Abstract: A method and apparatus for detecting a high fly write event in a computer disk drive is provided. The method and apparatus allow the detection of high fly write events occurring over very short time spans. In addition, the present invention provides a method and apparatus for detecting high fly write events with a great deal of sensitivity. The method and apparatus of the present invention provide quick response and high sensitivity by monitoring the strength of a signal derived from a servo sector position burst or a group of bursts, and signaling a high fly write event if the monitored signal strength is less than a predetermined or threshold amount.

Abstract: A disk drive, a servo controller, and a controller which have realized high-degree control by lightening processing load to a microprocessor unit (MPU) without increasing cost is disclosed. An analog/digital (AD) converter (ADC) performs the AD conversions of the regenerated levels A, B, C, and D of burst patterns supplied from a channel and retains the converted levels in an ADC register. A servo assist (SA) computes parameters, such as the position error of a head, independently of an MPU, based on the regenerated levels of the burst patterns retained in the ADC register and an instruction from the MPU retained in a SRAM. Based on the computed parameters, the SA computes servo data (DACOUT) for driving a voice coil motor and supplies the servo data to the DAC section of a VCM driver section through a SIO.

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

Abstract: A method and system for determining data sector splits across servo bursts in a disc drive having a data disc with an embedded servo configuration. The disc drive includes a data transducer selectively positionable over the data disc for transferring data to and from the data disc, and the data disc includes a plurality of zones of predefined tracks. The method includes locating one or more frame table parameters based on a new zone position, creating a plurality of new frame table entries, while the disc drive is in operation, based on the frame table parameters, and moving the data transducer from a past zone position to the new zone position. The disc drive includes parameter memory and frame table memory. The parameter memory contains a plurality of zone records, with the zone records containing a plurality of zone table parameters. The frame table memory is utilized to store a frame table.

Abstract: A clocking method and apparatus for a rotating storage medium uses a single reference frequency from which both the pattern frequency of a servo pattern signal and the rotational frequency of the storage medium are derived. During the servo track writing process, a clock track is read from the storage medium to obtain a clock signal having a clock frequency and the phase of the servo pattern signal is digitally adjusted relative to the clock signal so that the servo pattern signal is in phase with the clock signal.

Abstract: A disk device that has displacement of servo signals in the circumference direction and radius direction between a plurality of disks, prevents a drop in performance due to the displacement when the heads are switched. To deal with the displacement in the circumference direction, the sector numbers on the disk are converted by a table for each head. Also the servo gate time is corrected by the table according to the eccentricity of the disk, so the servo signal detection accuracy improves. Also to deal with the displacement in the radius direction, the track numbers on the disk are converted by the table using the difference value based on the reference head.

Abstract: Defects of a hard disk drive servo pattern stamper are detected by comparing a scattered light beam pattern against the known servo pattern. A magnetic field is applied to stamper and the beam is linearly polarized. Variations in the physical offset of the beam, its scatter, are indicative of physical defects. Variations in the Kerr rotation of scattered beam are indicative of magnetic defects.

Abstract: The present invention is a method of correcting radial position error signal (PES) values by utilizing predetermined error correction values located at predetermined locations in advance of their associated servo fields. Calculated correction values are written to zero-acceleration path (ZAP) fields on the disc during the manufacture process. ZAP fields are positioned before the servo fields whose PES they are designed to correct. The ZAP field is comprised of two or more correction data elements to correct subsequent PES values. As the read/write head flies along a track, it reads a ZAP field, and stores the PES correction data in local random access memory (RAM). Subsequently, the corresponding servo field is read and the stored PES correction data is used to correct the PES. Two types of ZAP fields are written on the disc—one type for read operations, another type for write operations.

Abstract: A technique for detecting a current position of a head of a hard disk drive detects the position of the head by using an analog-to-digital conversion value of a single crossing point of one of first and second servo burst signals written up and down with respect to the center of a selected track and a third burst signal written symmetrically with respect to the center of the selected track.

Abstract: A disk drive and related method, the disk drive including a rotating magnetic disk and read and write elements for reading and writing data from and to the rotating magnetic disk, comprising: a magnetic characterization pattern recorded on the rotating magnetic disk for use in characterizing widths of the read and write elements using a plurality of track profiles of differing width. The magnetic characterization pattern is uniquely formed from a first plurality of characterization segments of a first radial width disposed circumferentially about a full circumference track on the rotating magnetic disk and a second plurality of characterization segments of a second radial width that is different than the first radial width disposed circumferentially about the same full circumference track on the rotating magnetic disk. The beneficial result is that two measurements can be accomplished within the STW in roughly the same time it ordinarily takes to accomplish only one.

Abstract: A disk drive is disclosed comprising a disk having a plurality of tracks, each track comprising a plurality of data sectors for storing user data and a plurality of embedded servo sectors for storing servo data. The disk drive further comprises a head comprising a read element and a write element, wherein the read element is offset from the write element. The disk drive stores a plurality of read repeatable runout (RRO) estimated values and a plurality of write RRO estimated values which are introduced into a servo loop to compensate for the different RRO disturbances which manifest during read and write operations.

Abstract: A Viterbi detector receives a signal that represents a binary sequence having groups of no more and no fewer than a predetermined number of consecutive bits each having a first logic level, where the groups are separated from each other by respective bits having a second logic level. The Viterbi detector recovers the binary sequence from the signal by calculating a respective path metric for each of no more than four possible states of the binary sequence, and determining a surviving path from the calculated path metrics, where the binary sequence lies along the surviving path. Or, the Viterbi detector recovers the binary sequence from the signal by calculating respective path metrics for possible states of the binary sequence, calculating multiple path metrics for no more than one of the possible states, and determining the surviving path from the calculated path metrics.

Abstract: Written-in runout due to vibration of the cage of a spindle motor of a disc drive is detected by identifying an initial cage frequency value of the motor. A written-in magnitude of successive servo burst closures, D(nc), is read over a plurality of tracks, and a maximum servo burst closure D(ncp) is identified from the plurality of read servo bursts. A magnitude of the cage frequency at a servo sector n0 is calculated based on a difference between the read magnitudes of the servo burst closures at servo sectors nc and nc+1, and a phase of the cage frequency is calculated based on the magnitude of the written-in cage frequency at servo sector n0. The profile, in the form of cage frequency, maximum servo burst closure magnitude, and initial phase, is stored in a memory or table for each of a plurality of radial zones of tracks. The profile is combined with a position error signal and applied to the controller in a feed forward scheme to adjust the position of the head based on the written-in runout.

Abstract: A method (and structure) senses a rotational vibration of a disk drive. The disk drive includes a rotating disk. The disk includes a plurality of reference bits across a surface thereof. The method (and structure) includes detecting the reference bits across a pattern on the rotating disk, and analyzing a time interval between adjacent ones of the reference bits.

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

Abstract: A disk drive is disclosed which detects a defective servo sector during a write operation and identifies a defective range of data sectors associated with the defective servo sector. A block relocation procedure is executed to identify a plurality of data sectors within the defective range and to relocate the plurality of data sectors to spare data sectors outside of the defective range.

Abstract: A magnetic disk apparatus includes a following compensator for measuring a frequency characteristic of an under-control object to stabilize a vibration mode of the under-control object with phase condition and a resonance filter having a resonance point in the vicinity of a frequency at which positioning accuracy is to be enhanced, being coupled in parallel to the under-control object. Polarity of mode constant of the resonance filter is so determined as to stabilize a vibration mode brought about by the resonance filter on the basis of a relation between the frequency stabilized by a control system and the phase−180° crossover frequency. Positioning accuracy at a specific frequency can be enhanced without involving unstability in the control system even in a frequency range where sensitivity function of the control system is higher than 0 dB inclusive.

Abstract: The present invention provides a magnetic recording unit, including: a magnetic head; a magnetic recording medium having a servo pattern for adjusting a position of the magnetic head; a frequency detecting element for detecting a frequency in the servo pattern on a track corresponding to the position in a radial direction of the magnetic recording medium, on the basis of a reproduction signal obtained by reading the servo pattern with the magnetic head; a storage element for storing in advance information on predetermined frequencies corresponding to the positions of tracks of the magnetic recording medium; a tracking element for comparing the frequency detected on the track by the frequency detection element and the information on the frequency corresponding to the same track, the information being stored in the storage element, and for generating a signal for adjusting the position of the magnetic head, the signal being generated on the basis of a difference between the frequencies.

Abstract: A servo sector format for a patterned media, such as a magnetic media, includes a first patterned servo timing mark, a patterned gray code, a plurality of PES burst separators, and a second patterned servo timing mark. The first patterned servo timing mark indicates the start of a servo sector. The plurality of PES burst separators are areas where no data can be written. A plurality of servo burst fields are written magnetically between the plurality of PES burst separators, and are used to determine at least one position error signal. The servo sector format further includes magnetically written gray code positioned after the second servo timing mark. The patterned gray code is used in addressing the tracks located on the surface of a disk when the magnetically written gray code is self-written.

Abstract: A disk device and a disk medium are disclosed in which a plurality of servo cylinders on the surface of at least one disk are divided into several areas, and a different servo signal frequency is set and recorded for each of the areas. The servo cylinders are divided into predetermined areas, and a different servo signal frequency for each of the areas is set so that the recording density of the servo signal recorded in the disk can be set so as to allow the servo signal demodulation characteristic to be included in a relatively superior range. In the disk device, the boundary between the area of a first servo signal frequency and the area of a second servo signal frequency adjoining the first servo signal frequency area is preferably formed with an area in which a servo signal pattern written with the first servo signal frequency and a servo signal pattern written with the second servo signal frequency are arranged on the same servo cylinders.

Abstract: The present invention maintains the low frequency run-out at a desired level during self-servo track writing. Included in the present invention is a method that keeps the low frequency track shape errors (the first few harmonics of the spindle rotational frequency) at a desired level during self-servo track writing. To that end, the present invention generates a correction signal. The correction signal is injected into the servo loop and modifies the path of the actuator while writing the next servo track, and thus modifies the shape of the next servo track. One embodiment injects the correction signal in the servo loop prior to the servo controller and combines it with the position error signal. Another embodiment injects the correction signal after the controller, and directly modifies the actuator input signal. The method does not require any extra disc revolutions, and therefore, it does not increase the time required for the self-servo writing process.

Abstract: The present invention proposes a new servo track writing technique called Extended Copying with Head Offset (“ECHO”). The read and write elements of the read/write head are offset from each other. A servo writer writes a guide pattern on the magnetic media disc. ZAP correction factors are added to the guide pattern. The head disc assembly is then connected to an electrical control system for self-propagating servo writing. The actuator arm is displaced until the read head is aligned over the guide pattern. A new servo track is written by the write element. ZAP correction factors are added to the newly written servo track. The actuator arm is displaced until the read element is aligned with the newly written servo track. A new servo track is written. ZAP correction factors are added to the newly written servo track. The process is repeated until a desired number of servo tracks are written.

Abstract: A method and apparatus are provided for generating a feedforward cancellation signal for a next sector of a disc in a disc drive. To form the cancellation signal, the method and apparatus generate a trigonometric value having the phase and frequency of a nonrepeatable runout error by passing a position error signal through a phase lock loop. An amplitude is determined for the cancellation signal based on the position error signal. The amplitude is then multiplied by the trigonometric value to from the cancellation signal.

Abstract: An apparatus and method for removing baseline shift in low frequency readback signals of a disc drive, such signals characterized by peaks separated by baseline portions. The disc drive comprises a head controllably positionable adjacent tracks on a rotatable disc, a servo circuit which controls the position of the head in response to the readback signals and an adjustable filter operably connected to and serially disposed between the head and the servo circuit. When baseline shift is detected in the baseline portions of the readback signals at a predetermined margin threshold, the response characteristics of the adjustable filter are adjusted to remove the detected baseline shift from the readback signals.

Abstract: An apparatus and method for correcting static track spacing errors in a data storage device having a plurality of concentric servo tracks. The data storage device includes a disc having a plurality of concentric servo tracks, an actuator assembly including a head adjacent the disc, and a controller operable for controlling the position of the head relative to the disc and operable to determine a correction factor indicative of a static track spacing error between servo tracks. The correction factor is used during operation of the data storage device to generate a corrected position signal for use by the data storage device in positioning the head with respect to the disc.

Abstract: A method, disc drive, and data handling system for optimizing the data writing/transmitting process are disclosed. The disc drive implemented method involves detecting at a current burst whether data written to a previous wedge is recoverable and making the disc drive's buffer space holding that data available for holding other data when the written data is recoverable. The disc drive implemented method also involves detecting at the current burst whether data to be written to a following wedge will encroach upon data written in adjacent tracks and allowing the data to be written in the following wedge when the encroachment is not too severe.

Abstract: A method and apparatus for detecting and respond to low-amplitude-write/skip-write events in a disc drive. The invention involves characterizing the gain factor of a variable gain amplifier embedded in the read path of a disc drive during at least two instances in which the read head passes over a servo sector, prior to a write event. Next the write event is executed. After the write event, the gain factor employed by the variable gain amplifier is acquired as the read head passes over the following servo sector. Finally, the acquired gain factor is compared to the characterization in order to detect a low-amplitude-write/skip-write event.

Abstract: A data storage system includes a data storage disc for storing magnetically encoded data and servo information. The data storage disc includes a data layer adapted to be magnetically encoded with data to be written to the data storage disc, and a servo information layer formed beneath the data layer and having magnetic servo pits formed therein to provide servo information. The magnetic servo pits are positioned in portions of the servo information layer which are at least partially directly beneath magnetically encoded data regions on the data layer such that a data head can read both magnetically stored data and servo information from the disc at substantially the same time. A method of fabricating a magnetic data disc is also disclosed.

Abstract: A method for allocating tracks into servo sector zones in a disk drive such that each zone has an equal range of channel bit densities is provided. In addition, a disk drive having servo sector zones that each have an equal range of channel bit densities is provided. According to the method and apparatus of the present invention, servo sector zones are sized such that the range of servo sector channel bit densities encompassed by each zone is constant from zone to zone. By constraining the range of channel bit densities encompassed by the servo sector zones, the equalization or conditioning of signals derived from the servo sectors can be optimized for a given number of zones. Accordingly, the method and apparatus of the present invention increases the accuracy with which servo sector data is detected while decreasing the complexity of the detector circuit.

Abstract: Apparatus and method for improving operational performance of a disc drive by detecting defective servo burst patterns. A rotatable disc is provided with servo data which include a plurality of servo burst patterns to define a plurality of tracks. A head transduces the burst patterns to provide burst signals to a servo circuit which controllably positions the head with respect to the surface of the disc by determining a position error signal from a combination of the burst signals. The servo circuit identifies a selected servo burst pattern as defective in relation to differences between absolute values of successive pairs of peak amplitude samples from the burst signal.

Abstract: The present invention involves a recordable disk having a first plurality of S1 servo sample wedges in a first servo zone at an outermost position on the disk, a second plurality of S2 servo sample wedges in a second servo zone which is radially adjacent the first servo zone, and a third plurality of S3 servo sample wedges in a third servo zone which is radially adjacent the second servo zone. The S1 servo sample wedges of the first plurality are equally spaced apart circumferentially around the disk by a first angle &thgr;1, the S2 servo sample wedges of the second plurality are equally spaced apart circumferentially around the disk by a second angle &thgr;2=&thgr;1*N1, and the S3 servo sample wedges of the third plurality are equally spaced apart circumferentially around the disk by a third angle &thgr;3=&thgr;2*N2.

Abstract: A magnetic storage system is disclosed which has one or more rotating disks. In one embodiment, the system includes a first transducer and a second transducer operatively associated with a respective first surface or second surface. Each of the first and second surfaces has a data track with a data region and an embedded servo sector. The first transducer has a data reader which includes a first MR strip and a servo reader which includes a second MR strip. The first MR strip is electrically isolated from the second MR strip. The first transducer performs a servo reading operation of the servo sector while the second a transducer performs either a data writing operation to the data region or a data reading operation from the data region. Also disclosed is a method for reading within a magnetic storage system. The storage system includes a first magnetic surface, a data reader and a servo reader. The first magnetic surface includes a first data region and a first servo sector.

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

Abstract: A system and method for correcting interference errors in data encoded on storage media comprising position marks disposed on a storage medium, the position marks being configured to encode a plurality of track addresses and at least four track types. A correction module detects and corrects errors in the track addresses by combining each of the track addresses with one of the track types and then recognizing incorrect addresses. The correction module replaces incorrect addresses with correct addresses using a look-up table, wherein each incorrect address is not identical to one of the correct addresses. The plurality of position marks that encode the track types are also used to generate a position error signal for position correction of a head device.

Abstract: A technique, including a method and associated system, for multitrack positioning during self-servowriting on a storage medium, and for controlling error growth as the servowriting steps across the storage medium. Readback amplitudes of multiple bursts from previously written tracks are combined using a parabolic interpolation relationship, for positioning when writing bursts on a subsequent track. This technique is especially useful for systems in which the read element is separated from the write element in the direction in which the servowriting steps across the medium. Also disclosed is an associated technique for controlling error growth, in which a reference waveform is derived and stored for use when writing subsequent tracks. The individual reference adjustments resultant from the multitrack positioning signal are combined in a weighted sum which controls error growth when the weights are calculated properly, as disclosed herein.

Abstract: An improved sampled amplitude read/write channel is provided. The system is an integrated Generalized Partial Response Maximum Likelihood (GPRML) read channel incorporating Read, Write, and Servo modes of operation. One implementation includes a 32/34 rate parity code and matched Viterbi detector, a 32 state Viterbi detector optimal parity processor, robust frame synchronization, self-adaptive equalization, thermal asperity detection and compensation, adaptive magneto-resistive asymmetry compensation, low latency interpolated timing recovery and programmable write precompensation.

Abstract: A hard disk includes at least one recording surface. The recording surface bears a plurality of servo sectors with each one of the servo sectors including a servo field and a data sector. The servo field has a gray code, a servo address mark and servo bursts with a servo identification recorded in the servo bursts. The servo identification is recorded in the servo bursts by encoding pulse timing intervals of the servo bursts.

Abstract: Disclosed are a method and a device that exhibit better performance against factors inhibiting an increase in track density than the current system. A servo pattern is constituted of a plurality of patterns arranged on both sides of the center lines of tracks, the patterns on one side of the center line being shifted in the track direction from the patterns on the other side along the center line, and patterns A and B are each constituted of two types of phase patterns arranged in the track-width direction, which are patterns 11 and 12 and patterns 13 and 14, respectively. The positional signal of a magnetic head is decoded by determining a sinusoidal function, which roughly agrees with the waveform of the reproduced signal of the servo pattern, based on the information on the frequency of the reproduced signal which has been stored in advance.

Abstract: Sampling data with wide bi-phase code symbols includes sampling a wide bi-phase code symbol in the data a number (N) of times to produce samples of data, selecting a subset of the samples, determining which sample in the subset of samples has a largest magnitude, and selecting a subset of samples in a subsequent wide bi-phase code symbol based on a sample in a previous subset that has the largest magnitude.

Abstract: The invention provides a high-speed interface that transfers servo position data from the read channel integrated circuit to the drive control integrated circuit or another integrated circuit. The high-speed interface eliminates the need for analog pins on the integrated circuits to lower the cost of the system. The high-speed interface also eliminates the use of the serial interface to transfer the servo position data which speeds up the data transfer. Examples of servo position data include high-resolution servo position data and coarse-resolution servo position data. A read channel integrated circuit transfers the user data and the high-resolution servo position data to a data bus, such as an NRZ bus. The data bus transfers the user data and the high-resolution servo position data to another integrated circuit, such as a drive control integrated circuit. The other integrated circuit receives the user data and the high-resolution servo position data from the data bus.

Abstract: The present invention provides a system, method and data format wherein a redundant sync byte or group of sync bytes is provided in a data sector at a distance sufficient to isolate the redundant sync byte from the primary sync byte in the event of multiple byte defects. In a first embodiment, a redundant sync byte, or group of sync bytes, is provided in the AGC field preceding the primary sync region. Upon failure to detect the primary sync byte, an attempt is made on a subsequent revolution to read the secondary sync byte, either by holding the AGC gain prior to reaching the data block, or initiating an “early read” just prior to reaching the data block. In a second embodiment of the invention, the redundant sync byte is provided within the data field subsequent to the primary sync region. On failing to detect the primary sync byte, the secondary sync byte can be read immediately or can be postponed until a subsequent revolution.

Abstract: A method of interleaving servo information fields on a recording medium, and a corresponding recording medium having interleaved servo information fields, that reduce the amount of disk surface area needed for servo information, to thus increase disk surface area available for data storage. The track layout includes regular sector servo fields and reduced sector servo fields interleaved with data fields. The regular sector servo fields include servo correction information such as repetitive run-out (RRO) cancellation values. The servo correction information of the reduced sector servo field does not include servo correction information. The servo correction information of the reduced sector servo field is merged into the regular sector servo field.

Abstract: A first amplifier which amplifiers a faint read signal read by a head is connected to a second amplifier which further amplifiers the read signal amplified by the first amplifier, via a signal line. The signal line is used to transmit the read signal from the first amplifier to the second amplifier, and also to transmit a control signal from the second amplifier to the first amplifier. On the basis of, for example, a point in time at which a servo mark is detected from servo data, a control unit sets a period of time in which the transmission of the control signal from the second amplifier to the first amplifier is permitted, so that it does not overlap a period of time in which the servo data is read.

Abstract: A disk drive has a channel circuit for demodulating data sectors and servo sectors stored on a rotating medium to provide data-sector data and servo-sector data. The channel circuit transmits the data-sector data and servo-sector data to a disk controller circuit in an order which is different than the order in which they are stored on a rotating medium to allow for demodulation latency while maintaining real-time updates of embedded servo information.

Abstract: A system and method for precompensating for tangential misalignment in a direct access storage device adjusts a SID timing window individually for every track or surface of the direct access storage device. The system and method generate a calculation of the tangential misalignment and adjust, in accordance with the calculation of tangential misalignment, a timing window during which the transducer head reads the information located on the storage surface. The calculation of tangential misalignment may be the result of a direct measurement of the tangential misalignment, or may be converted from radial misalignment data. The adjustment of the timing window may comprise opening the timing window an amount depending upon the degree of misalignment of each track, and may comprise shifting the window in time either forward or backward depending upon the nature of the calculated misalignment.

Abstract: An apparatus and method for improved servo control in a disc drive. A rotatable disc has first, second, third and fourth radially staggered servo burst patterns which define a plurality of concentric tracks. An actuator assembly supports a transducing head adjacent the tracks. A servo circuit combines respective at least third order polynomial functions of burst signals from the first and second, and third and fourth, burst patterns to generate a continuous function position error signal (PES) with normalized absolute magnitudes of 0 when the head is positioned at track centers, 0.5 at track boundaries, and 0.25 at quarter-track locations, and with substantially linear slope therebetween. The servo circuit applies current to an actuator motor to position of the head relative to a selected track in relation to the magnitude of the PES.

Abstract: There is a need for low-cost and reliable shock-sensing methods in magnetic hard-disk drives to maintain data integrity when a drive is subjected to external shocks. The present invention uses a novel shock-sensing method that is both reliable and low-cost, using a modified head preamplifier to detect servo fields from adjacent disk surfaces, as well as the disk surface being written or read. Servo fields on adjacent surfaces may be staggered. When a write head is writing data to a data field on a disk surface, a read head may be reading a servo field from an adjacent surface, insuring that the write head is on-track. By staggering the servo fields from surface to surface, shock may be sensed by measuring displacement of read heads on adjacent surfaces between servo sectors on the write surface. In addition, the use of a shock sensor or the like may be eliminated, reducing drive component cost.

Abstract: A patterned magnetic storage medium has a plurality of data sectors separated by respective servo sectors with each servo sector having a pattern of pits representing servo data. Grooves in each data sector separate adjacent tracks. Non-uniform structures patterns the grooves to a model of minimum or zero fly height perturbations of a slider adjacent the medium. The non-uniform structures preferably include lands pseudo-randomly spaced along each groove to form segmented grooves of pseudo-random length, with the lands being pseudo-randomly positioned across the data sector. In other embodiments, the servo sectors have lengths along each track to define a null frequency that matches a pitch frequency of modulation of a slider due to the pits of the servo sectors.

Abstract: A signal processing device for analog-to-digital converting a burst signal has a feature of selecting a data bus to notify a disk control device of a conversion result via an NRZ data bus. The disk control device stores the result of the analog-to-digital conversion of the servo positional signal. The positional signal of a head of the disk device is digitized in a R/W channel. Sampling for digital conversion is performed in only a window which is defined only in the vicinity of peaks of the positional signal. The values of peaks which are obtained by sampling are averaged by an averaging circuit. This enables the influence of noise occurred outside of the window to be eliminated. Although the noise in the window is sampled, its adverse influence is suppressed by the averaging processing.

Abstract: A discrete Kalman filter 12 and a disturbance estimating unit 13 are added to a feedback loop for feeding back a detected value of position from a position detector 6. The Kalman filter estimates position and velocity of an object to be controlled, thereafter outputting an estimated value of position and an estimated value of velocity. The disturbance estimating unit estimates from a command value of current and the estimated value of velocity the disturbance that is added to a load 5. The estimated value of position is fed back to a position controller 1, and the estimated value of velocity is fed back to a velocity controller 2. Further, a difference between a target value of current outputted from the velocity controller and the estimated value of disturbance is output as the command value of current.