Hitachi Global Storage Technologies Netherlands B.v.

Nobuhiko Wasa

Sayaka Nojiri

Masahiro Shimizu

Isao Yoneda

Shinya Sakamoto

Kenichi Kuramoto

Kohji Takasaki

Yasuhiro Iihara

Hidefumi Tominaga

Sumio Obata

Embodiments of the present invention help to perform appropriate servo control in response to detected vibration in a disk drive device having a vibration sensor. In an embodiment of the present invention, an HDD switches a correction servo mode to perform vibration correction in head positioning and a normal servo mode not to perform the vibration correction. The HDD performs servo positioning in either one of the serve modes and determines servo positioning accuracy in the servo mode from the measured positional error signal. The HDD obtains data indicating the servo positioning accuracy in the other servo mode from a table. The HDD compares the accuracy in the two servo modes and selects the servo mode with higher accuracy. The table contains previous measurements on servo positioning accuracy in the servo modes.

Disk drive device and servo control method thereof

Embodiments of the present invention help to prevent destabilization in voice coil motor (VCM) velocity control. According to one embodiment, a hard disk controller/multiprocessing unit (HDC/MPU) calibrates a correction operational coefficient of a detected back electromotive force (EMF) voltage before unloading. The calibration is carried out in a state that an actuator is pivoting. The HDC/MPU calibrates the correction coefficient according to a motion equation of the actuator using VCM current applied to a VCM and a detected value of a back EMF voltage detection circuit.

Disk drive and calibration method therefor

Embodiments in accordance with the present invention provide a disk drive capable of verifying whether the speed of an actuator is true or not, the speed being detected while the actuator is being moved between a retracted position and a recording surface of a magnetic disk, and to provide a control method for controlling the disk drive. In a particular embodiment, a hard disk drive (HDD) comprises: a head for accessing a disk; an actuator for supporting the head, the actuator being driven by a voice coil motor (VCM); a speed monitor for, on the basis of a cylinder ID written to the disk, monitoring the speed of the actuator while the actuator is being moved between a ramp which is provided outside a data area of the disk and the data area; and a speed verifier for, if an abnormal speed condition of the actuator is detected by the speed monitor, verifying the abnormal speed condition on the basis of the counter electromotive voltage of the VCM. If the speed based on the counter electromotive voltage is also abnormal, the speed verifier records the speed as the overspeed.

Disk drive and control method therefor

In an embodiment of the present invention, a Hard Disk Controller Microprocessing Unit (HDC/MPU) supplies, prior to the unloading process, different currents to a VCM, with an actuator positioned in place and kept at a standstill. The HDC/MPU determines a correction factor from VCM speeds vmeas, each of which is detected at each of VCM currents Ivcm. If the determined correction factor falls outside a reference limit, the HDC/MPU determines a new circuit parameter for a VCM speed detection circuit. Further, the HDC/MPU calculates a new correction factor appropriate to the circuit parameter. The HDC/MPU and the VCM speed detection circuit control the speed of the VCM in the unloading process using the new circuit parameter and the new correction factor.

Disk drive and calibration method for the same

Embodiments of the invention provide a magnetic disk drive having increased efficiency of generation of power for its internal low-voltage blocks. In one embodiment, a magnetic disk drive comprises a main power supply unit for supplying power of a predetermined voltage to a load, the main power supply unit including a switching regulator; a power monitoring circuit for detecting the power supplied from the main power supply unit to the load and for determining whether the detected power exceeds a predetermined power level; and a third power supply unit, if it is determined that the power supplied from the main power supply unit to the load exceeds the predetermined power level, for supplying power of the predetermined voltage to the load, the third power supply unit including a linear regulator.

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Kanagawa, Japan

Nobuhiko Wasa