Abstract: An index determining unit determines that a current position in a disk medium corresponds to a true index when reaching a true index pattern of servo information recorded in the disk medium. The determination is used for reading predetermined servo information so as to perform a servo control operation of a disk reading/writing head. The disk medium has the true index pattern in a first portion of the disk medium and also untrue index patterns of servo information in a predetermined number of second portions in proximity to the first portion along a track direction. The true index pattern and the untrue index patterns form a predetermined sequence.

Abstract: This invention relates to a disk drive and a method of writing data to the disk drive. In a disk drive including a write head, a read head and a positioning unit of a head which includes a write element and a read element, the present invention provides the disk drive with a position error measuring unit for measuring the amount of a position error of the write element and the read element; and a write/read control unit for obtaining an offset amount of the head in accordance with the amount of the position error of the head, setting the offset amount to the positioning unit so as to offset the head, and effecting data write/read operation. When format write operation is executed, only an ID portion is offset in the same direction as the direction of the position error so measured in accordance with the measured amount of the position error, and is written.

Abstract: A head positioning control system including a head for reading and writing data from and to a magnetic recording medium such as a magnetic disk of a magnetic disk drive, and an actuator for moving the head, effects head positioning control by driving the actuator on the basis of a position signal generated from the signal read out from the head. The control system compares a first velocity signal obtained by differentiating the position signal with a second velocity signal obtained by integrating a driving current fort driving the actuator, and so operates so as to correct the driving current of the actuator in a direction in which the difference of these velocity signals is offset. Preferably, the control system stores in advance the ratio of the velocity signals as correction data.

Abstract: A seek control system in a disk system, in which the object measured is a mechanism including a voice coil motor which positions a head, and in which the temperature of the voice coil motor is detected and seek operations are controlled based on the thus detected temperature, includes a unit for determining the amount of heat causing the temperature rise of the object under measurement as the square of a voice coil motor current command value multiplied by predetermined coefficients; a unit for integrating the result obtained by subtracting the amount of naturally radiated heat from the amount of heat including the amount of heat causing the thus determined temperature rise, to determine the amount of heat in the object; and a unit for detecting the temperature of the object in accordance with the thus determined amount of heat in the object.

Abstract: A data head offset detecting circuit in a magnetic disk unit includes a first offset detector that detects an offset .beta. based on servo information on a data surface read by the data head, a second offset detector that detects an offset .gamma. based on servo information on the servo surface read by the servo head, and an offset calculator for calculating a real offset .alpha. resulting from the subtracting of the offset .gamma. from the offset .beta.. By using the above circuit, an offset for a correction of an offtrack is detected accurately even when the heads are vibrating.