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This paper presents an analytical model suitable for analyzing permanent magnet motors with slotted stator core. By including the effect of the interaction between the pole transitions and slot openings, the model is able to predict the airgap field and magnetic forces with high accuracy, which cannot be achieved using the previously available analytical methods. The results of electromagnetic forces, i.e., the cogging torque and unbalanced magnetic pull, computed analytically agree well with numerical simulations using the finite-element method. The model is used to analyze the magnetic forces developed in permanent magnet brushless motors when the design parameters vary in wide ranges. The model is useful in design and optimization of permanent magnet motors. Index Terms--Airgap field, analytical solution, electromagnetic forces, permanent magnet (PM) machines.

We present an analytical method to study magnetic fields in permanent-magnet brushless motors, taking into consideration the effect of stator slotting. Our attention concentrates particularly on the instantaneous field distribution in the slot regions where the magnet pole transition passes over the slot opening. The accuracy in the flux density vector distribution in such regions plays a critical role in the prediction of the magnetic forces, i.e., the cogging torque and unbalanced magnetic pull. However, the currently available analytical solutions for calculating air-gap fields in permanent magnet motors can estimate only the distribution of the flux density component in the radial direction. Magnetic field and forces computed by the new analytical method agree well with those obtained by the finite-element method. The analytical method provides a useful tool for design and optimization of permanent-magnet motors. Index Terms--Air-gap field, analytical solution, electromagnetic forces, permanent-magnet brushless motor.

This paper presents numerical simulation of high-density magnetic recording process with perpendicular head and media. The simulation is based on three-dimensional mieromagnetie model of the media and an analytical model of the single pole perpendicular recording write field. The physical problem is modeled with a hybrid FEM-BEM formulation and the evaluation is accelerated using a new Fast Fourier Transform on Multipoles method. The model is suitable for studying magnetization transition configuration in perpendicular media with softmagnetic underlayer, and in turn can be used to derive microtrack model for evaluating the performance of recording systems. Index Terms--Fast multipoles method, FFT, hybrid FEM-BEM, micromagnetic modeling, microtrack model.

This paper discusses the application of response surface methodology (RSM) to design optimization for brushless dc permanent magnet motors for a hard disk driver to reduce cogging torque. The feasibility of using RSM with the finite-element method in practical engineering problems is investigated with computational examples and comparison between the fitted response and the results obtained from an analytical solution. Index Terms--Cogging torque, optimization, response surface methodology (RSM).

This paper studies radial magnetic forces developed in permanent magnet motors having rotor eccentricity. Such forces represent the source of magnetically induced vibration in a disk-spindle assembly, and are of concern in design stage. A new analytical model suitable for studying the relationship between eccentricity effect and design parameters of slotted permanent magnet motors is introduced. The effectiveness of the model to study the effects of the rotor eccentricity and other leading design parameters is demonstrated through comparisons with numerical simulations. Index Terms--Permanent magnet motor, rotor eccentricity, unbalanced magnetic pull.

This paper presents a theoretical study of nonlinear transition shift (NLTS) in perpendicular recording process. The study is carried out using numerical simulations, and an analytical method is introduced in this paper. In analyses of the effect of recorded transitions, the demagnetization field due to written patterns on the recording medium is taken into consideration in the field solution for a write head with shield poles. The influence of the gap length between the shield and the pole-tip is also studied using the new analytical model. Index Terms--Medium demagnetization field, nonlinear transition shift, write field model.

This paper presents a numerical method for accurate predictions of magnetic fields in permanent magnet brushless dc motors with slotted stator core. The method allows both the radial and tangential component of the air gap field to be computed accurately in an analytical form. It is shown that a significant improvement in the accuracy of magnetic force predictions is achieved when compared to the existing analytical solutions. The method is validated using finite element simulations and experimental results. Index Terms--Brushless dc motor, magnetic field, permanent magnet.

This paper describes a direct calculation method for medium fields in perpendicular recording systems. The method accounts for the effect of the zig-zag transition in the written medium pattern which can be obtained using micromagnetic simulations. The described method is useful for studying the cross-track characteristics of read sensors. The method is able to deal with a recording medium layer with nonunity relative permeability. The computed medium field in the gap region under the read head is compared with that obtained using the finite-element method. The purpose of this study is to develop a fast and effective tool for producing read-back signals based on computer modeling and simulation. Index Terms--Magnetic field, perpendicular recording, read sensor, recording medium.

The write field distribution for a perpendicular writer was investigated using finite-element (FE) analysis. The slanted write fields due to shield pieces at the trailing edge and the leading edge of the pole tip, and the side shields are analyzed. The analysis shows that the use of the shielded pole leads to a change in the saturation levels in the main pole tip, affecting the write field distribution. The effects of the side shield and other design parameters on the write field in cross-track direction are discussed. Index Terms--Finite-element analysis, perpendicular recording, single pole write heads, slanted write field.

An analytical model is used for analyzing magnetic forces developed in permanent magnet motors of radial field topology. The model has improved the prediction of the air gap field and magnetic forces, thus making it applicable to a wider range of parameter changes.