Abstract: Embodiments in accordance with the present invention provide a drive unit that is capable of satisfactorily performing the positioning control with disturbance components included in a position error signal being effectively controlled. According to one embodiment, an error signal generator of a drive unit generates a position error signal (PES) on the basis of servo data read out from a magnetic disk. On the assumption that a frequency of a periodic variation component included in the PES is a target frequency, if a target frequency deviates from an effective frequency range of a digital filter, a downsampler down-samples the PES, and then supplies the PES to the digital filter so that the effective frequency range is shifted. As a result, within the shifted effective frequency range, a setting changing unit can control a setting frequency of the digital filter so that the setting frequency follows the target frequency.

Abstract: A servo track writer (STW) clockhead radius jig is disclosed. One embodiment provides a hard disk drive assembly including a base having a cutaway portion to provide visual access therein. In addition, a disk is mounted in the hard disk drive assembly, this disk having an indicator thereon to indicate a required radius setting for a clockhead.

Abstract: According to one embodiment, a disk drive includes a detection signal producing module configured to produce a detection signal by reading each of the spiral servo patterns, the spiral servo patterns being read by a head while the head scans a circumferential direction region on the disk media. A position error computation module is configured to produce servo burst signals A, B, C, and D using a plurality of frames obtained by dividing the detection signal at even time intervals, at least one burst signal of the servo burst signals being produced using at least two frames in the frames, and to compute a position error of the head based on amplitude values of the produced burst signals.

Abstract: According to one embodiment, there is provided a disk drive that can perform dynamic offset control (DOC). The disk drive has a magnetic head, a disk, and offset calculating modules. The magnetic head has read head. Offset-measuring position data is written in a non-servo area provided in the disk. The read head reads the offset-measuring position data from the disk. Based on the offset-measuring position data thus read, the offset calculating modules calculate an offset value that changes during a one-rotation period of the disk.

Abstract: A method for correcting a track pitch error in servo tracks written on a magnetic recording media coupled with a disk surface, by using a subsequent servo-write pass, comprises propagating servo tracks across the magnetic recording media in a previous servo-write pass. The servo tracks have radial positioning servo code. The servo tracks enable a magnetic transducer to be positioned to at least one radial position on the magnetic recording media. At least one corrected radial reference point is calculated for the track pitch error written on the magnetic recording media, by identifying at least one inconsistency between a mechanical response of an actuator and the track pitch. A corrected location for at least one servo track is identified. At least one new servo track at the corrected location is propagated with the subsequent servo-write pass. Optimum data track distribution across the disk surface and optimum reading and writing of data to and from the magnetic recording media is enabled.

Abstract: An acceleration sensor outputs a signal in accordance with acceleration. A differentiator outputs a differential signal of the output signal. A comparator inverts the state of an output when the differential signal goes beyond a threshold. A monostable multivibrator maintains the state-inverted signal of the output for a predetermined period of time. An integrator integrates the acceleration detection signal. A comparator inverts the state of an output signal when an integrated signal goes beyond a threshold. A fall determination processor outputs a signal out indicating that a fall has been detected in a situation in which, when the output of the monostable multivibrator is active, the state of the output of the comparator is inverted.

Abstract: A storage medium reproducing apparatus includes a storage medium that records data; a reproducing head that reads the data recorded in the storage medium; a positioning controlling unit that performs positioning control of the reproducing head with respect to tracks based on servo signals from the servo area included in the storage medium; and a reproducing processing unit that reproduces the data recorded in data area in the storage medium by reading recording dots of the data area using the reproducing head the position of which is decided on the tracks, wherein the reproducing head has a head width capable of simultaneously reading a plurality of servo dots.

Abstract: A track following control apparatus and method for a hard disk drive (HDD) is disclosed and includes an estimator receiving a position error signal from a HDA and generating estimated state information for a magnetic head in response to the position error signal, and a controller receiving the estimated state information and generating a control signal controlling operation of the HAD, wherein the estimator and controller are variably configured according to a write mode or a read mode.

Abstract: A magnetic disk apparatus including: a disk holding data as magnetic information on a magnetic recording film; a head to perform writing and reading of the magnetic information; a rotary actuator to move the head in a radial direction of the disk; plural heat elements in the head to locally heat the disk; a write element in the head to apply a magnetic field to the disk; and means for selecting at least one heat element from the plural heat elements, wherein the means for selecting the heat element selects at least one heat element from the plural heat elements so as to bring a center line of an area heated by the heat element and a center line of the position of the magnetic field generated by the write element into approximate correspondence, in correspondence with a relative angle between the head and a direction of movement of the disk.

Abstract: A magnetic recording-reproducing apparatus for recording or reproducing information on or from a magnetic recording medium constituted of plural recording areas containing sectors joined together, comprises a memorizing unit for memorizing information on positional deviation of the sectors at the boundary between adjacent recording areas, and a controlling unit for controlling movement of a magnetic recording head in accordance with the information on positional deviation in the memorizing unit when the magnetic recording head moves between the sectors at the boundary between adjacent recording areas.

Abstract: Embodiments of the present invention allow for controlling a microactuator based at least in part on an output of a temperature sensor. Also, embodiments of the present invention allow for adjusting a control of a microactuator so as to compensate for changes in a gain of the microactuator due to changes in temperature.

Abstract: A positioning control device executes disturbance observer control having a disturbance suppression function, wherein changes of control characteristics are prevented even if the disturbance frequency is suppressed. When a control value of an actuator is computed using estimated gains of the actuator and estimated gains of disturbance according to an estimated position error by disturbance observer control including a model of the actuator and model of the disturbance, the disturbance frequency is estimated according to the estimated position error, and the estimated gains of the actuator and the estimated gains of the disturbance, corresponding to the disturbance frequency, are changed. Therefore appropriate observer control according to the disturbance frequency can be implemented.

Abstract: Embodiments of mitigating the effects of disturbances of a disk drive are disclosed. One method includes sensing a position error signal of a transducer coupled to a surface of the disk drive, wherein the position error signal aids in control of an actuator of the disk drive. A first disturbance signal is generated by sensing a disturbance of a first sensor attached to the disk drive, wherein the first disturbance signal aids in control of the actuator. A second disturbance signal is generated by sensing a disturbance of a second sensor attached to the disk drive, wherein the second disturbance signal aids in control of the actuator. Effects of the disturbances on the position error signal are reduced by adaptively adjusting a gain of the first disturbance signal and a gain of the second disturbance signal.

Abstract: Embodiments in accordance with the present invention erase a desired area on a recording surface of disk or disk drive apparatus. According to an embodiment, a hard disk drive (HDD) performs erase on a recording surface by moving a head element unit at one-half a servo track pitch with reference to a servo address. Before actual erase is started on the recording surface, the HDD generates a management table configured based on servo addresses from a management table configured based on data tracks. At an erase process, the HDD sets parameters in accordance with the zone and skips a management area with reference to this management table based on the servo addresses.

Abstract: A control system including a filter module generates a filtered disturbance signal based on a disturbance signal and a transfer function of the filter module. A set point adjustment module generates an adjusted set point signal based on a set point signal and the filtered disturbance signal. A servo control module generates an error signal based on the adjusted set point signal and a position feedback signal. A filter adjustment module generates a filter adjustment signal based on the disturbance signal and the error signal. The filter adjustment signal adjusts the transfer function.

Abstract: A method determines RW head radial position relative to tracks within a magnetic data disc. This involves sensing both a S-burst signal and a P-burst signal with the RW head. The S-burst signal and P-burst signal are associated with a two-burst servo pattern on the magnetic disc. The S-burst pattern has a phase that remains constant radially across tracks within the magnetic disc. The P-burst has a second phase that rotates radially across tracks within the magnetic disc. By determining a phase difference between a sensed S-burst signal and P-burst signal, it is possible to determine the RW head radial position relative to the tracks on the magnetic disc.

Abstract: Methods of controlling a transducer that is adjacent to a rotatable data storage disk in a disk drive are disclosed, the disk drive having an actuator configured to position the transducer, a rotational acceleration sensor configured to generate a rotational acceleration signal, a position error sensor configured to generate a position error signal, and a controller configured to control the actuator to move the transducer to a target track during a seek operation. The methods include dynamically adjusting a gain factor in response to the position error signal and the acceleration signal during a settle period following the seek operation, multiplying the rotational acceleration signal by the gain factor to generate an adjusted rotational acceleration signal, and adding the adjusted acceleration signal to the position error signal to generate an adjusted position error signal, and moving the transducer in response to the adjusted position error signal.

Abstract: Provided are a bit patterned medium having a super-track, a method of tracking a track of the bit patterned medium, a head appropriate for the bit patterned medium, and an information recording/reproducing apparatus including the bit patterned medium and the head. The bit patterned medium includes a substrate, and a recording layer comprised of a plurality of bit cells which are formed on the substrate by being separated from each other, along a plurality of tracks. Each of the plurality of tracks includes a super-track comprised of a plurality of sub-tracks. Bit cells formed on a sub-track from among the plurality of sub-tracks in the super-track are disposed so as to deviate from bit cells formed on another sub-track from among the plurality of sub-tracks in the super-track. A track ID (identification) for recognizing the super-track, and a servo burst generating a position error signal when a head tracks the super-track, are arranged in an area of each of the plurality of tracks.

Abstract: A method and apparatus position a beam spot on a recording medium. The positioning includes (a) observing a first center error in a first closed loop control during tracking mode, the first center error including a repeatable run out (RRO) error, (b) estimating a center error (CE)-RRO from the first center error, the CE-RRO being part of the first center error caused by the RRO, (c) observing a second center error in a second closed loop control during a rough seek, (d) subtracting the CE-RRO from the second center error, (e) controlling the beam spot based on the second center error less the CE-RRO during the rough seek, and (f) adding an open loop control to the second closed loop control during the rough seek, the added open loop control inducing a motion of the lens relative to an optical center of the OPU during the rough seek.

Abstract: Positioning of a transducer is controlled in response to real and imaginary component signals that are formed from a position error signal (PES) which is indicative of the transducer location on a media.

Abstract: Embodiments in accordance with present invention provide a magnetic head and a magnetic disc drive capable of preventing a side erase while providing excellent recording characteristics. According to one embodiment, in order to prevent the side erase in an increased skew angle state, a first magnetic pole surface is formed in such a shape that the projection area of the first magnetic pole surface follows a track edge positioned on the boundary side in the track in the state where the first magnetic pole surface is positioned on the track at the innermost periphery thereof included in a first region. Likewise, to prevent the side erase in the increased skew angle state, a second magnetic pole surface is formed in such a shape that the projection area of the second magnetic pole surface follows a track edge positioned on the boundary side with respect to a track in the state where the second magnetic pole surface is positioned on the track at the outermost periphery thereof included in a second region.

Abstract: Embodiments of the present invention provide a perpendicular magnetic recording medium suitable for high density recording. According to one embodiment, a magnetic recording layer comprises four layers in which a first magnetic layer, a magnetic coupling layer, a second magnetic layer, and a third magnetic layer are formed above a substrate. The first magnetic layer and the second magnetic layer are perpendicular magnetization films containing an oxide, and ferromagnetically coupled with each other by way of the magnetic coupling layer, and they are, more preferably, a Co alloy layer containing an oxide. The third magnetic layer is ferromagnetically coupled with the second magnetic layer. The concentration of the oxide contained in the third magnetic layer is lower than the concentration of the oxide in the second recording layer, or the third magnetic layer does not contain the oxide.

Abstract: A system and method for a servo controller (SC) used in an embedded disk controller for adjusting stored servo skew values based on measured skew values is provided. The system includes, a servo timing controller, wherein the servo timing controller includes a first register that stores measured servo skew values at a given time; a first set of registers that receive stored skew values and the measured skew values; and firmware that adjusts the skew values based on the measured skew values measured by a reference timer. The process includes, measuring actual skew values during a head change in a read operation; comparing the measured skew values with the stored skew values; adjusting the skew value based on the comparison; and adjusting a servo field timer based on the adjusted skew value.

Abstract: In a magnetic disk device, oscillation occurring at a frequency higher than Nyquist frequency is suppressed. In one embodiment, a multi-late filter having a resonance point at a frequency higher than the intended Nyquist frequency is introduced in a previous stage of a controlled object. At that time, since a resonance characteristic of the multi-rate filter is aliased by a sampler, the multi-rate filter is designed such that the resonance point after the aliasing is stabilized in phase by a following compensator.

Abstract: Embodiments of the invention reduce the information (storage) overhead for determining the rotational position of a magnetic disk medium, as well as reducing the rotational position detection time. In one embodiment, a sector servo magnetic disk medium is configured such that: each track is divided into blocks each including a series of sectors; each block stores a positional information bit string as rotational position information; the positional information bit string is made up of a position code and an identification code, the position code including a block number, the identification code being used to identify the start or the end of the position code; and each bit of the positional information bit string is stored in a different sector of the block. When each block is made up of 12 sectors, for instance, if the block number is denoted as b0b1b2b3b4b5, the positional information bit string may be expressed as 00001b0b1b21b3b4b5, where the first 5 bits “00001” constitute an identification code.

Abstract: A positioning control device based on an observer control has a disturbance suppression function to which a disturbance suppression function is added without affecting the control characteristics of the observer. Models of an actuator and a disturbance model are separated, and for the disturbance model, state information is generated using an estimated gain determined from a disturbance model defined by a transfer function of which denominator is a numerator of a filter in which degrees of denominator and numerator for shaping a sensitivity function are the same, and the disturbance suppression value of the actuator is computed from the state information. The vibration of the head can be prevented adapting to a wide range of disturbance frequencies without affecting the control characteristics of the observer.

Abstract: Embodiments in accordance with the present invention provide a drive unit that is capable of satisfactorily performing the positioning control with disturbance components included in a position error signal being effectively controlled. According to one embodiment, an error signal generator of a drive unit generates a position error signal (PES) on the basis of servo data read out from a magnetic disk. On the assumption that a frequency of a periodic variation component included in the PES is a target frequency, if a target frequency deviates from an effective frequency range of a digital filter, a downsampler down-samples the PES, and then supplies the PES to the digital filter so that the effective frequency range is shifted. As a result, within the shifted effective frequency range, a setting changing unit can control a setting frequency of the digital filter so that the setting frequency follows the target frequency.

Abstract: In a settling judgment method for judging whether an object is settled in a target position, the settlement is judged accurately at high-speed. In a positioning device for controlling a position of an object using a position error between a target position and a current position, a plurality of judgment blocks, each of which has a different judgment slice value and continuous sample count, are created in a settling judgment block for judging whether the object is settled within the positioning accuracy range of the target position, the judgment value of the position error computed by the judgment formula is judged in each judgment block each having a different judgment slice value and continuous sample count respectively, and OR of the judgment results is output. According to the settling judgment formula, settling can be judged accurately at high-speed, and both improvement of positioning accuracy and high-speed judgment can be implemented.

Abstract: A post-assembly head/disk offset adjuster is disclosed. One embodiment provides a housing and at least one disk coupled with the housing. In addition, an adjustable pivot plate is coupled with the housing such that access to at least one adjustment point of the adjustable pivot plate is provided regardless of a state of assembly of the hard disk drive. Furthermore, an actuator is coupled with the adjustable pivot plate. In so doing, an adjustment to the at least one adjustment point of the adjustable pivot plate results in an adjustment to the actuator regardless of the state of assembly of the hard disk drive.

Abstract: Embodiments of the present invention provide a magnetic disk drive, in which a disturbance component contained in an output signal from a rotational vibration detector, can be appropriately suppressed irrespective of frequency of the component, and a method of controlling the drive. According to one embodiment, in a magnetic disk drive having a rotational vibration detector for detecting rotational vibration of a drive housing, a main control circuit performs a head moving step of driving a voice coil motor to move a magnetic head on a magnetic disk, a frequency estimation step of estimating a frequency of each disturbance component contained in an output signal from the rotational vibration detector after moving the magnetic head, and a suppressor setting step of setting a notch filter for suppressing the disturbance component based on the estimated frequency.

Abstract: A patterned disk medium includes a disk-shaped flat substrate including a first surface and a second surface located an opposite side of the first surface. First servo pattern areas including portions provided with magnetic members and portions provided with no magnetic members are provided on the first surface. Second servo pattern areas including portions provided with magnetic members and portions provided with no magnetic members are provided on the second surface. The magnetic members of the first and second servo pattern areas are magnetized in a direction perpendicular to the first and second surfaces. The magnetic polarity of the surfaces of the magnetic members of the second pattern areas differs from that of the surfaces of the magnetic members of the first pattern areas.

Abstract: An apparatus, system, and method are disclosed for writing magnetically encoded data. A servo module positions a write head relative to a first land such that a first edge of the write head is positioned substantially over a first land edge of the first land. The write head has a radial width greater than the sum of a radial width of the first land and radial widths of interior and exterior grooves such that the write head is also positioned over at least a portion of a second adjacent land. The write head writes magnetically encoded data to the first land. The servo module further positions the write head relative to a second land such that the first edge of the write head is positioned substantially over a second land edge of the second land and the write head is not positioned over the first land.

Abstract: Embodiments of the present invention provide a magnetic disk device and a method for production thereof, the magnetic disk device being characterized in that the magnetic disk therein permits a plurality of tracks thereon to record correction data when necessary without decreasing its storage capacity. According to one embodiment, the magnetic disk device is characterized in that the magnetic disk has the first tracks and the second tracks formed thereon, the first tracks having servo data regions arranged cyclically, with a portion of a region between them being the correction data region and the remaining regions being the user data region, and the second tracks having the servo data regions arranged cyclically, with the region between them being the user data regions, and the multiprocessing unit (MPU) switches the servo extraction timing of the position information sampler depending on whether the track for servo reproduction by the magnetic head is the first track or the second track.

Abstract: A head position control device uses a current observer control which performs two degree of freedom control, with which a current step difference due to the difference of eccentricities between heads is prevented without affecting the seek waveform after switching heads. The head position control device has a locus generation section, which calculates an initial value of the correction locus for canceling the current step difference of the output current based on an output current supplied to an actuator before switching, and an eccentricity correction current and initial velocity of another head after switching; and a two degree of freedom control system to which a seek locus is input, and supplies a correction locus according to the initial value to the two degree of freedom control system. One parameter can correct the initial velocity and the current step difference.

Abstract: A noise canceling system includes a signal generator module that generates a set point signal based on a desired position signal and a position feedback signal, a summation module that generates an output control signal based on the set point signal and a correction signal, and a filter module that generates the correction signal based on a disturbance signal and that minimizes a correlation between the disturbance signal and an error signal. The error signal represents a difference between the desired position signal and the position feedback signal.

Abstract: The invention applies to servo controllers for at least the voice coil motor of a hard disk drive. Today, many control algorithms require 80 to 90 percent of the sampling period to complete their calculation of the next control, making computation time delay no longer negligible. The invention accommodates the transport delay, such as computation time delay, into the state estimator and into the whole control system. Experimental results using a commercial hard drive, as well as simulation results, show that the invention's method effectively improves the hard disk drive control system stability by increasing the phase margin and gain margin. The invention includes the method of operating the servo-controller, as well as the apparatus implementing that method. The invention also includes hard disk drives containing servo-controllers implementing the method, and program systems residing in accessibly coupled memory to a computer within the servo controller implementing the method.

Abstract: According to embodiments of the present invention, tracks can be formed on a magnetic recording medium on a zonal area at intervals of either a first track pitch or a second track pitch, both of which differ from each other. For a reference track defined in each zonal area, regardless of whether tracks are formed with the first track pitch or the second track pitch, the first track pitch and the second track pitch are specified so that a head position at the time of writing or reading information to or from the reference track, is common to both of the first track pitch and the second track pitch.

Abstract: In general, the invention is directed to servo techniques that utilize servo patterns to facilitate head positioning relative to the data tracks. For example, the servo techniques may include a first series of servo patterns configured to allow calculation of a position error signal that substantially mitigates error resulting from a variation in velocity of the data storage tape during detection of the at least one of the servo patterns in the first series. The servo techniques may also include a second series of servo patterns interleaved within the first series of servo patterns in order to encode data. The encoded data may include linear position information. Embodiments may allow a data storage tape meeting a currently accepted data storage tape specification, e.g., an LTO Ultrium specification, to record data in a higher density than currently implemented with the specification.

Abstract: Stable recording and reproduction of data onto and from a recording medium that requires precise tracking is provided by using a simple head tracking mechanism. In a hard disk drive (200), a piece of sector data to be written or read is pre-associated with a sector number of a sector where the piece of sector data is to be written or read. A seek control unit (260) corrects first-order run-out relative to a revolution axis of a DTM magnetic disk (100) and permits second-and-higher order run-out relative to the revolution axis, and moves a read/write head (122, 124) gradually in one radial direction of the DTM magnetic disk at a shift pitch smaller than the track pitch for each revolution in accordance with the sector numbers of the sectors where pieces of sector data are to be written or read, within a range of tracks containing the sector numbers of the sectors where the pieces of sector data are to be written or read.

Abstract: Embodiments of the present invention help to achieve a read error recovery, and suppress decreases in the capacity of the disk drive device and degradation in performance. In one embodiment, a hard disk drive (HDD) performs following control without use of repeatable run-out (RRO) compensation information on a magnetic disk in a normal reading process. When an error occurs in a normal reading process, the HDD moves a read element to a position different from a target position of the normal reading process. At the position where the read element has been moved, the read element reads out the RRO compensation information. In a recovery procedure for the reading process where the error has occurred, the HDD performs following control with compensation by the servo compensation information read out by the read element.

Abstract: A method determines RW head radial position relative to tracks within a magnetic data disc. This involves sensing both a S-burst signal and a P-burst signal with the RW head. The S-burst signal and P-burst signal are associated with a two-burst servo pattern on the magnetic disc. The S-burst pattern has a phase that remains constant radially across tracks within the magnetic disc. The P-burst has a second phase that rotates radially across tracks within the magnetic disc. By determining a phase difference between a sensed S-burst signal and P-burst signal, it is possible to determine the RW head radial position relative to the tracks on the magnetic disc.

Abstract: System and method for generating a Position Error Signal (PES) reference curve in data storage devices are provided. The method includes scanning a distance of at least one Track Pitch (TP) in a cross-track direction in each servo-burst along a predefined path. One or more TPs in each servo-burst are scanned with a read head. The method further includes, calculating a plurality of samples of each differential signal. A differential signal corresponds to a first read-back signal and a second read-back signal. Thereafter, a plurality of normalized signals are determined. A normalized signal is determined by dividing each sample of the differential signal with a normalization constant. The plurality of normalized signals are combined to generate the PES reference curve.

Abstract: Embodiments of the present invention provide a data recording device capable of achieving desired performance while increasing the convergence rate. According to one embodiment, in a data recording device, an update-width determination unit included in a setting updating unit determines an update-width of a set frequency ƒ in a digital filter according to the size of a position error signal PES, and an update-width adjuster included in the setting updating unit changes the update-width of the set frequency ƒ determined by the update-width determination unit according to the size of the set frequency ƒ. Thus, while the convergence rate being kept properly, the set frequency ƒ can precisely be converged on a frequency of a disturbance component.

Abstract: Methods of controlling reading/writing by a read/write head of a disk drive include generating a position error signal indicative of a displacement of the read/write head from a desired radial location on a surface of a data storage disk. A control signal for moving the read/write head to the desired location is calculated responsive to the position error signal. Writing by the read/write head is inhibited responsive to the control signal exceeding a control signal threshold value. A disk drive includes a controller configured to generate a position error signal indicative of a displacement of a read/write head from a desired location on a surface of a disk, and to generate a control signal for moving the read/write head to the desired location. The controller is further configured to inhibit writing by the read/write head responsive to a predictive metric that is predictive of the position error signal exceeding a threshold.

Abstract: A hard disk drive with a circuit that provides a control signal to a voice coil motor to move a head across a disk. The disk drive includes a circuit that provides a control signal to the voice coil motor to move the head. The circuit also has a state predictor and an inversion filter that compute a vibration estimate used to detect a vibration in the drive. When a threshold vibration is detected a vibration estimate is combined with the control signal to compensate for the vibration. The circuit detects the vibration without the need for an accelerometer or other sensor.

Abstract: A head is moved in a lateral direction on the boundary between a separation track and a recording track on a recording medium. The separation track isolates the adjacent recording tracks from each other. A variation is detected in the output supplied from the head based on the recording track. Positional information indicating the position of the head is generated based on the variation. The output supplied from the head varies in response to the movement in the lateral direction, namely the elapsed time. The positional information can thus be generated based on the variation in the output. The generated positional information contributes to an accurate positioning in a facilitated manner. Moreover, information required to position the head can be omitted from the recording medium. The processes can be simplified in the production of the recording medium. The operation time can thus be shortened.

Abstract: A waveform generator generates an acceleration orbit, a velocity orbit, and a position orbit from the seek time. Each orbits multiplied by respective gains, whereupon the orbits are synthesized by a first adder. The resulting composite orbit is multiplied by a seek distance and then passed through a FIR filter to obtain the target position orbit that is to be applied to the later-stage two-degree-of-freedom control system. The two-degree-of-freedom control system has a characteristic whereby it is able to approximate a second-order low-pass filter.

Abstract: Embodiments of the invention provide a disk drive capable of writing information on data tracks even more positively when a shingle write method is adopted. In one embodiment, the disk drive is characterized in that, when information is to be written on a plurality of adjacent data tracks on a recording medium through the shingle write method, writing of information is controlled by detecting an actual writing position based on servo information recorded on the recording medium and determining whether or not the detected actual writing position meets a predetermined condition.

Abstract: According to one embodiment, a servo writing apparatus that writes a multi-spiral servo pattern to a disk medium is disclosed. The apparatus has a servo controller that generates a servo clock determining a head seek start timing, a servo pattern generator that generates a sector index pulse determining the interval at which a multi-spiral servo pattern is written to the disk medium, a clock phase difference measuring unit that measures a phase difference between the servo clock and the sector index pulse, and a controller that adjusts the measured phase difference.

Abstract: A self-servowriting (SSW) method that, with the actuator fully engaged against a compliant structure (e.g., a crashstop), first writes a tightly-spaced open-loop sequence of servo bursts in a segmented spiral path and then continues writing this tightly-spaced sequence under closed-loop servo control while reading back amplitude information from the servo bursts written earlier until the tightly-spaced burst pattern extends over several read-write head (RWH) offset intervals. With the actuator still engaged against the compliant structure, this tightly-spaced startup sequence is then read back by the closed servo control loop to write a number of concentric servo seed tracks, which are then self-propagated across the remainder of the disk surface to produce a final servopattern.