested that edge effects of a demagnetizing field and a magnetostatic coupling can be reduced by etching the soft layer at both ends of the wire.

Magnetic position sensing is used in many applications, especially in environments where the sensor is subjected to vibrations, temperature variations, or high humidity. The Hall effect position sensors, due to their simplicity and versatility, are elegant solutions to many application requirements, although the disadvantage are a maximum operating temperature of about 175°C, airgap operation limited to no greater than about 2.5mm and sensitivity to external pressure acting on the sensor package [1]. The need for sensors is growing, for example, in automotive applications, where, in engine control applications, the number of sensors used will increase from about ten in 1995, to more than thirty in 2010 [2]. Magnetic position sensing is based on the measurement of the magnetization pattern of a di-pole, or multi-pole, magnetic ring using a Hall sensor, which shows the variation of the magnetic field density along the circumference of the ring. The ideal magnetic behavior of the permanent magnet ring has a sinusoidal hall-sensor output, which makes it suitable for sensing applications. However, practical measurements show that the sinusoidal behavior sometimes occurs with errors. This paper describes the investigation of these errors by means of mismatch in the magnetization pattern of the di-pole permanent magnet (PM)-ring. The PM-ring yields that the developed magnetic flux is purely sinusoidal, where the geometrical dimensions of the PM-ring influence the magnitude Hall-sensor output voltage level. A deviation in the sinusoidal behavior is influenced by a non-ideal PM-ring by means of varying magnetic flux density magnitude and orientation.

This paper presents an adaptive-speed/CAV algorithm which regulates the disc velocity in a CD-ROM system to accomplish high data throughput (bit rate) during continuous playback and low power consumption during continuous data access. The adaptive-speed profile is based upon quasi-CLV control which allows drive optimisation towards both data throughput and access time. The presented algorithm can automatically distinguish between two operating modes-continuous access and continuous playback. By detecting the state of continuous access, the CD-ROM drive switches its spindle-motor loop into a constant angular velocity (CAV) mode, avoiding therefore the acceleration/braking of the motor, and thus reducing the power consumption. By detecting the state of continuous playback, the spindle motor will be set to follow an adaptive-speed profile which is highly optimized for data transfer rate. The software and hardware implementation of the CAV/quasi-CLV switching technique in a CD-ROM system is also described.

This paper reviews our recent results on some applications of new nanocrystalline soft magnetic Fe-M-B (M=Zr, Hf, Nb) alloy ribbons "NANOPERM(R)". NANOPERM(R) has a structure consisting of nanoscale bcc grains and a small amount of an intergranular amorphous layer. NANOPERM(R) exhibits high saturation magnetic flux density above 1.5 T as well as excellent soft magnetic properties. Furthermore, its remanence ratio can be controlled according to the demands of various applications. Toroidal cores with gap, common mode choke coils, ISDN (integrated service digital network) interface pulse transformers and flux gate magnetic detectors made of "NANOPERM(R) have been developed. The excellent characteristics of the components were confirmed in trial. NANOPERM(R) is therefore expected to be used widely in the magnetic application field.

This paper describes the numerical simulation of the dynamic behavior of a ferromagnetic thin plate vibration in a magnetic field. The behavior of a ferromagnetic cantilevered plate, which is set in the direction of a uniform magnetic field, shows that its natural frequency increases with the external magnetic induction. Two methods were applied to evaluate this phenomenon. The magnetic field of the deformed shape has been analyzed by 3D analysis and 1D approximation. The natural frequencies were evaluated by the energy method in the 3D case and by a transient response in the 1D case. The results show that the natural frequency change can be explained by the magnetic stiffness effect caused by magnetization including its saturation.

In this paper, we describe the asymmetrical field dependence of a high-frequency carrier-type thin-film magnetic field sensor (or so-called magneto-impedance sensor) consisting of Ni-Fe/Fe-Mn multilayer film. We fabricated a ferro/antiferro exchange-coupled multilayer film constituted of five 100-nm-thick Ni-Fe layers and four 30-nm-thick Fe-Mn layers by RF sputtering. The multilayer film had a unidirectional anisotropy of 600 A/m that was four times larger than that of a Ni-Fe (200 nm)/Fe-Mn (30 nm) bilayer film. Furthermore, the asymmetrical applied field dependence and high sensitivity of 19 k/spl Omega//T (1.9 /spl Omega//Oe) around an applied field of zero were obtained with the multilayer sensor element. The sensitivity was about 15 times larger than that of the bilayer sensor element. We conclude that the sensor element with high sensitivity can be realized by the Ni-Fe/Fe-Mn multilayer film without dc bias field.

This paper presents a quantitative analysis of the orthogonal-core type linear variable inductor. The orthogonal-core has wedge gaps for reduction of harmonics of the output currents. The analysis is based on a 3-dimensional nonlinear magnetic circuit of the orthogonal-core. Using the magnetic circuit, one can calculate accurately the operating characteristics of the variable inductor. Furthermore, they develop a VAr compensator for a 6.6 kV AC distribution system using the three-phase variable inductor.

In this paper we present results on how both the resistance and the magnetoresistance of magnetic spin-tunnel junctions depend on the oxidation time used to form the AlOx barrier. The bias voltage dependence of junctions with barriers created with different oxidation times is measured and found to be optimal when the oxidation time is chosen to give sufficient oxygen for the barrier to be stoichiometric Al2O3. The oxygen content of the barrier was determined by Rutherford backscattering spectrometry and elastic recoil detection.

This paper reports on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} thin films prepared on (100) MgO substrates by rf magnetron sputtering irradiated with ultra-violet (UV) light in He gas of about 500 Pa using a low pressure mercury lamp The zero-resistance temperature and the critical current density were gradually decreased with irradiation time. X-ray photoemission spectra showed that the mean Cu valence of the film was decreased approximately form +2 to +1 by the irradiation while the valence of Bl ions was not changed. These imply that the UV light tradition selectively reduces Cu ions and the superconductivity strongly depends on the Cu valence.

This paper presents a comparison of several three-degrees-of-freedom (DoFs) semispherical actuator topologies, which can mimic a shoulder joint of an actuated support system. A semianalytical model is applied to determine the torque performance as function of the position. Hence, the current distribution through the coils with minimized ohmic losses can be determined. The performed topology comparison is based on the average power dissipation and on a set of torque and range of motion requirements.

This paper reports the performance of a new micro magnetic thin-film magnetic field sensor which makes use of LC resonance of the sensor element as well as the impedance change due to the permeability change of the magnetic film. A large impedance change of 105% was achieved at a carrier frequency of 100 MHz. The large change was realized when the LC resonance frequency of the sensor element was lower than the frequency at which the eddy-current losses increased.

New magnetic configurations in 2D and 3D artificial lattices are studied by solving the non-linear equation based on the classical Heisenberg models for 2D and 3D artificial lattices. The results indicate a strong possibility of use as an ultra-high density magnetic recording media achieved by magnetic multi-valued (MMV) recording. The MMV states are based on the magnetic anisotropic configurations in 2D and 3D artificial lattices. In this paper, the magnetic properties of these artificial lattices and the density of MMV recording are discussed.

A novel single pole head with laminated thin film coils is proposed in this paper. Laminated thin film coils, between which a main pole is laid, are put very close to the media to capture most of the reproduced flux. In addition, a ferrite return yoke is placed just under the lower conductor to shorten the head magnetic flux path. These approaches bring high read/write efficiency and small head noise owing to low head impedance. With only one or two-turn coils, Co-Cr/Fe-Ni-Nb double-layered media were saturated at magneto-motive force of 0.05 ampere-turn, and overwrite of the two-turn head reached 35 dB. High normalized output of 1000 nV/sub p-p///spl mu/m/spl middot/turn/spl middot/m/s was obtained. Much higher recording and reproducing sensitivity than ordinary inductive single pole heads was achieved.

This paper presents the experimental results of stabilization of a model power transmission system by using a Superconducting Magnet Energy Storage (SMES). The SMES, which was composed of two sets of GTO (Gate Turn Off thyristor) power converters and a superconducting coil, is capable of controlling active power (P) and reactive power (Q) simultaneously in four quadrants by changing the firing angles of power converters. The model power transmission system was designed to simulate the behavior of a real scale long distance bulk power transmission system with voltage of 500 kV, capacity of 2000 MVA and length of 280 km. In this study, we have experimented power system stabilizing control by applying P-Q simultaneous control ability of SMES. From the results of experiment it was demonstrated that stabilizing effect by means of SMES is very significant.