Abstract: A disk drive is disclosed comprising a head actuated over a disk, and a fly height actuator operable to control a fly height of the head over the disk. A periodic control signal is applied to the fly height actuator, a frequency response of a touchdown metric at a frequency of the periodic control signal is measured, and a touchdown event is detected in response to the frequency response of the touchdown metric.

Abstract: A disk drive is disclosed comprising head actuated over a disk comprising a reference pattern. The head is positioned at a first radial location, a first phase error is measured in response to the reference pattern at the first radial location, and a first repeatable runout (RRO) of the first phase error is measured. The head is positioned at a second radial location, a second phase error is measured in response to the reference pattern at the second radial location, and a second repeatable runout (RRO) of the second phase error is measured. The first and second RROs are processed to estimate an offset r0 representing a difference between an axial rotation of the disk and an axial rotation of the reference pattern.

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: A disk drive is disclosed comprising a head actuated over a disk, wherein a bootstrap spiral track is written on the disk. While servoing on the bootstrap spiral track at least one circular reference track is written on the disk. A velocity profile is adjusted in response to the circular reference track, and a plurality of spiral tracks are written to the disk in response to the velocity profile.

Abstract: A method is disclosed of servo writing a disk drive comprising a first head actuated over a first disk surface, and a second head actuated over a second disk surface. A first repeatable runout (RRO) of the first disk surface is measured, and a seek is performed to seek the first head over the first disk surface in response to the measured first RRO while writing a first spiral track to the second disk surface using the second head. As a result, the first spiral track comprises a second RRO that substantially matches the first RRO of the first disk surface.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks. During a seek operation, a demodulation window is opened in response to a window offset during a first revolution of the disk, wherein the demodulation window corresponds to the head approaching a spiral track. A window position error signal (PES) is generated representing a difference between a target framing of the demodulation window around the spiral track crossing and a detected framing of the demodulation window around the spiral track crossing. The window offset is adjusted in response to the first window PES, and the demodulation window is opened in response to the adjusted window offset during a second revolution of the disk.

Abstract: A method is disclosed of servo writing a disk drive comprising a first head actuated over a first disk surface, and a second head actuated over a second disk surface. A first repeatable runout (RRO) of the first disk surface is measured, and a seek is performed to seek the first head over the first disk surface in response to the measured first RRO while writing a first spiral track to the second disk surface using the second head. As a result, the first spiral track comprises a second RRO that substantially matches the first RRO of the first disk surface.

Abstract: A disk drive that approximates spiral slope in spiral patterns is disclosed. The disk drive includes a disk having at least one spiral pattern that extends radially across the disk, a head to read a portion of the at least one spiral pattern, and a processor to approximate a spiral slope of the portion of the at least one spiral pattern. The processor approximates the spiral slope of the portion of the at least one spiral pattern by implementing operations including: reading amplitude values for the portion of the at least one spiral pattern; determining an amplitude value distribution based on the amplitude values; determining a curve-fitted function for the amplitude value distribution; and determining an approximate spiral slope based on the curve-fitted function.

Abstract: A disk drive is disclosed comprising a first disk surface and a second disk surface, wherein the first disk surface comprises a plurality of concentric servo sectors extending across substantially an entire radius of the first disk surface. The concentric servo sectors are read across substantially the entire radius of the first disk surface using the first head to generate a read signal. The read signal is processed to generate a position error signal (PES) representing a radial location of the first head relative to the first disk surface. The PES is processed to generate a control signal applied to the VCM to move the second head radially over the second disk surface while writing a spiral servo track on the second disk surface.

Abstract: A disk drive is disclosed comprising a disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. A first spiral track comprises a first sync mark from an outer diameter of the disk to a reference radial location and a second sync mark from the reference radial location toward an inner diameter of the disk. A second spiral track comprises the second sync mark from the outer diameter of the disk to the reference radial location and the first sync mark from the reference radial location toward the inner diameter of the disk. The first sync mark is different than the second sync mark.

Abstract: A disk drive is disclosed comprising a disk and a head actuated over the disk, wherein the disk comprises a plurality of spiral tracks, each comprising a high frequency signal interrupted by a sync mark at a sync mark interval. The head is used to read a spiral track to generate a spiral track crossing signal g(xn), where xn is a time in a demodulation window. A position error signal (PES) is determined in response to g(xn), and a deviation index is computed by correlating g(xn) with a nominal track crossing signal shifted by the PES. When the deviation index is less than a threshold, the PES is used to servo the head over the disk.

Abstract: A disk drive is disclosed comprising a disk, and a head actuated over the disk. The head is positioned at a radial location over the disk, and a servo burst is written at the current radial location. The servo burst is read to generate a read signal, and the read signal is processed to generate a position error signal (PES). The head is moved radially in response to the PES, and the process is repeated multiple times to form a spiral track spanning at least one revolution of the disk.

Abstract: A disk drive is disclosed comprising a disk including a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval, and a head actuated over the disk. The spiral tracks are demodulated by reading a spiral track to generate a spiral track crossing signal g(xn), where xn is a time in a demodulation window, and determining a position error signal (PES) by determining a time-shift L that maximizes a correlation between g(xn) and a function that estimates a nominal spiral track crossing signal having the time-shift of L.

Abstract: A disk drive is disclosed comprising control circuitry for self servo writing a disk. An estimated reader/writer offset is initialized, servo bursts in a first servo track are read, the head is moved radially using the estimated reader/writer offset, and propagated servo bursts are written to a target servo track. The propagated servo bursts are read from the target servo track to generate a read signal, the read signal is processed to generate a burst crossing signal (BCS), and the estimated reader/writer offset is adjusted in response to the BCS.

Abstract: A method is disclosed for writing product servo sectors to the disk of a disk drive by demodulating spiral tracks recorded on the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The high frequency signal is demodulated into a plurality of servo burst signals, and a position error signal is generated from the servo burst signals. A correlation between the position error signal and an off-track displacement of a head is calibrated, for example, by moving the head radially over the disk until the servo burst signals attain a first predetermined relationship, and then calibrating the correlation in response to the corresponding position error signal.

Abstract: A method of servo writing a plurality of servo sectors to a disk of a disk drive to define a plurality of data tracks is disclosed. The disk drive comprises the disk, an actuator arm, a head coupled to a distal end of the actuator arm, wherein the head comprises a read element and a write element. A voice coil motor (VCM) rotates the actuator arm about a pivot to actuate the head radially over the disk, and a secondary actuator adjusts a skew angle for the head while using the write element to write the servo sectors to the disk.

Abstract: A method is disclosed of writing product servo sectors to a disk of a disk drive to define a plurality of product servo wedges, the disk comprising a plurality of spiral tracks. The spiral tracks are spaced apart circumferentially by a substantially equal spacing, and the number of spiral tracks equals a non-integer multiple of product servo wedges. The head internal to the disk drive is used to read the spiral tracks to generate a read signal, and the sync marks are detected from the read signal to generate a sync mark detect signal. A timing recovery measurement is generated in response to the sync mark detect signal, and a frequency control signal is generated in response to the timing recovery measurement. A servo write clock is generated in response to the frequency control signal which is used to write the product servo sectors to the disk.

Abstract: A method and apparatus is disclosed for adjusting the track density by changing the slope of spiral tracks used to servo write a disk drive. A target track density is established for a disk surface, and a plurality of spiral tracks are written to the disk surface in response to the target track density. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark, and a slope of the spiral tracks is selected in response to the target track density. The head internal to the disk drive is used to read the spiral tracks in order to write product servo sectors to the disk to define a plurality of data tracks, wherein the slope of the spiral tracks determines the density of the data tracks.

Abstract: A method of writing product servo sectors on a disk of a disk drive is disclosed. The disk comprises a reference pattern having a plurality of sync marks written around the disk. The sync marks are detected to generate a sync mark detect signal, and a timing recovery measurement is generated in response to the sync mark detect signal. A frequency control signal is generated in response to the timing recovery measurement, and a servo write clock is generated in response to the frequency control signal. A feed-forward compensation value is generated in response to the timing recovery measurement and the frequency control signal, and the timing recovery measurement is adjusted in response to the feed-forward compensation value to compensate for a repeatable phase error in the timing recovery measurement. The servo write clock and the head internal to the disk drive are used to write the product servo sectors to the disk.

Abstract: A method of servo writing a disk for use in a disk drive is disclosed by writing discontinuous spiral tracks on the disk to protect against overheating the head and/or preamp circuitry. A write clock is synchronized to the rotation of the disk, and a plurality of discontinuous spiral tracks are written on the disk. Each discontinuous spiral track is written at a predetermined circular location determined from the write clock, and each discontinuous spiral track comprises a plurality of segments separated by gaps. Each segment comprises a high frequency signal interrupted at a predetermined interval by a sync mark.