Abstract: According to one embodiment, a magnetic disk apparatus includes a magnetic disk, a magnetic head, and a controller. The magnetic disk includes a plurality of tracks. The magnetic head performs read/write from/to the plurality of tracks. The controller controls, in a first case in which, during execution of write to a first track among the plurality of tracks, a position of the magnetic head is displaced from a target position corresponding to the first track toward a second track, and a first distance exceeds a first threshold, write to the second track under a condition different from a condition in a second case in which the first distance is less than the first threshold. The second track is a track different from the first track among the plurality of tracks. The first distance is the distance between the target position and the position of the magnetic head.

Abstract: According to one embodiment, a magnetic disk apparatus includes a magnetic disk, a magnetic head, and a controller. The magnetic disk includes a plurality of tracks. The magnetic head performs read/write from/to the plurality of tracks. The controller controls, in a first case in which, during execution of write to a first track among the plurality of tracks, a position of the magnetic head is displaced from a target position corresponding to the first track toward a second track, and a first distance exceeds a first threshold, write to the second track under a condition different from a condition in a second case in which the first distance is less than the first threshold. The second track is a track different from the first track among the plurality of tracks. The first distance is the distance between the target position and the position of the magnetic head.

Abstract: A magnetic disk device according to an embodiment includes: a head slider; a magnetic head provided in the head slider; a heater provided in the head slider; and a controller that determines, in seek operation of the magnetic head, a preheat start scheduled position from a remaining seek distance at which a time required for preheating of the head slider can be secured, the controller starting the preheating from the preheat start scheduled position in a case where no bump exists in an area from the preheat start scheduled position to a seek target position, the controller changing a preheat start position to an arbitrary position in an area from the bump to the seek target position in a case where the bump exists in the area from the preheat start scheduled position to the seek target position.

Abstract: According to one embodiment, a position demodulator includes a demodulator, a phase corrector, and a position demodulating module. The demodulator demodulates a first demodulated signal and a second demodulated signal having a phase difference of 90 degrees from the first demodulated signal as a result of discrete Fourier transform operation on a read signal of a null servo pattern recorded in a servo area of a medium read out by a head. The phase corrector carries out correction to tilt respective vectors of the first demodulated signal and the second demodulated signal represented on a phase plane by a predetermined angle. The position demodulating module demodulates a positional signal for determining the position of the core of the head based on the first demodulated signal and the second demodulated signal corrected by the phase corrector.

Abstract: According to one embodiment, a position demodulation method includes demodulating a first demodulation signal and a second demodulation signal having a phase difference of 90 degrees to the first demodulation signal based on a read-out signal obtained by reading out a servo pattern recorded on a medium by the head for positioning of a head with respect to the medium; correcting the first and second demodulation signals in which, when a trace of a Lissajous figure is drawn representing the first and second demodulation signals as values on coordinate axes different from each other on a plane, a ratio of respective lengths between intersections of the trace intersecting with two axes orthogonal at an origin of the plane is kept constant; and demodulating a positional signal for determining a position of the head based on the first and second demodulation signals after being corrected at the correcting.

Abstract: According to one embodiment, a position demodulation method includes demodulating a first demodulation signal and a second demodulation signal having a phase difference of 90 degrees to the first demodulation signal based on a read-out signal obtained by reading out a servo pattern recorded on a medium by the head for positioning of a head with respect to the medium; correcting the first and second demodulation signals in which, when a trace of a Lissajous figure is drawn representing the first and second demodulation signals as values on coordinate axes different from each other on a plane, a ratio of respective lengths between intersections of the trace intersecting with two axes orthogonal at an origin of the plane is kept constant; and demodulating a positional signal for determining a position of the head based on the first and second demodulation signals after being corrected at the correcting.

Abstract: According to one embodiment, a position demodulator includes a demodulator, a phase corrector, and a position demodulating module. The demodulator demodulates a first demodulated signal and a second demodulated signal having a phase difference of 90 degrees from the first demodulated signal as a result of discrete Fourier transform operation on a read signal of a null servo pattern recorded in a servo area of a medium read out by a head. The phase corrector carries out correction to tilt respective vectors of the first demodulated signal and the second demodulated signal represented on a phase plane by a predetermined angle. The position demodulating module demodulates a positional signal for determining the position of the core of the head based on the first demodulated signal and the second demodulated signal corrected by the phase corrector.

Abstract: Track pitches of all the tracks of a disk medium provided in a storage apparatus are examined in a manufacturing examination step. First of all, a target position path which varies a target track position so that the position crosses the tracks is generated, and a head actuator is subjected to feedback control so that head detection positions track the target position path. Track pitch abnormality is determined when an error between the target position path and the head detection positions exceeds a predetermined threshold value, and the track number is recorded in a track skip table of the medium. As the target position path, a target position sine-wave path having the amplitude of the width of plural tracks is generated in synchronization with rotation of the medium. As another target position path, a target position straight-line path which passes each track interval in certain time between the outermost and the innermost of the medium is generated.

Abstract: In a storage device, a BEMF control is not performed on a motor and the motor is stopped if the motor is in a BEMF-control possible state. Once the motor has completely stopped, a start-up control is performed on the motor.

Abstract: A default gain table stores values of loop gain of a spindle motor control unit predetermined for each number of media. A loop gain setting unit detects the number of media, reads out a loop gain corresponding to the detected number of media from the default gain table and sets it in the spindle motor control unit. A loop gain measuring unit measures the loop gain of the spindle motor control unit during a test in the manufacturing process, adjusts it into an optimum loop gain, and stores it as a default lop gain in the apparatus.

Abstract: In a storage device, a BEMF control is not performed on a motor and the motor is stopped if the motor is in a BEMF-control possible state. Once the motor has completely stopped, a start-up control is performed on the motor.

Abstract: Track pitches of all the tracks of a disk medium provided in a storage apparatus are examined in a manufacturing examination step. First of all, a target position path which varies a target track position so that the position crosses the tracks is generated, and a head actuator is subjected to feedback control so that head detection positions track the target position path. Track pitch abnormality is determined when an error between the target position path and the head detection positions exceeds a predetermined threshold value, and the track number is recorded in a track skip table of the medium. As the target position path, a target position sine-wave path having the amplitude of the width of plural tracks is generated in synchronization with rotation of the medium. As another target position path, a target position straight-line path which passes each track interval in certain time between the outermost and the innermost of the medium is generated.

Abstract: A default gain table stores values of loop gain of a spindle motor control unit predetermined for each number of media. A loop gain setting unit detects the number of media, reads out a loop gain corresponding to the detected number of media from the default gain table and sets it in the spindle motor control unit. A loop gain measuring unit measures the loop gain of the spindle motor control unit during a test in the manufacturing process, adjusts it into an optimum loop gain, and stores it as a default lop gain in the apparatus.

Abstract: A switch drive motor apparatus, includes: a switch drive motor which is rotatable by making a sequential switching; and a motor speed controller configured to drive the switch drive motor while varying a speed of the switch drive motor.

Abstract: In an optical disk reproducing device, through a provision of a control circuit, movement of focus point of laser beams is set at positions ahead or back to the focus position causing to enter into an automatic focus control loop, and a retry search signal for searching the focusing position is caused to be generated by the search signal generation means, thereby, a refocusing control in case when an automatic focusing servo loop can not be maintained can be started from the positions ahead or back to the focus position causing to enter into the automatic focus control loop.

Abstract: An optical disk reproducing device, comprises a judgement circuit which, under an operating condition in which demodulated data amounting for one frame are being stored in a memory in synchronism with internally supplemented synchronous signals, and when an external first synchronous signal is detected from read-out signals, judges whether the external first synchronous signal appears in the first half or in the second half in the period of the internally supplemented synchronous signal, and when the judgement circuit judges that the external first synchronous signal appeared in the first half of the period of the internally supplemented synchronous signal, the demodulated data amounting for one frame are stored in the memory at a memory position for the immediately previous frame.

Abstract: Through a provision of a level holding circuit in a focus servo mechanism for an optical disk reproducing device, a detection signal level with regard to a focusing position error, when a detection signal corresponding to a received optical beam amount shows a maximum value under a condition when not being changed over to an automatic focus loop, is sampled as an offset amount and, is held in advance in the level holding circuit, and the thus held level is utilized for effecting an automatic focusing under a just focusing servo condition.