Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by servo bursts. The head is positioned at a first radial location over the disk and a first burst correction value is generated by reading at least one of the servo bursts. The head is positioned at a second radial location over the disk and a second burst correction value is generated by reading at least one of the servo bursts. The head is positioned at a third radial location over the disk and the first burst correction value and the second burst correction value are written at the third radial location. The head is servoed over the disk by reading the first and second burst correction values.

Abstract: A disk drive is disclosed comprising a head actuated over a disk, and a dynamic fly height (DFH) actuator operable to control a fly height of the head over the disk. A DFH control signal is applied to the DFH actuator to decrease the fly height of the head, wherein the DFH control signal comprises a DC component and an AC component comprising an excitation frequency. A touchdown metric is measured over an interval, and the head contacting the disk is detected in response to a frequency component of the touchdown metric at the excitation frequency.

Abstract: A disk drive is disclosed comprising a voice coil motor (VCM) configured to actuate a head over a disk. The VCM is controlled to seek the head over the disk during a first seek, and a back electromotive force (BEMF) voltage generated by the VCM during the first seek is measured. Feed-forward compensation is generated based on the measured BEMF voltage, and the VCM is controlled to seek the head over the disk during a second seek using the feed-forward compensation while writing servo data to the disk.

Abstract: A method for writing servo onto a disk of a hard disk drive. The method includes writing a plurality of spiral servo signals with a head. The spiral servo signals are used to generate position error signals and write a plurality of servo patterns. A write current of the head is varied for at least one servo pattern. A PES/WC relationship between the position error signals and the write current is determined and a plurality of final servo patterns are written by utilizing the PES/WC relationship and varying the write current. Varying the write current changes the trailing edge of the servo bits and controls the position of the track center. The PES/WC relationship allows the system to compensate for excursions within a single revolution of the disk.

Abstract: In accordance with various embodiments, an angular location of a first servo field along an annular track is determined in relation to a difference between a first code value of the first servo field and a second code value of a second servo field along the track. A radial location of the track is obtained in relation to the determined angular location of the first servo field.

Abstract: A method for writing servo onto a disk of a hard disk drive with a servo writer. The method includes writing a plurality of spiral servo signals onto a disk. The spiral servo signals include a plurality of short spirals separated by unequal distances. The short spirals are detected by determining the unequal distances and used to write a plurality of servo patterns. The unequal distances provide information of the short spirals at different quadrants of the disk. The distances between a bank of odd short spirals is different than a bank of even short spirals which allows the servo writer to determine whether the bank is odd or even without switching banks. Either the even or odd bank of short spirals can be used to locate a starting reference point from which the servo writer can count spirals and write A, B, C and D servo bursts.

Abstract: A method for writing servo onto a disk of a hard disk drive with a servo writer. The method includes writing a plurality of spiral servo signals onto a disk. The spiral servo signals include a plurality of short spirals separated by unequal distances. The short spirals are detected by determining the unequal distances and used to write a plurality of servo patterns. The unequal distances provide information of the short spirals at different quadrants of the disk. The distances between a bank of odd short spirals is different than a bank of even short spirals which allows the servo writer to determine whether the bank is odd or even without switching banks. Either the even or odd bank of short spirals can be used to locate a starting reference point from which the servo writer can count spirals and write A, B, C and D servo bursts.

Abstract: A method for writing servo onto a disk of a hard disk drive. The method includes writing a plurality of spiral servo signals with a head. The spiral servo signals are used to generate position error signals and write a plurality of servo patterns. A write current of the head is varied for at least one servo pattern. A PES/WC relationship between the position error signals and the write current is determined and a plurality of final servo patterns are written by utilizing the PES/WC relationship and varying the write current. Varying the write current changes the trailing edge of the servo bits and controls the position of the track center. The PES/WC relationship allows the system to compensate for excursions within a single revolution of the disk.

Abstract: In accordance with various embodiments, an angular location of a first servo field along an annular track is determined in relation to a difference between a first code value of the first servo field and a second code value of a second servo field along the track. A radial location of the track is obtained in relation to the determined angular location of the first servo field.

Abstract: Methods for making a disk drive, apparatus for writing servo bursts on a disk, and disk drive apparatus are provided. The disk drive includes a disk and transducer adjacent to the disk. The transducer includes a read element and a write element. A width of the read element is determined. A servo track pitch is determined based on the read element width. Servo bursts are written in servo tracks on the disk with the write element based on the servo track pitch.

Abstract: Track pitch for writing tracks on a disk is determined based on an available stroke across the disk. The available stroke is identified by searching across the disk for where information can be written and read. The track pitch is determined for writing tracks on the disk based on the available stroke across the disk. Tracks are written on the disk based on the determined track pitch.

Abstract: A spindle motor control for a disk drive including a spindle motor for rotating a data disk at a desired rotational speed, and a data transducer head positionable relative to selected ones of a multiplicity of concentric data tracks formed on a data storage surface of the data disk by a head position actuator structure operating within a head position servo loop, wherein the concentric data tracks are periodically interrupted by a plurality of servo sectors per rotation, each servo sector recorded with head position information.

Abstract: Methods and apparatus for ascertaining a position of a read/write head relative to a reference position on a rotatable disk in a computer disk drive are disclosed. In one aspect of the present invention, a method for determining the position of a read/write head relative to a reference position on a rotatable disk in a computer disk drive includes reading amplitudes of a set of servo bursts embedded in tracks of the disk and classifying the servo bursts into a converging servo burst set and a detection servo burst set around the reference position. The method also includes forming a position error signal by augmenting a detection servo burst signal with a converging servo burst signal as well as a normalization factor. The converging servo burst signal is formed from amplitudes of the converging servo burst set at the position of the read/write head. The detection servo burst signal is formed from amplitudes of the detection servo burst set at the position of the read/write head.

Abstract: A method for ascertaining a position of a read/write head relative to a reference position on a rotatable disk in a computer disk drive. The method includes reading amplitudes of a set of servo bursts embedded in tracks of the disk and classifying the servo bursts into a converging servo burst set and a detection servo burst set around the reference position. The method also includes forming a position error signal by normalizing a detection servo burst signal with a converging servo burst signal. The converging servo burst signal is formed from amplitudes of the converging servo burst set at the position of the read/write head. The detection servo burst signal is formed from amplitudes of the detection servo burst set at the position of the read/write head. The position error signal represents an offset from the reference position.

Abstract: Embedded servo sectors within a data track of a hard disk drive including a rotating data storage disk and a closed loop rotary actuator structure for positioning a data transducer head relative to the data track are written by a method including the steps of positioning the rotary actuator structure relative to the data track with a laser-interferometer-based servo writer and writing a pattern of circumferentially sequential, radially offset fine position bursts within each servo sector with the data transducer head, this step including writing-in undetermined position errors within each pattern being written, moving the disk drive to a self scan environment away from the servo writer, operating the rotary actuator structure in closed loop for following the data track by reference to the servo burst pattern, extracting the undetermined position error from each pattern thereby to iteratively determine written-in position errors, generating burst correction values from the determined written-in position errors

Abstract: Embedded servo sectors within a data track of a hard disk drive including a rotating data storage disk and a closed loop rotary actuator structure for positioning a data transducer head relative to the data track are written by a method including the steps of positioning the rotary actuator structure relative to the data track with a laser-interferometer-based servo writer and writing a pattern of circumferentially sequential, radially offset fine position bursts within each servo sector with the data transducer head, this step including writing-in undetermined position errors within each pattern being written, moving the disk drive to a self scan environment away from the servo writer, operating the rotary actuator structure in closed loop for following the data track by reference to the servo burst pattern, extracting the undetermined position error from each pattern thereby to iteratively determine written-in position errors, generating burst correction values from the determined written-in position errors

Abstract: A servowriter capable of non-invasively servowriting a magnetic recording disk drive controls the drive's on-board electro-mechanical head-position actuator system and read/write interface to self-servowrite the target drive. A head within the drive is used to write, open loop, a set of spiral tracks having embedded timing information. The spiral tracks are subsequently used to position the head so that standard embedded servo wedges can then be written. After the standard embedded servo wedges are written, the spiral tracks may be overwritten with user data.

Abstract: A combustion control system which utilizes non-linear parameters for controlling a combustion process with greater efficiency than has heretofore been available is disclosed. According to the method, the quantity of carbon monoxide, unburned hydrocarbons, and/or opacity is measured and compared with a predetermined value for that parameter. Error signals for each parameter are generated and supplied to an error selector which chooses the error signal of the largest magnitude. The error signal is then compensated for the non-linear relationship between the parameter and the amount of excess air supplied to the combustion process. Other operations, including checking the proposed control signal output against one or more constraints are performed, and if satisfactory, an output signal is supplied to a servo-mechanism for controlling the air flow to the combustion process.

Abstract: A control system for use in combination with a bushing assembly of the type wherein glass fibers are drawn through an orifice plate having a flat undersurface against which bulk gas is directed to effect cooling and fiber attentuation. The system controls operation in the event of fiber "break out," by lowering the temperature of the bushing assembly, increasing the rate of flow of bulk gas against the orifice plate, controlling the drawing action of the collet used to draw fibers from the plate, and spraying cooling water against the fibers being drawn from the plate. Control is effected through means of a common main control unit and manual controls are provided to permit operation of the control system to selectively control the operating mode of the system and increase the bulk flow of gas for orifice plate clearing purposes.