Shinobu Yoshida

Non-symmetrical three-lobe bearing spindle technology: a drive technology to increase aerial density

A fluid-film spindle for 2.5 inch hard disk drive is described that effectively reduces nonrepeatable runout to less than 0.05 /spl mu/m, making it possible to increase track density. The spindle is used with a newly designed three-lobe bearing of which each lobe is asymmetrical. The influence of stiffness and temperature in a prototype spindle using this bearing are discussed and comparisons are made with a conventional ball-bearing spindle.

Analysis of Built-in Speaker-Induced Structural-Acoustic Vibration of Hard Disk Drives in Notebook PCs

This study is to develop a methodology and model to analyze the built-in speakers induced structural acoustic vibration of hard disk drive (HDD) in Notebook PC. First, a structural finite element (FE) model is built for the notebook PC to be analyzed using ANSYS. This FE model is subsequently verified by experiments. Second, the effects of acoustically transmitted and structurally transmitted oscillating forces, induced by the speakers, acting on the HDD, are investigated by acoustic FE model (SYSNOISE) and structural FE model. The acoustic transmission effect on the vibration of HDD is also investigated by experiment, which shows that the simulation results have a good agreement with experimental results. Finally, the effects of stiffness and damping ratio of the HDD supporters on the vibration of HDD are analyzed by the verified FE model.

Design of HDD Servo Controller with Adaptive IMC Structure

A robust controller design method with adaptive internal model control (IMC) structure for hard disk drive (HDD) servo is presented in this paper. To handle the unmodeled dynamics, the internal model control method is adopted to guarantee the robust stability. The model reference adaptive control (MRAC) technique is further incorporated into the IMC structure to deal with the gain variations of the VCM motor. The proposed method is applied to a HDD servo control system, and the experimental results show the effectiveness of the method

A New Sensorless Write Fault Protection Mechanism For HDD

A new sensorless write fault protection mechanism for hard disc drives (HDDs) is proposed in this paper. It was observed that with the proposed protection mechanism, head offtrack positions at protection moments have been greatly restricted. It has been implied that much better performance on data integrity can be expected under shock/vibration environment.

Optimization for vibration problems : Junction layout of a combined structure under oscillation

We proposed a method for optimizing the layout of junctions between two structures so as to minimize the relative displacement between them when one of them is oscillated by noise disturbances. Layout optimization yields the minimum number of junctions, which means fewer joint components or fewer spot-welding operations leading to higher production efficiency.

Structural Optimization by Density Distribution for Maximization of Natural Frequency

This paper proposes a basic method for designing light and rigid structures that have a maximum natural frequency for a designated mode. A design variable “density,” related to the material properties of a three-dimensional solid element, is introduced into the finite element method (FEM). Thus, a structure is expressed as a density distribution inside its design domain, and the optimal structure is obtained by searching for the most suitable such distribution.

Attenuation of High Frequency Mechanical Resonances Using Multirate Low-Pass Filter in HDDs

In this paper, the design method of a multirate digital filter to handle high frequency resonant modes in hard disk drives (HDDs) or other mechanical actuators is proposed. Instead of using many notch filters, one low-pass filter will handle multiple mechanical resonance modes. The proposed multirate digital filter has robust resonance cancellation capability with comparable or even lower phase loss than using notch filters. The proposed scheme can well handle the high frequency mechanical resonances in the sense of robustness to variations of resonance frequencies and simplicity to implement in practice. The effectiveness of the proposed method is verified by application to a real HDD servo system.

Simulation Study on Reduction of Heat-Induced Head-Alignment Errors and Main-Resonance Amplitudes for Pivot-Shaft-Combined Head-Positioning Mechanisms

Reducing track miss-registration is important for achieving high-accuracy, high-speed head positioning for hard disk drives. In a rotary-type head-positioning mechanism, which employs a pivot-shaft-combined magnet-yoke assembly, head-alignment errors due to thermal deformation and moving-part structural vibrations must be reduced to meet above requirements. We examined yoke fixing methods to minimize alignment errors among heads and to reduce main-resonance amplitudes. Calculated results show that the heat-induced head-alignment errors become minimum and the main-resonance amplitudes decrease when the center part of the yoke is fixed to the base. The out-of-plane structural vibrations, harmful influence to the mechanism, are eliminated by attaching damping materials to both ends of the yoke. This fixing method can be used to achieve high-accuracy, high-speed head-positioning.

Numerical Simulation of Touchdown/Takeoff Hysterisis of Spherical Pad Slider by Considering the Liquid Bridge Between the Slider and Lubricant-Disk

This work carries on a numerical simulation of the touchdown/takeoff (TD/TO) hysterisis of the spherical pad slider. It numerically studies the meniscus bridge’s formation and meniscus force interaction between the spherical pad and lubricant over the disk surface. It proposes a geometry model for the lubricant bridge, and correspondingly, a force model for the meniscus force acting on the spherical pad slider due to the lubricant bridge. By solving the liquid balance state at the meniscus boundary, it obtains the geometry of the liquid bridge. A parametric study is done to study the effects of the geometry of spherical pad, Hamaker constant of lubricant-disk, and surface energy of lubricant on the formation of the liquid bridge. The overflow phenomenon is analyzed to find out the acceptable dimension of the spherical pad design. Moreover, a three-dimensional (3D) model of spherical pad slider/disk interface is built to study the steady-state flying of the spherical pad slider. The different parameters are analyzed to study their effects on the TD/TO hysteresis.Copyright

Write Fault Protection for Shock Disturbance in HDDs Without a Shock Sensor

Write fault protection capability directly determines the data integrity performance in HDDs. For HDDs with a shock sensor, the data integrity performance is rather uniform with different shock disturbance. However, this is not the case when shock sensors are not available and only off-track thresholds are used to detect shock loads. This paper studied the relationship between the write fault protection capability and shock disturbance