Abstract: In a data storage medium, which includes a servo information area where information on the position of a head is recorded and a data information area where actual data information is recorded, the servo information area is divided into an A/B burst section and a C/D burst section, and the A/B burst section has a servo pattern in which phases of burst signals A and B are recorded to be different from each other and the C/D burst section has a servo pattern in which phases of burst signals C and D are recorded to be different from each other. Thus, when the length of a bit recorded on a data storage medium is reduced considerably, an output signal of a head and a burst signal can be detected without distortion and accordingly an accurate control of head tracking is possible.

Abstract: Methods and systems for detecting and correcting for undesirable vibrations impacting the servo systems in data storage devices. A detection technique is provided wherein a detection filter is configured to scan a position signal of the servo system across a range of frequencies, and, at each respective scanned frequency, record an amplitude associated therewith. The recorded amplitudes are examined to determine whether any exceed a threshold, thereby locating a peak frequency of the vibration. Using the detected peak frequency of the vibration, a corrective filter is configured to operate about the peak frequency of vibration, thereby reducing its impact on the position signal in the servo system.

Abstract: When the amount of position error PE of a magnetic head meets the condition of Ewf>PE>=Eww for two threshold values Ewf and Eww meeting Ewf>Eww, the track is registered in the track information table as a track requiring rewrite and the tracks on both sides neighboring to the track are temporarily write-inhibited. The data of the track is rewritten on another track later so as to maintain the data.

Abstract: A method of testing a performance of an HGA includes a step of obtaining a displacement performance of a precise positioning actuator by driving this actuator to displace and by executing a track profile measurement of at least one thin-film magnetic head element.

Abstract: By increasing the gain of a controller for coarse motion CFBV within a frequency band in which the gain of a sensitivity function SP=1/(1+PP·CFBP) of fine motion actuator DP and controller for fine motion CFBP exceeds 0 dB, the gain of a sensitivity function SV=1/(1+PP·CFBV) of coarse motion actuator PV and coarse motion controller CFBV is decreased. Through this, in a two-stage actuator control system, a disk apparatus can be provided in which a sensitivity function SPES=1/(1+PP·CFBP)·1/(1+PP·CFBV) indicative of a disturbance compressive ratio in a signal path ranging from disturbance components to a head position error signal is rendered to be 0 dB or less at all frequencies concerned.

Abstract: The present invention implements a servo system which can support changes of the higher resonance frequencies of the actuator with a simple configuration at low cost.

Abstract: A significant change in the static angular position can be produced from a small physical displacement of the flexible member. The flexible member 12 in a magnetic head unit 95 is stressed for adjusting the static angular position. Simultaneously, the stressed areas 14 are irradiated by a laser beam LA.

Abstract: A method of handling resonance effects on disc drives includes the steps of monitoring a position error signal (PES) for an actuator arm of a disc drive, generating a feedforward compensation signal from the PES using a bandpass filter, and applying the compensation signal to a servo control signal. The bandpass filter has a center frequency set to a known resonance frequency. A disc drive includes an actuator assembly including an arm for carrying a head in a transducing relation with respect to a disc in response to a control signal, and a controller that monitors a PES for the arm and generates the control signal. The controller includes a servo controller that generates a servo control signal from the PES, and a feedforward compensation element which bandpass filters the PES to generate a compensation signal which is combined with the servo control signal to generate the control signal.

Abstract: A sector servo type magnetic disk apparatus is provided with, in addition to servo signals, a sensor such as an accelerometer for detecting a state of a magnetic head or a support for the magnetic head at a period shorter than a sampling period of the servo signals. Since an accelerometer mounted on the magnetic head or the support for the magnetic head detects an acceleration, the control performance of a servo control system can be improved, such as reduction of generation of mechanism resonance vibrations of a carriage and improvement on detection precision of a speed signal.

Abstract: A system for controlling movement of a head over tracks on a disc in a disc drive includes a servo positioner for positioning the head over a desired track, a sectoring circuit for determining when the head is over a data sector on the desired track, a formatter for controlling data transfers to and from the desired track, and a controller for providing the servo positioner with a track address indicative of the desired track. A track change system is coupled to the formatter and the servo positioner, and provides a direct communication channel between the servo positioner and the formatter. Thus, the data transfer can be carried out utilizing communications between the formatter and the servo positioner, without waiting for the microcontroller to be interrupted.

Abstract: A digital servo system for a disk drive provides servo information signal demodulation. The system includes a digital demodulator including a burst signal accumulator that accumulates terms according to respective burst timing intervals to produce a digital, quadrature position error signal (PES). The demodulator also can include a dibit burst filter with synchronous dibit sampling preferably implemented as a Hilbert Transform filter. Alternatively, the demodulator does not include a filter and a squarer and, instead, the squarer comprises a sum-and-squarer that sums the squares of odd and even digitized samples. In another embodiment, the system employs a digital demodulator having a digital squarer that removes any phase component of the digitized servo information signal and includes a burst signal accumulator that accumulates the squared terms according to respective burst timing intervals to produce the PES. The demodulator may include a filter comprising a harmonic notch filter.

Abstract: A repetitive learning compensator for a servo system of a disc drive includes a memory buffer having a length N/m where N is the number of servo sectors in a track, m is a parsing factor greater than 1 and N/m is an integer. A down sampler supplies servo signals containing error signals to the repetitive learning compensator at a frequency of fs/m, where fs is a sampling frequency based on N and a fundamental frequency f0 of the spindle motor. An up sampler supplies filtered signals from the repetitive learning compensator to the actuator assembly at the sampling frequency fs. One aspect of the disclosure includes tuning the repetitive learning compensator with a phase advance represented by NPA and a cutoff frequency fc, where NPA and fc are selected as a pair to provide the greatest transfer function amplitude at the harmonic frequencies for the repetitive learning compensator.

Abstract: A disc drive including a rotatable data track, a dual-stage actuator with a primary actuator motor supporting an actuator arm, a read/write head supported by the actuator arm and communicating with a secondary actuator motor, and steps for controlling range of motion of the secondary actuator motor. The controlling steps include supplying and sustaining a bias signal to a single-sided unipolar device driver that then apply a bias voltage the secondary actuator motor to induce the secondary actuator motor to expand substantially one half of its expansion capabilities. And, confining correction signals provided by a control circuit of the disc drive, used in correcting mechanical position of the secondary actuator motor, to a voltage ranging substantially between a positive “+” and negative “−” voltage substantially equal to the applied bias voltage.

Abstract: A disk device, track positioning method, and method for generating a position error signal in which the occurrence of a wrong correction operation can be prevented by creating an appropriate PES without using a burst pattern having a defect, and reassign sectors can be decreased by decreasing defective sectors thereby to reduce the performance degradation is disclosed. In the disk device and track positioning method, the defect of a burst pattern read out from a disk is detected, and if a defect is detected in the burst pattern, a data value corresponding to the sum data of the burst pattern pair having the defect detected is obtained by measuring the maximum amplitude value of the burst pattern pairing with the burst pattern having the defect detected, and a PES is created according to the amplitude of the burst pattern having the defect detected and the maximum amplitude value.

Abstract: A low cost sensorless technique for attenuating an actuating force experienced by the actuator arm assembly due to an external vibration and shock during a track following operation includes, in one example embodiment, measuring an applied signal and a position error signal during the track following operation within a sampling time. Then, the method includes the step of computing an acceleration signal from the measured position error signal. Further, the method includes comparing the acceleration signal with the applied signal to obtain a correction signal. Then, the force experienced by the actuator arm due to the external vibration and shock is attenuated by filtering the correction signal using one or more low-pass frequency filters.

Abstract: When the amount of position error PE of a magnetic head meets the condition of Ewf>PE>=Eww for two threshold values Ewf and Eww meeting Ewf>Eww, the track is registered in the track information table as a track requiring rewrite and the tracks on both sides neighboring to the track are temporarily write-inhibited. The data of the track is rewritten on another track later so as to maintain the data. By doing this, the offtrack of the recording track can be made smaller without sacrifice of the access speed and the occurrence probability of write fault can be reduced. Furthermore, the reliability of a magnetic disk apparatus can be improved.

Abstract: A head suspension supporting a head at the tip end is allowed to swing at the tip end of a carriage in a recording disk drive. A microactuator is interposed between the head suspension and the carriage. A resistor is connected to the microactuator in serial. The microactuator is allowed to function as a capacitance. A combination of the microactuator and the resistor enables establishment of a so-called low pass filter. A high frequency noise involuntarily introduced in the driving voltage for the microactuator can be eliminated or removed from the driving voltage. Elimination of the high frequency noise enables a reliable prevention of the mechanical or physical resonance or vibration in the head suspension. A tracking action of the head related to a target recording track can reliably be stabilized.

Abstract: A controller for read/write head actuator of a hard disk drive system includes a feedback unit providing a voltage to a servo-actuator motor. The feedback unit includes a first fuzzy logic rule-based algorithm unit for the seek mode and a second fuzzy rule-based algorithm unit for the track mode. In the seek mode, the first algorithm unit, based on present position and delta (velocity) parameters, determines an optimum velocity. A signal representing the optimum velocity is compared with a signal representing the present velocity and an appropriate signals applied to the head actuator unit. The use of the fuzzy logic rule-based algorithm permits a near-minimum seek time even in the presence of non-linear and varying parameters. The output signal from the seek mode apparatus or the output signal from the track mode apparatus is selected based on position and velocity parameters.

Abstract: In a magnetic recording apparatus including a support arm movable with respect to a magnetic recording disk, a first actuator for moving the support arm with respect to the magnetic recording disk, a pair of support members at least one of which holds a magnetic head thereon and each of which is connected to the first actuator through the support arm to be driven by the first actuator through the support arm, and a pair of second actuators for moving respectively the support members with respect to the support arm so that the support members are respectively moved with respect to the magnetic recording disk by the first actuator and the second actuators, the second actuators move simultaneously the support members respectively with respect to the support arm in respective directions opposite to each other.

Abstract: This invention relates to head position control method for a disk device the uses a disk medium whose tracks have been formatted externally, and the disk device that effectively uses the range of motion of an actuator. In a disk device that has a disk medium (2), head (3), actuator (5), a control circuit (8), there is a conversion mechanism (31) that sets a data area in the writing range of the disk (2) that corresponds to the range of motion of the actuator, and converts a logical address to a physical address in the data area. This invention makes it possible to set a storage capacity that makes maximum use of the range of motion of the actuator for any device, even when there is position offset in the range of motion of the actuator.

Abstract: A data recording and/or reproducing apparatus which scans a head over a disc on which a servo pattern for moving the head to a predetermined position is recorded in an arc forming a part of a concentric circle. The apparatus comprises a track No. detector and fine signal detector, for detection of the servo pattern, a circumferential position detector to detect a circumferential position on the disc, an offset calculator to calculate an offset of a current position on the disc from the detected circumferential position, and a positional difference calculator. The calculated offset of the current position is added to the positioning signal to control the head scanning orbit on the disc to be spiral.

Abstract: A magnetic storage system having one or more rotating disks is disclosed. In a preferred embodiment, each rotating disk has two magnetic surfaces which each contain a number of tracks. Each track has one or more data regions and one or more embedded servo sectors. First and second transducers are respectively suspended over first and second tracks corresponding to first and second magnetic surfaces. The second transducer determines an off-track position with respect to the second track by reading from the data region of the second track. Once the off-track position is determined for the second transducer, that information is used to position the first transducer with respect to the first track and position the second transducer with respect to the second track as the first transducer writes to the first track. Furthermore, the first transducer is positioned at a correction rate that exceeds the rate at which the first transducer encounters embedded servo sectors in the first track.

Abstract: A servowriting method for a hard disk drive is performed by detecting a servo-pattern on a first surface of a disk with a trailing coil of a first head slider positioned over the first surface of the disk. The detected servo-pattern is written onto the first surface of the disk with a first leading coil of the first head slider spaced-apart from the trailing coil, while the servo-pattern is simultaneously written onto a second surface of the disk opposite to the first surface with a second leading coil of a second head slider positioned over the second surface.

Abstract: A disk drive has a sampled servo system controller and a disk with a plurality of angularly spaced servo wedges. Each of the servo wedges contains angularly aligned servo burst fields that are radially adjacent to one another and spaced apart by an erase field. In order to eliminate or minimize servo position signal errors caused by a wide-reading transducer head encountering signals from both of a pair of angularly aligned servo burst fields, the servo burst fields are recorded in opposing phase.

Abstract: The present invention relates to a servo control apparatus of a disk recording system and particularly to a servo control apparatus and method which are capable of controlling position of a head for recording digital data on a disk as recording media and reading the digital data.

Abstract: A magnetic disk device that has a sufficient tracking control capability and a sufficient capability, and has the rotational speed of a magnetic disk reduced to record moving-image information. A magnetic disk device accesses a magnetic disk with a magnetic head by effecting tracking control of the magnetic disk at predetermined angular intervals, each of the servo areas being formed in synchronism with a clock signal and having a reference pattern for the tracking control. The clock signal is generated by referring to a playback signal from a number of servo areas. Thus, a clock area in one servo can be shortened. The recording density of the magnetic disk is prevented from being reduced even if a number of servo areas area formed on the magnetic disk are effective to prevent the sampling frequency from being lowered. As a result, a sufficient tracking control capability and a sufficient recordable density can be achieved, and the speed of the magnetic disk can be reduced to record moving-image information.

Abstract: An arrangement for recording servo signals on a magnetic tape has first and second adjoining write heads respectively driven by first and second write signals. Each write signal includes a servo signal and a bias signal, the bias signals being phase displaced periodic signals which result in the magnetic tape being magnetized alternately by the first and second write heads. This provides a sharp transition in the servo signals produced from adjoining servo tracks during read-out.

Abstract: A method for detecting servo data and an interleaved dibit detection apparatus are provided for servo data detection in a direct access storage device. The interleaved dibit detection apparatus includes a new dibit threshold detector for detecting a predefined threshold level of a new interleave servo signal and providing a new detected dibit output. An old dibit threshold detector detects the predefined threshold level of an old interleave servo signal and provides an old detected dibit output. A combining function coupled to the new dibit threshold detector and the old dibit threshold detector provides a combined detected dibit output.

Abstract: In a magnetic disk apparatus in which heads integrally having write heads and read heads are arranged correspondingly to data surfaces of plural media, servo information including phase servo patterns is written discretely in a track direction onto the data surfaces of the plural media. For this reason, at first, displacement amounts of the read heads with respect to the write heads are measured in each head and each cylinder position of the media. Next, phases of the phase servo patterns are adjusted so that relative displacement amounts between the reads heads are eliminated in each head and each cylinder position of the media, and the phase servo patterns are written.

Abstract: Servo-pattern information is magnetically recorded on a product disc by magnetic print-through from a master medium. The master servo-writing medium is brought into close proximity with the product “slave” disc, and the two are subjected to an external magnetic field which assists in transferring magnetic servo-patterns to the slave disc in a print-through process. The preferred external magnetic field alternates and rotates with respect to the master/slave combination. In an alternative product disc structure, the magnetic layer is magnetically altered in a servo-pattern configuration. Non-magnetic portions of the servo pattern are created which define both gray code and servo burst information for the product disc.

Abstract: A servo-demodulator for a pair of alternating signals generated by a magnetic disc read head and indicative of the position of the read head in relation to the center of a recorded track. The servo-demodulator comprises a peak detector for successively and individually sampling the amplitude of each of a plurality of peaks of the pair of alternating signals, and a capacitor periodically connected to the output of the peak detector by a control logic for deriving a weighted average of the various successively sampled amplitudes. In this manner, the control logic obtains an averaged measure of amplitude with high immunity to noise.

Abstract: A multi-task system employs a single interrupt occurring at fixed time intervals to initiate the control functions. The actuator control, servo control and spindle control routines are operated on a priority basis so that if a control function having a high priority is not ready to be executed, the processor immediately performs execution of the next available control function. More particularly, the spindle control process is operated in the foreground with the actuator control and servo control routines operated on an interrupt basis of the spindle control routine. Upon receipt of the interrupt signal, priority is first given to an actuator control routine for execution. Upon completion of the actuator control routine, or if the actuator control is not ready to be executed, access is given to a servo control routine. At the conclusion of the servo control routine, the interrupt exits to the spindle control routine.

Abstract: A hard disk drive (HDD) magnetically reading and writing digital data, and measuring the track pitch of a hard disk drive to detect more accurately the position error signal on each disk. The track pitches are calculated according to heads and zones, and compared with a reference track pitch as measured and averaged over all of the disks. The track pitches corresponding to the calculated track pitches are updated when detecting the calculated track pitches are the same for less than the reference track pitch. The track pitches corresponding to the calculated track pitches measured in accordance with head number and zone number are updated when detecting that the calculated track pitches are greater than the reference track pitch.

Abstract: A method and apparatus for protecting a disk from overwrites during mechanical shock. If the PES exceeds an off-track threshold for a predetermined number of servo samples, the read/write is suspended for a predetermined duration. The predetermined duration allows for the mechanical shock or disturbance to abate and allows the heads to settle with respect to the track. The off-track threshold being exceeded for several servo samples is used as an indicator of the mechanical force and subsequent undesirable vibration. The writes can then be suspended for the predetermined duration, thereby avoiding overwriting data on adjacent tracks.

Abstract: A servo system uses a disk on which two pairs of burst data items A and B and burst data items C and D are prerecorded, and the servo system performs positioning control for positioning a head within a range of a track on a disk. The servo system sets a range of a track to be divided into a first area regarding the track center as a reference position, a second area regarding a boundary position between tracks as a reference position, and a third area regarding a middle position between the reference positions, as a reference position. In the first area, the servo system calculates position information of the head by a first calculation formula using the burst data items A and B. In the second area, the servo system calculates position information of the head by a second calculation formula using the burst data items C and D. Further, in the third area, the servo system calculates an average value of calculation results from the first and second calculation formulas, as position information.