Abstract: A disk storage apparatus including a position detection section for producing position error information corresponding to the current position of a head from servo information which has been previously recorded on a disk and is detected by the head, a position control section for producing position control information corresponding to the position error information, a voltage detection section for detecting a voltage generated in driving an actuator for positioning the head with respect to the disk, and for outputting a voltage signal, a disturbance estimation section for estimating the magnitude of a disturbance exerted on the head from the voltage signal by the voltage detection section and from a drive signal by a drive section of the actuator, and producing disturbance estimation information, a correction section for correcting the position control information by the position control section with the disturbance estimation information and producing the drive signal, and a disturbance monitor section for m

Abstract: The present invention solves a problem that useless or wasted space exists on a data recording disk between read/write heads of narrower head width than others in the case that an uniform track pitch is used, and a head width of each head varies due to a fabrication tolerance. A data recording disk of the present invention comprises a first data recording surface and a second data recording surface, and a track pitch of adjacent data recording tracks of the first data recording surface differs from a track pitch of adjacent data recording tracks of the second data recording surface. All data recording tracks of the first data recording surface have substantially the same track width, and all gaps of the first data recording surface have substantially the same gap width, and, all data recording tracks of the second data recording surface have substantially the same track width, and all gaps of the second data recording surface have substantially the same gap width.

Abstract: A magnetic disk apparatus has: a head (2) that performs data recording and playback while moving relative to a magnetic disk (26) rotating at the prescribed speed; an actuator (3) that positions said head relative to said magnetic disk (26); and a controller (4) that detects the position of said head by means of servo sector that have positioning information recorded magnetically on said magnetic disk (1) and performs control to position said actuator (3) by means of this detection signal, wherein said magnetic disk (1) has at least a part in which the arrangement of tracks is spiral. The magnetic patterns on the disk include a servo sector and a data sector both formed on the same spiral track. The servo sector includes burst patterns for servo control.

Abstract: The storage device comprises a magnetic disk having a servo region with a two lines of servo pattern for each track, a servo demodulator for detecting a position of a head on the disk according to the servo patterns as a detected position signal, a comparing section for outputting a difference between a target position signal and the detected position signal as a positional error signal, an amplifying section for amplifying the positional error signal with a gain G1 lower than a gain G0 at the time of data reading, and a controlling section for outputting a VCM operation rate signal according to an operation rate for a VCM for moving the magnetic head to the VCM according to the amplified positional error signal.

Abstract: There is disclosed an error correction and detection method and apparatus for retreiving predetermined data, e.g. servo data, from the position error signal (PES) fields of a disk in a data storage system . In the preferred embodiment the PES data such as the track number is mapped into codewords of an error correction code (ECC) which are then further divided into a set of symbols which are mapped onto a second set of bit vectors which have a constant weight. The preferred encoding method is selected to equalize the analog signal characteristics of the PES fields so that minimal, if any, change in the conventional servo detection circuitry needed to use the PES fields of the invention both as analog and digital information.

Abstract: A robust and efficient method for determining the location of a transducer head in a mass storage system. A position-indicative signal characterized by a fundamental frequency F is received from a data path including the transducer head. Energy in the signal at frequencies smaller than F/10 is substantially attenuated by a special filter, which may be an analog or digital differentiator. A sequence of bits indicative of the transducer head position indicator is then extracted from the digitized, filtered signal.

Abstract: During self-servowriting, burst information is written within slots defined on tracks of a recording medium. In writing the burst information, write to read interference, caused by large offsets in separate read and write elements of a recording transducer, is to be avoided. In order to avoid the write to read interference, the slots are carefully chosen. The choice of a particular slot can be independent of any predefined order, such as a successive order. Further, the order in which slots are chosen may be altered during the propagation process.

Abstract: A disk drive seek control system device to reduce track pitch. When data is recorded, an offset value is added to the position of a read head element along the width of a track corresponding to an offset &Dgr;w between the read head element and a write head element. The value of the offset depends on the yaw angle &thgr; of the head. When data is read, the position of the read head element is chosen to be either the position of the write head element during write operations, or the midpoint between the position of the write head element and the read head element during write operations, or the center of a track.

Abstract: Write and read processes for a disk drive handle data and overhead fields in a data frame that extends between two servo sectors on a disk. A write process fills a buffer with both data values and overhead values sufficient to fill a data frame and then writes the entire data frame based on the values in the buffer. Accordingly, activation of a separate formatting circuit is not required as those fields are written, and the write operation does not require sector pulses to control the timing for writing individual data sectors in the data frame. The overhead fields written include VFO fields and data synchronization fields. The read process uses timing signals derived from detection of servo sectors and data synchronization fields but otherwise sequentially reads data and overhead fields and transfers those fields to a buffer. The data in a requested sector can be separated from overhead information and data of other sectors in the buffer, when the disk drive outputs the requested data.

Abstract: A disk drive includes a disk having a disk surface, the disk surface having a plurality of tracks arranged in an embedded servo format. The disk surface includes a plurality of radially-extending user-data regions and a plurality of radially-extending servo-data regions. Each user-data region has a plurality of data zones in each of which user data are stored in a plurality of track segments at a data channel frequency particular to that data zone. Each servo-data region has a plurality of servo zones in each of which servo data are stored in a plurality of track segments at a servo channel frequency particular to that servo zone, wherein in at least one of the tracks having servo data and user data, the servo channel frequency differs from the data channel frequency.

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: In a servo information detection method and disk apparatus of the present invention, it is determined whether a pattern of detection bits, detected from a vicinity of a servo sync mark of a disk, matches with a given comparison bit pattern. A pattern of tolerance bits is changed based on a location of the disk where the servo sync mark is detected, so that the matching between the detection bit pattern and the comparison bit pattern is performed based on the changed tolerance bit pattern.

Abstract: A disk device comprises a disk having predetermined information sectors recorded at a constant interval; a head scanning the disk; and a disturbance-compensation unit obtaining an amount of a disturbance based on a time-interval measurement in reading the predetermined information sectors so as to compensate a position of the head according to the amount of the disturbance.

Abstract: A disk which incorporates a variable-phase servo burst pattern is disclosed. The disk has servo information thereon. The servo information includes a first servo burst pattern written on a first track and a second servo burst pattern written on a second track. Both the first servo burst pattern and the second servo burst pattern have a plurality of transition pulses. The corresponding transition pulses of the first servo burst pattern and the second servo burst pattern are 180 degrees out of phase from one another. Furthermore, a method of writing servo-information which is used to position a magneto-resistive head on a centerline of a track is also disclosed.

Abstract: A method, apparatus, and an article of manufacture for calibrating a position error signal for controlling the position of a read transducer with respect to a storage media having positioning information written at a location thereon. In one embodiment, the invention is embodied in a method comprising determining a relationship between a read transducer position and the positioning information by measuring the positioning information while passing the read transducer across the location, determining a measured position error signal from the measured positioning information, and computing a relationship between the measured position error signal and the read transducer position.

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 radial trajectory at a first radius of the disk, and 2) during the same rotation of the disk, writing a second timing mark at a second radius of the disk. The second timing mark is located at least one of a) where at least a portion of the second timing mark overlaps at least a portion of the radial trajectory of the first timing mark, and b) where the second timing mark is in close proximity to the radial trajectory of the first timing mark. The second timing mark is written based on different parameters such as a measured time interval, a calculated time interval, and a predetermined delay.

Abstract: A phase modulated servo method and apparatus are provided for use in a disk file. The disk file includes at least one disk mounted for rotation about an axis and the disk has at least one disk surface for storing data. At a predefined location of the disk surface a series of servo tracks of a predetermined high gain servo pattern are written. The predetermined high gain servo pattern includes 360° phase difference information within each data cylinder. The servo tracks are detected for identifying servo phase information.

Abstract: An asynchronous demodulator and method is provided which determines a position error of a read head relative to a position on a medium in a storage device. The read head generates a-read signal as the read head passes over a servo area on the medium. The demodulator generates a normal demodulating signal that is asynchronous with the read signal and a quadrature demodulating signal that is ninety degrees out of phase with the normal demodulating signal. The read signal is multiplied by the normal demodulating signal and the quadrature demodulating signal to produce a normal position signal and a quadrature position signal. The demodulator produces a position error magnitude and a position error direction based on the normal position signal and the quadrature position signal.

Abstract: A magnetic recording medium and a data reproducing apparatus are provided in which, with the use of a required number of bits, the address information may be reliably reproduced even during the track-traversing seek operation without increasing redundancy to the track specifying address information. On a magnetic disk, there are recorded track addresses in which, with the bits magnetized in the running direction of the magnetic head being 1 and with the bit magnetized in the opposite direction being 0, the direction of magnetization represents a Grey code, and data “1” in the air gap of the track address. A servo detection circuit has a viterbi decoder for viterbi decoding the reproduced signals of the track addresses and the playback signal for the air gap for reproducing the track addresses.

Abstract: A magnetic disk medium patterned linear magnetic channels in a radial direction of the disk is employed in a magnetic disk drive unit. The magnetic channels are patterned by high-resolution patterning techniques and are separated by channel boundaries to reduce magnetic coupling between the magnetic channel. The lithographically determined magnetic channel widths are matched with the head width to optimize the storage capability of the disk drive unit. The magnetic medium is further patterned into spatially modulated sections that provide for an inherent servo-signal that reduces or eliminates the need for pre-recorded servo data.

Abstract: A method of storing data on a surface of a storage disk, the data being capable of verifying an identity of the surface, includes determining first check data from first alignment correction data associated with a first storage surface. The method also includes determining second check data from second alignment correction data associated with a second storage surface such that the second check data is different from the first check data if the first and second alignment correction data are identical. The method further includes writing the first and second check data to the first and second storage surfaces in association with the first and second alignment correction data, respectively.

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: A storage device with a disk-shaped recording medium having servo areas in which servo sectors are recorded and data areas in which data sectors are recorded; a read/write head to read and write the data sectors, and to read the servo sectors on the disk-shaped recording medium; a head actuator to control the position of the read/write head; a storage controller to control data sector read and write operations by the read/write head; a servo controller to determine a position of the read/write head from the servo sector output read by the read/write head; a servo assist unit, separate from the storage controller, to calculate servo data for controlling the head actuator based on position information extracted by the servo controller and read/write head; and an interrupt generator to generate interrupt requests to the storage controller as determined by results of calculations by the servo assist unit.

Abstract: A method of writing servo information for hard disc drives, and disc drives built according to the method are disclosed. The method includes writing position reference information on a reference disc surface prior to mounting a disc assembly into a hard disc drive. Once the disc assembly is mounted in the disc drive, servo information is written onto the disc surfaces based upon the pre-written position reference information. Subsequently, the position reference information can be erased or written over by user data.

Abstract: A hard disk drive has a pattern detector for providing fault-tolerant detection of a data sync mark represented by a substring of a concatenated string of error-prone read symbols and for providing a reduced risk that a nonmark substring of the concatenated string of error-prone read symbols will be misdetected as a sync mark. The data sync mark write string corresponds to an ordered set of m expected symbols selected to have maximum distance from all non-mark substrings of m consecutive expected symbols that exist in the concatenated string of expected symbols.

Abstract: A plurality of patterns are formed so that each is deviated slightly from another in each sector in the track width direction. Then, the pattern is followed up, thereby obtaining both a full-track profile and a 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: Apparatus and method for improving index reference position detection on a disc of a disc drive. The disc includes servo fields used by a servo circuit to control position of a head adjacent the disc and data fields used to store user data, with at least one data field between each successive pair of servo fields. Each servo field includes a binary index field used to indicate angular position. A multi-bit index detection word is selected having at least two bits at a first logical state and at least two bits at a second logical state. A plurality of index fields leading up to, and including a selected index field at the index reference position, are written with respective patterns corresponding to the logical sequence of the index detection word. As the disc rotates, the servo circuit reads each of the successive index fields and identifies the index reference position upon detection of the index detection word.

Abstract: A system and method are disclosed to facilitate independent positioning of a plurality of heads relative to associated disk surfaces in a disk drive system. Circuitry is provided to route position data from at least one of the heads while concurrently reading data from or writing data to another head. The position data is employed to control the position of the heads, each of which may be independently positioned by an associated positioning motor. Servo wedges associated with each surface also may be offset from each other to facilitate acquiring position data from one or more heads while data is concurrently communicated relative another head.

Abstract: A transducer position sensing system in a disc drive to take frequent data measurements from micro-servo sectors on the disc and to interpret the information to predict recording failures. The disc drive is formatted with many small or micro-servo sectors containing, among other things, a servo address mark, encoded disc location information, and radial track position information. The sensing system frequently retrieves this information through the transducer, compares the measurements to expected values, and given unexpected measurements predicts errors. The time elapsed between the passing of servo address marks can be used to predict adjacent sector overwrites. The radial track position information can be used to predict off-track write errors. The radial track position signal amplitude can be used to predict the transducer moving too far from the disc, resulting in skip write errors.

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 magnetic disk recording and reproducing apparatus comprising a unit for inserting an error correcting code related to control information into said control information on data; a recording control unit for recording in a plurality of sectors formed by dividing the recording area of a magnetic disk, each sector having an ID area for recording said control information and a data area, provided adjacent to and behind said ID area, for recording said data; and a error correcting unit for correcting said control information of said ID area by said error correcting code before data is read from said data area corresponding to said ID area or data is recorded in said data area corresponding to said ID area.

Abstract: A method and apparatus for writing a servo signal for controlling the position of a head on a disk during the manufacture of a hard disk drive. The present invention provides a method and apparatus for writing servo information on a magnetic disk through a magnetic head by driving an actuator of a hard disk drive (HDD) directly without employing a servo writer using control of a laser. Furthermore, when there is need for increasing the density in tracks per inch (TPI) to obtain a high capacity HDD, HDD manufacturers do not have to produce a new servo writer, thereby reducing production cost.

Abstract: A method and disc drive system identify defective servo information elements on a disc. Servo information elements are read from the track on the disc to receive first servo data status values associated with the servo information elements. If the first servo data status value associated with a first servo information element fails to satisfy a first predetermined criterion, the first servo information element is identified as a suspected servo information element. Location and error type information associated with the suspected servo information element is recorded in a hit table. The servo information elements from the track on the disc are reread with a second servo information element masked, and second servo data status values for the servo information elements are received.

Abstract: Noise level superposed on the head position detected by a position detector 103 is measured by a noise measuring unit 110, and an estimate position gain corresponding to the measured noise level is determined by a gain determining unit 111. An estimator 106 adds the logically calculated model position, and the result of the difference between the detected position and model position multiplied by the estimate position gain, so that the estimate position is calculated at high precision.

Abstract: A disk drive having multi-burst servo wedges and single-burst servo wedges for improving shock performance with less impact on data space than otherwise possible and a method of increasing the servo sampling rate for effecting reasonable shock detection in such a disk drive using such multi-burst and single-burst servo wedges. The additional single-burst servo wedges may contain certain desired servo wedge fields, or may consist of just the servo burst itself. In operation, the multi-burst and single servo wedges are processed in series. The multi-burst servo wedge is read to develop a position error signal and control the head, and the single-burst servo wedge is read, the single burst amplitude is compared to one of the plurality of burst amplitudes and, if the single burst amplitude differs by more than a predetermined threshold amount from the one previous burst amplitudes, the system aborts a data write operation.

Abstract: An apparatus and method for extending the service life of an MR element incorporated in a read/write head involves detecting periods of disk drive system inactivity and selectively switching between the heads for purposes of reading servo information during the inactive periods. Switching between heads may involve selecting each of the heads for reading servo information during one or more periods of disk drive system inactivity or selecting each of the heads in sequence during a respective period of system inactivity. Selecting between heads may also involve selecting a head having a minimum of usage, such as a head having an MR element with a minimum of cumulative operational time or energy dissipation relative to other MR elements provided in the disk drive system. Selecting between heads may further include selectively activating each of the heads for reading servo information for a predetermined duration of time during one or more periods of system idleness.

Abstract: A method, apparatus, and article of manufacture for controlling a disk drive with multiple VCMs is disclosed. The apparatus comprises a first disk storage surface and a second disk storage surface. The first disk storage surface has a plurality of first data segments and a plurality of first servo track segments interspersed therebetween, and is readable and writeable by a first head controllable according to a first servo track signal read from at least one of the first servo track segments. The second disk storage surface has a plurality of second data segments and a plurality of second servo track segments interspersed therebetween, and is readable and writeable a second head separately controllable from the first head according to a second servo track signal read from at least one of the plurality of second servo track segments.

Abstract: An apparatus, method and computer program product for a hard disk drive defect detection system. In one embodiment, a method of detecting defects on the surface of a disk having a plurality of tracks is recited. The method comprises reading, one or more times, the servo bits for a plurality of sectors and determining a burst measure for at least one sector, where the burst measure is a function of the burst signals for the sector. This method further comprises determining a reference value, where the reference value is a function of the burst signals of the plurality of sectors, and comparing the burst measure of at least one sector to the reference value to identify a potential defect. In one embodiment, a sector is mapped as defective where its burst measure differs from the reference value by at least 5 percent.

Abstract: The present disclosure relates to a system for detecting a plurality of defect types on the surface of a disk in a hard disk drive. In particular, the disclosure relates to utilizing information obtained from a plurality of servo bits to determine if a sector contains a physical defect. Where such a defect is found, the sector's write gate is disabled and its burst signal data is ignored for track following purposes. In addition, large changes in PES are used to identify closure spike defects. Such defects are managed by providing a compensation signal to the read value of the PES to improve track following. Finally, high PES values are used to signal a third defect type where no other signs of defect are present. In such case, the sector is mapped as defective, but the burst signals continue to be used for track following purposes.

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: A PES linearization scheme using small excitation bode measurements is provided to account for non-linearity characteristics during measurements of head element positions so to generate a more accurate read and write operation by a head element of a disk drive assembly. The PES linearization scheme of this invention provides making gain measurements as the head element moves across the track, and then integrating the result to get a relative PES profile. By then finding two points on the profile a known distance apart, we can multiply the profile by the appropriate gain factor to get an absolute PES profile. This profile can be then be used as a look up table to convert raw PES numbers into actual position.

Abstract: Herein is disclosed a method and apparatus for optimizing a disc drive for audio-visual data storage and retrieval by responding to a certain write-time error in a manner that preserves data flow. In response to a write-time error in which information obtained from a servo burst indicates that the disc drive's head was either off course or anticipated to go off course, the disc drive responds by ceasing to write to the disc in synchronization with the end of writing a sector, so that a sector is not left half-written. The disc drive then transfers the sector numbers of the sectors which were improperly written or unwritten to the host. The disc drive attempts to continue writing to the disc in subsequent sectors, as soon as servo sectors once again indicate that the head is sufficiently re-centered on the track.

Abstract: Steps for isolating and correcting total written-in repeatable run-out error written into servo sectors of a disc drive include, determining a total repeatable run-out error value for each servo sector, isolating a repeatable error value component of the total written-in repeatable run-out error value for each servo sector, removing the repeatable error value component from total written-in repeatable run-out error value to provide a non-repeatable error value component of the total written-in repeatable run-out error value for each servo sector, providing both the repeatable and non-repeatable error value components to a processor for generation of compensation signals, and applying the compensation signals into a servo control circuit of control loop of the disc drive using compensation circuits to compensate for each component of the total written-in repeatable run-out error.

Abstract: Head disc assembly serial number information is encoded in the servo bursts recorded during servo track writing. Specifically, the HDA serial number information is written to the disc during disk manufacture as part of the Servo Track Writing process in between the normal servo frames. The serial number is preferably written on preexisting unique system (non-user) tracks in-between normal servo frames. The encoded serial number can be retrieved by increasing the sampling interval of the servo information, i.e., by over-sampling the servo information. More specifically, by writing the serial number in a servo burst exactly in the middle of two normal servo frames, the information can be retrieved by 2× over-sampling routines called by system diagnostic routines or disc drive certification routines. In addition, a disc drive apparatus having a retrievable encoded head disc assembly serial number is provided.

Abstract: In a data storage medium, which includes a servo information area where information on the position of a head is recorded and a data information area where actual data information is recorded, the servo information area is divided into an A/B burst section and a C/D burst section, and the A/B burst section has a servo pattern in which phases of burst signals A and B are recorded to be different from each other and the C/D burst section has a servo pattern in which phases of burst signals C and D are recorded to be different from each other. Thus, when the length of a bit recorded on a data storage medium is reduced considerably, an output signal of a head and a burst signal can be detected without distortion and accordingly an accurate control of head tracking is possible.

Abstract: A method and disc drive are disclosed that write servo wedges to a plurality of tracks of a disc. A head having a read element offset from a write element reads a first servo wedge on a first track as a propagation guide and writes a second and third servo wedge to be used as a subsequent propagation guide on a second track, all during one instance of a sector position of the disc rotating by the head. Additionally, a fourth servo wedge that is radially continuous from the outer to inner diameter is also written for each sector of the track during the revolution and is used for track-following during normal operation. In this manner, all radially continuous servo wedges for each sector of a given track can be written during one revolution of the disc, thereby reducing the amount of time necessary for servowriting.

Abstract: A servo test is performed on a disc drive. The servo test includes performing a position error sample (PES) threshold test on tracks in the disc drive and identifying those tracks that fail the PES servo sample test. Zero acceleration path (ZAP) learning is performed on the identified tracks, and is performed on less than all of the tracks on the disc drive. Another PES servo threshold test is performed on the identified tracks to determine whether they pass the servo test, given the ZAP learning process.

Abstract: A servo system positions a transducer over a disc surface in a disc drive system. Disc surfaces in the drive each have a plurality of spaced servo samples recorded thereon. The servo samples on at least two of the disc surfaces are recorded in skewed relation to one another. A plurality of transducers are provided and one transducer is associated with each one of the plurality of disc surfaces. An actuator arm assembly is coupled to the transducers to move the transducers relative to the disc surfaces. A servo control system is coupled to the actuator arm assembly to control position of the actuator arm assembly. The servo control system includes a reader configured to read servo samples from at least two disc surfaces such that at least two servo samples are read within one servo time period.

Abstract: A digital servo control system for disk drives is an “embedded” system—one in which servo control information is embedded on the same disk surface as the user data. In contrast to known embedded-servo systems in which a space-consuming series of many dibit pairs is present, the present system provides only a single dibit pair in a fractional positional error (PESF) area. Thus, the disk drive's read head encounters only a single dibit pair per sample period (or per data sector), thus saving valuable disk space that may be used for user data. Various pre-processing methods may be provided so as to pre-process the measurement derived from the single dibit pair per sample period (or data sector), so as to compensate for non-ideal characteristics of the dibit measurement. The system thus provides an accurate and robust servo control system, while sacrificing a minimum amount of valuable disk space to the servo information field.

Abstract: A disc storage system servo code detector is disclosed that provides enhanced error correction capabilities during both tracking and seeking by increasing a minimum distance dmin between valid codewords and by increasing a minimum distance {circumflex over ( )}dmin from the signal space between adjacent codewords to the decision boundaries of all other valid codewords. The signal space with respect to the minimum distances is not a limiting aspect of the invention; however, in the preferred embodiment the codewords are selected to maximize the minimum distances in Euclidean space. Thus, the read signal is sampled and equalized according to a partial response spectrum, and maximum likelihood detection is employed to detect the servo codewords in Euclidean space. The code rate is selected according to certain design criteria such as the amount of error correction desired, the data density, and the cost and complexity of the encoder/decoder circuitry.