Hitachi Global Storage Technologies Japan, Ltd.

Hitachi Global Storage Technologies Netherlands B.v.

Hgst Netherlands, B.v.

Kazuhisa Shishida

Isao Yoneda

Chikako Sakagami

Hiroshi Uchida

Takehiko Hamaguchi

Hideaki Maeda

Kazuaki Usui

Takahiro Inoue

Yasutaka Nishida

Kenji Okada

Shinji Matsushita

Kenji Tomida

Takeshi Saito

Yosuke Seo

Takenori Atsumi

Takao Horiguchi

Makoto Horisaki

Katsuhiko Ohta

Kiyotada Itou

Youichi Kusagaya

Takashi Konishi

A disk drive comprising a head for accessing a disk, an actuator for moving the head in the radial direction of the disk and a controller. The controller for servo control of the actuator based on servo data read out from the disk by the head. The controller is configured for maintaining a width of the adaptive chasing notch filter below a specified value in servo system control and estimating an oscillation frequency of the actuator.

Servo control of a disk drive

A disk drive. The disk drive includes a head, an actuator, and a controller. The head accesses a disk. The actuator is configured to support the head and to move the head by action of a voice-coil motor in a substantially radial direction of the disk. The controller is also configured to perform servo control of the actuator by using servo data read out by the head. The controller includes at least one of a plurality of notch filters having a fixed center frequency inserted in a servo-control loop. The controller is configured to increase an attenuation rate by at least one of the plurality of notch filters having the fixed center frequency at a designated frequency, when a target position of the head is at a position selected from the group consisting of a position outside of a specified region and a position within the specified region.

Disk drive and servo-control method therefor

A disk drive. The disk drive includes a head, a moving mechanism, a first peak filter, an adaptive peak filter, and a filter controller. The head is configured to read servo data on a disk at sampling frequency. The moving mechanism is configured to move the head in proximity with a recording surface of the disk. The first peak filter has a fixed peak frequency and a variable gain, and is configured to be inserted into a servo loop. The servo loop is configured to position the head with position error signals between servo data read by the head and a target position. The adaptive peak filter has a variable peak frequency and a variable gain, and is configured to be inserted into the servo loop. The filter controller is configured to control the gain of the adaptive peak filter according to the gain of the first peak filter.

Disk drive and method for head servo control of the disk drive

The invention provides a servo pattern that is stable for long time, easily writable, and excellent in S/N. DC-signal area included in a burst area of a servo pattern comprises combination of positive and negative DC-signals, low-density dummy bit, or pattern having phases that are deviated each other so that the sum of magnetization of the burst area of the servo pattern is equalized to 0.

Alternative DC-burst servo pattern for perpendicular recording

Embodiments of the invention provide optimum servo patterns for perpendicular magnetic recording method. In one embodiment, a burst field of servo patterns is composed of burst-signal parts in each of which a constant frequency occurs successively and zero-signal parts each of which has been demagnetized to a state of zero-magnetization, and the total magnetization of the burst field is made approximately 0. The zero signal portions are formed by shutting off a write current at a time during an operation to record servo patterns on a disk initialized to a state of zero-magnetization. The total magnetization of all servo patterns is made approximately 0 by encoding an address mark field and a track code field of servo patterns by a phase shift method.

Servo information recording method, magnetic recording media, and magnetic disk apparatus

In a disk drive, since high-frequency repeatable runout (RRO) components own low correlative relationships between adjoining tracks, a servo control system of a magnetic head is followed to the high-frequency RRO components, and thus, in the worst case, there is a possibility that data which have been previously recorded on these tracks are destroyed. To avoid this problem, both a tracking type repetitive control unit which is followed to low-frequency RRO components, and a rejection type repetitive control unit which cancels the high-frequency RRO components are provided in a following control loop in order that the following control system is not unnecessarily followed to the high-frequency RRO.

Disk drive

In order to achieve narrow track pitch by measuring, storing and compensating common average values for repeatable runout components between adjacent tracks in a head positioning control system for a magnetic disk drive, a compensation signal is calculated for the average value of the repeatable runout of each servo sector of at least two tracks of servo information reproduced from a magnetic disk, on the basis of an inverse function of the sensitivity characteristics of the tracking control system. The compensation signal is stored, and thereafter used for compensating the servo signal.

Magnetic disk drive for compensating repeatable runout error

Growing community of inventors

Kanagawa, Japan

Kazuhisa Shishida