Yukihiro Uematsu

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.

Development of the pushpin free STW

In order to realize super-high density TPI, it is necessary to greatly reduce track misregistration. For this purpose, it is necessary to reduce the amount of repeatable position errors (RPE) and improve the writing accuracy of position error signals (PES) of servo track writers (STW), in parallel with reducing non-repeatable position errors (NRPE) with fluid dynamic bearings or piggyback actuators employed. This paper introduces a new, low-priced STW system of high efficiency, with a high precision writing performance.

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.

Development of the pushpin free STW [servo track writer]

In order to avoid thermal degradation in magnetic recording, it can be predicted that development will he made in the future toward higher track density (TPI) compared with that of bit density (BPI). For practical use of a super-high density TPI drive, it is essential to develop a servo track writer (STW). This paper introduces that we have successfully developed a high precision, highly efficient, and low-priced STW using a new sheet scale developed recently.