Hitachi Global Storage Technologies Netherlands B.v.

International Business Machines Corporation

Mantle M Yu

Mario Blaum

Bernd Lamberts

Kenneth G Yamamoto

Bruce Alexander Wilson

Shih-Ming Shih

Michael Anthony Moser

Craig N Fukushima

Michael L Workman

Bryan Rowan

Stephen F Edel

Kishan Kumar Kumbla

Richard J Spanel

Techniques are provided for identifying the servo sectors in a track on a data storage device. A data storage device identifies the servo sectors in a track by reading distributed index bits from multiple servo sectors in a track. The data storage device analyzes only one index bit from each servo sector to identify the index of a track. In some embodiments, the index of a track can be identified after examining the index bits stored in a particular number of consecutive servo sectors, even in the presence of errors. The index bits in each track can have an error tolerance with a minimum Hamming distance greater than one. In other embodiments, a data storage device compares a sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within a pattern of the index bits stored on a track.

Techniques for identifying servo sectors in storage devices

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.

Read write offset error correction using geometric reference in self servo write process

Embodiments of the present invention provide a magnetic disk drive system in which the write element leads the read element in the tangential direction of rotation of the magnetic disk. In addition, the servo sector information is preferably arranged such that information that is not needed for write operation is placed at the end of the servo sector. In this way, the servo read operation can be terminated sooner and the write operation can initiate sooner after going over the servo sector. The write element in a write operation writes data to the data sector of a track until an end of the data sector before reaching a front end of a servo sector following the end of the data sector. The read element reads information in the servo sector needed for the write operation. The write element starts writing data in a next data sector following the servo sector after the write element reaches the next data sector and after the read element has read all information in the servo sector needed for the write operation.

Write element before read element with early servo termination on write

During normal operation of a hard disk drive, control logic controls a plurality of switching elements to provide electrical power to a spindle motor and head motor of the disk drive from a voltage source coupled to first and second voltage supply nodes (e.g., Vcc and ground), the spindle motor has a set of motor windings to which the electric power is applied to rotate the spindle motor, and the control logic is configured to enter a regenerative braking state during normal operation where the switching elements are controlled to isolate the spindle motor from the first voltage supply node and cause regenerative braking of the spindle motor so that kinetic energy due to rotation of the spindle motor is converted to electrical power that is supplied to the head motor by virtue of inductance of one or more motor windings in the set.

Motor drive circuitry with regenerative braking for disk drive

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.

Method for operating disk drive having improved timing marks

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.

Disk drive having improved timing marks

In a disk drive system, a servo controller is operative to perform a process of inhibiting write operations for writing data to tracks of a disk during a head settling period following a track seek operation. During each of a first plurality of sampling intervals transpiring during a first time period, the servo controller determines a present position value indicative of the position of the head during the present sampling interval, and also determines a predicted position value indicative of the position of the head during a subsequent sampling interval. Also during each of the first plurality of sampling intervals, the servo controller determines: whether the present position value is within a first error margin from the center of a target track; and whether the predicted position value is within the first error margin. If the present position value and the predicted position value are both within the first error margin, the servo controller enables write operations. During each of a second plurality of the sampling intervals transpiring during a second time period, the servo controller determines a predicted position value indicative of the position of the head during a subsequent sampling interval. Also during each of the second plurality of sampling intervals, the servo controller determines whether the predicted position value is within a second error margin from the center of the target track. If the predicted position value is not within the second error margin, the servo controller inhibits write operations.

Early write enable with off-track write protection

A data recording disk file with a voice coil motor (VCM) actuator and a digital servo control system for positioning the read/write heads to selected concentric data tracks includes means for calculating the factor relating acceleration of the heads to VCM input current. This permits each disk file to compensate for any variation in the nominal VCM physical parameters, thus enabling VCMs to be manufactured to less demanding tolerances. The disk file also calculates a unique acceleration factor for each head position during movement of the heads from one track to another, thereby improving the arrival time of the heads to the target track. During an initialization procedure, the disk file performs a track seek, during which VCM current and head velocity information are acquired and used by the microprocessor in the digital servo control system to calculate a value representing an average actual acceleration factor unique to that disk file. This value, together with predetermined constants representing the characteristic relationship of acceleration factor to head position in a disk file with a nominal VCM, are used by the microprocessor to calculate the actual acceleration factor for each head position during a track seek.

Disk file digital servo control system with compensation for variation

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.

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San Jose, CA, United States of America

Mantle M Yu