Abstract: A data storage device is disclosed comprising a first actuator configured to actuate a first head over a first disk surface, and a second actuator configured to actuate a second head over a second disk surface. A seeking control signal is generated and used to control the first actuator to seek the first head over the first disk surface. The seeking control signal is filtered with a decoupler to generate a decoupler control signal, wherein the decoupler comprises a nominal decoupler and an adaptive decoupler. A tracking control signal is generated based on the decoupler control signal, and the tracking control signal is used to control the second actuator in order to access the second disk surface using the second head.

Abstract: A data storage device is disclosed comprising a first actuator configured to actuate a first head over a first disk, and a second actuator configured to actuate a second head over a second disk. The first actuator is controlled based on a first feed-forward seek profile to seek the first head over the first disk, and the second actuator is controlled to position the second head over a second data track on the second disk including to process the first feed-forward seek profile to attenuate a coupling disturbance from the first actuator.

Abstract: A data storage device is disclosed comprising a first disk comprising first servo sectors A0-AN distributed around a circumference of the first disk, and a second disk comprising second servo sectors B0-BN distributed around a circumference of the second disk, wherein the second servo sectors B0-BN are offset circumferentially from the first servo sectors A0-AN. While the first and second disks are rotating second servo information is transmitted from a second servo channel to a first servo channel. One of the first servo sectors Ai is read to generate first servo information, and a first command value is generated based on the first servo information and the second servo information, wherein a first actuator is controlled based on the first command value.

Abstract: A magnetic recording hard disk drive (HDD) includes, in addition to conventional servo sectors with position error signal (PES) blocks, data position error signal (DPES) blocks that are written into the data sectors when data is written in the data sectors of the data tracks. During readback the PES blocks from the servo sectors are decoded into PES values to allow the head to follow the servo track, while the DPES blocks are decoded to obtain DPES values that are used in the servo control loop to modify the head position so the head follows the center of the data track. In a shingled magnetic recording HDD, wherein the write head is at least two shingled data tracks wide, a DPES block is written in two radially adjacent data tracks when data is written into the data sectors of the shingled data tracks.

Abstract: A hard disk drive with adjustable data track pitch has repeatable runout (RRO) fields stored in he servo sectors for each servo sector of each servo track, and thus without the need to store the RRO fields in the data tracks. The RRO fields for each servo sector have a radial length of at least two servo tracks (i.e., equal to or greater than twice the servo track pitch). The RRO fields in each servo track are shifted radially from RRO fields in adjacent servo tracks and circumferentially spaced from RRO fields in adjacent servo tracks. The read head reads two different RRO fields from the two servo tracks closest to the data track and the servo electronics interpolates a RRO value from these two RRO values. Thus even if the data track pitch is changed, RRO values can be obtained.

Abstract: A data storage device with improved data storage densities, coupled with lower hard error and write-inhibit events is described. A feed-forward write inhibit (FFWI) method enables data tracks to be written more densely. Alternatively, the FFWI method may reduce the hard error and write inhibit events to improve data storage performance. A concept of virtual tracks enables the FFWI method to be applied to the writing of circular data tracks with non-circular servo tracks, or to the writing of non-circular data tracks with PES data from circular servo tracks—in both cases, improvements to performance and/or storage densities are enabled. The FFWI method may also be applied to the case of both non-circular servo and data tracks.

Abstract: A two-dimensional magnetic recording (TDMR) disk drive has a disk with servo tracks with a track pitch that varies across the radius of the disk. The servo track pitch (STP) is related to the cross-track spacing (CTS) of the multiple read sensors in the TDMR head structure. The CTS is given by the equation: CTS=(CTO)cos ?+(ATO)sin ?, where ? is the skew angle, and CTO is the cross-track spacing and ATO the along-the-track spacing of the read sensors at zero skew angle. The optimal variable STP profile results in track misregistration reduction because it allows each read sensor to read a different servo half-track and thus noise sources not correlated to noise sources read by the other read sensors. The servo tracks may be arranged into a plurality of annular bands, with the STP in each band being fixed and different from the STP in the other bands.

Abstract: A data storage device with improved data storage densities, coupled with lower hard error and write-inhibit events is described. A feed-forward write inhibit (FFWI) method enables data tracks to be written more densely. Alternatively, the FFWI method may reduce the hard error and write inhibit events to improve data storage performance. A concept of virtual tracks enables the FFWI method to be applied to the writing of circular data tracks with non-circular servo tracks, or to the writing of non-circular data tracks with PES data from circular servo tracks—in both cases, improvements to performance and/or storage densities are enabled. The FFWI method may also be applied to the case of both non-circular servo and data tracks.

Abstract: A data storage device with compensation for coercivity variations in a magnetic disk storage medium is disclosed. Two procedures are executed to perform the coercivity compensation. In a first procedure, typically performed prior to writing of data, the coercivity at a number of locations on the disk is measured and stored. A second procedure writes data to locations on a magnetic disk storage medium having varying coercivities. To maintain writing widths within predefined limits, a writing parameter is varied according to a predetermined relationship between the value of the writing parameter and the coercivity. Choices of writing parameter comprise the writing current and fly height. The method may be employed for both data writing and self-servo writing of servo patterns.

Abstract: A data storage device with improved data storage densities, coupled with lower hard error and write-inhibit events is described. A feed-forward write inhibit (FFWI) method enables data tracks to be written more densely. Alternatively, the FFWI method may reduce the hard error and write inhibit events to improve data storage performance. A concept of virtual tracks enables the FFWI method to be applied to the writing of circular data tracks with non-circular servo tracks, or to the writing of non-circular data tracks with PES data from circular servo tracks—in both cases, improvements to performance and/or storage densities are enabled. The FFWI method may also be applied to the case of both non-circular servo and data tracks.

Abstract: A data storage device with compensation for coercivity variations in a magnetic disk storage medium is disclosed. Two procedures are executed to perform the coercivity compensation. In a first procedure, typically performed prior to writing of data, the coercivity at a number of locations on the disk is measured and stored. A second procedure writes data to locations on a magnetic disk storage medium having varying coercivities. To maintain writing widths within predefined limits, a writing parameter is varied according to a predetermined relationship between the value of the writing parameter and the coercivity. Choices of writing parameter comprise the writing current and fly height. The method may be employed for both data writing and self-servo writing of servo patterns.

Abstract: A method, apparatus and a data storage device are provided for implementing data frequency and data bits per sector (BPS) calibration for data written on a recordable surface including non-circular disk tracks of a storage device. A sector based BPS profile is created for data sectors on the recordable surface. The sector based BPS profile is used for modifying a number of data clock cycles based upon longer or shorter data sectors; and data clock frequency is dynamically adjusted based upon velocity jitter.

Abstract: A thermally-assisted magnetic recording (HAMR) disk drive uses a thermal sensor to accurately monitor laser power during writing. The disk drive controller, or a separate processor, computes a prediction of the laser power from a history of laser power settings. This predicted value is compared with the measured value from the thermal sensor. If the difference is too large or too small, indicating that the laser power is too high or too low, an error signal is sent to the disk drive controller. The disk drive controller may adjust the laser power setting and initiate a re-write of the data. The predicted laser power is calculated from a convolution of a sequence of current and prior laser power settings with a sequence of coefficients. A calibration process generates the sequence of coefficients when the disk drive is idle or just after it is powered on.

Abstract: A magnetic recording hard disk drive has a servo clock that provides a varying frequency to the sync mark detector as a function of the radial position of the head as it crosses a servo section. The varying frequency compensates for circumferential misalignment of the sync marks in the servo sections. As the head moves radially across the tracks in a servo section during a seek, the frequency of the servo clock is continually adjusted based on the known radial velocity of the head and the known sync mark circumferential misalignment. The sync mark misalignment as a function of radius is measured as part of a calibration process, typically during disk drive manufacturing. The adjusted frequency adjusts the sample rate at which the sync mark detector samples the incoming sync marks.

Abstract: Disk drives are described with a write inhibit control system with an adaptive head position predictor, e. g. an adaptive FIR filter, that includes a set of coefficients (weights) that are updated for each iteration based on the difference between past predictions and actual location measurement. Standard PES signals are used as the measure of the actual head position. The adaptive head position predictor uses a sequence of the most recent PES measurements and a corresponding set of coefficients (weight values) to calculate a predicted (future) PES value during each iteration. The write inhibit decision is then made by determining whether either a) the absolute value of the current measured PES is less than predetermined value L; or b) the absolute value of the estimated future PES is less than predetermined value L.

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 method, apparatus and a data storage device are provided for implementing data track pitch adjustment for data written on a recordable surface of a storage device under operational vibration conditions. An operational vibration disturbance spectrum is detected during a write operation and the data track pitch is selectively adjusted based on the detected operational vibration disturbance spectrum. The adjusted track pitch information is saved and used during a read operation.

Abstract: A HDD comprising a temperature sensor disposed inside the HDD configured to periodically measure temperature inside of said hard disk drive; a magnetic disk; a read head; a write head; memory for storing RWO data. The RWO data is a function of a distance between the read head and the write head. The HDD also includes a RWO data adjustor configured to adjust the RWO data in response to a change in temperature of the HDD to compensate for a change in the distance between the read head and the write head based on the change in temperature.

Abstract: A magnetic data storage system having a magnetic disk having burst patterns for providing a position error signal (PES) wherein each magnetic burst pattern is offset from an adjacent burst pattern by ¼ track pitch. All of the magnetic bits of the burst patterns can be unipolar magnetized, and the bits of each burst pattern can be aligned with one another in radial and circumferential direction. The magnetic media can be a bit patterned media wherein the magnetic bits of the burst patterns are magnetically isolated portions separated by non-magnetic spaces or non-magnetic material.

Abstract: A data storage device with improved data storage densities, coupled with lower hard error and write-inhibit events is described. A feed-forward write inhibit (FFWI) method enables data tracks to be written more densely. Alternatively, the FFWI method may reduce the hard error and write inhibit events to improve data storage performance. A concept of virtual tracks enables the FFWI method to be applied to the writing of circular data tracks with non-circular servo tracks, or to the writing of non-circular data tracks with PES data from circular servo tracks—in both cases, improvements to performance and/or storage densities are enabled. The FFWI method may also be applied to the case of both non-circular servo and data tracks.