C. Bi

Electromagnetic design for hard disk drive spindle motors with fluid film lubricated bearings

This paper discusses the problems associated with the electromagnetic design of hard disk drive (HDD) spindle motor having fluid film bearings. It will highlight the effect of the unbalanced electromagnetic pull in the radial direction of FFB spindle which uses permanent magnet brushless DC motors with slotted stator core. An analytical approach is employed for predicting the magnetic field and motor performance. Results obtained from this approach are compared with finite element analysis.

A genetic algorithm combined with finite element method for robust design of actuators

This paper describes a design optimization procedure based on a genetic algorithm combined with the finite element method. It adopts the concepts of Orthogonal Array for design parameter settings, and Signal-to-Noise Ratio (S/N) for evaluating the individual fitness. Taking advantage of the unique features of genetic algorithms, the robust solution is achieved by a rapid global search. The approach is applied to the robust design problem of a magnet actuator to demonstrate its effectiveness.

Motor "identity"-a motor model for torque analysis and control

This paper introduces a novel concept in torque analysis and torque controller design, using motor identity. The concept of identity is defined and analysis for generating an optimal input current which can produce smooth and maximum torque output is described. The extraction process of identity from a motor is also provided. Simulations and experiments applying this identity concept in torque control on a permanent magnet synchronous motor are given. The results are compared with a conventional motor controller using 3-phase sinusoidal currents.

A combined numerical and analytical approach for magnetic field analysis of permanent magnet machines

This paper discusses finite element analysis of permanent magnet machines using an annular macro-element for the air gap and magnet region. It is shown that in comparison with the conventional finite element scheme, the proposed method provides stable computational prediction of magnetic field problem, and can be used as design and analysis tool for permanent magnet machines. >

Modelling and torque analysis of permanent magnet spindle motor for disk drive systems

This paper discusses the modelling of magnetic field distributions in disk drive spindle motors using a combined finite element and analytical approach. The torque analysis of a spindle motor having NdFeB magnet poles is also presented. It is shown that the proposed method provides an effective tool for reliable torque computation in contrast to conventional finite element schemes. >

Analysis Of Iron Loss In Hard Disk Drive Spindle Motors

The paper presents analysis of iron loss in permanent magnet spindle motors used for hard disk drives. The analysis is based on the finite element method and uses the information on local flux density variation in the motor components. The iron loss distribution and the effect of the stator dimensions on the total iron loss are discussed.

A hybrid technique for electromagnetic torque and force analysis of electric machines

In electric machines, the electromagnetic torques and forces are developed as a result of the interaction of the magnetic fields. These forces can be computed from the results of field analysis, using numerical or analytical methods. Describes a hybrid technique, which is suitable for the calculation and analysis of electromagnetic torques and forces. This method exploits the advantages of numerical and analytical methods for field analysis, and thus provides a more efficient and effective tool for torque/force computation, in comparison with traditional methods. The computational examples presented show that the method is particularly useful for accurate prediction of the electromagnetic torque and unbalanced magnetic pull in electric machines.

Investigation of core loss in PM micro-motor made using MIM technology

Research has been conducted into the effects of particle size on the core losses of soft magnetic materials. Various types of micro PM BLDC motors, produced with solid hog-out alloy steel, laminated alloy steel and Metal Injection Molding (MIM) alloy steel powders have been studied. The results show that the core loss of micro PM BLDC motors made by the MIM technique is in the acceptable level when compared with the laminated core motor.

Motor 'identity'-a motor model for torque analysis and control

Production of smooth and maximum torque are two main goals for achieving good performance in torque control of permanent magnet synchronous motors (PMSMs). This paper presents a new approach for modelling the motor for torque analysis and control. This method is unconventional in that no parametric model of the motor is required; instead a new concept of motor identity is introduced and used. This identity is defined as the per-phase torque profile of the motor and it can be represented in a matrix form-called the identity matrix. This characterizes the motor and this matrix can be used for torque analysis and control. This concept is also applicable to all synchronous machines but a PMSM is used here for the illustration of this concept. An analysis is also presented for deriving optimal drive currents by using the motor identity. A method to extract the motor identity experimentally is also given in this paper.<<ETX>>

Identity control for spindle motors in hard-disk drives

A novel control technique for hard-disk spindle motors is presented that improves the efficiency of the motor drive system. A spindle motor is first characterized by its identity, which is the per-phase torque profile, and then the identity is used to generate an optimal drive current or voltage for driving the spindle. The harmonic content in the drive current is significantly reduced.