Abstract: A hard disk drive having a self servo write offset error correction mechanism to improve self servo write process is disclosed. In accordance with certain aspects of the present invention, there is provided a self servo write method that can measure an accurate position offset between the read-head element and write-head element incorporated in a disk drive before servo data is recorded on the disk provided in the disk drive.

Abstract: A magnetic disk for a hard disk drive comprising a distributed track identifier is described. The disk includes a first portion of a track identifier physically located at a first location on a disk sector and a second portion of the track identifier physically located at a second location on the disk sector wherein the first portion and the second portion of the track identifier are discontinuous on the sector.

Abstract: A hard disk drive having a self servo write offset error correction mechanism to improve self servo write process is disclosed. In accordance with certain aspects of the present invention, there is provided a self servo write method that can measure an accurate position offset between the read-head element and write-head element incorporated in a disk drive before servo data is recorded on the disk provided in the disk drive.

Abstract: A method for operating a disk drive having timing marks (TMs) on the disk that are chosen to reduce the probability of misidentification of a TM in the presence of read errors. The disk drive searches for TMs within a fixed TM search window which extends past the TM on the disk. A TM preferably maximizes the post-shift sliding distance for m post-shifts of the TM pattern, where m corresponds to the TM search window boundary. In this manner, the probability of a misidentification of the TM due to a post-shift having a small distance from the TM pattern is reduced. The TM pattern also provides pre-shift error resistance.

Abstract: A disk drive has timing marks (TMs) on the disk, that are chosen to reduce the probability of misidentification of a TM in the presence of read errors. The disk drive searches for TMs within a fixed TM search window which extends past the TM on the disk. A TM preferably maximizes the post-shift sliding distance for m post-shifts of the TM pattern, where m corresponds to the TM search window boundary. In this manner, the probability of a misidentification of the TM due to a post-shift having a small distance from the TM pattern is reduced. The TM pattern also provides pre-shift error resistance.

Abstract: A method and apparatus is disclosed that detects servo sectors that contain defects that need to be rewritten and writes in the servo field to correct the detected defects. The system includes a disk for storing data in data regions, the disk further comprising a plurality of servo regions formed radially between the data regions, a motor for rotating the disk, an actuator arm assembly including a head for reading and writing data on the disk and drive electronics for detecting defective servo sectors on the disk and rewriting a servo in the servo sector to correct the detected defective servo sectors.

Abstract: An adaptive technique for calibrating a disk drive based on real time measurements. The invention includes a sensor for measuring a performance characteristics of a disk drive, a control circuit for comparing the measured performance characteristics to reference characteristics, and memory for storing performance parameters. The performance parameters are updated when the measured performance characteristics differs from the reference characteristic by a predetermined value, and the processor performs drive operations in accordance with the updated performance parameters. In the specific embodiments, the performance characteristic include disk runout and seek settle performance. A calibration flag may be set in the interface processor in response to the comparison of the measured performance characteristics to reference characteristics.

Abstract: A no-ID zone-bit-recording sectored servo data recording disk drive system is described wherein track seek time is substantially reduced by storing only partial cylinder address on each servo sector of each track. According to the system and method described herein, a cylinder address is divided into high order bits, middle order bits, and low order bits. The low order bits is stored on each servo sector of each track. The high order bits is stored only on even number servo sectors and middle order bits is stored only on odd number servo sectors. During the seek operation, as the head passes over the tracks toward the desired track, the partial cylinder address stored on odd and even numbered servo sectors on each track is retrieved and stitched together to form a complete cylinder address. The completed cylinder address is then compared with the desired cylinder address to determine whether desired cylinder is reached or not.

Abstract: In a data recording disk file, a digital servo control system generates an estimate of the sinusoidal function representative of the dominant component of nonrepeatable runout (NRRO) and derives from this function a NRRO signal to add to the digital control signal to eliminate the NRRO component from the head position error signal (PES). The estimate of the sinusoidal function is made from the measured PES and from predetermined constants representative of known disk file physical parameters. In the preferred embodiment, a new estimate of the sinusoidal function, and accordingly a NRRO signal derived from the newly estimated function, is made during every PES sample time during track following. During track seeking the estimate of the NRRO sinusoidal function is not updated during PES sampling; rather the NRRO signal is derived from the last estimate of the sinusoidal function.

Abstract: A disk file digital servo control system utilizes a state estimator wherein the voice coil motor (VCM) current is modeled, rather than measured, thereby eliminating the need for analog-to-digital conversion of the actual VCM current. The VCM current is fed back directly to the input to the power amplifier where it is summed with the control signal output. This effectively changes the integrating power amplifier into a low pass filtering power amplifier, with linear input-output characteristics. Thus, during track following or short seeks, the VCM current is estimated based on this linear model. During long seeks, when the power amplifier is saturated, the VCM current is modeled based upon the known VCM characteristics during saturation, which include the effects of the back electromotive force and the coil current rise time. The microprocessor in the digital servo control system determines which VCM current model to use by a determination of when the power amplifier is in saturation.

Abstract: A digital servo control system in a data recording disk file has a single processor which generates the control signal to the actuator at two different rates, depending on whether the read/write head is being moved between data tracks or is following a specific track. A sampling clock generator receives servo timing information from a recorded servo disk surface and generates interrupt signals to the processor at predetermined frequencies selected by the time required for the processor to run the algorithm which generates the control signals. Upon receipt of a seek command to move the head of a target track, or a predetermined head position error signal indicative of arrival of the head to the target track, the microprocessor enables or disables appropriate interrupts so as to select one of the appropriate rates for generating the control signals. The digital servo control system thus allows servo position information to be sampled at a higher frequency during track following.