Abstract: Embodiments of the invention lower the servo sector's share of each track and ensure that servo sector numbers are reliably determined. According to the embodiment, in the servo sector number (SSA) section of each servo sector, servo sector number information whose bit length (k bits) is shorter than the bit length required to express the servo sector number itself is preliminarily written. The servo sector number of each servo sector is determined by using the servo sector number information in m successive servo sectors, that is, a total of m×k bits of information. Note that they satisfy the m(2m×k?1)?N relation where N denotes the total number of servo sectors per track.

Abstract: In a disk device in which heads are positioned by a servo mechanism, the object of the present invention is to prevent data from being destroyed by incorrect selection of a head and to improve reliability in recording or reproducing information and to prevent format efficiency from being decreased thereby. For this object, a SAM pattern in a servo information region is changed for each head and recorded. Then, the SAM pattern is read to determine which head makes access to a disk surface and the head is compared with a head to which a direction of making access is given thereby to make an error check. Moreover, by the use of a marker pattern of rotational synchronization compensating data added to the servo information, an error check of the head making access to the disc surface is conducted.

Abstract: Head-to-head variations in the head gap distance between write and read heads is compensated by measuring the head gap distance in each head by writing and reading a predetermined unique pattern, and compensating the timing to start the data writing by changing it in a head-to-head manner based on a time gap that corresponds to the measured head gap distance in each head. This allows data to be written at a desired physical position regardless of the variation of the head gap distance, thereby allowing formatting efficiency to be improved.

Abstract: Embodiments of the invention lower the servo sector's share of each track and ensure that servo sector numbers are reliably determined. According to the embodiment, in the servo sector number (SSA) section of each servo sector, servo sector number information whose bit length (k bits) is shorter than the bit length required to express the servo sector number itself is preliminarily written. The servo sector number of each servo sector is determined by using the servo sector number information in m successive servo sectors, that is, a total of m×k bits of information. Note that they satisfy the m(2m×k?1)?N relation where N denotes the total number of servo sectors per track.

Abstract: 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.

Abstract: Head-to-head variations in the head gap distance between write and read heads is compensated by measuring the head gap distance in each head by writing and reading a predetermined unique pattern, and compensating the timing to start the data writing by changing it in a head-to-head manner based on a time gap that corresponds to the measured head gap distance in each head. This allows data to be written at a desired physical position regardless of the variation of the head gap distance, thereby allowing formatting efficiency to be improved.

Abstract: In a disk device in which heads are positioned by a servo mechanism, the object of the present invention is to prevent data from being destroyed by incorrect selection of a head and to improve reliability in recording or reproducing information and to prevent format efficiency from being decreased thereby.

Abstract: 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.