Abstract: A direct access storage device (DASD) employs head-specific off-track read capability (OTRC) in data access operations. A method of operation of the DASD involves providing within the DASD a rotating data storage medium and one or more read heads positionable for interaction with the data storage medium. The OTRC particular to each read head is determined and then applied in accessing data from the data storage medium. One manner of applying the OTRC to access data is to use the OTRC in scheduling random queued seeks. The OTRC for a head is referenced within buffer memory and applied to determine which target data can be accessed most quickly. The seeks are scheduled accordingly. A single table with a nominal seek time can be used for all heads, with a custom adder being added for each particular head. The OTRC can also be applied to alter the seek algorithm.

Abstract: A disc drive with an information portion previously written on a rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing a reference mark to the rotatable disc surface in substantial time alignment and phase and frequency coherent with the information portion previously written to the rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing the reference mark, a pulse detector circuit for creating logic level signals from the reference mark, a pattern generator for generating reference mark write signals from the logic level signals, a memory buffer for storing radial position correction tables and values for writing the reference mark, and a self-servo control and sequencing circuit synchronizing timing signals for writing the reference mark to rotatable disc surface of disc drive.

Abstract: A signal reproducing method reproduces servo information recorded on a recording medium by use of a head. A current calculation related to a current and an observer calculation related to a position and a velocity of the head are made based on reproduced servo information, and a current value for driving the head is calculated based on the above calculation result. Only computations which require a demodulation result of a present sample are made during a first time after demodulation of the position of the head to a time when the current value is output, and computations which require a demodulation result of a past sample are made during a second time other than the first time.

Abstract: The present invention offers a time efficient means to determine and eliminate dynamic track squeeze error. The present invention can be used to correct imperfections in tracks written by a conventional servowriter or using self-propagating servo writing. The dynamic track squeeze is determined within a single disc revolution. The read head is positioned half way between two servo tracks. Positioning information for track following is obtained from either track as one disc revolution is completed. During the disc revolution, position measurement is simultaneously collected from both tracks. The difference between the position measurements from each track, which represents the dynamic track squeeze between the two tracks, is determined. An appropriate ZAP correction factor is determined and written to the servo sector of the desired track. The ZAP correction factor is input to the disc drive servo controller and eliminates the dynamic track squeeze.

Abstract: A servo burst pattern for use in positioning a read/write head with respect to tracks on a magnetic disc medium includes a first set of servo bursts adjacently disposed on the tracks along a first axis perpendicular to the centerlines. Each of the first set of bursts is disposed on an individual track, from the inside track edge to the outside track edge, and alternates between a first frequency and a second frequency for consecutive servo bursts. The servo burst pattern also includes a second set of servo bursts adjacently disposed on the tracks along a second axis perpendicular to the centerlines and parallel to the first axis. Each of the second set of servo bursts is disposed on two adjacent tracks, from the centerline of one track to the centerline of a next adjacent track, and alternates between the first frequency and the second frequency for consecutive servo bursts.

Abstract: Written-in runout due to vibration of the cage of a spindle motor of a disc drive is detected by identifying an initial cage frequency value of the motor. A written-in magnitude of successive servo burst closures, D(nc), is read over a plurality of tracks, and a maximum servo burst closure D(ncp) is identified from the plurality of read servo bursts. A magnitude of the cage frequency at a servo sector n0 is calculated based on a difference between the read magnitudes of the servo burst closures at servo sectors nc and nc+1, and a phase of the cage frequency is calculated based on the magnitude of the written-in cage frequency at servo sector n0. The profile, in the form of cage frequency, maximum servo burst closure magnitude, and initial phase, is stored in a memory or table for each of a plurality of radial zones of tracks. The profile is combined with a position error signal and applied to the controller in a feed forward scheme to adjust the position of the head based on the written-in runout.

Abstract: Marks with curved edges are used in data patterns and sensed with proximity recording. Circular, elliptical, and oval marks are examples of marks with curved edges that can be used in the present invention. The marks with curved edges are used to define data patterns (e.g. position error signal patterns) as a function of radius. If the marks with curved edges have been recorded longitudinally, an amplitude of a read back signal, such as a peak amplitude, is determined in order to generate a position error signal. If the marks with curved edges have been recorded vertically, an area under the curve of the read back signal is determined in order to generate a position error signal.

Abstract: A recording disk contains at least two types of servo sector format, including a first type having a relatively larger track identifying field containing the track number, and a second type having an abbreviated track identifying field identifying a track within a range of tracks, the range being less than the full range of tracks on the disk surface. Preferably, Gray code encodings are used, the first type of track field contains sufficient Gray code bits to identify the ful track number, every Nth servo sector is of the first type, and all servo sectors in between are of the second type, N being at least 2. As a result, the disk area required for track identification is reduced, and the additional disk space available can be used to expand the PES field.

Abstract: Apparatus and method for reducing nonlinearities in a position error signal (PES) of a disc drive data handling system. The disc drive data handling system includes a disc recording surface having a number of tracks and a controllably positionable read/write head. A servo circuit generates a sequence of PES samples indicative of head position with respect to a selected track using servo position data samples transduced from the selected track and a first set of compensation values selected to reduce nonlinearities in said PES samples. The PES samples are combined with the first set of compensation values to generate an updated set of compensation values. This process is preferably repeated a number of iterations to converge to a final set of compensation values which provide a substantially linear PES across the radial width of each track.

Abstract: Methods in accordance with the present invention can be applied to reduce frictional effects in a bearing of a rotary actuator on the motion dynamics of the rotary actuator. In one such method a disk having a first magnetic servo pattern on a surface written, for example, by a media writer, is rotated at a first frequency. The first magnetic servo pattern is read using a head. A second magnetic servo pattern based on the first magnetic servo pattern can be written to the surface by the head such that the second magnetic servo pattern is defined by the oscillation of the head at a second frequency. This description is not intended to be a complete description of, or limit the scope of, the invention. Other features, aspects, and objects of the invention can be obtained from a review of the specification, the figures, and the claims.

Abstract: A method of interleaving servo information fields on a recording medium, and a corresponding recording medium having interleaved servo information fields, that reduce the amount of disk surface area needed for servo information, to thus increase disk surface area available for data storage. The track layout includes regular sector servo fields and reduced sector servo fields interleaved with data fields. The regular sector servo fields include servo correction information such as repetitive run-out (RRO) cancellation values. The servo correction information of the reduced sector servo field does not include servo correction information. The servo correction information of the reduced sector servo field is merged into the regular sector servo field.

Abstract: To improve the track density by reducing the discontinuity of servo patterns to be generated by a servo track writer, some servo areas existing in one circuit of a magnetic disk are formed at the consecutive first and second circuits of a servo track writer by averaging a plurality of position signals detected from servo patterns at the first and second circuits of the magnetic disk.

Abstract: A disk drive system has a servo pattern with bursts that are recorded without multiple passes per burst and without trimming, so that the servo pattern bursts have the same width as the data tracks. The servo write steps occur in partial data track pitch (DTP) increments. A magneto-resistive (M-R) head is used to both record the servo pattern and transduce it. In a two-frequency system, relative gain calibration is performed using AGC circuitry to first calibrate one frequency and then the other. The resulting servo position error sensing (PES) signal has improved linearity and is simpler to write.

Abstract: A disk drive having a marker for identifying the transition between the first and last written servo wedges on a servo track. The marker indicates the likely position where closure error may occur during the operation of the hard disk drive. The marker is used by the control system of a hard disk drive to provide appropriate position control signals to the transducer assembly to maintain the proper positioning of the transducer about the disk surface. A method for forming the marker on a disk surface is further disclosed.

Abstract: A servo method and system for generating a position error signal in a disk drive including a magnetic data storage disk rotating relative to a base, a data transducer assembly positioned at concentric data tracks by a rotary actuator referenced to the base and controlled by a digital servo system, the data transducer assembly having a magnetoresistive (MR) read element, the digital servo system employing multiple servo bursts in servo sectors embedded within the data tracks. During servo track positioning/following for each target head position relative to a track, a plurality of the servo bursts are selected, and combinations of the burst amplitudes of the selected servo bursts are obtained. A substantially continuous position error signal (C_PES) is generated based on the combinations of the burst amplitudes, indicating radial position of the read head relative to the target position.

Abstract: Systems are provided for improving servo-demodulation robustness. Multiple occurrences of a SAM pattern are searched for in a single servo wedge. Each detection of the SAM pattern in the servo wedge is charactered as a good SAM detection or a bad SAM detection. If more than one detection of the SAM pattern in the servo wedge are characterized as good SAM detections, one of the detections is selected as the best good SAM detection. Further servo functions can then be performed based on the best good SAM detection.

Abstract: In order to increase the performance and reliability of devices including rotatable storage media, individual characteristics of device elements or heads can be determined and used to set performance criteria. The off-track capability and track mis-registration of an element or head can be determined and used to set individualized thresholds for elements or heads of devices including rotatable storage media.

Abstract: Methods are provided for improving servo-demodulation robustness. Multiple occurrences of a SAM pattern are searched for in a single servo wedge. Each detection of the SAM pattern in the servo wedge is charactered as a good SAM detection or a bad SAM detection. If more than one detection of the SAM pattern in the servo wedge are characterized as good SAM detections, one of the detections is selected as the best good SAM detection. Further servo functions can then be performed based on the best good SAM detection.

Abstract: Systems are provided for improving servo-demodulation robustness. SAM pattern detections are characterized as either good SAM detections or bad SAM detections. Further servo functions are then based on whether the detection of the SAM pattern in a servo wedge was characterized as a good SAM detection or characterized as a bad SAM detection.

Abstract: In order to increase the performance and reliability of devices including rotatable storage media, individual characteristics of device elements or heads can be determined and used to set performance criteria. The off-track capability and track mis-registration of an element or head can be determined and used to set individualized end-of-seek criteria for elements or heads of devices including rotable storage media.

Abstract: In order to increase the performance and reliability of devices including rotatable storage media, individual characteristics of device elements or heads can be determined and used to set performance criteria. The off-track capability and track mis-registration of an element or head can be determined and used to set individualized thresholds for elements or heads of devices including rotatable storage media.

Abstract: In order to increase the performance and reliability of devices including rotatable storage media, individual characteristics of device elements or heads can be determined and used to set performance criteria. The off-track capability and track mis-registration of an element or head can be determined and used to set individualized end-of-seek criteria for elements or heads of devices including rotatable storage media.

Abstract: A magnetic disk apparatus includes a magnetic disk with normal and double servo sectors arranged alternately. If a servo interruption period corresponding to adjacent first servo sectors is a first servo interruption period, then a second servo interruption period that is a servo interruption period corresponding to adjacent first servo sector and second servo sector is equal to or less than half of the first servo interruption period.

Abstract: Methods are provided for improving servo-demodulation robustness. A SAM pattern is searched for in a servo wedge. If the SAM pattern is detected in the first servo wedge, a determination is made whether to characterize the detection of the SAM pattern as either a good SAM detection or a bad SAM detection. If the detection of the SAM pattern is characterized as a good SAM detection, at least one channel control value (e.g., servo AGC and/or PLL values) associated with the first servo wedge is used as a starting channel control value (or to predict a starting channel control value) when beginning to read a next servo wedge. However, if the SAM pattern is not detected, or a SAM detection is characterized as bad, at least one previously stored channel control value is used as a starting channel control value (or to predict a starting channel control value) when beginning to read the next servo wedge.

Abstract: Systems are provided for improving servo-demodulation robustness. The SAM pattern is searched for in a servo wedge. If the SAM pattern is detected in the first servo wedge, a determination is made whether to characterize the detection of the SAM pattern as either a good SAM detection or a bad SAM detection. If the detection of the SAM pattern is characterized as a good SAM detection, one or more channel control values (e.g., servo AGC and/or PLL values) associated with the first servo wedge are used as (or to predict) starting values when beginning to read a next servo wedge. However, if the SAM pattern is not detected, or a detection is characterized as bad, one or more previously stored or predicted channel control values are used as (or to predict) starting values when beginning to read the next servo wedge.

Abstract: Radial correction factors are calculated for each ruler on a patterned media in a data storage system. A ruler is a position-sensing pattern that defines the radial position of a recording head. Rulers are patterned onto each disk before the disks are assembled into a storage system. The radial correction factors are then added to the measured position information during read and/or write operations of the data storage system. The radial correction factors correct for any radial misalignment created by disturbances in the data storage system. Circumferential correction factors are calculated for each patterned media in the data storage system. A corrected sector number is then determined by redefining the original sector numbers using the circumferential correction factors.

Abstract: A spindle motor control for a disk drive including a spindle motor for rotating a data disk at a desired rotational speed, and a data transducer head positionable relative to selected ones of a multiplicity of concentric data tracks formed on a data storage surface of the data disk by a head position actuator structure operating within a head position servo loop, wherein the concentric data tracks are periodically interrupted by a plurality of servo sectors per rotation, each servo sector recorded with head position information.

Abstract: The invention relates to control systems for data storage media. More particularly, the invention relates to a system, method and apparatus for forming various frequency modulation patterns on storage media for providing position error signals. The invention also relates to forming various frequency modulation patterns on storage media for providing position error signals having a continuously varying frequency that is proportional to the position of a read/write transducer head within a track defined on a storage medium. The invention also relates to providing a demodulated signal that is proportional to a continuously varying position error signal frequency and thus to the position of the read/write head within a track defined on a storage medium.

Abstract: Many parallel tracks on a storage surface of a data handling device are arranged in a longitudinal direction. Each track has a track center comprising reference points for fine lateral positioning. Each successive pair of track centers has a succession of lateral offset distance having an average. Because there are many successive pairs of tracks, there are many average lateral offset distances defining a statistical distribution having a variance. The device includes a laterally movable transducer head and a longitudinally movable data surface. A signal is received from the transducer head while the data surface moves past the head. Many values each indicative of a lateral offset distance between a corresponding pair of lateral reference points are derived from the received signal. These offset-indicative values are used to shift at least some of the latitudinal reference points laterally so as to reduce this variance.

Abstract: A patterned media having recordable and non-recordable regions is initialized by first erasing (e.g. DC magnetizing) at least a portion of the recordable regions. At least one offset may then be determined. The at least one offset may compensate for a read to write delay in the electronics and/or at least one delay caused by the space separation between a read and a write head. A plurality of position error signal (PES) bursts may then be written on at least a portion of the recordable regions. During the write process, the previously written PES bursts are read and used to determine PES signals (e.g. servo signals) in order to guide the write head while writing new PES bursts. Magnetically written gray code may then be written on the media. The magnetically written gray code may be used to define a track number for the data tracks with no eccentricity.

Abstract: A head position control system for a dual stage actuation disk drive system. A feedback system is provided for modifying a primary and a secondary input command signal to produce primary and secondary error signals. A controller receives the primary error signal and transmits primary actuator arm positioning information to the primary actuator. A secondary controller receives the secondary error signal and transmits secondary actuator arm positioning information to the secondary actuator. The feedback system creates a position error signal (PES) using information from servo wedges and runout information and the PES is used to produce the secondary error signal. The feedback system produces a reconstructed error signal including angular position information for the primary actuator arm by processing a back electromotive force signal from the primary actuator. The primary error signal is produced by modifying the primary input signal with the reconstructed error signal.

Abstract: Position error values are obtained from a transducer head while following a plurality of servo tracks with a servo loop that band-blocks a frequency range that includes F, a nominal rotation frequency. An estimated difference distribution is derived from the position error values, the difference distribution having a first frequency component at a positive frequency ≦2*F. A scalar track squeeze magnitude indicator is derived from the estimated difference distribution so that the indicator to be transmitted depends on the frequency component.

Abstract: The invention relates to a method for recovering from shock event to a disk drive. Embedded servo wedges are read to generate position error signal (PES) values. The disk drive is transitioned to a write unsafe state if a PES value is greater than a write unsafe (WUS) threshold and is less than a shock detection threshold. The disk drive is transitioned to a shock recovery state if a PES value is greater than the shock detection threshold. The disk drive is transitioned from the shock recovery state to the write unsafe state if a first number of consecutively generated PES values remain less than the WUS threshold. The disk drive is transitioned from the write unsafe state to the on-track state if a second number of consecutively generated PES values remain less than the arrival threshold, which threshold is less than the WUS threshold.

Abstract: A method for writing timing marks on a rotatable storage medium, such as on a disk in a disk drive, includes the steps of: 1) during a rotation of the disk, detecting the passage of at least a portion of a first timing mark located at a first radius of the disk, and 2) writing a second timing mark at a second radius of the disk, the location of the second timing mark being based at least in part on a stored calculation of a delay from the time of passage of the first timing mark during a rotation of the rotatable storage medium. The location of the second timing mark is calculated based on alternative time intervals between detected timing marks and on various functions of the time intervals.

Abstract: A multi-actuator disk storage device has at least two actuators respectively mounting plural product heads. Servo writing is performed using the product heads themselves. A first servo write operation is performed that includes operating a product head of the first actuator as a first clock head to generate first clock reference information for the product heads of the second actuator, which are operated as servo write heads to perform servo writing of disk areas associated with the second actuator using the first clock reference information. To servo write disk areas associated with the first actuator, a second servo write operation is performed. This operation includes operating a product head of the second actuator as a second clock head to generate second clock reference information for the product heads of the first actuator, which are operated as a servo write heads to perform servo writing using the second clock reference information.

Abstract: An apparatus and method for writing a product information code (PIC) to a head-disc assembly (HDA) of a disc drive data handling system to facilitate subsequent identification of the HDA. The PIC is configured as a sequence of n multi-bit encoded words. Servo data are written to a disc of the HDA as a number of p angularly spaced apart servo data fields, the servo data used by a servo control circuit to effect head positional control. The n encoded words are distributed across a subset n of the p servo data fields so that the n encoded words replace at least a portion of the servo data in the n servo data fields. Preferably, the n encoded words are written to Gray code (track address) fields of the n servo data fields and are provided with error detection and correction capabilities.

Abstract: The present invention relates to a head positioning method and device for positioning a head to read information from disk media at prescribed positions using a rotary actuator, in which eccentricity errors of the rotary actuator are corrected. In a disk device having disk media, a head, a rotary actuator, and a control circuit, memory is provided to store eccentricity correction information for each region of a disk divided in the radial direction. Eccentricity correction information corresponding to the head position is read, and eccentricity correction signals are created. Optimal eccentricity correction corresponding to the position of the head on the disk is made possible, and rapid seeking is enabled.

Abstract: A plurality of patterns are formed beforehand so that each of those patterns is deviated slightly from another in each sector in the track width direction, then the pattern is followed up, thereby obtaining both full-track profile and micro-track profile. A variation of a position signal is detected from this profile, thereby creating a table for correcting the non-linearity error of the position signal. Consequently, the distribution of the write/read-back property is measured, thereby enabling the track density to be improved. Furthermore, a variation of the position signal caused by a property variation of the head read-back element is detected and corrected, thereby enabling a high reliability and a high track density to be realized for the object magnetic recording disk apparatus.

Abstract: Provided is a data storage device in which read and write heads can be desirably located with respect to servo tracks from the viewpoint of linearity of a PES on the premise that a read write offset exists. A read write offset value, which is a deviation amount between write and read heads in a radial direction of a disk-shaped storage medium, is set equivalent to an integer number N of servo tracks.

Abstract: The present invention may be embodied in a method, implemented in a disk drive, for adaptively reducing an effect of vibration during a track following operation. The disk drive includes a disk and a rotary actuator. The disk includes distributed position information in a plurality of servo wedges. The actuator carries a transducer and pivots on a base of the disk drive. The actuator may exhibit an imbalance that may be affected by a linear vibration. In the method, a sensor signal is generated that is responsive to a vibration to the disk drive. The sensor value is modified based on an adaptive-filter gain to generate a position error adjustment signal for modifying a nominal position error signal. The adaptive-filter gain is then altered based on an adjusted position error signal and the sensor value associated with the current servo wedge for use during a next servo wedge.

Abstract: A method, apparatus, and computer program product for linearizing a position error signal of a transducer in a hard disk drive. In one embodiment, a disk including a first plurality of tracks each includes first and second servo bursts defining a track reference line, and a second plurality of the first plurality of tracks on the disk each includes third and fourth servo bursts defining a second plurality of different position offsets from the track reference line of the second plurality of tracks. Each of the second plurality of different position offsets being at a different value than any other position offset. The second plurality is no greater than the first plurality. The second plurality of different position offsets are used for linearizing a position error signal.

Abstract: A method and apparatus are provided for enhanced performance in the presence of stationary position error signal (PES) outliers in a direct access storage device (DASD). A plurality of PES samples are obtained from a plurality of servo sectors around a track. Utilizing the PES samples, a normalized outlier value is computed for each of the plurality of servo sectors around the track. The computed normalized outlier values are sequentially stored and compared with a set threshold value. A stationary PES outlier is identified responsive to each stored outlier value being greater than the set threshold value. Each identified stationary PES outlier is utilized during predefined operations of the DASD. During a recalibration mode of the DASD, a different track for feedforward generation is selected to avoid an identified stationary PES outlier.

Abstract: The present invention may be embodied in a method and a disk drive for improving head position accuracy during track following through real-time identification of external vibration. A selected track is followed using a servo control loop having a nominal gain and being responsive to position error signal samples generated based on a difference between head position samples and a reference head position value. A spectral power value within a predetermined frequency band is determined from a sequence of the position error signal samples. If a property of the spectral power value exceeds a threshold, the gain of the servo control loop is increased within the predetermined frequency band to attenuate the effect of external vibration on the position of the head over the selected track during track following.

Abstract: A method and apparatus for generating a position information signal for the head of a hard disk drive. The disk has a track which contains a plurality of servo bursts that allow the head to be centered with the centerline of the track. The servo bursts are first sensed and an upper and a lower threshold values, based on the values of servo bursts, are generated. A position error signal based on the upper and lower threshold and the values of the servo bursts are generated and stored in a memory device.

Abstract: The present invention may be regarded as a disk drive comprising a disk having a plurality of data tracks and at least one reserved track. At least one of the data tracks for recording user data along a circumferential path offset from the centerline of the data track, and the at least one reserved track for recording data track micro-jog values along a circumferential path substantially aligned with the centerline of the reserved track.

Abstract: A method and apparatus are provided for improved position error signal (PES) demodulation in the presence of thermal baseline wander. A plurality of samples is obtained within each period of a burst signal for each servo burst in a servo sequence. A difference value is identified between a largest sample value and a smallest sample value of the plurality of samples within each period of the burst signal. The difference values for each period of the burst signal for each servo burst in the servo sequence are summed to produce a burst sum value for each servo burst. Then the burst sum values are used to identify a position error signal (PES) value. The identified PES value is independent of any transient baseline voltage offset disturbances, for example, resulting from the occurrence of baseline wander offset, such as caused by a thermal asperity (TA), in the servo sectors.

Abstract: A method of writing servo tracks on the disk surfaces of a hard disk drive. The method involves simultaneously writing partial servo tracks, called servo wedges, until a complete first set of servo wedges is written on all the disk surfaces. Then the disks are rotated until the heads of the disk drive are correctly positioned to simultaneously write subsequent servo wedge sets. This process is repeated until enough servo wedge sets are written to complete a first servo track on all the disk surfaces. Then, the heads are pivoted to a new radial position to begin writing a new servo track just as before. Simultaneously writing servo wedges advantageously expedites the often costly servo writing process.

Abstract: Off-track time shift estimates are determined and used in order to write subsequent trigger patterns on a storage medium at different track pitches. Various procedures for determining an off-track time shift estimate are provided. These procedures include measuring time intervals between a related set of trigger patterns and another trigger written on the storage medium; measuring time intervals between a motor index and a particular trigger pattern at two different radial locations; measuring the difference in the center location of two trigger patterns written at different radial locations; and microjogging a recording transducer during the interval between two different trigger patterns.

Abstract: A system and method for improved self-servo-writing of multi-slot timing patterns is described. Individual timing marks are replaced with groups of timing mark slots. At each timing mark location, a time measurement is made by detecting a timing mark in one of the slots. Also, extensions to the existing timing marks are written in other slots. The combination of timing measurements at every timing mark and extensions to those timing marks written at every opportunity improves the overall precision of the timing propagation. The improved accuracy of timing mark placement produces a commensurate improvement in the placement of the concomitantly written servo-data. In addition, the alignment accuracy of the written pattern is less sensitive to variations in rotation speed and variations in the shape of written transitions. Moreover, only a single disk revolution is required at each servo radius to write servo data and propagate the timing marks to maintain timing alignment.

Abstract: A disk drive system is disclosed that includes a disk device coupled to control circuitry. The control circuitry includes a read channel with a detector that detects servo mark sub-patterns and correlates the detected servo mark sub-patterns to detect a servo mark. The detector includes matched filters to detect the sub-patterns.