Abstract: A self servo-write process in performed on two or more recording surfaces simultaneously. In a dual-stage servo system, a first fine positioning servo system that includes a first microactuator independently controls the position of a first read/write head over a first recording surface of a hard disk drive, while a second fine positioning servo system that includes a second microactuator independently controls the position of a second read/write head over a second recording surface of the hard disk drive.

Abstract: A data storage device is disclosed comprising a voice coil motor (VCM) having a resonance frequency, a first disk surface comprising a first set of servo sectors written at a frequency less than twice the VCM resonance frequency, and a second disk surface comprising a second set of servo sectors circumferentially offset from the first set of servo sectors and written at a frequency less than twice the VCM resonance frequency. An access of the first disk surface is performed by reading at least one of the first set of servo sectors to generate a first position error signal (PES), reading at least one of the second set of servo sectors to generate a second PES, and controlling the VCM based on the first PES and the second PES to position a first head over the first disk surface while accessing the first disk surface.

Abstract: A control system for a power steering system includes an error module that generates an error signal based on a difference of an estimated output vector and an output vector, a scaling module that calculates a feedback correction signal based on the error signal and an observer gain value, an extended state vector estimation module that determines an extended state vector estimate based on the feedback correction signal and a motor torque command, and a gain module that applies a gain to the extended state vector estimate to generate an estimated driver torque signal, the estimated driver torque signal is applied in control of the power steering system.

Abstract: A control system for a power steering system includes an error module that generates an error signal based on a difference of an estimated output vector and an output vector, a scaling module that calculates a feedback correction signal based on the error signal and an observer gain value, an extended state vector estimation module that determines an extended state vector estimate based on the feedback correction signal and a motor torque command, and a gain module that applies a gain to the extended state vector estimate to generate an estimated driver torque signal, the estimated driver torque signal is applied in control of the power steering system.

Abstract: A storage device includes read circuitry having a read head having a detector that outputs signals representing data from a first track and an adjacent track. The read head is subject to off-track excursions during which the read head detects signals from both the first track and an adjacent track. Data on each track includes a preamble including a repeating pattern. The repeating pattern in any first track is orthogonal to the repeating pattern in any track adjacent to the first track. The read circuitry also includes respective Discrete Fourier Transform circuits to identify components in the signals corresponding to respective frequencies characteristic of the repeating pattern on the first track and the repeating pattern on the second track, and computation circuitry to determine from the components a ratio by which the read head is off-track. Corresponding methods are provided for operating such a storage device and for reading data.

Abstract: A tape drive-implemented method, according to another embodiment, includes: determining a length of a window of a servo pattern to use for calculating a lateral position estimate, determining a number of the windows of the servo pattern to use for calculating a lateral position value, receiving signals corresponding to each of the number of the windows of the servo pattern from a single servo channel, calculating a lateral position estimate for each of the number of the windows of the servo pattern, calculating the lateral position value by using the lateral position estimates, and using the lateral position value to control a tape head actuator. Other systems, methods, and computer program products are described in additional embodiments.

Abstract: A system includes a controller and a detector. The controller is configured to read servo spirals written on a magnetic surface of a disk drive. The servo spirals are written on the magnetic surface of the disk drive based on seed wedges. The seed wedges are written on the magnetic surface of the disk drive prior to writing the servo spirals on the magnetic surface of the disk drive. The controller is configured to write a servo pattern on the magnetic surface of the disk drive based on reading the servo spirals written on the magnetic surface of the disk drive. The detector is configured to detect, while reading the servo spiral written on the magnetic surface of the disk drive, interference caused by the seed wedges written on the magnetic surface of the disk drive.

Abstract: A tape head assembly includes a set of data readers configured to simultaneously read data from a set of adjacent data tracks of a tape storage medium, each data track having a width; wherein the width of each data reader of the set along a lateral extension of the tape head assembly is equal to or less than the width of a data track wherein the lateral extension of the tape head assembly is orthogonal to a longitudinal extension of the tape storage medium when arranged in a tape drive containing the tape head assembly spanning at least the set of data tracks during reading; and a servo reader arrangement containing at least one servo reader arranged laterally offset from one of the data readers by less than the width of a data track.

Abstract: A tape head assembly includes a set of data readers configured to simultaneously read data from a set of adjacent data tracks of a tape storage medium, each data track having a width; wherein the width of each data reader of the set along a lateral extension of the tape head assembly is equal to or less than the width of a data track wherein the lateral extension of the tape head assembly is orthogonal to a longitudinal extension of the tape storage medium when arranged in a tape drive containing the tape head assembly spanning at least the set of data tracks during reading; and a servo reader arrangement containing at least one servo reader arranged laterally offset from one of the data readers by less than the width of a data track.

Abstract: A data storage device is disclosed comprising a voice coil motor (VCM) and a secondary actuator configured to actuate a head over a disk. A control signal is applied to the secondary actuator while processing a sensor signal generated by the secondary actuator. A vibration signal is generated based on the sensor signal, wherein the vibration signal is a high-pass signal.

Abstract: A tape head assembly includes a set of data readers configured to simultaneously read data from a set of adjacent data tracks of a tape storage medium, each data track having a width; wherein the width of each data reader of the set along a lateral extension of the tape head assembly is equal to or less than the width of a data track wherein the lateral extension of the tape head assembly is orthogonal to a longitudinal extension of the tape storage medium when arranged in a tape drive containing the tape head assembly spanning at least the set of data tracks during reading; and a servo reader arrangement containing at least one servo reader arranged laterally offset from one of the data readers by less than the width of a data track.

Abstract: A disk drive is disclosed comprising a disk comprising a plurality of tracks, and a head comprising at least three read elements including a first read element, a second read element, and a third read element. When the head is within a first radial band of the disk, data recorded on the disk is detected using the first read element and the second read element. When the head is within a second radial band of the disk different from the first radial band, data recorded on the disk is detected using the first read element and the third read element. The first read element is substantially aligned down-track with the third read element when the head is over a first radial location of the disk.

Abstract: A method for operating a tape storage system includes simultaneously receiving readback signals from a set of data readers reading from data tracks of a set of adjacent data tracks extending along a longitudinal extension of a tape storage medium. Each data track has a width and each data reader has a width that exceeds the width of a data track. In the readback signal, of one of the data readers of the set a simultaneous presence of two defined waveforms is detected stemming from two different servo patterns arranged in servo sections of adjacent data tracks of the set. At least one of lateral position, velocity, gain and timing information is derived from a measure of the energy of the two defined waveforms detected in the readback signal of the data reader and applying this information in the operation of the tape storage system.

Abstract: Systems and methods are provided for throughput optimization of a hard disk drive (HDD) using position error signaling (PES) that includes determining a PES for a HDD mounted in a chassis based on a dynamic disturbance. The method also includes calculating a critical parameter of the PES. The method further includes indicating a mechanical design modification of the HDD or the chassis if the critical parameter of the PES exceeds a pre-defined threshold.

Abstract: Systems and methods are provided that may be implemented to provide a mechanical indicator to correlate magnetic disk drive IOP performance with features of mechanical and/or acoustic vibrational frequencies that are generated and captured or sensed outside of the disk drive itself. In one example, disk drive PES data may be collected concurrently with the capture of mechanical and/or acoustic vibrational data at different and progressive locations of vibration source, vibration path and vibration receiver in a disk drive operating environment, e.g., such as for disk drives installed within a server and/or storage chassis enclosure. In such case, PES threshold may be utilized to correlate performance of Drive IOP or drive servo-mechanical performance as a function of measured characteristics of vibration source/s that impart vibration to a disk drive.

Abstract: Various embodiments provide a recording medium. The recording medium may include a dedicated servo layer for providing servo information. The dedicated servo layer may include a plurality of tracks. A first track may include a first servo signal. A second track may include a second servo signal. The first servo signal and the second servo signal may include a plurality of common transitions. The transitions may be provided at a pre-determined frequency.

Abstract: An implementation of a circuit disclose herein comprises a vibration sensor circuit that generates a sensor signal from a disturbance signal, a lattice filter circuit that decorrelates the sensor signal to generate orthogonal backward prediction errors, and a multiple regression filter that estimates a disturbance correction signal using the orthogonal backward prediction errors.

Abstract: Methods, systems and computer program products for detecting an end of a reference spiral band are described. A first portion of servo information may be written on a disk using the reference spiral band. By detecting an end of a reference spiral band, a new reference spiral band may be launched. A read/write head of a hard disk drive may subsequently use the new spiral band to write the remaining portion of the servo information, which aids the writing of data tracks on the disk.

Abstract: Various embodiments of the present inventions provide systems and methods for adaptive servo address mark detection.

Abstract: A magnetic recording disk has nondata regions that contain a group of first nondata islands with one area and a magnetization in one perpendicular direction, and a group of second nondata islands with a smaller area and a magnetization in the opposite direction. To magnetize the nondata islands with the proper magnetization directions, a DC magnetic field much greater than the coercive field of the magnetic recording layer is applied in one direction to the entire disk to magnetize all of the nondata islands in the same direction. Then the disk is heated to a predetermined temperature, and while the disk is at this temperature, a second DC magnetic field less than the first DC magnetic field is applied for a predetermined time in the opposite direction to the entire disk. This reverses the magnetization direction of the smaller islands without switching the magnetization of the larger islands.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks, each spiral track comprising a high frequency signal interrupted at a predetermined interval by a sync mark. The head is used to read the spiral tracks to generate a read signal representing spiral track crossings. A position error signal (PES) is generated in response to the spiral track crossings, and the head is servoed over the disk in response to the PES. Timing feed-forward compensation values are generated in response to the PES, and the timing feed-forward compensation values are used to open a demodulation window at each spiral track crossing, wherein the timing feed-forward compensation values compensate for a repeatable runout (RRO) of the spiral tracks.

Abstract: Methods, systems, and apparatus, including computer program products, are described for calibrating servos, and in some implementations for calibrating spiral servos for use in self servo write processes. In one aspect, a method is provided that includes measuring a slope of a spiral written to a machine readable medium, and adjusting a parameter in accordance with the measured slope to calibrate spacing of servo tracks, with respect to variation between a target slope and the measured slope for the spiral, for writing the servo tracks to the machine readable medium using the spiral as a reference and the adjusted parameter to generate a same radial spacing between servo tracks from spirals with different slopes.

Abstract: The present disclosure includes systems and techniques relating to self-servo-writing. In some implementations, a method includes determining a spiral velocity associated with writing a plurality of reference spiral sets; identifying a plurality of launching tracks based on a predetermined ratio and the spiral velocity, where each of the plurality of launching tracks is associated with one of the plurality of reference spiral sets; writing each of the plurality of reference spiral sets starting at its associated launching track; and writing one or more sets of servo wedges using the plurality of reference spiral sets, where the reference spiral sets and the one or more sets of servo wedges are written at the predetermined ratio.

Abstract: A disk drive is disclosed comprising a disk, a head, and a voice coil motor (VCM) operable to actuate the head over the disk, wherein the VCM generates a back electromotive force (BEMF) voltage. At least one reference track is written on the disk, and the head is positioned near a first diameter of the disk. While moving the head from the first diameter toward a second diameter of the disk, the reference track is read and a first estimated state error is measured. While moving the head from the second diameter of the disk toward the first diameter of the disk, the reference track is read and a second estimated state error is measured. A gain and an offset of a velocity sensor are adjusted in response to the first and second estimated state errors.

Abstract: According to one embodiment, a position demodulator includes a demodulator, a phase corrector, and a position demodulating module. The demodulator demodulates a first demodulated signal and a second demodulated signal having a phase difference of 90 degrees from the first demodulated signal as a result of discrete Fourier transform operation on a read signal of a null servo pattern recorded in a servo area of a medium read out by a head. The phase corrector carries out correction to tilt respective vectors of the first demodulated signal and the second demodulated signal represented on a phase plane by a predetermined angle. The position demodulating module demodulates a positional signal for determining the position of the core of the head based on the first demodulated signal and the second demodulated signal corrected by the phase corrector.

Abstract: Methods, devices and systems include, in some implementations, a method including: writing, using a head having a read element and a write element, a band of spiral sets, the band of spiral sets including a first spiral set and a second spiral set different from the first spiral set; writing, using the write element, servo information that includes one or more sets of servo wedges while the read element is servoing on the first spiral set; and servoing the read element on the second spiral set based on one or more determined conditions under which writing the servo information coincides with reading data from the first spiral set.

Abstract: A method for monitoring a plurality of servo channels, providing a finite state machine (“FSM”) comprising a single servo channel mode and a combined servo channel mode, and moving a sequential information storage medium comprising a plurality of servo bands across a read/write head comprising a corresponding plurality of servo sensors. The method further asserts an acquisition flag by a servo channel if that servo channel is tracking a servo pattern, and asserts a bit flag by a servo channel if a new LPOS bit is decoded. If at least one acquisition flag is asserted, the method determines if a bit flag is asserted by a servo channel associated with said asserted acquisition flag, and if an acquisition flag and a bit flag are asserted by a servo channel, the method determines a relative positioning of each servo sensor with respect to an associated servo pattern.

Abstract: One embodiment includes a track recording head for creating discrete tracks in a rotating magnetic storage medium. The track recording head includes a main body, at least one stylus, and a stylus actuator. The main body is configured to be attached to a head gimbal assembly. The main body has an air bearing surface configured to face a corresponding surface of the rotating magnetic storage medium. The stylus is formed on the air bearing surface and is configured to be actuated towards the surface of the rotating magnetic storage medium to contact and apply stress to the rotating magnetic storage medium to create isolation regions of non-directionally magnetizable material. The stylus actuator is formed in the main body and is configured to actuate the stylus.

Abstract: A system includes a self-servo-write (SSW) module, a read module, and a write module. The SSW module writes servo spirals on a magnetic medium of a hard disk drive (HDD) via a write head of the HDD. The read module reads the servo spirals via a read head of the HDD and generates read signals. The write module writes non-servo data on the magnetic medium via the write head based on the read signals before the SSW module writes servo wedges on the magnetic medium.

Abstract: Methods, systems and computer program products for detecting an end of a reference spiral band are described. In some implementations, a band of spirals and servo information are written onto a storage medium. One or more characteristics associated with the band of spirals are determined. Then, one or more spirals of the band of spirals are identified as reference spirals based on the one or more determined characteristics. The writing of at least one of the band of spirals and the servo information is terminated upon identifying the one or more reference spirals.

Abstract: According to one embodiment, an information storage apparatus comprises a storage medium with a first servo pattern having absolute position information and a second servo pattern having relative position information, a pitch correction module configured to move a head with an initial feed pitch by using the second servo pattern by a target distance determined from the first servo pattern, and to correct the initial feed pitch based on a moving distance of the head and a target distance, a head position controller configured to position the head based on the initial feed pitch corrected by the pitch correction module and information of the first and the second servo patterns, and a recording signal generator configured to generate a control signal for making the head record the third servo pattern having the absolute position information.

Abstract: Systems, methods, and apparatuses, including computer program products, are described for, in at least one implementation, determining a measured slope of a spiral, calibrating radial spacing between servo tracks according to a relationship between a target slope and the measured slope, wherein an amount of calibration for the radial spacing varies directly with the relationship between the target slope and the measured slope, and generating servo tracks according to the calibrated radial spacing.

Abstract: Systems and techniques relating to writing servo information on a machine-readable medium. An apparatus can include a self-servo-write controller configured to direct writing of at least two bands of ramp-tracks to different surfaces of at least one machine-readable medium based on a given rotational relationship between the at least one machine-readable medium and at least two collectively controlled transducers, the controller including a self-servo-write clock generator, an angular position generator, a ramp-track pattern generator, and a servo wedge window period generator.

Abstract: An encoder module with a sliding assembly comprises a cover, a disk, a reading head, a bottom plate, and a sliding unit; wherein in assembly, the disk is installed at an upper front side of the bottom plate; the reading head is installed upon a front side of the sliding unit; the sliding unit is pushed into a lower hole of the bottom plate so that a front end of the sliding unit exposes from the lower hole of the bottom plate; in that the reading head serves to read signals from the disk; finally the cover covers upon an outer side of the bottom plate, the sliding unit and the reading head so as to form as an encoder module with a sliding assembly.

Abstract: A disk drive is disclosed comprising a first and second disk surfaces. A defect list is generated comprising a plurality of entries, wherein each entry comprises a track number comprising a defect. A first cluster across the first and second disk surfaces is identified, wherein a maximum data track number X1 in the first cluster on the first disk surface is less than a maximum data track number Y1 in the first cluster on the second disk surface. A second cluster across the first and second disk surfaces is identified, wherein a maximum data track number X2 in the second cluster on the first disk surface is less than a maximum data track number Y2 in the second cluster on the second disk surface. An entry from the defect list is selected in response to X1, and the entry of the defect list is mapped into the second cluster.

Abstract: The present disclosure includes systems and techniques relating to magnetic recording devices, such as disk drives. A recording medium of a magnetic recording device can include multiple helicoid patterns arranged in multiple helicoid groups. A described technique includes receiving a waveform produced by a head operated with respect to the medium; determining, based on the waveform, first phase difference(s) corresponding to a first helicoid group; affecting an alignment of the head with respect to the medium based on the first helicoid group by compensating for the first phase difference(s) to maintain the alignment; determining, while compensating for the first phase differences, second phase difference(s) corresponding to a second helicoid group; and affecting, responsive to a switch from the first helicoid group to the second helicoid group, the alignment of the head with respect to the medium by compensating for the second phase difference(s) to maintain the alignment.

Abstract: Methods, systems and computer program products for launching one or more reference spiral sets using different tracks are described. In some implementations, a method can be used that includes writing a first spiral set starting at a first track and determining a radial offset. Then a second track is determined based on the radial offset. A second spiral set is also written starting at the second track. A spiral set-to-wedge ratio is determined based on a number of spiral sets to be written. Subsequently, servo information can be written using the first spiral set and the second spiral set. The servo information can include one or more sets of servo wedges, which can be written based on the spiral set-to-wedge ratio.

Abstract: A method for writing servo sector sets that include a plurality of separate servo sectors on a disk so that servo sectors are present at same circumferential positions but different radial positions. The method includes reading a first servo sector set in a track with a read element such that the track includes first, second and third servo sector sets. The method also includes writing the third servo sector set with a write element at a different radial position from the read element with positional control and timing control using the first servo sector set while skipping the second servo sector set if all servo sectors of the first servo sector set are non-defective. Moreover, the method includes using positional control and timing control using the second servo sector set in the writing of the third servo sector set if the first servo sector set includes a defective servo sector.

Abstract: A magnetic recording disk drive has a disk with a head positioning servo pattern of multiple circumferentially-spaced chevron patterns of discrete patterned servo islands. The disk drive has servo electronics that decodes the chevron patterns to determine the absolute radial position of the head without the need for separate track identification fields. The chevron pattern with the smallest radial period has a radial period P1 and each of the other chevron patterns has a period which is a unique multiple of P1. In one embodiment the first chevron pattern read by the head has period P1 and each successive chevron pattern read by the head has a period that is greater than the period of the chevron pattern immediately preceding it such that the period of each chevron pattern progressively increases.

Abstract: A method and apparatus for writing magnetization states in magnetic islands of a multi-level patterned magnetic recording medium with more than two recording levels and a method and apparatus for reading readback waveforms representing written magnetization states of the magnetic islands in the multi-level patterned magnetic recording medium. Writing each magnetization state includes selecting the magnetization state, determining a write current sufficient to write the magnetization state, and applying the write current to a magnetic write head to write the magnetization state, including simultaneously writing associated magnetic states in each magnetic island of at least one pair of magnetic islands. Reading the readback waveform representing a written magnetization state is implemented through use of a magnetic read head and includes: identifying the written magnetization state by decoding the readback waveform; and displaying and/or recording the written magnetization state.

Abstract: In a method for providing an estimate of a head position for a disk drive, a readback signal is filtered. The readback signal includes a first position signal component corresponding to a first position pattern on a disk, and includes a second position signal component corresponding to a second position pattern on the disk. Filtering the readback signal includes using a filter determined based on statistical information regarding a noise component of the readback signal. An estimate of an amplitude of the first position signal component is generated based on the filtered readback signal, and an estimate of an amplitude of the second position signal component is generated based on the filtered readback signal. An estimate of a head position with respect to a track on the disk is generated based on the estimate of the amplitude of the first position signal component and the estimate of the amplitude of the second position signal component.

Abstract: A method for writing servo sector sets that include a plurality of separate servo sectors on a disk so that servo sectors are present at same circumferential positions but different radial positions. The method includes reading a first servo sector set in a track with a read element such that the track includes first, second and third servo sector sets. The method also includes writing the third servo sector set with a write element at a different radial position from the read element with positional control and timing control using the first servo sector set while skipping the second servo sector set if all servo sectors of the first servo sector set are non-defective. Moreover, the method includes using positional control and timing control using the second servo sector set in the writing of the third servo sector set if the first servo sector set includes a defective servo sector.

Abstract: A disk drive is disclosed comprising a disk having servo data defining a plurality of servo tracks. The servo data comprises a preamble comprising a varying length across a radius of the disk, and a plurality of slanted line servo bursts recorded at a tilt angle with respect to the preamble. The tilt angle varies across the radius of the disk commensurate with the varying length of the preamble. A position error signal (PES) is generated in response to a phase difference when reading the preamble and the slanted line servo bursts.

Abstract: A disk drive comprising a head for accessing a disk, an actuator for moving the head in the radial direction of the disk and a controller. The controller for servo control of the actuator based on servo data read out from the disk by the head. The controller is configured for maintaining a width of the adaptive chasing notch filter below a specified value in servo system control and estimating an oscillation frequency of the actuator.

Abstract: A servo control system includes an input that receives spiral signals generated by reading spirals that are prewritten on a magnetic medium. The servo control system further includes a control module that generates spiral correction values for the spirals based on the spiral signals and that determines positions of the spirals based on the spiral correction values.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The head is positioned over the disk and used to read the spiral tracks to detect a plurality of spiral-to-spiral times each representing a time between consecutive spiral crossings. A velocity of the head is estimated in response to the spiral-to-spiral times, and velocity feedforward compensation values are generated from the estimated head velocity. A control signal is generated to position the head over the disk in response to the velocity feedforward compensation values. When the detected spiral-to-spiral times are substantially constant, position feedforward compensation values are initialized in response to the velocity feedforward compensation values.

Abstract: A recording medium can include multiple helicoid patterns arranged in multiple helicoid groups, e.g., first and second helicoid groups. Operating a disk drive can include switching between helicoid groups to maintain the alignment of the head with respect to a target track of the rotating recording medium. Enabling a switch can include receiving a waveform produced by a head operated with respect to a rotating recording medium, generating first information from one or more portions of the waveform corresponding to the helicoid patterns of the first helicoid group; generating second information from one or more portions of the waveform corresponding to the helicoid patterns of the second helicoid group; and analyzing the second information with respect to the first information to generate calibration information. The calibration information can compensate for operational differences between using the helicoid patterns of the first helicoid group and the helicoid patterns of the second helicoid group.

Abstract: A method includes estimating a phase difference between components of a position signal in a servo position estimation system, and correcting the phase difference of the components of the position signal to provide a phase-compensated position signal.

Abstract: Systems and techniques relating to writing servo information on a machine-readable medium. A method of performing post-assembly operations in a recording apparatus, including a rotating recording medium, includes writing sloped tracks to the recording medium using a calibrated current profile, and writing servo information to the recording medium using the sloped tracks. An apparatus can include an input; an output; and signal processing circuitry coupled with the input and the output to control a transducer to write to a rotating recording medium, the signal processing circuitry including one or more control units configured to cause performance of post-assembly operations including writing sloped tracks to the recording medium using a calibrated current profile, and writing servo information to the recording medium using the sloped tracks.

Abstract: Techniques for performing metrology on magnetic media disk formations that are arranged in curvilinear patterns are disclosed. Small integrated test patterns having rectangular or hexagonal periodicity are integrated among the concentric circles of patterned media formations. The test patterns cover only very small areas of the disk so as to not significantly affect disk capacity. The periodicity of the test patterns allows their formations to be more readily measured by metrology technology than those having a curvilinear periodicity.