Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks, wherein each spiral track comprising a high frequency signal interrupted at a predetermined interval by a sync mark. An offset r0 representing a difference between an axial rotation of the disk and an axial rotation of the spiral tracks is estimated. Radial dependent timing compensation values are generated in response to the estimated r0. A phase error is generated in response to the sync marks in the spiral track crossings. A control signal is generated in response to the phase error and the radial dependent timing compensation values, and a frequency of an oscillator is adjusted in response to the control signal.

Abstract: A method is disclosed for selecting a global digital-to-analog setting for a plurality of heads in a disk drive, the disk drive comprising a plurality of disk surfaces and a plurality of respective heads. The method comprises: adjusting a first digital-to-analog setting for a first head to generate a first signal, adjusting a second digital-to-analog setting for a second head to generate a second signal, selecting a first scalar setting for scaling the first signal, selecting a second scalar setting for scaling the second signal, and selecting the global digital-to-analog setting in response to the adjusted first digital-to-analog setting, the adjusted second digital-to-analog setting, the first scalar setting, and the second scalar setting.

Abstract: A servo writer is disclosed operable to write servo sectors on a disk to define non-circular servo tracks. The servo writer comprises control circuitry including a servo control system operable to measure a position of a head over the disk to generate a position signal, generate a position error signal (PES) representing a difference between the position signal and a reference signal, process the PES with a servo compensator to generate a control signal, and position the head over the disk in response to the control signal. A disturbance is induced into the servo control system, and while positioning the head over the disk in response to the control signal, a plurality of servo sectors are written on the disk to define a servo track, wherein the disturbance induced into the servo control system causes the servo track to be non-circular relative to a rotation axis of the disk.

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: A process is disclosed for determining one or more edges of usable portions of a disk drive. Such knowledge can be used to determine the range of valid tracks of the disk and improve utilization of available disk space. The process can detect the edges by processing one or more disk controller signals, such as an adaptive feed-forward (AFC) injection signal, or a position error signal (PES).

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 for writing data to the disk, and control circuitry coupled to the head. The control circuitry is operable to determine a first set of fly height values and determine a threshold based on the first set of fly height values. The control circuitry determines a second set of fly height values, adjusts the threshold based on the second set of fly height values, and detects a head characteristic based on the adjusted threshold. The head characteristic is detected by detecting a head touchdown event and/or detecting contamination related to the head based on the adjusted threshold.

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 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 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 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 method is disclosed for selecting a dynamic fly height (DFH) control setting for a head in a disk drive, the disk drive comprising a plurality of disk surfaces and plurality of respective heads. The method comprises servoing a first head over a first disk surface in response to servo data recorded on the first disk surface, adjusting a DFH control setting for a second head, and while servoing the first head over the first disk surface, detecting whether the second head has contacted a second disk surface.

Abstract: A method is disclosed for selecting a dynamic fly height (DFH) control setting for a head in a disk drive, the disk drive comprising a plurality of disk surfaces and plurality of respective heads. The method comprises servoing a first head over a first disk surface in response to servo data recorded on the first disk surface, adjusting a DFH control setting for a second head, and while servoing the first head over the first disk surface, detecting whether the second head has contacted a second disk surface.