Tomoyoshi Yamada

Microactuator control for disk drive

The nonlinear response of a conventional actuator which depends on the ball-bearing friction is the main factor for determining the high track density of hard disk drives. We cannot get enough servo loop gain in the low-frequency region with a conventional single actuator because of its hysteresis characteristics. We have developed a new planar piezoelectric microactuator which is lightweight and applicable for a hard disk drive. Also we introduced a two-stage servo controller and realized a high servo bandwidth over 1 kHz and enough tracking-error reduction in the low-frequency region.

Hard disk drive servo technology for media-level servo track writing

Hard disk drive (HDD) servo technology for media-level servo track writing (MLSTW) is developed. MLSTW is the process of writing servo signals on magnetic disks before they are assembled in drives. It supplies a solution to achieve low-cost and accurate means of servo-signal writing. The HDD servo controller for MLSTW drives compensates for radial and rotational distortions of the servo signals (e.g., track-address, eccentricities, and servo-signal timing) that are inherent in the MLSTW method. The authors prove that the positioning accuracy is improved and the seek time is unchanged by using the new servo controller for HDDs with MLSTW disks.

Shear mode piezoelectric microactuator for magnetic disk drives

We developed a new piezoelectric microactuator for dual-stage actuator systems in magnetic disk drives. This actuator exploits the shear mode of piezoelectric elements and drives the head suspension assembly. This paper describes the structure of our piezoelectric actuator, its mechanical characteristics, and the experimental results of a life test after driving the piezoelectric elements in an atmosphere of high temperature and humidity.

High-speed orthogonal power effect actuator for recording at over 10000 TPI

A new type of rotary actuator for HDDs is presented. To suppress the resonance gain in the quasi-rigid body mode caused by the stiffness of support bearings, we propose orthogonal driving. The designed actuator for a 3.5-inch drive shows a quasi-rigid body mode gain of less than 5 dB, and a fundamental resonance frequency of approximately 10 kHz. The results agree with those from finite element analysis.

Dynamic characteristics of a magnetic head slider

The estimation of the dynamic characteristics of magnetic head sliders is essential for the design of the recent disk file systems with reduced head-to-disk spacing. This paper presents a method for measuring the head slider flying height fluctuation caused by disturbances on the disk and head arm vibration. A numerical analysis of the head assembly including suspension spring and gas-bearing slider is presented. The experimental and analytical results are compared and it is clarified that the many resonant peaks of head sliders spacing fluctuation in the low frequency region are caused by the resonance of the suspension spring.

A study of head-disk interface shock resistance

We observed slider and suspension behavior under external shock using a still camera with a stroboscope. This paper shows experimental results of the relationship between disk failure and using Hertzs contact stress formula with energy conservation. We describe a technique to improve shock durability based on this relationship.

A negative pressure microhead slider for ultralow spacing with uniform flying height

A negative-pressure head slider for ultralow flying has been developed which features a newly shaped air bearing surface that gains sufficient suction force because the distance between the two side rails gradually widens from the leading to the trailing edge of the slider. The slider has a fast takeoff, and the flying height is insensitive to disk velocity. It also avoids the dust accumulation problem seen in the conventional negative-pressure slider. The sliders absence of taper suppresses generation to floating force, resulting in a microslider with relatively wide siderails. The flare angle of the siderails also contributes to making the flying height insensitive to the yaw angle, resulting in a uniform flying height over the entire disk surface. The recess needed to generate suction is a shallow 2 mu m, so the flexible rail shape is easily manufactured using photolithography. >

Effect of dual-stage actuator on positioning accuracy in 10 k rpm magnetic disk drives

We have developed a piezoelectric micro-actuator for dual-stage actuator systems in magnetic disk drives. This microactuator, which drives the head suspension assembly, is based on the shear deformation of piezoelectric elements. We installed the microactuator in one of Fujitsus 3.5-inch commercial drives for evaluation of the servo system of dual-stage actuator. This paper describes the effect of the dual-stage servo system on positioning accuracy compared with the single actuator.

A high-performance and low-profile moving-magnet actuator for disk drives

We have developed a high-performance moving-magnet rotary actuator for very low-profile magnetic disk drives. A small moving magnet and efficient low-profile magnetic circuit construction give high acceleration and reduce power consumption to 50% that of moving coil actuators. The arrangement of the coils and yokes increases the design flexibility. The actuator does, however, suffer from a magnetic bias force and large inductance. >

Dynamics of inline flying-head assemblies

Heads for high-performance disk storage must be able to withstand an acceleration of dozens of G-force and be capable of positioning to submicron precision. A measuring technique that can totally analyze the flight stability and access ability of the slider was developed. It involves three-dimensional modal analysis of the suspension using a laser Doppler anemometer, a laser Doppler vibrometer, and simultaneous measurement of spacing fluctuation. Using this system to examine an inline head, it was found that notable lateral and torsional modes of the suspension vibration were caused by the access acceleration of the rectangular wave, and that there is pronounced spacing fluctuation. In addition, these lateral vibrations cause the pivot to slip, which may cause problems in high-speed head access. >