Abstract: A method and apparatus for detecting a high flying condition of a transducer head in a computer disk drive is provided. The method and apparatus allow the detection of high fly write events that occur over one or a small number of data sectors. In addition, the present invention provides a method and apparatus for detecting high fly write events with a great deal of sensitivity. The method and apparatus of the present invention provide quick response and high sensitivity by monitoring the strength of a signal derived from data written to the disk, and signaling a high fly write event if the monitored signal strength in connection with a particular piece of data is less than a stored high fly write number corresponding to that piece of data by a predetermined amount.

Abstract: The present invention is a method and apparatus for positioning a read/write head in a hard disk drive. The method comprises providing a disk having a at least one side with a plurality of tracks, where each of the tracks has a servo field with servo bits. The servo bits are read to provide a position signal for positioning a read/write head. The method determines a difference in position between an initial and a subsequent position of the read/write head on a track, where the subsequent location occurs after the read/write head has moved one revolution from the initial position on the track. The initial and subsequent positions are offset laterally. The method generates a compensation signal based on the initial position, the subsequent position and the difference. The position signal and the compensation signal are combined to provide a compensated position signal for positioning the read/write head. Various embodiments are described.

Abstract: A disk drive has a sampled servo system controller and a disk. The disk has a plurality a plurality servo burst fields, the plurality of servo burst field including first and second normal burst fields, and first and second quadrature burst fields. A portion of the first quadrature burst field is circumferentially contiguous with the first normal burst field and spans a portion of a radial extent of the first normal burst field. The second normal burst field is radially aligned with and away from the first normal burst field and spans a portion of a radial extent of the first quadrature burst field. The second quadrature burst field is radially aligned with and away from the first quadrature burst field and spans a portion of a radial extent of the second normal burst field. The first normal burst field and the first quadrature burst field have a same first phase and the second normal burst field and the first quadrature burst field have a same second phase. The first phase is different than the second phase.

Abstract: The magnetic disk drive system has a read head and a write head, writes data on the track of the disk, and reads data on the track of the disk. In the present invention, the distance between the heads in the circumferential direction of the disk is computed. The distance between the heads is computed based on the distance between the position of the write head where said data is written and the position of the read head where said data is read. The timing when data is written by the write head is determined by adding said distance to the position where the data is written. Thus, the efficiency of the format of the disk is improved.

Abstract: A method is disclosed for determining repeatable runout (RRO) cancellation values in a disk drive having a head disk assembly (HDA) and a sampled servo controller. The HDA includes a disk having distributed position information in servo wedges, a rotary actuator carrying a head that periodically reads the position information, and a voice coil motor circuit that responds to a control effort signal. The servo controller periodically adjusts the control effort signal during a track-following operation. In the method, the position information related to a predetermined track is read during track following for more than one disk rotation. The position information is averaged for each servo wedge obtained during the disk rotations. The averaged servo position values are filtered with a filter for compensating effects of the sampled servo controller, which tend to distort the averaged servo position values, to generate the RRO cancellation values for the predetermined track.

Abstract: A data recording medium, such as a magnetic recording hard disk, has data tracks with pseudo-random binary sequences for the servo information used to control the position of the recording head in the disk drive. A first pseudo-random binary sequence (PRBS) and a second PRBS identical to the first PRBS but shifted by a portion of the period of the first PRBS are located between the track boundaries in alternating tracks in a first region of the servo pattern and between the track centers in alternating tracks in a second region spaced along the track from said first region. A servo decoder in the disk drive has two correlators, one for each PRBS. Each correlator outputs a dipulse when its PRBS repeats. The difference in amplitude of the dipulses represents the head position signal. The dipulses also control the amplifier for the signal read back by the head and the timing of the track identification (TID) detector.

Abstract: A disk drive is disclosed wherein a BEMF speed error is measured during a BEMF spindle speed control mode, and a spindle control current is updated in response to the BEMF speed error to drive the disk at an operating speed. A reference time period (RTP) is calibrated, and a sinusoidal error in a wedge time period (WTP) due to eccentricity in the disk rotating is estimated to generate an eccentricity compensation value. After switching to a wedge spindle speed control mode, an actual WTP is detected and a wedge speed error is generated in response to the RTP, the detected actual WTP, and the eccentricity compensation value. The disk is then maintained at the operating speed by updating the spindle control current in response to the wedge speed error.

Abstract: A data recording system, such as a magnetic recording hard disk drive, has a recording medium in which the data tracks have pseudo-random binary sequences for the servo information used to control the position of the recording head. A first pseudo-random binary sequence (PRBS) and a second PRBS identical to the first PRBS but shifted by a portion of the period of the first PRBS are located between the track boundaries in alternating tracks in a first region of the servo pattern and between the track centers in alternating tracks in a second region spaced along the track from said first region. A servo decoder has two correlators, one for each PRBS. Each correlator outputs a dipulse when its PRBS repeats. The difference in amplitude of the dipulses represents the head position signal. The dipulses also control the amplifier for the signal read back by the head and the timing of the track identification (TID) detector.

Abstract: A hybrid servo pattern, which is printed onto a disk, for use in a disk drive. The hybrid servo pattern is used to position a head relative to the disk. In one embodiment, the hybrid servo pattern includes gray code and chevrons. The gray code provides coarse positioning information, and the chevrons provide fine positioning information.

Abstract: Disclosed is a control system for processing sampled servo data in a disk drive. The control system includes a microprocessor and a servo processing accelerator circuit for performing operations on the sampled servo data while the microprocessor is executing firmware code. The accelerator circuit supports the use of a higher servo bandwidth thus allowing a higher track density resulting a greater storage capacity for the disk drive. Also, the accelerator circuit relieves the microprocessor of the ordinary servo processing function. Thus, the microprocessor's limited processing capacity to be directed to other controller and interface functions of the disk drive. Only under unusual conditions, such as a write-unsafe (WUS) limit exception, does the microprocessor need to direct processing capacity to the servo processing function. Further, the accelerator circuit may be a decreased response time after reading the servo data from the disk.

Abstract: An apparatus and method of tracking repeatable runout in a disc drive servo loop is provided in which a feedforward signal having harmonic components that are updated at a sample rate that is a fraction of a servo sector sample rate is employed during track following.

Abstract: A head position is demodulated by two-phase servo signals of PosN and PosQ from output of the head, so as to acquire a more accurate demodulated position. Saturation of PosN and PosQ is judged from the ratio of each absolute value of PosN and PosQ, and a different demodulating method is used for a saturated area and for an unsaturated area, and a demodulating formula is constructed so that the edge of each demodulating area matches with the edge of the adjacent demodulating area. Also saturated/unsaturated is judged by comparing the absolute value of PosN and the absolute value of PosQ, and determining whether the ratio thereof is greater or small than a predetermined saturation coefficient r.

Abstract: A method and disc drive are disclosed that write servo wedges to a plurality of tracks of a disc. A head having a read element offset from a write element reads a servo wedge on a first track as a propagation guide and writes two or more servo wedges to be used as a subsequent propagation guide on a second track, all during one instance of a sector position of the disc rotating by the head. Additionally, a one of the written servo wedges can be radially continuous from the outer to inner diameter and is used for track-following during normal operation. In this manner, all radially continuous servo wedges for each sector of a given track can be written during one revolution of the disc, thereby reducing the amount of time necessary for servowriting.

Abstract: Rotary positioners integrally and pivotally stack a read magnetic head for reading a master disk and servo heads for writing to each surface of magnetic disks, the master disk and magnetic disks being stacked on a shaft of a spindle motor. Every surface of every magnetic disk is written by the servo heads in parallel while sharing a range of tracks. Simultaneously with the writing, checking magnetic heads stacked on a checking-dedicated rotary positioner read written data on the master disk and on each surface of the magnetic disks. A comparison logic circuit compares the read data from the magnetic disk surfaces with the data from the master disk. If an inconsistency is found, the contents of the master disk are overwritten on the corresponding magnetic disk surface through a correction servo pattern generator by the checking magnetic head.

Abstract: In a first mode, an R/W channel starts to monitor read information to thereby detect a servo mark contained in servo information, each time a servo controller generates a servo gate pulse. Upon detecting the servo mark, the R/W channel detects, from the read information, position information contained in the servo information and following the servo mark, at a timing determined by the detection timing of the servo mark. When the first mode has been switched to a second mode, the R/W channel detects the servo mark and position information using the synchronous method.

Abstract: There is disclosed a self-supporting-type servo writing apparatus in which a head of a disk drive is used to write a servo pattern on a disk. In the disk drive, the disk is incorporated in which a clock pattern is pre-written as a signal pattern for position detection in a rotation direction. The servo writing apparatus uses the servo pattern written on the disk by a write head device to successively add the servo pattern into the whole surface on the disk.

Abstract: Methods are provided for improving servo-demodulation robustness. SAM pattern detections are characterized as either good SAM detections or bad SAM detections. Further servo functions are then based on whether the detection of the SAM pattern in a servo wedge was characterized as a good SAM detection or characterized as a bad SAM detection.

Abstract: Distinct servo patterns are written on data storage media of a data storage device. Servo patterns of a first type are written for transducers of the data storage device having a first transducer characteristic. Servo patterns of a second type are written for transducers that do not have the transducer characteristic. The transducer characteristic can be a geometric criterion such as read head and write head track width, an operating characteristic such as frequency response, or otherwise. The first servo pattern may be a seamless untrimmed PES burst and the second servo pattern may be a seamed trimmed PES burst.

Abstract: A first amplifier which amplifiers a faint read signal read by a head is connected to a second amplifier which further amplifiers the read signal amplified by the first amplifier, via a signal line. The signal line is used to transmit the read signal from the first amplifier to the second amplifier, and also to transmit a control signal from the second amplifier to the first amplifier. On the basis of, for example, a point in time at which a servo mark is detected from servo data, a control unit sets a period of time in which the transmission of the control signal from the second amplifier to the first amplifier is permitted, so that it does not overlap a period of time in which the servo data is read.

Abstract: Reduced bit number wedge identification techniques for use within a rotating media storage device (RMSD) are disclosed. The RMSD includes a disk having a circumferential track that includes a plurality of embedded servo wedges utilized in track following. A substantial majority of the plurality of wedges include a reduced bit wedge ID field that does not have a sufficient number of bits to uniquely identify the wedge within the track. A combined wedge ID code is formed from reading at least first and second reduced bit wedge ID numbers from first and second wedges, respectively, which is used to uniquely identifying a wedge.

Abstract: A method and apparatus for preventing off tracking from occurring in a hard disc drive that has at least one track formed using servo signals. The method includes preventing off tracking from occurring when a hard disc drive drives a hard disc having at least one track formed by servo sectors on which servo signals are recorded, checking whether the width of the track is uneven using burst regions A, B, C, and D, the burst regions A through D being included on each servo signal, and preventing the occurrence of off tracking when the width of the track is not even. Accordingly, it is possible to prevent a potential occurrence of off tracking due to a track of an uneven width, thereby guaranteeing the reliability of a hard disc. Also, a track of uneven width with other tracks in the hard disc can be changed into a track of even width, thereby increasing the processing yield during manufacturing of the hard disc.

Abstract: A magnetic disk apparatus includes a following compensator for measuring a frequency characteristic of an under-control object to stabilize a vibration mode of the under-control object with phase condition and a resonance filter having a resonance point in the vicinity of a frequency at which positioning accuracy is to be enhanced, being coupled in parallel to the under-control object. Polarity of mode constant of the resonance filter is so determined as to stabilize a vibration mode brought about by the resonance filter on the basis of a relation between the frequency stabilized by a control system and the phase-180° crossover frequency. Positioning accuracy at a specific frequency can be enhanced without involving unstability in the control system even in a frequency range where sensitivity function of the control system is higher than 0 dB inclusive.

Abstract: In a positioning control apparatus, a distance between an actual position at which absolute values of N and Q head positioning signals whose amplitudes vary cyclically in accordance with a position of a magnetic head and whose phases are different from each other by 90 degrees are equal to each other and an optimum position at which the absolute values of N and Q head positioning signals should be equal to each other is calculated from a deviation of an actual position of the magnetic head with respect to a target value of zero which deviation is obtained when controlling the magnetic head to be positioned at a boundary between ranges in which the N and Q head positioning signals have respective linearities so that the absolute values of N and Q head positioning signals become equal to each other.

Abstract: The present invention may be embodied in a method for adjusting a servo sector detection delay time between detection windows in a disk drive. The disk drive includes a magnetic disk with a spiral track having contiguous storage segments. Each storage segment has a servo sector and a predetermined number of uniformly-sized data sectors. The storage segments are written at a relatively constant linear density along the spiral track. In the method, the magnetic disk is rotated at a constant angular velocity. A servo sector is detected. An adjustable delay time is provided for opening a window to detect a next servo sector. The window is opened after the adjustable delay time expires. A next servo sector is detected in the window. A time between the servo sector detections is measured and the adjustable delay time is adjusted based on the measured time.

Abstract: A disk storage system having servo data stored thereon for accurate head position control over a magnetic or other storage medium. The servo data is seamless and untrimmed and consists of a primary servo burst set (AB burst) that defines the desired tract pitch for the surface. Multiple secondary servo burst sets (e.g., CD burst and EF burst) are written at the desired track pitch but radially offset from the primary burst set. The servo data is written in multiple servo sectors around the surface of the medium. From the servo data, PES (position error signals) are generated for providing linear position sensitivity information to the head position control logic. The resulting PES is more linear for smaller head sizes.

Abstract: Disclosed is a disk drive using an accelerometer to sense linear vibration and cancel its effects with an adaptive algorithm during track following. The accelerometer is oriented to detect acceleration associated with torque that tends to cause the actuator to move off-track notwithstanding the efforts of the servo control system. The accelerometer's filtered output is used to modify the control effort. The disk drive uses the position error signal to adaptively filter the accelerometer's output in an effort to mathematically converge on a set of optimal filter coefficients and thereby reduce the effect of vibration that may otherwise impose a torque on the actuator.

Abstract: Method and apparatus for operating a motor. During a commutation state current is applied to a motor while field effect transistors (FETs) are held in an enable or disable state to effect current in phases of the motor. The phases have a high FET and a low FET. Control circuitry is employed to detect back electromotive force and zero crossing (Zc) signals that indicate transition timing for the commutation states. At a transition state the current is decreased in accordance with a noninstaneous decay function and applying a pulse width modulated signal to a switching element. Alternatively, the current is decreased by enabling either all low side FETs or all high side FETs to allow the current to decay. The next commutation state is applied after the current has been reduced, avoiding negative current to be source from ground and reducing current spikes in the motor.

Abstract: A method and apparatus for dynamically detecting write fault errors is provided. According to the invention, transducer head control parameters are adjusted according to observed events. For instance, off-track events of a certain magnitude may trigger the implementation of a severe shock timer, which lengthens the delay between the off-track event and allowing write operations to resume, as compared to the standard off-track timer. According to another embodiment of the present invention, a lower write fault threshold is implemented following an off-track event of sufficient magnitude. According to yet another embodiment of the present invention, the average or accumulated position error of the transducer head is monitored, and a lower write fault threshold implemented if the average position error exceeds a threshold value.

Abstract: Track closure errors written into servo sectors of an information track of a disc of a disc drive are resolved from a position control signal generated by a servo control circuit of a data storage device by steps comprising: determining a value for the track closure error from a position error signal, establishing a track closure profile based on the value of the track closure error, and injecting the track profile into the servo control circuit as a feed forward compensation input for the position error signal to resolve the track closure error from the position control signal.

Abstract: An information recording medium, an information recording/reproduction head, and an information storage device are provided for performing a track servo operation at a smaller track pitch than that conventionally used without reducing the widths of servo burst patterns. The widths of servo burst patterns (107, 108, 109, 110) are increased over a track pitch (TP) and the end of the servo burst pattern is disposed so as not to coincide with a center line (111) of an information track. In addition, a servo magnetic head (112) and a reproduction magnetic head (113) are implemented in one magnetoresistance element (159).

Abstract: A read clock circuit for a disk drive includes a phase-locked loop/voltage controlled oscillator (VFO/PLL) and a frequency synthesizer. The VFO/PLL receives a servo sector transition signal that is related to detected transitions in a servo sector field of a magnetic recording disk, and outputs a servo frequency signal that is synchronous to the servo sector transition signal. The frequency synthesizer receives the servo frequency signal and generates the read clock signal that is synchronous with the servo frequency signal. In a banded recording disk drive the frequency synthesizer generates a unique read clock signal for each data band.

Abstract: The present invention involves a recordable disk having a first plurality of S1 servo sample wedges in a first servo zone at an outermost position on the disk, a second plurality of S2 servo sample wedges in a second servo zone which is radially adjacent the first servo zone, and a third plurality of S3 servo sample wedges in a third servo zone which is radially adjacent the second servo zone. The S1 servo sample wedges of the first plurality are equally spaced apart circumferentially around the disk by a first angle ?1, the S2 servo sample wedges of the second plurality are equally spaced apart circumferentially around the disk by a second angle ?2=?1*N1, and the S3 servo sample wedges of the third plurality are equally spaced apart circumferentially around the disk by a third angle ?3=?2*N2.

Abstract: A method for measuring servo pattern irregularity and other servo information of pre-patterned servo media mounted on a spindle with the center of the pre-pattern tracks off center from the axis rotation of the spindle. An actuator is stepped radially while measuring the PES signals from the servo sectors of at least one highly eccentric track to form a cross track profile of the PES signals for each sector. A mathematical algorithm removes step measurement error from the data. A second mathematical algorithm removes non-repeatable random noise from the data. The amount of phase-in that radially aligns the respective cross track profiles is computed. Servo pattern written-in repeatable runout is determined by unwrapping the phase-in values to form a periodic curve.

Abstract: A number of data pairs, each data pair comprises a write-to-read track misregistration (WRTMR) value and an average position error margin (APE) value, are determined for a data storage device. Each of the data pairs is associated with a unique predetermined non-repeatable runout (NRRO) error in the data storage device. Each of the predetermined NRRO errors is caused by subjecting the data storage device to a unique NRRO error stimulus. An ideal APE margin is then determined for the data storage device by using the data pairs to extrapolate an APE margin corresponding to a WRTMR value of zero.

Abstract: A data storage device that can perform a track following process even when vibrations are produced by a wide range of frequencies.

Abstract: A servo mark detector detects a servo mark from each servo information item detected by the servo detector. A counter measures a time period each time a servo mark is detected, thereby measuring a servo interval. A correction circuit corrects a time period T2 on the basis of the measured servo interval and an ideal servo interval. A determination circuit determines which one of the time period T2 and a time period T2? obtained by correcting the time period T2 should be used. A servo-sector-pulse-generating unit generates a servo sector pulse a time period T1 after the detection of each servo mark, and generates a pseudo servo sector pulse when the time period determined by the determination circuit has elapsed after the detection of each servo mark, if the next servo mark is not detected during the determined time period.

Abstract: A head position is demodulated by two-phase servo signals of PosN and PosQ from output of the head, so as to acquire a more accurate demodulated position. Saturation of PosN and PosQ is judged from the ratio of each absolute value of PosN and PosQ, and a different demodulating method is used for a saturated area and for an unsaturated area, and a demodulating formula is constructed so that the edge of each demodulating area matches with the edge of the adjacent demodulating area. Also saturated/unsaturated is judged by comparing the absolute value of PosN and the absolute value of PosQ, and determining whether the ratio thereof is greater or small than a predetermined saturation coefficient r.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: The data row Pw(i) of phase information obtained by reading preformatted phase patterns on an information recording medium by the head consists of the remainders obtained by dividing the data row of the phase information indicating the original track location by 2&pgr;.

Abstract: The invention provides a servo pattern that is stable for long time, easily writable, and excellent in S/N. DC-signal area included in a burst area of a servo pattern comprises combination of positive and negative DC-signals, low-density dummy bit, or pattern having phases that are deviated each other so that the sum of magnetization of the burst area of the servo pattern is equalized to 0.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: A hard disk drive and magnetic medium including a servo area, a data area divided into a plurality of sector blocks and at least one micro-servo area disposed between two sector blocks. There may be a micro-servo area immediately preceding each of the plurality of sector blocks. The micro-servo areas include an address mark and a track parity check code that allow the detection of an external shock that causes the recording (write) head to skip to an adjacent track in the hard disk medium. The micro-servo area is smaller than the servo areas, and various numbers of different track parity check codes can be used for different resolution of shock detection. An acceleration sensor may also be provided to detect larger external shocks. By detecting various external shocks with improved accuracy, and aborting the recording operation of data if an external shock is detected, the corruption of data in adjacent tracks is substantially reduced to improve disk drive performance.

Abstract: Techniques for detecting control data, such as servo data, from input or incoming data read from a magnetic recording medium in the presence of radial incoherence are provided. More specifically, the techniques employ multiple (i.e., two or more) data detectors for choosing between multiple sampling phases associated with the input data read from the magnetic recording medium. In the context of servo data detection, such techniques offer several orders of magnitude in performance improvement in detecting SAM and Gray data in the presence of RI and may advantageously be employed in a read channel integrated circuit. Furthermore, such techniques may be applied to any data encoding system.

Abstract: The present invention discloses methods for manufacturing MTJ cell of MRAM wherein the surface of a pinned magnetic layer having a crystalline structure of long range order is physically impacted with heavy ions or atom to form an amorphous layer having a crystalline structure of short range order. In accordance with the method, a metal layer for connection layer and a pinned magnetic layer are formed. A surface of the pinned magnetic layer is physically impacted with atom to form an amorphous layer. A tunneling barrier layer, a free magnetic layer and a MTJ capping layer are sequentially formed and the MTJ capping layer, the free magnetic layer, the tunneling barrier layer, amorphous layer and the pinned magnetic layer are patterned using a MTJ cell mask to form a MTJ cell.

Abstract: A position information signal pattern is recorded into a recording medium. The position information signal pattern is configured by arranging graphics having a circular shape, a rectangular shape or the like surrounded by a certain closed curve as pattern elements on a plane, and arranging the pattern elements in circumferential and radial directions of a disc so that a phase and a head position establish a proportional relationship in two or more frequency components of a reproduced signal. Position signals of the two frequency components included in the reproduced signal from the position information signal pattern are obtained, and the two position signals are added up with a certain ratio so that a position signal without error is obtained.

Abstract: A transducer position sensing system in a disc drive to take frequent data measurements from micro-servo sectors on the disc and to interpret the information to predict recording failures. The disc drive is formatted with many small or micro-servo sectors containing, among other things, a servo address mark, encoded disc location information, and radial track position information. The sensing system frequently retrieves this information through the transducer, compares the measurements to expected values, and given unexpected measurements predicts errors. The time elapsed between the passing of servo address marks can be used to predict adjacent sector overwrites. The radial track position information can be used to predict off-track write errors. The radial track position signal amplitude can be used to predict the transducer moving too far from the disc, resulting in skip write errors.

Abstract: Non-linearity in a position error signal (PES) for a data storage device is precisely characterized during a calibration phase in the manufacturing process. From this characterization of the PES non-linearity, the data storage device can be programmed with the necessary data to perform accurate, real-time linearization calculations of the PES in order to compensate for non-linearity in the PES during operation. The sequence of calibration steps includes a PES gain calibration, a first servo loop gain calibration, a PES linearization calibration, and an optional second servo loop gain calibration.

Abstract: An apparatus, method and computer program product for a hard disk drive defect detection system. In one embodiment, a method of detecting defects on the surface of a disk having a plurality of tracks is recited. The method comprises reading, one or more times, the servo bits for a plurality of sectors and determining a burst measure for at least one sector, where the burst measure is a function of the burst signals for the sector. This method further comprises determining a reference value, where the reference value is a function of the burst signals of the plurality of sectors, and comparing the burst measure of at least one sector to the reference value to identify a potential defect. In one embodiment, a sector is mapped as defective where its burst measure differs from the reference value by at least 5 percent.