Nay Lin Htun Aung

A Demodulation Technique for Spindle Rotor Position Detection With Resolver

This paper presents a demodulation technique for amplitude modulated signals from a resolver based on amplitude detection of a sinusoidal waveform by numerical integration. The proposed technique performs synchronous integration on output signals of the resolver. The integration period is determined from zero crossing detection of the same output signals. The actual envelopes of the signal waveforms are obtained by utilizing the phase relationship of the integrated waveforms with the delayed carrier signal. Due to integration, the noise and disturbance effects are averaged out and the achievable accuracy is improved without applying filters. The method is developed from exploration of detecting HDD spindle rotor position in high resolution. The effectiveness of the proposed technique is demonstrated with the simulations and compared to the other methods. Experimental results are also provided to support the proposed method.

Incline Unbalanced Magnetic Pull Induced by Misalignment Rotor in PMSM

This paper analyzes the incline unbalanced magnetic pull (IUMP) generated in the permanent magnetic synchronous motor (PMSM) with the rotor misalignment. The motor magnetic field in such a motor is asymmetric, and both the magnitude and the action point of UMP vary in motor operation. This paper presents an analytical model for analyzing the 3-D effects of the UMP induced by the misalignment rotor. The numerical simulation results prove the effectiveness of the proposed analytic model.

Influence of winding structure and the effect of MMF harmonics to the spindle motor performance for ultra-high TPI HDD

The technologies for maintaining high recording density to suppress mechanical vibration and media flutter for ultrahigh TPI hard disk drive (HDD) require advance spindle motor design and technology against the traditional norms. To realize multimagnetic poles with limited stator slots, spindle motors generally use concentrated windings which offer small end winding and simple structure suitable for mass production. There is a variety of ways to construct a motor with different winding structures based on different pole/slot combinations. Winding structures directly affect the producing of motor back-emf and torque which determine motor capacity, reliability and efficiency. In this work, detailed analysis is carried out to identify the optimal winding structures of the high speed spindle motor and analyze their effect on the motor performances by using magneto-motive force harmonics analysis and electromagnetic magnetic field analysis. Results are useful in preliminary and final optimal designs of the high speed spindle motors.The technologies for maintaining high recording densities to suppress mechanical vibration and media flutter require advance spindle motor design and technology. To realize multi-magnetic poles with limited stator slots, radial air gap field HDD spindle motor are normally used concentrated winding. Based on different pole/slots combinations, there would be a variety of winding configurations. In this work, detailed analysis is carried out to identify the optimal winding structures of the high speed spindle motor and analyze their effect to the motor performances by using MMF harmonics analysis and FEM. Results are useful in preliminary and final optimal designs of the high speed spindle motors.

Influence of Drive Current to Unbalanced-Magnetic-Pull in Spindle Motor

Both symmetric and asymmetric armature windings are applied in the spindle motors used in hard disk drives. Consider the influence of the drive current in the windings, the analysis to the unbalanced-magnetic-pull (UMP) generated in the motor becomes more difficult. Besides the intrinsic and extrinsic components, the additional UMP can also induced by the current, and the UMP could thus be serious. This paper analyzes this phenomenon, and presents a model which can describe clearly the influence of the drive current to the UMP. For verifying the effectiveness of the analytic method proposed, several spindle motors are analyzed, and compared with the results obtained by using FE method. The comparing proves the effectiveness of the UMP model presented.

Natural Frequency of Stator Core of PM Synchronous Motor

As the degree of office automation to improve, more and more automation equipments are utilized in office. Moreover, numbers of motors are employed in automation to realize multiple functions to attract customers. As a result, the motor which can run more quietly are highly demanded than ever. One of the main causes of noise production in motors is resonance between the electromagnetic forces e.g. Unbalanced Magnetic Pulls (UMPs) and the stator and the frame of the motor. Therefore, the accurate determination of the natural frequencies of stator at the design stage becomes very important [1]. Researchers have studied motor natural frequencies, vibration and acoustic signals in recent years [2]–[5]. In this paper, the PMSM stator mathematic model has introduced and validated by 12 slots and 5 pole-pairs PM surface mounting Synchronous motor M1 simulation case study. The dynamic responses of the model with high frequency excitation force are studied through simulation and experimental approach to further validate the analytical model.Copyright

Synthesis of a novel linear-rotary electromagnetic induction sensor using printed circuit coils

Encoders and resolvers are the commonly used sensors to measure the shaft position in motion control applications. Requirements of precise manufacturing and special electromagnetic or optic structures make those sensors expensive. Reduction of cost without degradation of performance is a challenging problem in sensor design. It demands novel and innovative designs to be explored. This paper presents the synthesis of a novel linear-rotary electromagnetic induction sensor using printed circuit coils. The operating principle of the new sensor adapts that of a resolver but the new sensor outputs have a piece-wise linear relationship with the shaft position. In this work, systematic design procedures are described and the prototypes are fabricated. Evaluation of the prototypes shows that the new sensor achieves the accuracy comparable to the accuracy of industrial resolvers.

Influence of Neutral Line to the Optimal Drive Current of PMAC Motors

The optimal drive current can reduce both the torque ripple and power loss in driving the permanent magnetic (PM) AC motor. This paper presents an analytical model for calculating the optimal drive current of the PMAC motor with surface mount PM rotor. Both the motors with and without the neutral line are analyzed. Theoretical analysis shows that, when the back-emf of the windings contains triple order harmonics, the neutral line of the motor can let the optimal drive current be different from the one without the neutral line, and it can also make the optimal drive current be more effective in the loss and torque ripple reduction. Two spindle motors are used in the analysis to show the influences of the optimal model presented.

Analysis of magnet field degradation on PM motor vibration

In this paper, the effect of magnet field degradation on vibration of the permanent magnet (PM) motor is analyzed. Combination of 2D and 3D FEM is carried out to identify the electromagnetic vibration sources. Vibration signals are analyzed by electromagnetic (EM) field coupled vibration analysis. Results are useful in optimal motor design for PM motor to minimize vibration and to detect the magnet field degradation failure in online and offline monitoring.

Comparison of 2-D and 3-D EM field and force simulation accuracy in numerical environment

In computer aided design and analysis of electrical machines, electromagnetic field problems are solved in 2 dimensional space (2D) or 3 dimensional space (3D) depending on the problem nature. This study reports the comparative analysis of computation in 2D and 3D, in terms of important machine performance indicators like average torque, varied torque and unbalanced magnetic pull. As an example, a Brushless DC (BLDC) motor is analyzed to evaluate accuracy and computational effort. The analysis highlights the difference in accuracy and the reasons for the discrepancy.

Initial Calibration and Online Error Compensation of a Resolver System

This paper presents a method for initial calibration and online compensation of systematic errors in a resolver system. Initial calibration at standstill condition is carried out for a few positions by applying Discrete Fourier Transform and Least Squares method. The error model is constructed based on complex Fourier expression of position angle signal obtained from non-ideal resolver signals due to amplitude imbalance, quadrature error and offset. Error parameters are determined online using the integral control loops which are initialized with the calibration results. Besides, single channel amplitude tracking is incorporated in the error compensation scheme. This makes the compensation adaptive to changes in error parameters. And thus accuracy of the resolver system is reasonably improved and the system becomes robust. The effectiveness of the proposed method is validated by simulation and experiments.