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The torque of magnetic coupling with different magnetic poles has been investigated by theoretical computations with both FEA and torque formula techniques. The torque of magnetic coupling is sensitive to the number of magnetic poles, and it decreases with increasing the distance between the magnetic rings. From our theoretical computations, we find that we can increase the torque by increasing the number of poles for magnetic coupling between magnetic rings with short distance; however, this is not true for magnetic rings with large separation. We also demonstrate that the theoretical computations of both MagNet software and torque formula established by Furlani are quite consistent and useful for computing the torque of various magnetic couplings. Finally, the theoretical calculation has been successfully tested by using an experimental data taken from a NdFeB magnetic coupling.

This paper presents a novel twelve-step sensorless drive scheme for a three-phase brushless DC motor, which combines the traditional six-step 120[degrees] and 180[degrees] conduction modes and has varied active angular period. The proposed scheme is implemented on a single FPGA-chip. Several experiments for various active angle periods from 124[degrees] to 168.75[degrees] are undertaken. The experimental results show that the torque constant is larger for the larger active angular period. Index Terms--Back EMF, brushless DC motor, sensorless drive, zero-crossing.

A four-wire voice-coil actuator is designed and optimized for use in a near-field optical drive. The first objective was to design a lens holder which could accommodate a large-size lens module while possessing a strong mechanical structure. The second objective was to optimize the yoke so that the magnetic field would be uniform within the stroke range of the voice coils. These improvements eventually helped to improve the bandwidth of the frequency response of the actuator. Index Terms--Actuator, near-field, optical drive.

This paper raises a valid method to design a voice coil motor (VCM) used ill the focusing system of a digital video camera (DVC). A better VCM performance, such as lower battery consumption, higher efficiency, and shorter focusing time, can be achieved by turning the diameter of a winding coil, the thickness of the magnet, and the winding spaces in a VCM. Index Terms--Battery consumption, digital video camera, focusing, voice coil motor.

The pin identification is to find the definition of each connecting pin of a three-phase brushless motor. The 11 pins of the motor can be distinguished into three groups by a simple resistance measurement method. An automatic method has two steps. In the first step, the motor is in an open-circuited mode; and the individual pins of the windings are identified by comparing back electromotive forces. A special integral is defined and used to match Hall signal pins with the Hall sensors. The polarity of each pair of the Hall signal pins is determined by the second step of a standstill method. The proposed method is illustrated and verified by an experiment. Index Terms--Identification, Lyapunov stability, motor characteristics, three-phase dc brushless motor.

An analytical method for calculating the incremental line inductance of a permanent-magnet synchronous motor is proposed in this paper. First, the incremental inductance is simplified as a linear combination of the slot inductance and the air-gap inductance, which are both estimated by the equivalent magnetic circuits. The reluctance of the rotor back irons and the stator back irons are ignored when the slot inductance is calculated. However, for the calculation of the air-gap inductance, the iron saturations and the perturbations of the permanent magnet are considered. The proposed method is verified by a finite-element method. Index Terms--Analytical method, finite-element method, incremental inductance, iron saturation, permanent magnet synchronous.

In this research, the cogging torque of a newly designed single-phase brushless DC motor used in CD-ROM application is investigated. A finite element method is employed to numerically analyze the magnetic field distribution inside the motor, in which a three-dimensional mesh is constructed. The torque due to the magnetic coupling between the rotor and stator is estimated based upon the virtual work concept. It is proposed in this paper that the salient pole be divided into several regions in the azimathal direction. By properly choosing the radii for these regions, the cogging torque can be greatly reduced. Index terms - cogging torque, salient pole.

This paper deals with the position control of the voice coil motor (VCM) with handshaking. A disturbance observer is proposed to estimate the low-frequency handshaking disturbance, so that a handshaking-robust controller can be constructed. While a handshaking stabilizer can compensate for the vibration of the whole lens set, a robust controller is still required to precisely hold the autofocusing lens by rejecting the handshaking disturbance. To meet the request of miniaturization, the control is implemented on a field programmable gate array chip. [ABSTRACT FROM AUTHOR]

Presents a study that examined magnetic patterns of bonded magnets affected by magnetizing fixtures using finite element method (FEM) simulation. Details of the finite element method used; Correlation between the magnetic peak and valley strengths and the number of cycles of winding and stretching; Comparison of the experimental results with results obtained from the FEM calculation.

Presents a study that investigated the effect of magnetization profiles on the torque of magnetic coupling. Illustration of a magnetic coupling with 10-pole magnets; Details on torque magnetic couplings using different magnetization profiles.