WO1998022940A1 - Dispositif et procede pour etalonner un systeme d'asservissement a disquettes - Google Patents

Dispositif et procede pour etalonner un systeme d'asservissement a disquettes Download PDF

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Publication number
WO1998022940A1
WO1998022940A1 PCT/US1997/007388 US9707388W WO9822940A1 WO 1998022940 A1 WO1998022940 A1 WO 1998022940A1 US 9707388 W US9707388 W US 9707388W WO 9822940 A1 WO9822940 A1 WO 9822940A1
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WO
WIPO (PCT)
Prior art keywords
servo
calibration
burst
read
track
Prior art date
Application number
PCT/US1997/007388
Other languages
English (en)
Inventor
Lawrence K. C. Ko
Fei Hong Zhu
Original Assignee
Swan Instruments
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Swan Instruments filed Critical Swan Instruments
Priority to AU28233/97A priority Critical patent/AU2823397A/en
Publication of WO1998022940A1 publication Critical patent/WO1998022940A1/fr

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B21/00—Head arrangements not specific to the method of recording or reproducing
    • G11B21/02—Driving or moving of heads
    • G11B21/10—Track finding or aligning by moving the head ; Provisions for maintaining alignment of the head relative to the track during transducing operation, i.e. track following
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B21/00—Head arrangements not specific to the method of recording or reproducing
    • G11B21/02—Driving or moving of heads
    • G11B21/08—Track changing or selecting during transducing operation
    • G11B21/081—Access to indexed tracks or parts of continuous track
    • G11B21/083—Access to indexed tracks or parts of continuous track on discs
    • G11B21/085—Access to indexed tracks or parts of continuous track on discs with track following of accessed part
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
    • G11B5/55—Track change, selection or acquisition by displacement of the head
    • G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
    • G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
    • G11B5/55—Track change, selection or acquisition by displacement of the head
    • G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
    • G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
    • G11B5/553—Details
    • G11B5/5534—Initialisation, calibration, e.g. cylinder "set-up"
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59627—Aligning for runout, eccentricity or offset compensation
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/82—Disk carriers
    • G11B5/825—Disk carriers flexible discs

Definitions

  • This invention relates generally to a system and method for head position servoing for ultra-high capacity removable diskette-type disk drives, and relates more particularly to a system and method for servo calibration for use in such disk drives employing servo calibration patterns.
  • ultra-high capacity diskettes have realized formatted data storage capacities in excess of 100 megabytes. These higher capacities are achieved by an at least order of magnitude increase in the disk rotational speed (from about 300 RPM to approximately 3,600 RPM), the use of advanced read/write head design such as thin film or double MIG, and advanced closed loop servoing techniques allowing track densities in excess of 2,500 TPI, including the use of embedded servo sectors which are pre-written at spaced-apart intervals along the data tracks.
  • Areal recording density is the product of the track density (i.e. the number of concentric tracks per inch or TPI) on the surface of a disk, and the bit density (i.e., the number of bits per inch or BPI) that can be recorded along a given track.
  • track density i.e. the number of concentric tracks per inch or TPI
  • bit density i.e., the number of bits per inch or BPI
  • Various prior art-type rigid disk drives, with non-removable media have been implemented including various known types of head-positioning servo systems.
  • Pertinent such servos include servo burst fields that are pre-recorded on the surface of a, for example, rigid magnetic disk, during manufacture of the disk drive.
  • Such servo burst fields typically comprise a sequence of magnetic flux reversals whereby write current flowing through the read/write head alternates in polarity thereby sequentially inducing magnetic flux reversals which define an oscillating, substantially constant frequency read back signal referred to herein as a servo signal.
  • the frequency of a servo signal is typically in excess of 1 MHz (megahertz).
  • the prerecorded servo burst fields occupy portions (servo sectors) of each recording surface, with the servo sectors being angularly spaced and interspersed among the data sectors of the track.
  • Each servo sector is pre-recorded on the disk's recording surface with each having a discrete angular position such that as the disk's recording surface is rotated beneath a read/write head, servo sectors pass beneath the head in time quantifiable phases.
  • Each servo phase represents the angular position of that servo sector on the recording surface and defines a time period for servo processing circuitry in which servo information is valid.
  • a read/write head "flies" above the disk media and reads servo burst fields during a sequence of time windows to produce a servo signal.
  • Signal processing circuitry responds to the servo signal to define sequential analog signals that represent the amplitude of the servo signal during successive time windows.
  • Additional circuitry operates on the sequential analog signals to define a position error signal (PES) which defines a magnitude and direction of an error between the actual position of a read/write head and the desired position of the head over the centerline of a data track.
  • PES position error signal
  • the position error signal is used to command a head-positioning actuator assembly to move the read/write head such that it is positioned most precisely over the centerline of the desired track.
  • A-B 2-burst servo pattern may comprise a radially spaced outer "A” servo burst field and a radially spaced inner “B” servo burst field, located in each servo sector along each data track.
  • Each "A" burst field occupies an arcuate space having burst-field centerline that is one half-track distance radially to one side of the centerline of an associated data track, and each "B" burst field occupies an arcuate space having a burst-field centerline that is one halftrack distance radially to the opposite side of the centerline of the data track.
  • the sequential reading of the "A” and “B” burst fields should cause the servo system to produce a null position error signal, and would do so under the following idealized circumstances.
  • the "A" burst signal i.e., the signal produced by the head during reading of the "A” burst field
  • the "B" burst i.e., the signal produced by the head during reading of the "B” burst field.
  • the ideal circumstances involve the two demodulated signals having the same value, such that the difference between them, as represented by the position error signal, is null.
  • the sequential reading of the "A" and “B” burst fields, and the demodulation and comparison thereof, should cause the servo system electronics to provide a position error signal with appropriate magnitude and direction to use in driving the head-positioning actuator assembly to move the head to the desired track centerline radial position on the track.
  • the analog magnitude value of the "A" burst demodulation signal should be larger than that of the "B" burst demodulation signal.
  • the analog magnitude value of the "A" burst signal should have a lower amplitude than that of the "B".
  • a servo can determine the head's transducer radial position relative to a data track centerline, and thereby determine the correction required of the head-positioning actuator assembly.
  • prior art servo systems While playing a particularly important role in the implementation and improvement of high-capacity rigid disk drives, such prior art servo systems are not easily adaptable for use with flexible disks such as comprise today's ultra-high capacity removable diskettes.
  • the main drawback of prior art servo approaches is that they have been designed to accommodate the eccentricities or wobble of hard disk drive systems, where the mechanical design of the rotating media system is such that the total resulting uncorrected radial position error of the mechanical system (i.e., motor bearing noise, spindle eccentricity, disk misalignment, recurring and non-recurring runout, and the like) are typically on the order of less than Vi of a data track width.
  • the mechanical system of any hard disk drive such that a read/write head could be mis-positioned, or be off-track by an entire track width, a re-seek operation would result. Such a mechanical design would be totally unacceptable in the marketplace.
  • flexible media disks used by floppy disk drives exhibit additional substantial and inherent mechanical instability and nonuniformity.
  • flexible media disks are susceptible to a significant degree of warping and/or lateral swelling caused by temperature and/or humidity changes in the surrounding ambient atmosphere.
  • flexible media disks are removable, they are exposed not only to the surrounding environment, but also to those mechanical systems whose dimensional tolerances vary from drive to drive.
  • a typical removable media diskette cartridge will be subjected to environmental and mechanical stresses that would cause a hard disk drive to cease to function.
  • the present invention provides a low cost, high performance servo system for an ultra-high capacity removable media diskette cartridge operating in combination with a floppy disk drive which increases the amount of useful data which may be stored thereon and which improves overall servo loop performance without significantly reducing the available user data megabyte storage space.
  • the present invention provides for an ultra- high capacity removable media diskette cartridge data storage system of the type including a UHD floppy-type disk drive.
  • the disk drive includes a head-positioning actuator assembly having a read/write transducer head for reading/recording data on a flexible media surface of a removable diskette cartridge and is adapted for linear motion radially across the surface of the flexible disk.
  • the disk drive includes a spindle motor assembly for rotating a flexible media disk at a constant, controlled angular velocity.
  • An ultra-high capacity removable media diskette cartridge comprises a flexible media storage disk that is rotatable at a controlled angular velocity by the spindle motor assembly, and defines thereon a plurality of concentric, pre-formatted data tracks each containing a plurality of sectors.
  • Each sector comprises a servo portion at the beginning of each sector followed by a data portion.
  • Each servo portion comprises a pattern of circumferentially, spaced-apart servo bursts with each burst having a pre-determined interval fraction radial offset relative to the others.
  • the read/write transducer head is radially positionable relative to the tracks in response to servo information derived from the spaced-apart servo bursts.
  • a microprocessor is provided for controlling the position of the read/write transducer head during track following operations in response to servo burst information read by the read/write head's transducer from each servo portion.
  • Servo information is provided to the microprocessor by circuit means which receive servo burst information from the read/write head's transducer and which senses the relative amplitudes of the servo bursts in order to allow electronic demodulation circuitry to determine thereby a position error signal.
  • the position error signal is processed by the microprocessor to define head-positioning actuator commands to maintain the actuator and read/write head in substantial alignment with the centerline of a select data track during track following operations of the device.
  • Calibration servo burst patterns are pre-formatted on selected ones of the concentric data tracks and provide calibration information to the circuit means, thus allowing the circuit means to define a magnitude and sign of the offset error introduced by the circuit means to the position error signal.
  • each servo portion includes four servo bursts, all written at a width of one full track pitch, in quadrature relationship and arranged such that a first burst in each servo portion is offset radially from a track centerline by one half of a track pitch or width increment, a second burst offset radially from the track centerline in the opposite direction by one half of a track pitch increment, and a third burst which spans the track centerline.
  • a read back null portion alternates between the third burst position and the fourth burst position on respective odd and even numbered tracks.
  • the qualification servo burst pattern comprises four servo bursts in which the first and second bursts span each respective track centerline and are written at a width of one full track pitch.
  • a third servo burst spans the centerline of each even numbered calibration track and is also written at a width of a full track pitch, and a read back null is provided in alternating third and fourth burst locations for the tracks comprising the calibration means.
  • the electronic circuitry comprises a preamplifier section comprising analog demodulation circuitry, which evaluates the relative magnitudes of the first and second servo burst signals and develops a position error signal representative of the difference in magnitude between the first and second signals.
  • the sign of the position error signal indicates the direction of the radial offset of the read/write transducer head off the track centerline.
  • the preamplifier and demodulator circuitry in combination with the first and second full track width burst patterns of the calibration sectors define means for determining a magnitude and sign of an offset error signal.
  • the offset error signal is representative of an offset error introduced into the position error signal by the analog components comprising the demodulator and preamplifier circuitry.
  • FIG. 1 is a semi-schematic, exploded perspective view of an ultra-high capacity disk drive detailing a head-positioning actuator assembly including a voice-coil motor and head- positioning carriage assembly and a diskette positioning carriage assembly useful in practice of principles of the invention;
  • FIG. 2 is a semi-schematic, diagrammatic view of a removable media disk drive subsystem, including a head and disk in accordance with practice of principles of the invention
  • FIG. 3 is a diagrammatic, signal pattern-level representation of the layout of a servo data sector in accordance with practice of principles of the invention
  • FIG. 4 is a diagrammatic, block-level representation of five contiguous concentric data tracks showing the arrangement of servo burst patterns in accordance with practice of principles of the invention
  • FIG. 5 is a diagrammatic representation of the read-back amplitude of odd and even track servo bursts in accordance with the four burst servo pattern of FIG. 4;
  • FIG. 6 is a diagrammatic, block-level representation of servo circuitry in accordance with the invention, including a preamplifier and demodulator section depicting the electrical input model for the four burst servo pattern of FIG. 4;
  • FIG. 7 is a diagrammatic, block-level representation of the layout of calibration tracks in accordance with practice of principles of the invention.
  • FIG. 8 is a diagrammatic flow chart depicting the calibration sequence in accordance with practice of principles of the invention.
  • a removable media disk drive 10 suitable for operation in combination with a host personal computer for data storage and retrieval purposes includes a base 12 formed of cast aluminum alloy through which a spindle hub/motor assembly 14 extends upwardly and which defines a central hub configured to receive and rotatably transport a flexible media data storage disk including an ultra-high capacity diskette cartridge.
  • a cover assembly (not shown) fits tightly over the disk drive base 12 to form an interior space into which diskette cartridge may be inserted.
  • the base and cover are sized and configured to locate and secure all of the movable components of the drive 10 and includes side walls which define the form factor of a standard three and one half inch floppy diskette drive.
  • a cover comprising a bezel 16 which includes an access door 18 is provided at one end of the drive 10 and completes the enclosure of the drive interior space.
  • the access door 18 is pivotally mounted to cover an access slot, formed in the bezel, which has horizontal and vertical dimensions suitable for receiving therethrough a diskette cartridge, for example, a three and one half inch removable diskette.
  • An electronically commutated three-phase direct drive brushless DC spindle motor 15 is mounted to the base 12 and includes a rotating spindle or hub 14 onto which the mating hub of a flexible media disk is mounted.
  • a flexible media disk is rotated counter clockwise at a controlled angular velocity of about 3,600 RPM by the spindle motor 15.
  • the magnets 24A and B are positioned such that they lie above and below each of the corresponding coils 22 A and B.
  • Ferromagnetic flux return plates 25 A and B are mounted so as to pass through the central opening of the coils such that the magnetic flux developed by the magnets is essentially directed to the region above and below the ferromagnetic flux return plates 25 A and B in which the coil travels.
  • the winding coils 22A and B are freely movable between the permanent magnets 24 A and B within a limited range of in-line displacement or stroke of the actuator's carriage assembly 21, in this instance, the stroke is approximately 1-1/8 inches.
  • the magnets 24A and B are premagnetized in a manner such that current passing through the winding coils 22A and B in one direction causes the actuator assembly 20 to move linearly toward the spinner motor hub 14, while current passing through the winding coils in the other direction causes the actuator assembly 20 to move linearly in the other direction, away from the hub 14.
  • the actuator assembly's range of linear motion is limited, at both ends, by crash stops (not shown). Indeed, the winding coils 22A and B would come into undesirable physical contact with the folded-over front and rear ends of the permanent magnets if the actuator assembly's range of linear motion were not so limited.
  • upper recording head loading means are provided to rotatably or pivotally move the upper head's load beam 30 away from the lower head support frame 36 which, in turn, separates the upper and lower read/write heads 32 and 34 a sufficient distance to allow a removable diskette cartridge to be inserted into the drive 10, with the recording disk positioned between the upper and lower read/write heads (32 and 34 respectively).
  • Such means suitably comprises a disk cartridge carriage assembly 60 which includes a support frame 64 movably mounted on the base 12 of the drive, in combination with a support housing 66 mounted for vertical displacement at the urging of support frame 64.
  • a pair of lifting fingers 86 extend rearwardly from the top surface of the support housing 66 and are separated by a slot-like opening having width sufficient for unobstructed motion of the head- positioning actuator's carriage assembly therebetween.
  • the slot between the fingers 86 extends into the material of the body portion of the support housing 66 a distance sufficient for the terminal edge of the slot to be positioned substantially over the drive hub 14 of the disk drive spinner motor 15. Accordingly, the slot allows the head-positioning actuator's carriage assembly to move linearly along the entire radial length of the recording band(s) of a flexible disk contained within a diskette cartridge.
  • the lifting fingers 86 engage the underside of a lateral lifting bar 88 coupled to the upper load beam 30 on the voice coil actuator's carriage assembly 21. As the support housing 66 is caused to move vertically, the lifting fingers 86 engage the lateral lifting bar 88 and forces the upper load beam 30 away from the lower support frame 36, thus separating the upper and lower read/write heads.
  • FIG. 2 A diagrammatic view of a removable media disk drive subsystem, including a head and disk in accordance with practice of the principles of the invention is shown in FIG. 2.
  • the head-positioning actuator assembly 20 (FIG.l) further comprises a head stack assembly, generally indicated at 28, which further includes an upper load beam 30 which supports a first magnetic read/write head 34 which is formed with a 70% slider of e.g. calcium titanate ceramic material.
  • the head stack assembly 28 further comprises a lower head support frame 36 which, in turn, supports a lower read/write head 38 (seen in FIG. 1) which is also formed with a 70% slider of e.g. calcium titanate ceramic material.
  • a flexible recording media disk 40 of the type typically contained within the casing of a diskette cartridge (not shown).
  • the disk is rotated by a spindle motor assembly 15 which is coupled to the recording medium by a spindle hub 14.
  • a magnetic recording medium which comprises a thin (approximately 0.1 to 0.5 microns) layer of metal particles coated over a non-magnetic titanium substrate layer, bonded in turn to a MylarTM disk body.
  • Each surface of the disks 40 comprises a multiplicity of radially spaced-apart concentric data tracks 42 and are further divided into a plurality of sectors, represented by sector boundary lines 43, each of which, as is well known in the art, comprises on each track a servo portion and a data portion.
  • the track density achieved by the system is approximately 2700 tracks per radial inch of the disk, and recording densities of approximately 71 ,000 bits per linear inch along each track (bit density being about 71 ,218 bits per inch as measured along the circumferential direction at the innermost concentric data track).
  • Electronic circuit elements for electronically controlling the operation of the head disk assembly are preferably formed on a printed circuit board having approximately the same length and width dimensions as the base portion (12 of FIG. 1) of a floppy disk drive (10 of
  • the major functional circuit elements of the electronic circuit elements include a preamplifier and demodulator 44, connected to an analog-to-digital converter 45, which provides digital signal information to a monolithic microprocessor 46 which operates under software or firmware program control to command and manage the various operations of the disk drive system.
  • a digital-to-analog converter 47 receives digital control words from the microprocessor 46 and converts those words to analog signal values which are operatively directed to a power driver circuit 48.
  • the power driver 48 generates an appropriate current which is directed through the voice coil motor windings of the actuator assembly 20 in order to radially move the head assembly from its current location to a destination track location during track seeking operations, and to maintain the head's magnetic recording gap in centerline alignment with a data track during track following operations.
  • each sector has recorded therein information for identifying the track number, synchronization signals and servo burst pattern signals which, when decoded by means of the preamplifier and demodulator 44 and analog-to-digital converter 45, provide a signal which may be processed by the microprocessor 46 to generate an indication of the position of a read/write transducer head 34 relative to the centerline of a particular data track.
  • Each data portion of a sector following the servo portion contains user data which may be read from and recorded to under software or firmware program control of a host computer (not shown).
  • the intelligent portion of the servo system is commonly implemented in the microprocessor 46 which calculates the head-positioning actuator motion control information, at least once per sample of information read from the tracks on the disk 40 during a seek operation by using one of a variety of conventional mathematical algorithms well known to those having skill in the art. Calculated values of the control motion are applied to control the head-positioning actuator motor through the digital-to-analog converter 47 and the power driver circuit 48.
  • the exemplary embodiment of the disk drive 10 has been depicted in FIG. 1 and described with a linear voice coil motor-type head-positioning actuator assembly 20.
  • a head-positioning actuator assembly is provided in accordance with the invention to accommodate positioning a read/write head within the media access openings commonly provided on a 3.5" flexible media diskette cartridge.
  • These conventional media access openings are configured to support linear motion of a head-positioning actuator, in well known fashion, in the radial direction along a flexible media disk.
  • practice of the present invention is not limited to a head-positioning actuator of the type depicted, with a linear voice coil motor-type actuator assembly.
  • a rotary voice coil motor-type head-positioning actuator such as are commonly employed in contemporary rigid disk or hard disk drives.
  • a rotary actuator may be easily positioned within the confines of the disk drive 10 in accordance with the invention, and configured to move the read/write head arcuately over the surface of a flexible media disk.
  • Such arcuate motion could easily be accommodated by a simple reconfiguration of the media access openings of a diskette cartridge, or by a variety of methods by which the two major surfaces of a flexible media disk could be exposed to contact by a pair of read/write heads.
  • Such a configuration i.e., a rotary voice coil motor-type head-positioning actuator, would allow the resulting floppy disk drive to be constructed with a smaller footprint, and allow for some degree of commonality between floppy disk drive components and those of contemporary hard disk drives. This would further result in an increase in production efficiency along with a consequent reduction in cost.
  • FIG. 3 illustrates the layout of an exemplary embodiment of the read back signals of a servo data sector, e.g. that portion of each data track lying between the sector boundaries (43 of FIG. 2).
  • the servo sector pattern depicted in FIG. 3 is replicated, in sequential fashion, along each servo data track in each servo data sector portion, and also replicated concentrically on each servo data track of the disk (40 of FIG. 2).
  • FIG. 3 the exemplary data sector is depicted in two different formats.
  • the upper portion of FIG. 3 depicts the exemplary data sector graphically, wherein the transitions are expressed by exemplary read back waveforms.
  • Beneath this graphical representation there is depicted a digital signal pattern-level representation, wherein the presence or absence of a magnetic flux transition is represented by a " 1 " or "0", respectively, in the "transition" row.
  • a "cycle” is equal to two transitions, which also may be referred to as a "di-bit".
  • the graphical representation of the sector layout of FIG. 3 is not intended to imply that the invention is limited to "waveforms”. The graphical representation is provided herein only for purposes of visual convenience and to assist in an understanding of the true scope of the invention.
  • each sector comprises a first, servo field portion, which is conventionally followed by a second, data field portion.
  • the servo field comprises a fully embedded servo pattern which defines each servo sector. Defining the time period during which a transition would be expected as "T", the servo sector pattern may be described as follows.
  • Each servo pattern suitably comprises an AGC field 52, servo detect pattern 54, a synchronization field 56, a 2 T's isolation zone 57, a 2 T's code bit 58, a 2 T's second isolation zone 59, a 2 T's index bit (optional) 60, a gray coded 24 T's track address 62 followed by servo burst fields, servo A, B, C and D (63, 64, 65 and 66 respectively) in quadrature.
  • a pad field (not shown) is typically included following the servo burst fields.
  • the AGC field 52 is typically 4 microseconds in duration and suitably comprises 32 flux transitions written at a transition frequency of about 8 Megatransitions per second.
  • the AGC field provides a constant and reproducible signal to the servo control electronics for purposes of automatic gain control, in a manner well known by those having skill in the art.
  • a servo detect pattern comprises a lower transition frequency (equally spaced transitions at 0.25 microseconds) signal to uniquely identify the servo field to a disk drive's control electronics from formatted data header and user data fields.
  • the servo detect field has twelve transitions for a duration of about 3 microseconds.
  • a synchronization field 56 is provided to generate signals by which a conventional servo decoder circuit may be synchronized.
  • the synchronization field is approximately 0.5 microseconds long and suitably comprises four transitions spaced at 0.125 microsecond intervals.
  • an isolation zone is provided between the preceding sync field and the following code bit field.
  • the isolation zone 57 is preferably a region of no transitions, approximately 0.25 microseconds in duration. The duration of the isolation zone will be chosen to provide a time interval of sufficient length for the disk drive's micro processor to shut off the servo decoder circuit such that the servo decoder will not receive, and be thereby confused by, any following information.
  • a two transition region, commonly termed a code bit, 58 is provided to identify the type of servo information which is to be demodulated. For example, in well known fashion, the absence of the code bit indicates that phase information is to be demodulated.
  • the code bit region has a duration of approximately 0.25 microseconds and is followed by a further isolation zone 59, comprising a 0.25 microsecond region of no transitions.
  • an index bit 60 is provided in the servo field of the first three sectors of each data track.
  • the index 60 may suitably comprise a pair of transitions (as exemplified in FIG.
  • the index 60 is a pair of transitions comprising a pattern having a duration of 0.25 microseconds.
  • Absolute track address, and, optionally, absolute sector address is directly encoded as a Gray code pattern in the Gray code field 62 from the decimal representation of the track number.
  • the Gray code pattern corresponds to a 12 bit binary representation of the decimal track number and is incremented (or decremented) by only one bit for each next concentrically inward data track on the disk (40 of FIG. 2).
  • a 12 bit Gray code field has 24 possible transitions and will have a duration of about 3 microseconds.
  • each Gray code "one" bit is written with two transitions, while each Gray code "zero” bit is represented by a similar time interval during which there are no transitions.
  • a third isolation zone 67 comprising no transitions and lasting 0.5 microseconds appears, followed by a servo burst field 68 comprising a multiplicity of laterally spaced-apart sequential servo bursts, each having a duration of 2.5 microseconds and each comprising 20 transitions written at a transition frequency of about 8 Megatransitions per second.
  • the servo burst field 68 is followed by a pad field (not shown) and a user data field (also not shown) capable of holding 512 bytes of user data and additional overhead information, such as error correction codes and speed tolerance filler gaps. Further details of the pre-recorded servo burst patterns are discussed below in the section entitled "Servo Burst Layout".
  • An ultra-high capacity flexible media recording disk in accordance with the invention typically includes a multiplicity of servo sector portions, with the particular number being defined by the number of sectors per track which is, in turn, determined by whether or not some form of "zoned" recording technique is implemented on the disk.
  • two data zones are preferably implemented on the disk with the first, outer zone comprising 89 sectors per track with approximately 650 tracks in the zone.
  • the second, inner zone comprises 71 sectors per track and includes approximately 356 concentric tracks in the zone.
  • Each sector is offset from a preceding sector by a predetermined angular distance such that when the flexible disk is rotated at a constant angular velocity, each sector, including the servo sector portion, passes under an active read/write head's transducer in a predetermined angular phase relationship with the other sectors.
  • Both servo sector phase timing and the length of a servo burst field within a servo sector phase are conventionally determined during the design process of an embedded servo system. Sector phase timing depends on the choice of rotational speed of the flexible recording disk and the number of servo sectors intended for an optimum servo loop sampling rate. The size of the servo burst fields within a servo sector are also a function of design choice.
  • Servo sector phase timing and servo burst field length are, therefore, determinable quantities whose values are typically stored by conventional software means in timing control registers comprising conventional servo timing and control circuitry provided with all disk drives having embedded servo systems. Accordingly, the servo timing and control circuitry defines a timing signal, synchronized with the servo sector phases, to define a succession of windows in time, such that each window opens while a servo burst is moving under the active read/write head's transducer.
  • FIG. 4 there is depicted a diagrammatic, block-level representation of 5 contiguous concentric data tracks showing the arrangement of servo burst patterns on the flexible disk in accordance with practice of principles of the invention.
  • FIG. 4 there are 4 servo bursts, burst A, burst B, burst C, and burst D, which are arranged both circumferentially consecutively, and radially in a particular pattern.
  • the A and B bursts are radially separated from each other by the distance of one full track pitch or width, as are the C and D bursts.
  • the C and D bursts are separated radially from the A and B burst pattern by one half of a full track pitch or width.
  • the servo burst pattern e.g. the radial and circumferentially sequential arrangements of the 4 servo bursts, preferably repeats itself in 2 track intervals.
  • the arrangement of servo bursts as sensed by a read/write head's transducer at data track 0, are the same as sensed on data tracks 2, 4, 6 and etc. (even data tracks).
  • the servo bursts as sensed at data track 1 are the same as sensed at data tracks 3, 5, 7 and etc. (odd data tracks) respectively.
  • the illustrated servo burst pattern comprises two alternating half maximum read-back amplitude bursts followed by a full maximum read-back amplitude burst as sensed by the read/write head's transducer.
  • each of the A bursts is written so as to straddle the boundary between data tracks and radially extend from the centerline of one data track to the centerline of an adjacent data track (in the example of FIG. 4, from the centerline of track 0 to the centerline of track 1, the centerline of track 2 to the centerline of track 3, and the like).
  • the B bursts are also written so as to straddle data track boundaries and extend from the centerline of one specific data track to the centerline of another, but the B bursts are written a full track pitch or width offset in the radial direction from the A bursts, such that were the A and B bursts not circumferentially consecutive, they would interleave.
  • the B burst straddles the boundary between data track 1 and data track 2, and radially extends from the centerline of track 1 to the centerline of track 2 straddling the data track 1 to data track 2 boundary.
  • the next B burst radially extends from the centerline of track 3 to the centerline of track 4 straddling the boundary between tracks 3 and 4.
  • the C burst is written a half track pitch or width from the A and B bursts, and spans the centerline of the odd numbered data tracks.
  • the D burst is also written a halftrack pitch on width from the A and B bursts, but straddles the centerline of the even numbered data tracks, thus alternating with the C bursts.
  • the active head's transducer will sense the A burst at approximately one half amplitude followed in time by sensing the B burst at approximately one half amplitude, and finally by sensing the D burst at full amplitude.
  • This particular condition is depicted in the upper portion of the exemplary read back signal diagram of FIG. 5. It should be noted that in the preceding example, the read/write head's transducer will not sense any signal from the C burst, when reading servo information on even numbered tracks.
  • a head when a head is reading servo information, while aligned with the centerline on an odd numbered data track, it will sense or read an approximately half amplitude A burst, an approximately half amplitude B burst, and a full amplitude C burst, as depicted in the lower portion of the exemplary read back signal diagram of FIG. 5. Due to the radial position location of the D burst, it is not sensed or read on odd numbered tracks. Thus, for each track, one or the other of the C and D bursts is entirely within the width of the read/write head's transducer, while the other is entirely outside. This arrangement provides signals in quadrature, such that the relative amplitudes of servo bursts read by the read/write transducer head at a known position will provide valid direction feedback information during track seek operations as well as during track following operations.
  • the amplified and demodulated amplitude values (the two half amplitude and the full amplitude values) are analyzed, in conventional fashion, by a microprocessor which determines the actual position of the read/write transducer head in relation to the centerline of the particular track of interest, and derives a correction signal value which is commanded to the head- positioning actuator to maintain or adjust the radial alignment of the read/write head to the data track centerline.
  • position error signals derived by the analog circuitry prevalent in the field of disk drive servo demodulation systems, are subject to electronic and mechanical offsets. Such offset signals are typically superposed over the true position error signal and represents a degree of unwanted error in the PES. Accordingly, it is desirable to calibrate out these offsets in order to determine exactly where the centerline of a particular track lies, and to ensure that the position error signal provides a true indication of a read/write head's position with respect thereto. For any particular ultra- high capacity disk drive, its mechanical transport system and its electronic circuitry, will exhibit generally the same offset characteristics throughout its useful life.
  • the recording media in this case a removable ultra-high capacity diskette cartridge
  • the electronic and mechanical offset characteristics experienced by any recording head/servo system combination will be different each time the media diskette cartridge is inserted into a different drive.
  • tracking accuracy and performance must be maintained across various combinations of disk drive and diskette combinations.
  • the servo patterns are not written on the media surface of ultra-high capacity recording disks by the disk drive's own read/write heads, capacity disks constrained to operate in combination with a single specific spindle motor assembly.
  • the eccentricities due to repeatable run out are generally the same over the operating life of any given disk drive. Since the servo pattern for a rigid disk drive is written while the disk is rotated under the influence of the same mechanical systems, such as bearings, as during data transfer operations, resulting repeatable runout in rigid disk type systems, tend to be small and are easily handled by the head-positioning servo loop performance. In other words, it is not difficult to define the precise center of each data track for contemporary rigid disk type disk drive systems. All that is required, is that servo loop performance have sufficient bandwidth to take the resulting repeatable runout into account.
  • ultra-high capacity replaceable and/or interchangeable recording media is subject to considerably greater degrees of repeatable offset than that experienced by rigid disk drives. Particularly, temperature and especially humidity cause significant warping of a flexible media disk with a consequent large excursion amplitude for the offset.
  • the read signal to noise ratio can easily change when different diskette cartridges are inserted into a particular floppy disk drive, and likewise when a particular diskette cartridge is inserted into a different floppy disk drive.
  • the absolute magnitude of a read signal may change over time and particularly with changes in ambient temperature and humidity. All of these factors combine in ultra-high capacity recording to require that the servo system is able to identify the centerline of a data track and be able to accurately position a magnetic recording or read/write head thereon.
  • a servo system for ultra-high capacity flexible media recording must be able to compensate for the electronic offsets, introduced by the disk drive servo system electronics, thereby developing an accurate position error signal (PES) for accurately determining the centerline of the data track.
  • PES position error signal
  • a servo system must be able to follow the defined centerline of each track by compensating for repeatable offsets such as those caused by changes in temperature and humidity.
  • means are provided to minimize the effect of electronic and mechanical offsets in a particular diskette/disk drive combination by providing calibration tracks at particular radially spaced-apart intervals on the media disk surface.
  • FIG. 6 depicts the electrical input offset model of a preamp and demodulator section in accordance with the invention
  • the A,B,C and D servo bursts are read from the servo surface of a particular track and input into respective ones of a plurality of comparators 70a, 70b, 70c and 70d in a preamplifier and demodulator circuit 72.
  • the servo burst amplitude signals are processed through a plurality of gain stages 74a, 74b, 74c and 74d which provide demodulated and amplified burst signals A', B', C, and D' respectively.
  • the demodulated and amplified burst signals are processed through a plurality of gain stages 74a, 74b, 74c and 74d which provide demodulated and amplified burst signals A', B', C, and D' respectively.
  • the demodulated and amplified burst signals are processed through a plurality of gain stages 74a, 74b
  • A' and B' are input to a summing amplifier 76 which evaluates the relative magnitudes of the A' and B' burst signals and develops a position error signal (PES) representative of the magnitude of the A' burst signal minus the magnitude of the B' burst signal.
  • PES position error signal
  • the sign of the PES signal indicates whether the A burst or the B burst was read with a larger relative magnitude, and thus indicates whether the active read/write head was positioned off the track centerline in the direction of the A burst or in the direction of the B burst.
  • a second summing amplifier 77 is provided, wherein the position error signal developed by the summing amplifier 76 is summed with a variable reference signal 78.
  • the reference signal 78 is variable in that its value may be incremented or decremented by, for example, a microprocessor operating under software program control. The microprocessor would write a digital word, representing a first reference signal value to, for example, a D-to-
  • a converter (not shown) which, in turn, outputs an analog signal suitable for summing with the position error signal in the second summing amplifier 77.
  • the microprocessor adjusts the value of the variable reference signal, in a manner defined in greater detail below, so as to cause a null signal value to appear at the output of the second summing amplifier 77 during offset calibration of the servo system.
  • the processed servo burst signals are provided to an analog to digital converter, from whose output, for example, microprocessor is able to determine command signals for moving the linear actuator, thus repositioning the active read/write head over the centerline of the data track.
  • an analog to digital converter from whose output, for example, microprocessor is able to determine command signals for moving the linear actuator, thus repositioning the active read/write head over the centerline of the data track.
  • the offset will be added prior to the gain stages 74A through 74D and are, in turn, amplified along with the servo burst information.
  • the calibration and reference track areas comprise three calibration tracks: a calibration track 0 centered between a calibration track -1 and calibration track +1.
  • Each of the tracks comprise the same track pitch or width as a nominal data track and further comprise an alternating arrangement of servo burst sectors arranged in odd sector, even sector periodicity.
  • each even sector comprises a servo burst pattern provided on the media surface in the same manner as the servo burst pattern of a non calibration-type track such as described above in connection with FIG. 4.
  • the A and B servo bursts are written with full amplitude values over the width of, and spatially aligned with, the three radially consecutive calibration tracks.
  • the A and B servo bursts span the full width of the calibration track region.
  • a read/write head's transducer reading the odd sector servo burst information on calibration track 0 will read three sequential full amplitude servo bursts followed by a null in the nominal D burst position.
  • a read/write head's transducer reading the odd sector servo burst information on calibration tracks -1 or +1 will read two sequential full amplitude bursts followed by a null in the C burst position, followed in turn by a full amplitude D burst.
  • the quadrature arrangement is maintained for the calibration track regions, while also providing an active track-following servo burst arrangement for the even sector servo fields, and providing a calibration region for the odd sector servo fields.
  • Calibration is performed by evaluating the A' - B' demodulated burst signals for the odd numbered (i.e., calibration) sector servo burst patterns. For these calibration sectors, it is clear that the PES may be expressed (with regard to the input offset model of FIG. 6) as:
  • the offset value for a particular calibration track can be determined from an evaluation of the full amplitude A' and B' bursts.
  • evaluation of the full amplitude A' and B' bursts occurs in first summing amplifier 76 wherein a position error signal is developed which represents the effects of the electrical offset of the input circuitry.
  • This unwanted position error signal is provided to the second summing amplifier 77 wherein it is summed with a variable reference signal which is, in turn, adjusted to cause a null output.
  • the value of the variable reference signal at this point, can be seen as representing a most nearly exact compensation to the electronic offset derived position error signal.
  • FIG. 8 there is depicted a high level flow diagram of a calibration technique in accordance with practice of the present invention.
  • the calibration system performs a read on the calibration A burst, followed by a read of the calibration B burst.
  • a demodulated and amplified A' and B' calibration burst signals are compared in a first summing amplifier (76 of FIG. 6) in order to define a position error signal which can be further expressed as "the absolute value of A' minus the absolute value of B'".
  • the position error signal should have a null value. In other words, a full value A burst minus a full value B burst would equal zero.
  • the calibration burst pattern position error signal is combined with a variable reference signal in a second summing amplifier (77 of FIG. 6), which signal is indeed varied until the output of the second summing amplifier achieves a null value. In other words, "the absolute value of the position error signal minus the absolute value of the variable reference signal equals zero".
  • an arbitrary value is initially selected for the value of the variable reference signal by, for example, a control processor.
  • This initial value may be a value which has been previously defined and stored during an earlier calibration process on a previously inserted diskette.
  • This initial value is converted to an analog signal by a D-to-A converter, and applied to the second summing amplifier (77 of FIG. 6) whence it is combined with the position error signal.
  • the output of the second summing amplifier is evaluated to determine whether it has a null value. If not, the variable reference signal is incremented, or decremented, depending on the magnitude and polarity of the second summing amplifier's output. This new variable reference signal value is again applied to the second summing amplifier and the output of the second summing amplifier is again evaluated for a null value.
  • the variable reference signal thus determined and stored, describes a mirror-image of the electronic offset introduced by the up-stream circuitry to the position error signal.
  • the position error signal can be seen as representing an accurate indication of the position of a read/write head with respect to the centerline of a data track.
  • the position error signal (PES) offset values can be further refined in order to minimize the effects of noise disturbance, by evaluating the offsets for a multiplicity of sequential odd sector calibration bursts in accordance with the following formula:
  • the servo burst information on even sectors of the calibration track area is the same as the burst pattern for normal sectors, the servo burst information on even sectors may be used to obtain both magnitude and phase information of the PES signal. Conventional feed forward servo techniques may then be used to correct the actuator position due to, for example, repeatable runout error.
  • such feed forward servo techniques include dividing the surface of a flexible media disk into seven arbitrary zones and causing the servo system to attempt to follow a particular data track for several revolutions of the disk. During this time, the magnitude and direction of a position error signal derived for each servo sector, which may be averaged with the PES readings for the same servo sector during subsequent revolutions, is stored in memory in a data table, which represents an excursion map of the position error signal for a data track in each of the arbitrary zones.
  • the PES values for each zone may be stored directly in the data table, or alternatively, the PES values for a particular data track may be processed by, for example, fast Fourier transform, in order to define a repeatable magnitude and phase value of the PES excursion due to repeatable offset caused by, for example temperature and humidity.
  • Calibration both for electronic offset and the repeatable offsets, is performed in accordance with practice of principles of the invention, at least following disk spin-up after insertion of the new diskette cartridge into a disk drive. Compensation values are determined and stored in memory for subsequent use by the servo system during track following operations.
  • the calibration routine may be invoked by firmware resident in the disk drive electronics, to perform a calibration sequence following a seek, read, or write failure, or preferably following the second retry after such a fault indication is returned by the drive. If the disk drive is being used in combination with conventional power saving features, calibration may be easily programmed to be performed following any sequence of power- down and recovery wherein the flexible media disk is spun down (the disk ceases revolving).
  • the calibration procedure may be performed at anytime during operation of the disk drive, including during periodic intervals during read and write operations. Such intervals may easily be programmed into firmware which controls operation of the drive, so as to provide an on-the-fly calibration capability.
  • the invention provides for a system and method for track formatting and head servoing for ultra-high capacity removable flexible media, and in particular provides a system and method for determining and calibrating out electronic and mechanically caused offsets from the head servoing system.
  • the embodiment of the invention described above is exemplary and that there are numerous ways in which the various calibration tracks and servo burst patterns described may be rearranged in order to provide the required functions.
  • the calibration burst sectors may be provided at any integral multiple of servo sectors along a particular band of tracks.
  • Calibration sectors may be provided at every third sector, fourth sector, fifth sector, or the like, so long as their location is periodic and determinable such that conventional control electronics are able to generate an appropriate timing signal to identify their occurrence.
  • location of the calibration track areas are a matter of design choice and need not be positioned in the exemplary inner region, outer region, or center region, but may instead be positioned anywhere on the surface of the media disk that the designer chooses. A greater number of calibration tracks, in a greater number of radial locations, would provide additional calibration information and improve the tracking accuracy and performance of the system at the expense of losing recording area on the disk that could be used for customers storage capacity.
  • the servo patterns of the exemplary embodiment of the invention have been depicted and described as written at the beginning of each data sector along a data track, the servo sectors and data sectors may be easily interspersed with one another in a manner well known by those having skill in the art. "Splitting" data sectors so as to accommodate a servo sector between the segments, is a well known technique that has been established for rigid disk drives implementing a "zoned" recording architecture. Implementing the present invention in a disk drive and flexible recording media combination with a "zoned" recording architecture and split-field data sectors is well within the comprehension of one having skill in the art and may be put into practice without any undue experimentation.

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  • Moving Of The Head To Find And Align With The Track (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)

Abstract

Un système de stockage de données à disquettes de très haute densité comprend un lecteur (10) de disquettes comportant un disque souple (40) qui peut tourner à une vitesse angulaire contrôlée et présente une configuration préenregistrée d'une pluralité de rafales d'asservissement répétées (A, B, C, D), chaque rafale étant décalée radialement d'une fraction entière par rapport aux autres. Une tête de lecture/écriture (34) peut être positionnée par rapport aux pistes de données (42) en réponse aux informations dérivées des rafales d'asservissement (A, B, C, D). Le système de stockage de données comprend en outre une pluralité de pistes d'étalonnage (-1, 0, +1), chaque piste comprenant une première série de secteurs d'asservissement de positionnement de la tête, intercalés avec une seconde série de secteurs d'asservissement d'étalonnage. Les secteurs d'asservissement d'étalonnage comprennent des rafales d'asservissement d'amplitude totale (A, B) qui sont lues et traitées par un circuit électronique (72) définissant un signal d'amplitude et de polarité qui représente le décalage électronique introduit par le circuit.
PCT/US1997/007388 1996-11-19 1997-05-02 Dispositif et procede pour etalonner un systeme d'asservissement a disquettes WO1998022940A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1037363A2 (fr) * 1999-03-09 2000-09-20 Sony Corporation Moteur pour la rotation d' un support d'enregistrement d'information en forme de disque dans un appareil d'entraínement des disques optiques

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1906137A1 (fr) * 2006-09-29 2008-04-02 Leica Geosystems AG Procédé et dispositif pour générer une longueur d'onde synthétique

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4890172A (en) * 1988-09-27 1989-12-26 Digital Equipment Corporation Automatic servo gain calibration system for a disk drive
US5170299A (en) * 1990-08-17 1992-12-08 Quantum Corporation Edge servo for disk drive head positioner
US5424885A (en) * 1993-01-11 1995-06-13 Seagate Technology, Inc. Method for following data tracks in a disc drive using an improved thermal calibration method
US5523902A (en) * 1993-10-25 1996-06-04 Syquest Technology, Inc. Servo burst pattern for removing offset caused by magnetic distortion and method associated therewith
US5550685A (en) * 1993-10-22 1996-08-27 Syquest Technology, Inc. Applying an adaptive feed-forward algorithm as a frequency selective filter in a closed loop disk drive servo system in order to compensate for periodic perturbations which otherwise appear in the servo system position error signal

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4890172A (en) * 1988-09-27 1989-12-26 Digital Equipment Corporation Automatic servo gain calibration system for a disk drive
US5170299A (en) * 1990-08-17 1992-12-08 Quantum Corporation Edge servo for disk drive head positioner
US5424885A (en) * 1993-01-11 1995-06-13 Seagate Technology, Inc. Method for following data tracks in a disc drive using an improved thermal calibration method
US5550685A (en) * 1993-10-22 1996-08-27 Syquest Technology, Inc. Applying an adaptive feed-forward algorithm as a frequency selective filter in a closed loop disk drive servo system in order to compensate for periodic perturbations which otherwise appear in the servo system position error signal
US5523902A (en) * 1993-10-25 1996-06-04 Syquest Technology, Inc. Servo burst pattern for removing offset caused by magnetic distortion and method associated therewith

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1037363A2 (fr) * 1999-03-09 2000-09-20 Sony Corporation Moteur pour la rotation d' un support d'enregistrement d'information en forme de disque dans un appareil d'entraínement des disques optiques
EP1037363A3 (fr) * 1999-03-09 2002-05-29 Sony Corporation Moteur pour la rotation d' un support d'enregistrement d'information en forme de disque dans un appareil d'entraínement des disques optiques
SG97861A1 (en) * 1999-03-09 2003-08-20 Sony Corp Motor for rotating a disk-shaped information recording medium in a disk drive apparatus
CN100392949C (zh) * 1999-03-09 2008-06-04 索尼公司 盘驱动装置中驱动盘状信息记录介质的电动机

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