367 results about "Position error signal" patented technology

A method of writing product servo sectors to a disk of a disk drive is disclosed. 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. The head internal to the disk drive is used to read the spiral tracks to generate a read signal. The read signal is integrated to generate a ramp signal, wherein a position error signal is generated from the ramp signal. The position error signal is used to maintain the head internal to the disk drive along a servo track while writing product servo sectors along the servo track.

A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.

Disclosed is a method for generating a repeatable runout (RRO) compensation value set for a circular track on a magnetic medium on a surface of a disk in a disk drive. The magnetic medium has a plurality of previously written spiral servo tracks for providing position information during a self servo-writing operation. In the method, servo burst patterns are written at a plurality of radial locations on the magnetic data storage surface during circular tracking operations using the spiral servo tracks, and respective position error signals generated during the circular tracking operations are stored. The servo burst patterns at the plurality of radial locations define a circular data track. The RRO compensation value set for the circular data track may be generated based on the respective stored position error signals generated during the circular tracking operations for writing the servo burst patterns at the plurality of radial locations.

A method for constructing and linearizing a position error signal (PES) derived from primary and quadrature servo burst pairs in an embedded servo disk drive. The construction method mathematically provides predetermined transition values at the commutation positions connecting adjacent PES segments so that the overall, indicated position signal is numerically continuous from segment to segment. The linearization method compensates for nonlinearity in the PES segments, and thereby in the indicated position signal, without affecting the predetermined transition values at all, or by modifying the predetermined transition values while maintaining continuity.

A disk drive is disclosed comprising a voice coil motor (VCM) for rotating an actuator arm about a pivot in order to actuate a head over a disk. The disk is rotated by a spindle motor, and a feed-forward compensation value is computed that compensate for a non-centric alignment of the disk with respect to the spindle motor. During a calibration mode, the VCM is controlled to press the actuator arm against a crash stop, and the feed-forward compensation value is computed in response to a position error signal (PES). The PES is generated in response to embedded servo sectors recorded on the disk, wherein each embedded servo sector comprises a track address for coarse alignment and servo bursts for fine alignment.

The present invention may be embodied in a method of determining a repeatable runout (RRO) compensation value set for a data track on a magnetic disk in a disk drive. The track comprises a plurality of embedded sectors that define a circumferential path having RRO requiring compensation during data read and write operation. In the method, track following is performed along the track and a position error signal (PES) is determined for each servo sector. An RRO compensation value is iteratively learned for each servo sector using the previously learned value for the servo sector and using the PES for the servo sector and for adjacent servo sectors.

A disk drive is disclosed comprising control circuitry for generating a control signal applied to a VCM in response to a position error signal (PES) generated from reading embedded servo sectors and a feed-forward compensation value that compensates for a repeatable runout (RRO) disturbance. The feed-forward compensation value is generated for each servo sector in response to an RRO estimate Ŝ computed recursively for each servo sector according to:S^n+1=S^n-λ⁡[S^n-1n⁢∑i=1n⁢⁢PESi]wherein: λ is a predetermined fraction;PESi is the position error signal generated for a selected servo sector during an ith revolution of the disk; andn represents a number of disk revolutions.

A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The read signal from the head is processed to detect a plurality of the sync marks in a spiral track crossing. A timing recovery measurement is generated in response to a selected one of the sync marks based on reliability metrics, wherein a servo write clock is synchronized in response to the timing recovery measurement. The read signal representing the high frequency signal in the spiral track crossing is processed to generate a position error signal (PES) used to maintain the head along a substantially circular target path while using the servo write clock to write product servo sectors along the circular target path.

A method is disclosed for improving head position accuracy in a disk drive during track following of concentric data storage tracks through real-time identification of external vibration and monitoring of write-unsafe (WUS) occurrences. In the method, after a seek operation to a predetermined data storage track, the track is followed using a servo control loop having a nominal gain and responsive to a position error signal (PES). After waiting a vibration detection delay period, occurrences of the PES exceeding a WUS limit are counted generating a WUS limit exception count. Also, a property of a variance is determined from spectral power values generated from the PES during track following. If the WUS limit exception count exceeds a first threshold, and if the property of the variance exceeds a second threshold, the nominal gain is increased to a vibration gain within a frequency band, to attenuate the effect of external vibration.

A method for reducing an estimation period for repeatable runout (RRO) errors in a disk drive comprising a head, a disk surface having a track partitioned by servo-wedges, and a servo control system for controlling the movement of the head relative to a track during revolutions of the disk. The method includes estimating the RRO errors of the track based on a) a series of position error signal values obtained during a current revolution of the disk surface, and b) a previous estimation of the RRO errors of the track obtained during a previous revolution of the disk surface and determining a differential value between a first measure of the estimated RRO errors and a second measure of the previous estimation of RRO errors, and repeating the estimating and determining for subsequent revolutions of the disk surface until the determined differential value is smaller than a pre-selected threshold value.

A method of reducing rotational vibration effects in a disk drive by sensing vibration in a sensor and generating corresponding sensor data; deriving a statistical sensor (SS) value based on the sensor data; deriving a statistical position error signal (SPES) value from servo sectors read by the head; comparing the SS value to a SS-threshold value; comparing SPES value to a SPES-threshold value; and generating a feed-forward command effort signal for reducing rotational vibration effects if the SS value exceeds the SS-threshold value and if SPES value exceeds the SPES-threshold value.

A method is disclosed for writing M spiral tracks (i=1 to M) to a disk of a disk drive. A head is positioned over a first radial location to write a concentric reference track comprising N concentric servo sectors. Prior to writing one of the spiral tracks, the concentric reference track is read and a position error signal first_PESi(j) is generated for at least one of the servo sectors j in the concentric reference track, wherein the first_PESi(j) represents an offset of the head from the first radial location, and the servo sector j corresponds to a circumferential location of the spiral track. At least one of a starting radial location and a velocity profile is adjusted in response to the first_PESi(j), and the spiral track is written to the disk using the starting radial location and the velocity profile.

A method of writing spiral tracks for a disk drive is disclosed. A first concentric reference track is written at a first radial location near an outer diameter of a disk surface, a second concentric reference track is written at a second radial location near an inner diameter of the disk surface, and a third concentric reference track is written at a third radial location between the first and second radial locations. Prior to writing one of the spiral tracks, the concentric reference tracks are read to generate position error signals used to adjust a velocity profile for writing the spiral tracks. The velocity profile is adjusted to compensate for linear and non-linear disturbances due, for example, to thermal expansion.

The present invention may be embodied in a method for preventing radial error propagation during self-servowriting of concentric tracks on a magnetic disk in a disk drive. Each written track comprises a plurality of embedded servo sectors that define a circumferential path and that eventually form corresponding servo wedges extending radially across the magnetic disk such that each servo sector t of a track corresponds to a particular servo wedge. In the method comprising, track following is performed along a previously written track and a position error signal is determined for each servo sector. A correction value is recursively estimated for each servo sector of an adjacent track. The correction value is for use in correcting a position error signal determined using the corresponding servo sector of the adjacent track to prevent radial error propagation from previously written track to the adjacent track.

A rotating media storage device (RMSD) includes a disk having at least one track with a plurality of servo wedges, a moveable head, and a microprocessor. The microprocessor receives a plurality of position error signal (PES) values during track following and sums PES values for a plurality of different sets of servo wedges of the track to generate a plurality of shifted summed position error signal (SSPES) values. The microprocessor shifts the plurality of generated SSPES values by a phase shift value to generate a plurality of corrected shifted summed position error signal (CSSPES) values, which correspond to the repeatable runout (RRO) of the disk.

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.

An embodiment of the present invention comprises a method of writing product servo sectors to a disk of a disk drive. The disk comprises a plurality of spiral tracks each having a high frequency signal interrupted at a predetermined interval by a sync mark. The head internal to the disk drive is used to read the spiral tracks to generate a read signal which is processed to detect the sync marks. An aberration is detected in the detected sync marks in order to locate an initial radial location of the head with respect to the disk. The read signal representing the high frequency signal in the spiral tracks is processed to generate a position error signal (PES) used to maintain the head along a substantially circular target path while using the head internal to the disk drive to write the product servo sectors along the circular target path.

A suspension system supports a seat with respect to a base mounted on a frame of a vehicle. The system includes a hydraulic actuator coupled between the seat and the base. A single accelerometer is attached to the base and generates a base acceleration signal in response to motion of the base. A control unit actively controls the hydraulic actuator as a function of the base acceleration signal. The control unit generates a base velocity signal by integrating the base acceleration signal, generates a seat position signal representing a position of the seat relative to the base, generates a seat position error signal representing a difference between a desired position and the seat position signal, and generates a command signal as a function of the velocity signal and of the position error signal. The control unit controls the actuator by applying the command signal thereto.

A method is disclosed for writing servo patterns for tracks on a rotating magnetic disk medium of a disk drive. Servo patterns are written on a reference track of the disk medium. Track following of the written servo patterns on the reference track is performed using a servo loop having a closed-loop response. A position error signal is generated for the reference track based on the track following. A correction signal is generated based on the track following using an observer of a one-dimensional state model that is equivalent to a two-dimensional state model of the servo loop. Servo patterns are written on a target track during track following of the reference track. The position error signal of the servo loop is adjusted based on the correction signal to reduce radial error propagation from the reference track to the target track.

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.

A method is disclosed for improving servo performance in a disk drive having a plurality of concentric tracks. Each track has a plurality of first-type servo sectors and a plurality of second-type servo sectors. In the method, track identification information and track position information are read from a first-type servo sector. A track number and a transducer position are estimated for a second-type servo sector. Track position information is read from the immediately following second-type servo sector. An odd / even property from the second-type servo sector is compared with an odd / even property for the estimated track number. The odd / even property of the estimated track number is conditionally adjusted such that the odd / even property of the estimated track number matches the odd / even property from the second-type servo sector. A position error signal is determined using the adjusted track number and the track position information read from the second-type servo sector.

A method is disclosed for defining tracks on a rotating magnetic disk medium of a disk drive. Reference tracks are followed using a servo control loop while writing servo burst patterns defining a first target servo track. The servo control loop includes a two-dimensional digital state compensator having a first input that receives position error signals, a first output that generates control signals for positioning a transducer head, a second output that generates track-following state variables, and a second input that receives processed and stored track-following state variables. The first target track is followed using the servo control loop while servo burst patterns are written, and while the processed and stored track-following state variables corresponding to the servo burst patterns defining the first target track are applied to the second input.

A method is disclosed for efficiently determining and writing repeatable runout (RRO) compensation value sets for data tracks on a magnetic disk in a disk drive. The disk drive has a magnetoresistive (MR) head having a read element and a separate write element, and a secondary actuator coupled to the end of a primary actuator for adjusting a head skew angle. In the method, the head skew angle is set such that the read and write elements are substantially aligned along the first track. A position error signal for each servo sector is determined over a predetermined number of disk revolutions during track following along a first data track. An RRO compensation value set is calculated for the first data track based on the position error signals. The RRO compensation value set is written for the first data track. A seek operation is then performed to a second data track.

Disclosed is a method of estimating repeatable runout (RRO) for a disk drive. The method includes: determining a plurality of position error signal (PES) values for a plurality of servo wedges of a track of a disk; and estimating repeatable runout (RRO) in the PES values for the servo wedges of the track by averaging determined PES values over a pre-determined number of revolutions of the disk of the disk drive and scaling the averaged PES values by a pre-determined ratio of the variance of non-repeatable runout (NRRO) to the variance of an optimal estimation of the RRO for the disk drive.

A disk drive is disclosed comprising a head actuated over a disk, the disk comprising a plurality of servo tracks defined by a plurality of servo sectors. An estimated radial location of the head is generated in response to an actuator control signal. A Gray coded track ID is detected from reading a servo sector, and decoded into a detected track ID. A burst position error signal (PES) is generated from reading servo bursts in the servo sector, wherein the burst PES represents a detected fractional servo track offset of the head. When the detected track ID is corrupt, a corrected track ID is generated using the estimated radial location and the burst PES, and the actuator control signal is adjusted in response to the corrected track ID and the burst PES.

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by servo sectors. The head is positioned over a first servo track, and a first position error signal (PES) by reading a first servo sector during a first revolution of the disk and in response to a first compensation value. A second compensation value is updated for a second servo sector based on the first PES during the first revolution of the disk. A second PES is generated by reading the second servo sector during the first revolution of the disk and in response to the updated second compensation value. The first compensation value is updated for the first servo sector based on the second PES during the first revolution of the disk. The head is actuated over the disk in response to the first PES and the second PES.

A fully synchronous longitudinal position (LPOS) detection system is provided for improving the reliability of servo channels in tape systems. The system is based on the interpolation of the servo channel output signal, which is sampled by an analog-to-digital converter (ADC) at a fixed sampling rate, using a clock at a nominal frequency, so that interpolated signal samples are obtained at a predetermined fixed rate, independent of tape velocity. This predetermined fixed rate is defined in terms of samples per unit of length, as opposed to samples per unit of time, which is the measure of the ADC sampling rate. The resolution with which the servo channel signal is obtained at the interpolator output is thus determined by the step interpolation distance.

The present invention is directed to a method and apparatus for performing seek operations in a disk drive having a disk surface with spiral servo information written thereon. In one embodiment, a disk surface is provided with a read head associated therewith. The disk surface has spiral servo information written thereon. The read head generates a read signal envelope when reading the spiral servo information. A plurality of integration windows is provided. The plurality of integration windows have a standard interval therebetween. A position error signal is generated based upon a location of a read signal envelope within an integration window. The interval between adjacent integration windows is adjusted from the standard interval to generate a position error signal. The read head is moved in a radial direction based upon the position error signal. This process may be repeated to seek across the disk surface.