Abstract: According to one embodiment, a magnetic disk drive comprising, a magnetic disk, a magnetic head, a voice coil motor, and a controller. The controller includes a seek control section, a velocity calculation section, a back electromotive voltage estimation section, and a coil resistance estimation section.

Abstract: According to one embodiment, a magnetic disk drive comprising, a magnetic disk, a magnetic head, a voice coil motor, and a controller. The controller includes a seek control section, a velocity calculation section, a back electromotive voltage estimation section, and a coil resistance estimation section.

Abstract: A conductor joining method includes: an initial-stage irradiation step in which an inner region of an end surface of each of first and second conductors is irradiated with laser light to form a pair of molten pools arranged side by side on the end surfaces of the first and second conductors in such a manner that an outer peripheral portion of each end surface forms a bank; a middle-stage irradiation step in which joint-side regions of the end surfaces of the first and second conductors which are close to each other are irradiated with laser light so that the molten pools are coupled to each other; and a late-stage irradiation step in which an entire end surface jointly configured by the end surfaces of the first and second conductors is irradiated with laser light in a substantially circular shape to form the molten pools into a hemispherical molten ball.

Abstract: According to one embodiment, in a disk device, a controller, when the rotation waiting time is present, increases an absolute value of a motor current in a fourth section in a second period in which a head is accelerated or decelerated, changes the absolute value of the motor current at a third average change rate in a fifth section after the fourth section in the second period, decreases the absolute value of the motor current at a fourth average change rate steeper than the third average change rate in a sixth section after the fifth section in the second period, and decreases the absolute value of the motor current at a fifth average change rate steeper than the fourth average change rate in a seventh section after the sixth section in the second period.

Abstract: According to one embodiment, in a disk device, a controller, when the rotation waiting time is present, increases an absolute value of a motor current in a fourth section in a second period in which a head is accelerated or decelerated, changes the absolute value of the motor current at a third average change rate in a fifth section after the fourth section in the second period, decreases the absolute value of the motor current at a fourth average change rate steeper than the third average change rate in a sixth section after the fifth section in the second period, and decreases the absolute value of the motor current at a fifth average change rate steeper than the fourth average change rate in a seventh section after the sixth section in the second period.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic disk, a motor, a magnetic head, and a controller. A first area, and a second area located on an inner diameter side of the first area are provided in the magnetic disk. The motor rotates the magnetic disk. The controller receives a write command. In a case where a first position that is a position designated as a write destination of data by the write command is included in the first area, the controller writes the data to the first position by the magnetic head while rotating the magnetic disk at a rotational speed of a first value. In a case where the first position is included in the second area, the controller writes the data to the first position by the magnetic head while rotating the magnetic disk at a rotational speed of a second value larger than the first value.

Abstract: According to one embodiment, a magnetic disk device comprises a JIT seek control unit, which uses second time series data of a current indication value of a VCM that sets a slope having an absolute value smaller than an absolute value of a slope of a first time series data in at least one of a monotonically decreasing interval of an acceleration interval and a monotonically decreasing interval of a deceleration interval of a head or an operation acceleration of the head.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic disk, a motor, a magnetic head, and a controller. A first area, and a second area located on an inner diameter side of the first area are provided in the magnetic disk. The motor rotates the magnetic disk. The controller receives a write command. In a case where a first position that is a position designated as a write destination of data by the write command is included in the first area, the controller writes the data to the first position by the magnetic head while rotating the magnetic disk at a rotational speed of a first value. In a case where the first position is included in the second area, the controller writes the data to the first position by the magnetic head while rotating the magnetic disk at a rotational speed of a second value larger than the first value.

Abstract: According to one embodiment, a magnetic disk device comprises a JIT seek control unit, which uses second time series data of a current indication value of a VCM that sets a slope having an absolute value smaller than an absolute value of a slope of a first time series data in at least one of a monotonically decreasing interval of an acceleration interval and a monotonically decreasing interval of a deceleration interval of a head or an operation acceleration of the head.

Abstract: According to one embodiment, a magnetic disk device which includes two or more independently drivable actuator blocks and performs seek control with a low jerk in which a jerk that is a derivative of acceleration is limited, wherein in a state where a first actuator block is not accessing a data sector of a disk, a second actuator block that is not the first actuator block accesses the data sector of the disk by seek control with a high Jerk.

Abstract: A magnetic disk device includes a plurality of magnetic heads, a storage unit that stores a table storing, for each of the magnetic heads, a track skew value obtained by adding a head shared value and a head unique value, and a control unit that reads out the track skew value corresponding to one of the magnetic heads to be operated from the table and performs seek control.

Abstract: According to one embodiment, a magnetic disk device which includes two or more independently drivable actuator blocks and performs seek control with a low jerk in which a jerk that is a derivative of acceleration is limited, wherein in a state where a first actuator block is not accessing a data sector of a disk, a second actuator block that is not the first actuator block accesses the data sector of the disk by seek control with a high Jerk.

Abstract: A magnetic disk device includes a plurality of magnetic heads, a storage unit that stores a table storing, for each of the magnetic heads, a track skew value obtained by adding a head shared value and a head unique value, and a control unit that reads out the track skew value corresponding to one of the magnetic heads to be operated from the table and performs seek control.

Abstract: According to one embodiment, a magnetic disk device includes a first disk including a first data sector, a second disk including a second data sector, a first head including a first read head, a second head including a second read head, a first controller that stops write operations of both the first head and the second head based on first data sector position error information obtained by reading and demodulating the first data sector by using the first read head, and a second controller that stops the write operations of both the first head and the second head based on second data sector position error information obtained by reading and demodulating the second data sector by using the second read head.

Abstract: According to one embodiment, a magnetic disk device includes a first disk, the second disk, and a first head which writes and reads to the first disk, a second head which writes and reads to the second disk, and a controller which calculates an estimated position at which the second head is estimated to be disposed on the second disk based on first relative position information related to a relative position in a radial direction between the first head and the second head when the first head is switched to the second head.

Abstract: According to one embodiment, a magnetic disk device includes a first disk including a first data sector, a second disk including a second data sector, a first head including a first read head, a second head including a second read head, a first controller that stops write operations of both the first head and the second head based on first data sector position error information obtained by reading and demodulating the first data sector by using the first read head, and a second controller that stops the write operations of both the first head and the second head based on second data sector position error information obtained by reading and demodulating the second data sector by using the second read head.

Abstract: According to one embodiment, a magnetic disk device includes a first disk, a second disk, a first head, a second head, a first actuator including the first head, a second actuator including the second head, a first arithmetic unit executing a first reordering process of a command stored in a first queue corresponding to the first actuator, and a second arithmetic unit executing a second reordering process of a command stored in a second queue corresponding to the second actuator, the first arithmetic unit executing the second reordering process, the second arithmetic unit executing the first reordering process.

Abstract: According to one embodiment, a magnetic disk device includes a first disk, the second disk, and a first head which writes and reads to the first disk, a second head which writes and reads to the second disk, and a controller which calculates an estimated position at which the second head is estimated to be disposed on the second disk based on first relative position information related to a relative position in a radial direction between the first head and the second head when the first head is switched to the second head.

Abstract: According to one embodiment, a magnetic disk device includes a disk including a first sector arranged at a first radial position deviated from a target position in a radial direction by a first offset amount larger than a first threshold value, a head that writes data to the disk and reads data from the disk, and a controller that reads the first sector by arranging the head at a second radial position deviated from the target position by a second offset amount different from the first offset amount.

Abstract: According to one embodiment, a magnetic disk device includes a disk including a first sector arranged at a first radial position deviated from a target position in a radial direction by a first offset amount larger than a first threshold value, a head that writes data to the disk and reads data from the disk, and a controller that reads the first sector by arranging the head at a second radial position deviated from the target position by a second offset amount different from the first offset amount.