Abstract: A magnetic disk device includes a disk, first and second heads, a motor, and a controller. The disk includes a first surface and a second surface opposite to the first surface. The first head is configured to perform reading and writing with respect to the first surface. The second head is configured to perform reading and writing with respect to the second surface. The motor is configured to move the first and second heads with respect to the first and second surfaces, respectively, along a radial direction of the disk. The controller is configured to alternately activate the first and second heads to perform writing of a plurality of spiral patterns on the first and second surfaces of the disk, respectively, while controlling the motor to move the first and second heads at a predetermined constant speed with respect to the first and second surfaces in the radial direction.

Abstract: A magnetic disk device includes a disk, first and second heads, a motor, and a controller. The disk includes a first surface and a second surface opposite to the first surface. The first head is configured to perform reading and writing with respect to the first surface. The second head is configured to perform reading and writing with respect to the second surface. The motor is configured to move the first and second heads with respect to the first and second surfaces, respectively, along a radial direction of the disk. The controller is configured to alternately activate the first and second heads to perform writing of a plurality of spiral patterns on the first and second surfaces of the disk, respectively, while controlling the motor to move the first and second heads at a predetermined constant speed with respect to the first and second surfaces in the radial direction.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic disk including at least one servo zone that includes a first data storage track with a first servo pattern having a first frequency and a second data storage track with a second servo pattern having a second frequency, wherein the first data storage track is located closer to an outer diameter of the magnetic disk than the first data storage track and the first frequency is greater than the second frequency; a magnetic head that faces the magnetic disk; and a zone servo switching unit that switches a servo pattern frequency employed to position the magnetic head in a radial direction based on a radial position of the magnetic head.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic disk including at least one servo zone that includes a first data storage track with a first servo pattern having a first frequency and a second data storage track with a second servo pattern having a second frequency, wherein the first data storage track is located closer to an outer diameter of the magnetic disk than the first data storage track and the first frequency is greater than the second frequency; a magnetic head that faces the magnetic disk; and a zone servo switching unit that switches a servo pattern frequency employed to position the magnetic head in a radial direction based on a radial position of the magnetic head.

Abstract: According to one embodiment, a magnetic disc device includes a magnetic disc in which servo data is recorded in a servo area; a magnetic head provided for the magnetic disc; a determination unit that determines an SSW range in the servo area; and a servo control unit that performs servo control of the magnetic head based on the servo data recorded in the SSW range.

Abstract: According to one embodiment, an estimation method comprises measuring and creating. The measuring is configured to measure a head velocity and a terminal voltage of a coil of a voice coil motor at least two times before unload in a control system eliminating an influence caused by a transient response of inductance of the voice coil motor. The calculating is configured to a calculate torque constant and a coil resistance based on command voltages and at least two measured head velocities and terminal voltages of the coil.

Abstract: According to one embodiment, a magnetic recording medium on which servo data is recorded by magnetic transfer recording, the medium includes a data recording area in which data is recorded on a plurality of data tracks extending in form of concentric circles, and a servo area comprising the servo data corresponding to the data tracks. The servo data includes a plurality of burst patterns for tracking detection, which are arranged in a circumferential direction of the data tracks, and the burst patterns comprise a number of recording crests which differs depending on a radial position on the magnetic recording medium.

Abstract: According to one embodiment, an estimation method comprises measuring and creating. The measuring is configured to measure a head velocity and a terminal voltage of a coil of a voice coil motor at least two times before unload in a control system eliminating an influence caused by a transient response of inductance of the voice coil motor. The calculating is configured to a calculate torque constant and a coil resistance based on command voltages and at least two measured head velocities and terminal voltages of the coil.

Abstract: A valve assembly comprises a diaphragm valve, a pressure regulator and a solenoid. The pressure regulator is operatively coupled to the diaphragm valve for maintaining a predetermined pressure in water exiting the diaphragm valve despite fluctuations in the pressure of water entering the diaphragm valve. The solenoid is mounted on the pressure regulator so that a plunger axis of the solenoid extends through a coil spring of the pressure regulator. The solenoid is operatively coupled to the diaphragm valve through the pressure regulator for opening and closing the diaphragm valve.

Abstract: According to one embodiment, a disk drive includes a heating element which is provided on a head and generates heat when supplied with power, thereby to adjust a dynamic flying height of the head. A head-movement detecting unit detects the abnormal movement of the head, a value of which is larger than a preset movement value during a head positioning control. In this case, a heating-element controller stops supplying power to the heating element.

Abstract: According to one embodiment, a disk drive includes a heating element which is provided on a head and generates heat when supplied with power, thereby to adjust a dynamic flying height of the head. A head-movement detecting unit detects the abnormal movement of the head, a value of which is larger than a preset movement value during a head positioning control. In this case, a heating-element controller stops supplying power to the heating element.