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Kawasaki, Japan

Paoletti U.,Hitachi Ltd. | Noma T.,Hitachi Ltd. | Nishiyama N.,HGST Japan Ltd.
IEEE International Symposium on Electromagnetic Compatibility | Year: 2015

A parallel strip line of very small size has been designed in order to study the susceptibility of hard disk drive heads. High accuracy and low cost design is obtained using printed circuit board technology. Details of the design are discussed. A special solution for implementing the termination is proposed. The parallel strip line has been fabricated and its usabilty up to at least 6 GHz has been confirmed in terms of the voltage standing wave ratio and internal to external field ratio. Calibration was conducted by measuring the field across the termination resistors. © 2015 IEEE. Source

The relationship between natural frequency, damping, the waveform of a feedforward acceleration input, and the transient vibrations of track-seek control is derived theoretically and a target for vibration design of the head actuator of a hard disk drive (HDD) is discussed from the viewpoint of the transient vibrations. When the acceleration feedforward input of the track-seek control is expressed as a polynomial function of time, the transient response of a single degree of freedom system is solved by applying integral by parts to the Duhamel’s integral repeatedly. The results show the transient vibrations are generated at the initial and terminal times of the input and their amplitude depends on the lowest orders of non-zero derivatives of the polynomial. They also show that increasing the damping ratio effectively reduces the transient vibrations for fourth and sixth order polynomials but not for fifth and seventh order polynomials. The results were confirmed by performing a continuous time simulation and analyzing the shock response spectrum. Also discussed is the relationship between the transient vibrations and the seek time and track pitch, which are key parameters associated with the data access time and the HDD capacity. This relationship indicated the requirements needed for vibration design of the head actuator to increase HDD performance and capacity. © 2015 Springer-Verlag Berlin Heidelberg Source

Suzuki K.,Hitachi Ltd. | Ohta M.,HGST Japan Ltd.
Microsystem Technologies | Year: 2013

We proposed a carriage called a two-layer coil carriage that attenuates an out-of-plane mode. The coil of the proposed carriage is divided into two parts that are stacked on one another. The ratio of the current for the two coils can be changed by optimizing the coil coefficients. We have clarified the mechanism of excitation of the out-of-plane mode. We constructed the two-layer coil carriage, and measured the frequency response from the voice coil motor current of the two coils to head displacement. The effectiveness of the proposed carriage in reducing excitation of the coil torsion mode was demonstrated through simulation and experiment. © 2013 Springer-Verlag Berlin Heidelberg. Source

Yabui S.,HGST Japan Ltd. | Okuyama A.,Tokai University | Atsumi T.,HGST Japan Ltd. | Odai M.,Hitachi Ltd.
Journal of Advanced Mechanical Design, Systems and Manufacturing | Year: 2013

This paper presents an adaptive feed-forward cancellation (AFC) technique with a damping function based on optimized AFC. The proposed AFC includes a mechanical resonance characteristic as an internal model that is realized by using the damping function and that achieves the best performance in the frequency domain. This makes it possible to apply the proposed AFC to suppress not only repeatable run-out (RRO) but also non-repeatable run-out (NRRO) of the head positioning system in hard disk drives. Simulation results showed that the proposed AFC can suppress NRRO such as disk flutter vibration and that the stability of the feedback loop was improved by the damping function. Copyright © 2013 by JSME. Source

Furukawa M.,HGST Japan Ltd. | Xu J.,HGST Japan Ltd. | Kato Y.,HGST Japan Ltd. | Wada T.,Hitachi Ltd.
Microsystem Technologies | Year: 2013

We developed a tester consisting of minor-loop and major-loop quasi-static test (QST) units in order to better understand head instabilities under conditions where the head slider was flying on the disk. The minor-loop QST unit, composed of a spin-stand and an electromagnetic coil, was used to understand the mechanism of head instabilities caused by thermal stress due to flying-height control using a thermal actuator and caused by mechanical stress due to contact between the head and disk under flying conditions. The major-loop QST unit was used to investigate head damage in detail. We designed and fabricated the tester and conducted experiments that focused on thermal and mechanical stress. The results confirmed that the new method was effective for studying head instabilities at the head disk interface of hard disk drives (HDDs). © 2013 Springer-Verlag Berlin Heidelberg. Source

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