Reduction of torque ripple and mechanical vibration of spindle motors in hard-disk drives using a sinusoidal driver

Mechanical vibration and acoustic noise are major obstacles in the development of high-density and high-spindle-speed hard disk drives. Torque ripple caused by the electrical driver is the main source of vibration and noise. This paper proposes a novel driver for spindle motors in hard disk drives based on the principle of position sensorless vector control. To reduce torque ripple, the proposed driver feeds the spindle motor in sinusoidal driving mode by which the sinusoidal current of the motor can be obtained. Experimental results of the proposed driver demonstrate the better driving performance in startup condition and fine sinusoidal current in steady state. Vibration testing shows significant improvement in the attenuation of vibration: the dominant vibration modes can be reduced to one tenth compared to that of a conventional driver. In addition, the mechanism of inducing torque ripple from time-harmonic currents is analyzed and the relationship between induced torque ripple and exhibited vibration modes is examined.     

Design and Implementation of a Hybrid Output EMI Filter for High-Frequency Common-Mode Voltage Compensation in PWM Inverters

This paper presents a hybrid output electromagnetic interference (EMI) filter for common-mode voltage compensation in pulsewidth-modulation (PWM) inverters. Its structure is composed of a single-leg four-level active filter connected in series with a low-frequency blocking capacitor and a small passive LC filter that which enhances the suppression of the common-mode voltage in the high-frequency range. The series capacitor helps in avoiding the core saturation of the common-mode coupling transformer caused by the low-frequency components of the common-mode voltage. Detection of PWM voltages by high-speed optoisolators is done at the inverter's output to achieve better common-mode voltage detection and compensation characteristics. Analysis and design guidelines for the hybrid filter are also given to facilitate systematic design in the real implementation of the filter. Experimental results with a real drive system clearly illustrate a significant reduction of the common-mode voltage, the leakage current, the shaft voltage, and the bearing current.     

Reduction of torque ripple and mechanical vibration of spindle motors in hard-disk drives using a sinusoidal driver

Mechanical vibration and acoustic noise are major obstacles in the development of high-density and high-spindle-speed hard disk drives. Torque ripple caused by the electrical driver is the main source of vibration and noise. This paper proposes a novel driver for spindle motors in hard disk drives based on the principle of position sensorless vector control. To reduce torque ripple, the proposed driver feeds the spindle motor in sinusoidal driving mode by which the sinusoidal current of the motor can be obtained. Experimental results of the proposed driver demonstrate the better driving performance in startup condition and fine sinusoidal current in steady state. Vibration testing shows significant improvement in the attenuation of vibration: the dominant vibration modes can be reduced to one tenth compared to that of a conventional driver. In addition, the mechanism of inducing torque ripple from time-harmonic currents is analyzed and the relationship between induced torque ripple and exhibited vibration modes is examined.

     

Design strategy of an adaptive full-order observer for speed-sensorless induction-motor Drives-tracking performance and stabilization

Design strategy of both feedback gains and adaptation gains for an adaptive full-order observer is a necessary issue to assure the stability and the tracking performance of the speed estimation in the sensorless drives. In this paper, novel design of feedback gains of the observer is proposed to achieve the stability over the whole operation especially in the low-speed region, including the regenerating mode. Stability improvement using the proposed feedback gains is rigorously proven by the method of Lyapunov. For the adaptation proportional-integral (PI) gains, the ramp response characteristic of the speed estimator is proposed as design guidelines. It is revealed that the integral adaptation gain determines the tracking error of the speed estimator during acceleration/deceleration while the sensitivity to current measurement noises depends on the proportional adaptation gain. It is also pointed out that a suitable corner frequency of the adaptation PI gains is required as a design tradeoff to avoid an oscillation. The validity of all theoretical results is verified by simulation and experiment.     

A speed-sensorless IM drive with decoupling control and stabilityanalysis of speed estimation

A new sensorless drive based on a decoupling control and an adaptive full-order observer is developed. A modified decoupling control is introduced and integrated with the adaptive observer to reduce the complexity of the whole system. The speed estimation based on adaptive control theory is analyzed and the necessary and sufficient conditions for stability of the speed estimation are analytically derived. It is indicated that the system can be unstable in the low-speed region with regenerative loads. However, assigning an appropriate feedback gain to the adaptive observer can restore the stability and reduce the unstable region. Sensitivity of the sensorless drive against parameter and measurement errors is also qualitatively discussed. Simulation and experimental results are then given to verify the validity of the theoretical results