Abstract: According to one embodiment, a disk drive includes an actuator, a servo controller, a calculation module and an adjustment module. The actuator is configured to move the head over a disk, in the radial direction of the disk. The servo controller is configured to make the head move along a target orbit on the disk, in accordance with the distance the actuator has been moved. The calculation module is configured to calculate, as disk runout, a virtual target orbit value supplied to the servo controller to suppress the disturbance at the target orbit. The adjustment module is configured to multiply the virtual target orbit value by a gain that has been preset.

Abstract: A method of operation of a data storage system includes: providing a disk having a reference servo; and positioning a read/write head over the disk with the reference servo including: collecting a raw phase error, estimating a phase delay error, estimating an estimated written-in error with the phase delay error subtracted from the raw phase error, calculating a remaining error based on the estimated written-in error, and adjusting a self-servo-writing clock based on the remaining error.

Abstract: Drive waveforms with which extension and contraction characteristics of an actuator corresponding to a number of track eccentricity amounts are stored as data. By reading servo information written in a disk is obtained as a signal indicating a head displacement amount from a track. The head is moved in a direction in which the track is displaced by obtaining an amplitude corresponding to a slip amount of the head position and a rotation angle of maximum eccentricity, reading drive waveforms which is optimal in driving the actuator from the memory and driving the actuator with a drive waveform matched with the rotation angle at which the eccentricity is maximum.

Abstract: Various embodiments of the present invention provide systems and methods for recovering data from a storage medium. As an example, a data recovery circuit is disclosed that includes: a controller circuit, a data processing circuit, a selector circuit, and a combining circuit. The controller circuit is operable to position a sensor over a track of the storage medium at a first distance from the center of the track to yield a first data set, and to position the sensor over the track of the storage medium at a second distance from the center of the track to yield a second data set. The data processing circuit is operable to process a processing data set, and the selector circuit is operable to select between the first data set and a combined data set as the processing data set. The combining circuit is operable to combine the first data set with at least the second data set to yield the combined data set.

Abstract: A storage medium has a first servo field having magnetic lands separated by nonmagnetic areas, the magnetic lands of the first servo field having a unipolar pattern. The medium further includes a second servo field having magnetic lands separated by nonmagnetic areas, the magnetic lands of the second servo field having a bipolar pattern.

Abstract: A storage system includes a first buffer configured to store a first repeatable runout profile (RRP) for a sector of a rotating storage medium. A second buffer is configured to store a second RRP for the sector. A controller: controls a servo of the rotating storage medium based on the first RRP during a first revolution of the rotating storage medium; and learns the second RRP (i) while operating in a track-following mode, and (ii) during the first revolution. The controller ceases learning of the second RRP when one of (i) the controller is operating in a seek mode and (ii) the rotating storage medium is in an off-track state. Subsequent to the first revolution of the rotating storage medium and based on whether the learning of the second RRP was stopped during the first revolution, the controller replaces the first RRP with the second RRP in the first buffer.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo sectors that define a plurality of servo tracks. The servo sectors comprise a plurality of servo bursts including a first servo burst, a second servo burst following the first servo burst and offset radially by approximately one half of a servo track from the first servo burst, a third servo burst following the second servo burst and offset radially by approximately one full servo track from the second servo burst, and a fourth servo burst following the third servo burst and offset radially by approximately one half of a servo track from the third servo burst. A PES is generated form the servo bursts that is substantially insensitive to a radial velocity of the head.

Abstract: A method for writing servo onto a disk of a hard disk drive. The method includes writing a plurality of spiral servo signals with a head. The spiral servo signals are used to generate position error signals and write a plurality of servo patterns. A write current of the head is varied for at least one servo pattern. A PES/WC relationship between the position error signals and the write current is determined and a plurality of final servo patterns are written by utilizing the PES/WC relationship and varying the write current. Varying the write current changes the trailing edge of the servo bits and controls the position of the track center. The PES/WC relationship allows the system to compensate for excursions within a single revolution of the disk.

Abstract: According to one embodiment, a disk device comprises a memory, detector, calculation module, and deactivation module. The memory is configured to store an offset control amount at a time of manufacture. The detector is configured to detect a disk run-out. The calculation module is configured to obtain an offset control amount when the detector detects the disk run-out. The deactivation module is configured to deactivate the offset control based on a difference between the offset control amount obtained by the calculation module and the offset control amount at a time of manufacture stored in the memory and based on the offset control amount obtained by the calculation module.

Abstract: Patterned discrete track magnetic media compatible with the constraints imposed by the use of self-assembly technology are described in which the PES servo portion of each servo sector has at least one offset segment used for the position error signal (PES). The downtrack length of the PES offset segment systematically varies according to the track position to encode information about the track position usable by the servo system. The downtrack length of the offset segment and, therefore, the time between the corresponding signal shifts is systematically varied from the inner diameter (ID) to the outer diameter (OD) according to the track position to provide coarse information to the servo system even if part of the track ID code cannot be read. Alternative embodiments include a preamble timing mark formed by another offset segment. A self-servo writing method is described using the preamble timing marks.

Abstract: A magnetic head-positioning servo system is provided to accurately test a magnetic disk with a track written in advance, by providing two fine actuators. The second fine actuator, to which a magnetic head is attached, is mounted on the first fine actuator. The second fine actuator has a larger generating displacement than a generating displacement of the first fine actuator, and lets the magnetic disk to follow the eccentricity of the track. In this way, the positioning accuracy can be increased.

Abstract: Methods, apparatuses, and systems implementing analog techniques to decode signals extracted from servo wedges of computer-readable storage media. A digital signal representing a repeatable runout (RRO) signal included in an analog signal of a computer-readable storage medium is obtained. The RRO signal includes a preamble that represents a magnitude of the RRO signal, and data. The digital signal includes a digital representation of the preamble. An estimate of the magnitude of the RRO signal is determined based on the digital representation. The estimate is compared with a specified level to generate an error signal based on a difference between the two. The provision of the error signal, for application to a subsequent RRO signal of the computer-readable storage medium, is delayed. The RRO signal is amplified prior to being represented as the digital signal to match a value established to decode the RRO signal.

Abstract: A method and apparatus is described for reducing RRO in storage systems. A disc may be partitioned into a number of equally spaced sectors. An RRO profile may be individually obtained for each sector, a runout control algorithm may be applied to each sector to generate an RROC waveform for the sector to suppress the RRO, and sector RROC waveforms may be assembled into an RROC waveform for a whole revolution and saved in a memory buffer for feed-forward control. The RROC is performed in the time domain, and it may be adapted for each sector to reject the RRO disturbance.

Abstract: A magnetic storage apparatus has a reproducing head to reproduce information from a perpendicular magnetic recording medium that is recorded with servo information, eccentricity correction data and read/write data. The apparatus further has a filter part to filter a reproduced output of the reproducing head by filtering the servo information which has a differentiated waveform by a non-differentiating characteristic and by filtering the eccentricity correction data and the read/write data which have rectangular waveforms by a differentiating characteristic, a demodulating part to demodulate the servo information, the eccentricity correction data and the read/write data that are filtered by the filter part, and a servo system to carry out a control process including an eccentricity control based on the servo information and the eccentricity correction data that are demodulated.

Abstract: Methods, systems and computer program products for compensating repeatable run-out (RRO) are described. In some implementations, RRO may be compensated by predicting the RRO and subsequently subtracting the predicted RRO from the actual value of the RRO to cancel out the undesired effect caused by the RRO during operation. More specifically, RRO generated at each spindle motor rotation may be predicted by measuring the position errors associated with the RRO with respect to a current position of a read/write head. A computational model then may be utilized to determine one or more correction factors to compensate for the RRO.

Abstract: A hard-disk drive. The hard-disk drive includes a magnetic-recording disk in which tracks adjacent to each other are magnetically separated, a spindle motor which drives the magnetic-recording disk, a magnetic-recording head equipped with write element and read element, an actuator for positioning the magnetic-recording head on a predetermined track on the magnetic-recording disk, and a control unit. The control unit is configured to store information about an over-write-only track that is provided for a plurality of tracks including n consecutive tracks in at least a partial radial area of the magnetic-recording disk and an offset amount. In a radial area of the magnetic disk where the over-write-only track is located, the control unit is configured to record with an offset by an offset amount from a center of a track toward the over-write-only track with respect to n?1 tracks of the plurality of n tracks, excluding the over-write-only track.

Abstract: According to one embodiment, a position control apparatus includes: a digital control module that performs position control including disturbance adaptive control with a predetermined sampling period with the use of a control constant, in accordance with a position error between a target position and a current position of the object; and a table that stores the control constant corresponding to a value of sin(?T/2), wherein the digital control module determines a control value of the actuator in accordance with the position error, calculates the value of sin(?T/2) according to an adaptive law from a signal based on the position error, reads the corresponding control constant from the table in accordance with the calculated value of sin(?T/2), and updates the control constant.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo sectors defining a plurality of tracks, wherein the servo sectors are written to the disk by servoing off of spiral tracks. The head is positioned over a target track in response to the servo sectors, and coefficients of a first sinusoid are generated corresponding to the target track, wherein the first sinusoid corresponds a repeatable position error of the head relative to the target track. The coefficients of the first sinusoid comprise a coherent component due to a repeatable runout of the disk and a spiral component due to writing the servo sectors by servoing off of the spiral tracks, where the spiral component varies based on a radial location of the head. The head is servoed over the target track in response to the coefficients.

Abstract: In a disk drive, a modified adaptive runout compensation algorithm is employed to measure non-coherent repeatable runout (RRO) of a track. The adaptive runout compensation algorithm is used to control the transducer head to follow the average RRO of adjacent tracks during the process of computing correction factors for non-coherent RRO for a given track. The adaptive runout compensation algorithm does not completely adapt to both the coherent and non-coherent RRO of a particular track because the transducer head is positioned over any one particular track for only a limited number of revolutions.

Abstract: According to one embodiment, a position control apparatus includes: a digital control module that performs position control including disturbance adaptive control with a predetermined sampling period using a control constant, in accordance with a position error between a target position and a current position of the object; and a table that stores the control constant corresponding to a value of sin(?T) or cos(?T), wherein the digital control module is configured to determine a control value of the actuator in accordance with the position error, calculates the value of sin(?T) or cos(?T) according to an adaptive law from a signal based on the position error, reads the corresponding control constant from the table in accordance with the calculated value of sin(?T) or cos(?T), and updates the control constant, to perform the position control including the disturbance adaptive control.

Abstract: The eccentricity of tracks defined on a rotating bit patterned media are measured using a readback signal, and the measured eccentricity may be used to control centering of the disk relative to a rotational spindle and/or to control movement of a read/write head relative to a selected track on the disk.

Abstract: A system including a self-servo-write, a position measuring module, and a compensation module. The self-servo-write module is configured to position a head of a hard disk drive to write a first set of servo wedges on a magnetic medium of the hard disk drive. The position measuring module is configured to measure a first position of the head when the head writes the first set of servo wedges on the magnetic medium. The compensation module is configured to generate first data to compensate a repeatable error based on the first position of the head measured by the position measuring module. The first data to compensate the repeatable error is written on the magnetic medium along with the first set of servo wedges.

Abstract: According to one embodiment, a position control apparatus includes: a digital control module that performs position control including disturbance adaptive control with a predetermined sampling period using a control constant, in accordance with a position error; and a table that stores the control constant corresponding to one of values sin(?T), cos(?T), and sin(?T/2), wherein the digital control module determines a control value of the actuator in accordance with the position error, calculates a value of one of estimated errors of sin(?T), cos(?T), and sin(?T/2) according to an adaptive law from a signal based on the position error, multiplies the calculated estimated error by an adaptive gain in accordance with a value of the angular frequency ?, updates one of the values, reads the corresponding control constant from the table based on the updated value, and updates the control constant.

Abstract: In a servo control loop, phase detection between a clock signal and servo burst fields on a movable storage media is carried out with compensation for phase error and frequency error in the timing of servo burst fields.

Abstract: A disk drive is disclosed comprising a disk having a plurality of servo tracks that define a plurality of data tracks, and a head actuated over the disk by a voice coil motor (VCM), wherein the head comprises a read element offset radially from a write element. The read element is positioned over a first servo track and the write element is positioned over a second servo track, and a first repeatable runout (RRO) of the first servo track is measured. The read element is positioned over the second servo track, and a second RRO of the second servo track is measured. A data center off-track is computed in response to the first RRO and the second RRO.

Abstract: In a position control device having a disturbance suppression function, loop gain is calibrated without stopping disturbance suppression control. The position control device has, for disturbance suppression control, a feedback controller for changing the loop characteristic, a table for storing a target gain according to a disturbance frequency, and a gain calibration section for calibrating open loop gain. The gain is calibrated using a target gain in the table according to the change of the loop characteristic of the feedback controller. Open loop gain can be calibrated without interrupting the disturbance suppression control, so the open loop gain can be accurately calibrated without being affected by disturbance, and accurate position control is possible.

Abstract: A control system is configured to receive an input signal. The control system includes a control module to generate an output signal that tracks the input signal to the control system. The output signal includes a repeatable disturbance component. A compensation module is configured to receive an error signal. The error signal corresponds to a difference between the input signal and the output signal. The compensation module is configured to generate an estimate of the repeatable disturbance component based on the error signal, and to combine the estimate with the input signal to compensate for the repeatable disturbance component associated with the output signal.

Abstract: An amplifier amplifies, according to a first gain value, a first input signal acquired by reproducing first information from first areas having the first information recorded therein area by area in order. The amplifier also amplifies, according to a second gain value, a second input signal acquired by reproducing second information pursuant to reproduction of the first information, from a second area adjacent to the first area and that has the second information recorded at a recording level different from that of the first information. When the first input signal is amplified, a first gain value following a change in the first signal is calculated so that the level of the amplified signal becomes constant. When the second input signal is amplified, a second gain value following a change in the first gain value is calculated so that the level of the amplified signal becomes constant.

Abstract: Embodiments of the present invention provide a magnetic disk drive capable of easily suppressing degradation of position error caused by disturbance resulting from vibration from the outside. According to one embodiment, the magnetic disk drive acquires, during a period of time of track following control, data necessary for determining a filtering characteristic required to newly be specified in a peak filter; in association with the start of subsequent seek control, determines the filtering characteristic required to be specified in the peak filter; and specifies the determined filtering characteristic in the peak filter.

Abstract: In described embodiments, effects of frequency and phase error introduced at the outer diameter or inner diameter of the disk when a read head is used to maintain timing lock while the write head is used to write new data might be eliminated with a simple compensation circuit. Compensation circuits, modules or methods receive as input information i) write head radial position (e.g., from a wedge number that indicates the circumferential position of the heads), and ii) read head and write head relative physical offset.

Abstract: Monitoring of the eccentricity of a pre-formatted servo pattern on a disk.

Abstract: A method for determining runout disc is disclosed. The method comprises: focusing on a focal point on a disc; driving the disc to spin the disc; generating a crossover signal according to a track of the disc crossing the focal point; and determining that the disc is a runout disc when the frequency of the crossover signal exceeds a pre-determine value.

Abstract: Data is written to a hard disk drive using shingled writing principles, i.e., each data track is partially overwritten when an immediately contiguous data track is written. One or more contiguous data tracks establish a hand, and a band establishes a respective segment in a log-structured file system.

Abstract: A servo control system configured to position a head in accordance with position error signals between servo data on a disk read by the head in a servo sampling cycle and a target position. The system includes a plurality of adaptive peak filters connected in parallel configured to filter the position error signals and configured to change filter coefficients adaptively, and an estimator configured to estimate head vibration caused by disturbances using the servo data read by the head. The system further includes a selector configured to select a portion of the plurality of adaptive peak filters at preset occasions, and a setter configured to update coefficient settings of the portion of the adaptive peak filters selected by the selector in accordance with an estimation by the estimator.

Abstract: A recording processing unit sets a track pitch narrower than a writing width of a recording element so that part of the recorded track overlapped with the unused track is overwritten, and continuously records information on a disk medium toward one direction in accordance with the track pitch. A first offset correcting unit reads a write/read offset from a storage table, in which the write/read offset is measured and saved in advance, and corrects the write/read offset in the state that a reading element is positioned at a target track. A second offset correcting unit corrects a write-once center offset, which is a positional deviation between a read center position of the reading element, which has undergone correction of the write/read offset by the first offset correcting unit, and a center position of an effective track width caused by write-once recording.

Abstract: An apparatus, system, and method are disclosed for the cancellation of repeatable runout signals. A signal processing module receives a position error signal and outputs a position compensated signal. A feed forward module receives the position error signal and outputs one or more cancellation signals to cancel one or more repeatable runout components from the position error signal when combined with the position compensated signal. A combining module combines the position compensated signal and the cancellation signals into a position command signal. A feedback module receives the position command signal and outputs the position error signal.

Abstract: In a disk drive, a wedge-based scheme is used to determine wedge offset correction values for a track of the disk drive. Correction values for the offset of each servo wedge are calculated wedge-by-wedge, based on the position error signal (PES) of the most recently measured servo wedge in combination with the measured PES of other servo wedges. To minimize transport delay of the servo, the majority of servo-control calculations may be pre-calculated prior to measuring the PES at the current wedge. Wedge offset correction values for a given servo wedge are corrected iteratively with each revolution of the storage disk.

Abstract: Various embodiments of the present invention are generally directed to adaptively determining an updated repeated runout (RRO) correction value to correct for RRO error in the placement of a servo seam, by iteratively combining a weighted initially estimated RRO correction value for the seam with a position error signal (PES).

Abstract: A method for repairing at least one defective servo segment of a servo sector having at least one defective servo track written on a magnetic recording media. The method comprises mapping the magnetic recording media for locations of the defective servo segment of the servo sector. A non-defective segment of the servo sector is replicated at least once on the magnetic recording media in a customer data zone, thereby creating at least one good servo segment copy of the servo sector. The good servo segment copy is propagated through the customer data zone associated with the defective servo segment. The good servo segment copy is copied onto the magnetic recording media previously occupied by the defective servo segment of the servo sector.

Abstract: In a method for implementing track shape control during a self servo-write process, an error in a targeted path for writing servo data onto a first track of a disk is detected. The error is correlated with a second error for a targeted path in a previously written track of the disk. A correction is generated for a feed-forward signal used to position a writing element which is used to write servo data for a subsequent track of the disk.

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: Some of the embodiments of the present disclosure provide a disk drive system comprising a disk drive system comprising a disk having a track upon a surface of the disk, the track including a first data-storing sector and a second data storing sector, and a servo sector located between the first data-storing sector and the second data-storing sector, the servo sector including a first flying height (FH) field having a predetermined pattern. Other embodiments are also described and claimed.

Abstract: A head position control method controls the position of a head by correcting components synchronizing rotation of a disk based on the head control amount. A correction signal for components synchronizing rotation is generated by using a filter function. The filter function that integrates the sine and cosine terms of DFT and inverse DFT and forms multiply of the complex values a(m) and b(m) and sine and cosine for frequency conversion, is measured in advance. The complex values are the m degree of RRO frequencies having frequency characteristics to be multiplied (1+C(z) P(z)) or ?(1+C(z) P(z)/P(z)).

Abstract: In a dual-stage actuator magnetic drive having a coarse actuator and a fine actuator, an amplitude level of a command signal for the fine actuator during a decoupling-path control depends on a gain of an applied fine actuator model. The fine actuator model gain depends on the amplitude level of the fine actuator command signal and needs to be calibrated to avoid performance degradation. The gain is calibrated by determining a deviation of the fine actuator model gain from the fine actuator gain during decoupling-path control. This deviation is obtained by comparing gain values of the open-loop transfer functions measured for the decoupling-path control case and the single coarse actuator control case with respect to the feedback loop of the coarse actuator at an excitation signal frequency, when the excitation signal is added to the coarse actuator.

Abstract: A disk drive. The disk drive includes a head, a motion mechanism, and a controller. The head is configured to access a disk configured to store data. The motion mechanism is configured to move the head. The controller is configured to determine a seek direction when an error occurred; and, the controller is configured to repeat a seek as a repeat seek to a target radial position from a direction opposite to the seek direction in an error-recovery process for the error which occurred in the seek in which the head moved to the target radial position.

Abstract: Embodiments of the present invention provide a disk drive capable of appropriately measuring non-linearity in a head position control system, and a control method therefore. According to one embodiment, a magnetic disk drive inputs a reference signal SR into a voice coil motor, inputs into the voice coil motor a control signal SC in which a harmonic component resulting from the reference signal SR is suppressed, and measures an error signal PES that may be obtained in the state where the reference signal SR and the control signal SC, in which the harmonic component is suppressed, are input in the voice coil motor.

Abstract: A magnetic disk device includes a head that reads position information, a position-information correction value for correcting the position information, and an error correcting code for the position-information correction value from a storage medium; a microcontroller unit (MCU) and an error check and correct (ECC) circuit for correcting an error in the position-information correction value based on the error correcting code; and a static var compensator (SVC) that performs position control based on either one of the position-information correction value read by the head and the position-information correction value with the error corrected by the MCU and the ECC circuit, and the position information read by the head so that the head is located at a target position on the storage medium.

Abstract: There is provided with a positioning control system which includes: a head moving unit configured to move a head for recording or reproducing information with respect to a disk capable of recording information; a position detecting unit configured to detect a position of the head; an error detecting unit configured to detect a position error signal of a detected head position with respect to a predetermined target position; a compensation controller configured to generate control input by performing phase lead compensation and phase delay compensation for the position error signal and supply the control input to the head moving unit; and a gain controller configured to control at least one of gains the phase lead compensation and the phase delay compensation based on frequency components contained in the position error signal and an amplitude of the position error signal.

Abstract: In a servo control loop, phase detection between a clock signal and servo burst fields on a movable storage media is carried out with compensation for phase error and frequency error in the timing of servo burst fields.

Abstract: A system includes a servo writing module, a position measuring module, and a compensation module. The servo writing module writes a first set of servo wedges on a magnetic medium of a hard disk drive (HDD) using a head of the HDD. The position measuring module measures a position of the head when the head writes the first set of servo wedges and generates a first measured head position. The compensation module generates first compensation data based on the first measured head position to compensate a repeatable error component of the first measured head position. The servo writing module writes the first compensation data on the magnetic medium when writing the first set of servo wedges and writes second compensation data generated based on the first set and the first compensation data read from the magnetic medium when writing a second set of servo wedges on the magnetic medium.