Abstract: A disk device has eccentric misalignment between a plurality of disk surfaces. In order to prevent transient phenomena due to differences in the eccentric trajectories during head switching, a head position control method performs feed forward control for a plurality of disk surfaces by application of the eccentricity correction current of respective heads, and when switching heads, predicts the velocity fluctuation or current step differential between heads from the eccentricity correction current, and thus corrects the control system to eliminate velocity fluctuation and current step differential.

Abstract: A head protection device in a data recording circuit is disclosed in which write-current of a given level that corresponds to a high or low level of coercive force of the magnetic recording portion of a recording medium is provided as an output and supplied to a magnetic head for data recording and reproduction. The data recording circuit comprises an alternate write-current supply portion for alternately providing, by a suitable current switching means, a low write-current corresponding to a low coercivity magnetic head and a high write-current corresponding to a high coercivity magnetic head, a common output portion for providing data to be recorded using a low current or a high current from the alternate write-current supply portion. The low coercivity magnetic head and the high coercivity magnetic head can be at least electrically switched. A current protection portion for a current switching means is provided so as to prevent generation of high write-current at the alternate write-current supply portion.

Abstract: a method for determining and varying the capacity, track per inch and bit per inch values of a hard disk drive. The method includes determining an optimal track per inch value for each head of the drive. The method then determines whether each head does not exceed a threshold BER value. If one or more heads do not exceed the threshold BER value then the BPI (data rates) of the non-performing heads are decreased until an acceptable BER is achieved. The BPI of performing heads may be increased to insure that the capacity of the disk drive still meets a target value. Likewise, if all of the heads are above the threshold value, the BPI of one or more of the performing heads may be decreased to improve the BER of the heads. The reduction in BPI is limited so that the drive always meets the target capacity value. The BPI and TPI values are stored in memory for use during the operation of the drive.

Abstract: A disc drive has transducers supported by an actuator to fly proximate data tracks on surfaces of rotating information storage discs. Each of the discs is partitioned into concentric regions. A control system arranges the deposition of data in write operations to the tracks on the disc surfaces, as data is written to the discs, such that the data is sequentially organized both on the tracks and within each of the regions. The control system writes data from a track adjacent a first region boundary in a first direction to a second region boundary until all tracks in a region are full. The control system executes a head switch between adjacent surfaces of the discs. The write sequence is repeated in each adjacent region until all regions are full. The resulting trapezoidal serpentine pattern of actuator movement and head switches is repeated until all of the write operations are complete.

Abstract: A method for obtaining relative positional relationships between a read-only head for reading data from an original disk and servo heads on each surface of magnetic disks (copy disks), in a magnetic data writing apparatus (disk servo writer) that stacks copy disks and an original disk to rotate the disks unitarily. The apparatus includes a rotary positioner on the periphery of the copy disks and a read-only disk, stacking the read-only head and servo heads rotatably. The apparatus causes the servo heads simultaneously to write servo data to respective assigned track ranges. The method includes stacking calibration disks storing servo data in place of the copy disks in a coaxial relation with the read-only head, in advance of writing magnetic data to the copy disks.

Abstract: This invention relates to a head position control method for a disk device that uses a disk medium whose tracks have been formatted externally, and a disk device that effectively uses the range of motion of an actuator. In a disk device that has a disk medium, a head, an actuator, a control circuit, there is a conversion mechanism that sets a data area in the writing range of the disk 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 a position offset in the range of motion of the actuator.

Abstract: A disk drive which incorporates separate actuators for each recording head so as to only place required recording heads over the recording media of multiple surface hard disk drives. The reduction in recording heads that are placed over the recording media reduces drag on the rotating disk holding the recording media and thereby reduces the power consumption. Reducing the number of recording heads over the recording media also reduces damage to the recording media surfaces in the event of a physical shock to the drive since inactive transducer heads are not in a position to damage the recording media.

Abstract: Magnetic tape experiencing transverse distortion may be read by selecting between longitudinally offset read elements to read a data track. The read elements are part of a tape head having an azimuth angle relative to the tape which creates a transverse offset between the data read elements. This transverse offset is exploited to minimize the effects of any transverse tape distortion.

Abstract: An apparatus and method for dynamic head switch timing recalibration are provided. With the apparatus and method, a determination is made as to whether a difference in a reference head switch timing and the head switch timing at a later time is sufficient to meet a certain criteria. If the difference meets the criteria, a recalibration of the head switch timing is performed. For example, in a preferred embodiment, the criteria is a number of address mark (AM) misses during a head switch operation. If this predetermined number of AM misses is detected, then it is determined that a recalibration is necessary since the predetermined number of AM misses is an indication that the head switch timing has changed significantly from the reference head switch timing.

Abstract: A conventional magnetic head has a structure, in which a MR element and a recording element are stacked. The influence of a recording magnetic field on the magnetically sensitive portion of a reproduction element is lessened and the performance of the MR element is stabilized. Also, the reliability of the magnetic disk drive using a MR element is enhanced. The magnetic disk drive uses a composite magnet head, which has a plurality of reproduction elements arranged such that the magnetically sensitive layer of a reproduction element of the composite magnetic head does not overlap with the normal direction projection of the recording element, and which lessens the influence of a recording magnetic field on the magnetically sensitive portion of each reproduction element.

Abstract: A programmable controller and method for correcting operation of a read/write head in a disc drive having an embedded servo system in which the head is not reading correctly operates by applying a write current to the failed head only after the head is positioned over an area of a disc that does not have useful data thereon. Movement and position of the head that is not reading correctly is determined from a signal from an adjacent head. The adjacent head is used to read servo information. After the adjacent head has provided servo information and the controller repositions the adjacent head in a safe area, a write current is applied to the failed head to realign the head without the potential of adversely impacting data stored in adjacent tracks.

Abstract: Radial correction factors are calculated for each ruler on a patterned media in a data storage system. A ruler is a position-sensing pattern that defines the radial position of a recording head. Rulers are patterned onto each disk before the disks are assembled into a storage system. The radial correction factors are then added to the measured position information during read and/or write operations of the data storage system. The radial correction factors correct for any radial misalignment created by disturbances in the data storage system. Circumferential correction factors are calculated for each patterned media in the data storage system. A corrected sector number is then determined by redefining the original sector numbers using the circumferential correction factors.

Abstract: A method and system of switching heads in a hard disk drive written using an off-line STW method. In the method, first, deviations between a reference head and each of the heads are calculated. Next, a mapping table having the deviations between the reference head and each of the heads is generated and stored in a memory. Thereafter, when a head switching operation is requested, a current head is switched to a new head to access a track whose number is the same as the track assessed by the current head. A deviation of a track on which the head is positioned, recorded in the mapping table, is applied to the virtual track address of the track on which the head is positioned, thereby obtaining the physical track address of the track on which the head is positioned. The requested track is then accessed based on the obtained physical track address.

Abstract: A write drive circuit (40) for a hard disk drive selectively providing a current mode operation for high speed data write of a single channel, and selectively providing a voltage mode operation during a servo write operation. A central buffer has a first circuit (50) providing a current mode drive signal to a head during a single channel write operation, and a second circuit (52) providing a voltage mode drive signal for multi-channel servo write operation. The outputs of both circuits (50, 52) is provided over a common differential connection (T1) feeding a pre-driver circuit (70) adapted to drive one or many heads, as determined by head select control lines (72). The circuit provides >1.6 Gb/s data write speed in single channel write operation, and has an architecture utilizing only two signal lines for four channels.

Abstract: Pursuant to this invention, the idleness of headsets contained in HDs is eliminated by distributing the signals of information among the headsets for parallel processing. Instead of having a form purely sequential of the data aligned on the sectors, as used in the state of the technique (FIG. 1), these data are distributed among the disk surfaces (FIG. 2), altering the physical form of the disposal of the data, however maintaining the logical form and total compatibility of use for this process.

Abstract: A system for adapting head switching sequence in a disc drive includes a method of measuring the time duration for a head switch operation and the time duration of a track switch operation. The system compares the two time durations to determine whether head switching or track switching should be utilized within a zone of tracks on the surface of the data disc. Track switch time durations and head switch time durations may be averaged within a zone and the averages compared to determine whether to use head switching or track switching.

Abstract: A magnetic disk device has an improved seek control in which a waiting time occurred in a first magnetic head while it is scanning a first track, is utilized efficiently and effectively by activating a second magnetic head such that the second magnetic head scans a second track during the waiting time of the first magnetic head.

Abstract: In a disk device in which heads are positioned by a servo mechanism, the object of the present invention is to prevent data from being destroyed by incorrect selection of a head and to improve reliability in recording or reproducing information and to prevent format efficiency from being decreased thereby.

Abstract: A set of coils wind around a magnetic core in a thin film magnetic head. Current supplying circuits are separately connected to the individual coils. The individual coils get shorter in the overall length as compared with the case where a set of coils consist of a single conductor. The impedance of the coils can be reduced. The reduction in the impedance enables the flow of the electric current to be established in a moment within the coils. The magnetic field of a sufficient intensity can be generated in a moment. Magnetization of a sufficient intensity can thus be established on a magnetic recording medium even when the frequency of a signal for recordation gets higher.

Abstract: An apparatus and method for compensation for variation in timing skew in a disc drive having at least one rotating disc is provided. A first head is positioned over a first disc surface and a second head is positioned over a second disc surface. The first disc surface includes a track having a first plurality of sectors and the second disc surface includes a track having a second plurality of sectors. Each sector of the second plurality of the sectors corresponds to a different sector of the first plurality of sectors, thereby forming a plurality of pairs of corresponding sectors. A timing skew value for each pair of corresponding sectors is computed to obtain a sequence of timing skew values. Data related to the sequence of timing skew values is utilized to compensate for variation in timing skew.

Abstract: Using a “reference” sensor, a reference position is detected in a frame of reference that is moving along a predetermined path relative to the reference sensor. The reference position is used to derive a position-dependent indicator of a position-dependent “longitudinal” offset component (i.e. along the path). An output from the target sensor is monitored using a “target window” that is partially based on the position-dependent indicator.

Abstract: A method of writing servo tracks on the disk surfaces of a hard disk drive. The method involves simultaneously writing partial servo tracks, called servo wedges, until a complete first set of servo wedges is written on all the disk surfaces. Then the disks are rotated until the heads of the disk drive are correctly positioned to simultaneously write subsequent servo wedge sets. This process is repeated until enough servo wedge sets are written to complete a first servo track on all the disk surfaces. Then, the heads are pivoted to a new radial position to begin writing a new servo track just as before. Simultaneously writing servo wedges advantageously expedites the often costly servo writing process.

Abstract: A disk device that has displacement of servo signals in the circumference direction and radius direction between a plurality of disks, prevents a drop in performance due to the displacement when the heads are switched. To deal with the displacement in the circumference direction, the sector numbers on the disk are converted by a table for each head. Also the servo gate time is corrected by the table according to the eccentricity of the disk, so the servo signal detection accuracy improves. Also to deal with the displacement in the radius direction, the track numbers on the disk are converted by the table using the difference value based on the reference head.

Abstract: A disk device has eccentric misalignment between a plurality of disk surfaces. In order to prevent transient phenomena due to differences in the eccentric trajectories during head switching, a head position control method performs feed forward control for a plurality of disk surfaces by means of the eccentricity correction current of respective heads, and when switching heads, predicts the velocity fluctuation or current step differential between heads from the eccentricity correction current, and thus corrects the control system to eliminate velocity fluctuation and current step differential.

Abstract: A matrix array of recording heads, wherein each head is independent from another both in terms of its magnetic circuit and excitation conductors. Each individual head has a planar magnetic circuit and an helical coil wrapped around the lower part of the magnetic circuit. The matrix array is collectively fabricated using full thin film technology on non-magnetic substrates. Preferably, the heads are aligned in an oblique lattice with the write gaps aligned along rows and offset by a constant value along columns. Each individual head is connected to the control electronics through interconnects to the backside of the wafer, allowing independent control of the write parameters. The die forming the device is shaped on its edges and top surface to optimize head/medium positioning and minimize wear.

Abstract: A first actuator for controlling positions of all of a plurality of heads within a wide area and a plurality of second actuators for individually controlling the heads within small areas are provided. When two or more of the heads are in write or read state, one or more of the heads, which are not in write or read state, is preliminarily move to a track position to be accessed next.

Abstract: A reproducing circuit for a MR head is proposed, wherein a MR head is interposed between a pair of current source circuits and a feedback amplifier is provided for controlling the current of the pair of the current source circuits so that a terminal voltage of the MR head becomes a predetermined value. Reproduced output from the MR head is derived from an amplifier having balanced input terminals for canceling noises and ripple components included in a power source.

Abstract: For the purpose of letting through a magnetic flux which reverses the magnetization of the magnetic layer of the magnetic disk, a write element requires a predetermined sectional area. However, if a cross section of a magnetic pole is structured as the one having a large aspect ratio, the pole becomes less capable of letting the magnetic flux through effectively. This phenomenon brings about a lower limit on the track width of the magnetic poles and the track density cannot be raised. In the present invention, by making the width of the write element larger than the track pitch and securing a write magnetic field strong enough to reverse the magnetization of the magnetic layer, and further by writing while shifting a write head comprising the write element, a magnetic disk drive, of which the track width is narrower than the write element width, and the storage capacity is large, is realized.

Abstract: An embodiment of the present invention may be described as a method of determining a disc drive head position over a data surface during a head switch operation. The method includes switching from a first head located over a first data surface on one disc to a second head located over a second data surface on a different disc. Each data surface has non-index servo sectors interspersed between a plurality of index servo sectors defined thereon, and each index servo sector has a unique index code corresponding to its angular track position. The method also includes reading an index code from an index servo sector on the second surface and determining an index servo sector number from the index code. Additionally, the method includes incrementing the servo sector number as the second head encounters subsequent servo sectors. A disc drive includes data storage discs arranged in a disc stack.

Abstract: A circuit (80) and method (84) for protecting read heads (18) of a hard-disk drive system (100). Capacitor C1 is controllably coupled to a dummy head Rdummy during a Vbias mode, so that capacitor C1 has a low, predictable voltage upon returning to Ibias mode, protecting the read heads (18) from damage. The circuit (80) includes logic (82) and algorithm (84) determining when to couple the capacitor C1 to the dummy head Rdummy during a servo bank write (SBW) sequence.

Abstract: The overvoltage applied on a head during switching of the head is prevented. At the time when the head switching signal changes, a switch S4 for turning on/off an operational amplifier Gm1 is turned off, and the operational amplifier Gm1 is turned off. Simultaneously, the switch S3 is turned on, the current source I1 is connected to a capacitor C1, and the capacitor C1 is discharged. Then, switches S1 and S2 for switching the MR head are switched. Finally, the switch S3 is turned off and the switch S4 is turned on, thus the switching of the MR head is finished.

Abstract: A recording target error rate is selected for one or more of data storage devices, and for each data storage device, a dither value is determined for each read/write head in the data storage device, wherein for each head, using a dither value for writing data, essentially provides the selected recording target error for all the heads.

Abstract: A preamplifier circuit for a hard disk drive system comprises a preamplifier circuit having a bias voltage circuit stage associated therewith. The preamplifier circuit further comprises a current bias boost recovery circuit operatively coupled to the bias voltage circuit stage which is configured to increase a rate of charging of a noise reduction capacitor associated with the bias voltage circuit stage. A head select boost recovery circuit is also operatively coupled to the bias voltage circuit and is configured to increase a rate of charging or discharging of a bias capacitor associated with the bias voltage circuit stage. Together the circuits allow for a concurrent head switch and current bias switch and avoids the problems associated with the prior art.

Abstract: In a magnetic recording device, a control element placed on a flexible wiring board between a control device and first actuators includes a plurality of actuator-driving-signal connecting terminals connected to a plurality of second actuators, an actuator-driving-signal input terminal to which driving voltage for the second actuators is input from the control device, connecting wires for connecting the actuator-driving-signal input terminal to the actuator-driving-signal connecting terminals, signal selection elements incorporated in the connecting wires, and a decoder for selecting one of the signal selection elements so that a specific actuator-driving-signal connecting terminal is connected to the actuator-driving-signal input terminal.

Abstract: In hard disk drives (HDD), a magnetic read head moves over a portion of the hard disk when reading data. A preamplifier, having an initial amplification stage of the single ended type, connects to the magnetic read head and amplifies a data signal picked up by the magnetic read head. The preamplifier typically has multiple read heads, or channels. In order to reduce noise coming into the read channels of the preamplifier from the substrate capacitances of the input transistors connected to the read heads, the input transistors are grouped together into multiple banks that are multiplexed, or turn on separately. To further aid noise reduction, the poles of the single ended amplifier are matched, that is, the frequency response of the constant voltage side is matched to the frequency response to the signal side. This effectively reduces both ground noise and Vcc power supply noise as the the noise becomes common mode on the inputs to a differential amplifier that is connected to the single ended amplifier.

Abstract: Apparatus and method for compensating for position signal distortion during a disc drive seek. A disc drive has first and second data recording surfaces on which tracks are defined, a moveable actuator which supports first and second magneto-resistive heads, and a servo circuit which applies current to an actuator motor to position the heads. During a seek in which the first head is moved from an initial track to a first destination track, upon loss of transduced servo data from the first data recording surface indicative of radial position of the head, the servo circuit switches from the first head to the second head and applies current to the actuator motor to move the second head to a known radial position with respect to the first destination track while transducing servo data from the second data recording surface. The servo circuit subsequently switches back to the first head to position the first head over the first destination track.

Abstract: An apparatus and method are disclosed for minimizing damage to a disc drive during head switching operations. The disc drive comprises a plurality of magnetic recording surfaces to and from which data are transferred using read/write heads, each head utilizing the application of a bias current during operation. To switch from a presently selected head to a target head, the disc drive determines a first value indicative of the magnitude of a bias current for the presently selected head and a target bias current to be applied to the target head. When the second value is greater than the first value, the disc drive switches from the presently selected head to the target head and then applies the target bias current; conversely, when the first value is greater than the second value, the target bias current is applied to the presently selected head and then the disc drive switches from the presently selected head to the target 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: For the purpose of providing technique by which even when large skew of a disk or a head occurs due to a thermal shock, an outside shock, or the like, a servo signal area is not extended, and a performance loss caused by head change is not produced, a servo detection control system according to the present invention comprises: a learning means by head change including a servo sector interval measuring unit for measuring an interval of servo signal areas, which may occur at the time of head change among a plurality of heads; a time difference calculating unit for calculating head-change time difference from a value measured by the servo sector interval measuring unit; and a time difference storage unit for storing a result of calculation made by the time difference calculating unit; and a compensation and control means for compensating start timing of servo detection after head change using a stored value of the time difference storage unit.

Abstract: A method is provided in which an optimal read gate delay duration for reading from a track of a hard disk drive is determined. The disk drive is of the type having read and write elements separated by an inter-element spacing and a platter including a plurality of radially spaced tracks. In one aspect the method comprises the steps of writing a bit pattern to a track, reading the bit pattern with each of a range of read gate delay durations, calculating a read bit error rate for each said duration and setting the optimal read gate delay to the delay duration corresponding to the lowest read bit error rate. In addition a computer program product, readable by a computer system for implementing the method is also provided.

Abstract: A single disk drive uses data mirroring techniques to store data within the drive. Each piece of data received by the disk drive for storage is written to at least two different storage locations within the drive. Preferably, each of the different storage locations occurs on a different disk surface, but within the same cylinder, of the drive. In one embodiment, each disk surface in the disk drive is divided into N distinct regions that are each 360/N degrees out of phase with one another. Each region on a disk surface is aligned with a corresponding region on each other disk surface in the disk drive. Data stored in each region on a disk surface is then mirrored within a different region on a different disk surface in the drive. Using such a technique allows a significant reduction in latency to be achieved during subsequent read operations.

Abstract: A method of manufacturing a disk drive (10) including determining and implementing skew values for each head (12a-12d) of the disk drive (10) during a production test phase is provided herein. The method for each head (12a-12d) includes initiating a head switch test series, measuring a head switch time, computing an average head switch time, computing a standard deviation of the head switch times, and computing a head skew based on the average and the standard deviation of the head switch times. The method for each head (12a-12d) further includes initiating a single-cylinder seek test, measuring a single-cylinder seek time, computing an average single-cylinder seek time, computing a standard deviation of the single-cylinder seek times, and computing a cylinder skew based on the average and the standard deviation of the single cylinder seek times.

Abstract: A disk drive recording apparatus includes an actuator arm with first and second heads extending from the actuator arm for writing and reading data to and from a first surface of a disk recording medium. The first and second heads are spaced apart from each other in a circumferential direction along the first surface of the disk recording medium. A switching device switches a data input/output path between the first head and the second head in response to a control signal. A microprocessor identifies a target position on the first surface of the disk recording medium and determines which one of the first and second heads is closer to the target position. The microprocessor then generates the control signal to switch the data input/output path to the first head when the first head is closer to the target position, and generates the control signal to switch the data input/output path to the second head when the second head is closer to the target position.

Abstract: Magnetic tape experiencing transverse distortion may be read by selecting between longitudinally offset read elements to read a data track. The read elements are part of a tape head having an azimuth angle relative to the tape which creates a transverse offset between the data read elements. This transverse offset is exploited to minimize the effects of any transverse tape distortion.

Abstract: Because a conventional magnetic head has a structure, in which a MR element and a recording element are stacked, there are cases in which a recording magnetic field affects the MR element, inducing changes in the characteristics of the MR element. An object of the present invention is to lessen the influence of a recording magnetic field on the magnetically sensitive portion of a reproduction element like this, stabilize the performance of the MR element, and enhance the reliability of the magnetic disk drive using a MR element. Further, another object of the present invention is to provide a magnetic disk drive that is capable of improve reliability by using a composite magnet head, which makes a plurality of reproduction elements/reproduction heads correspond to one recording head.

Abstract: Tape recorder having a group of write heads which are arranged like a matrix in rows and columns, with each write head assigned in one row line and in one column line, and having a driver circuit for passing current through the row and column lines. A write head magnetizes a magnetic tape permanently only when its associated row and column lines have currents applied to them causing magnetic fields that reinforce one another in the magnetic tape. A common row return line is provided to which all the row lines are connected and a common column return line is provided to which all the column lines are connected.

Abstract: The present invention is directed to a disk drive that utilizes a multi-stage actuator associated with two or more heads that are each associated with a separate disk surface to realize high speed data transfers. In one embodiment, the multi-stage actuator is used to simultaneously transfer portions of a data file between the heads and the associated disk surfaces and to perform simultaneous seek operations for the heads between data transfer operations. In another embodiment, the multi-stage actuator is used to alternatingly transfer portions of a data file between the heads and the associated disk surfaces and to perform alternating seek operations for the heads such that one head is transferring data while another head is performing a seek operation.

Abstract: A system for adapting head switching sequence in a disc drive includes a method of measuring the time duration for a head switch operation and the time duration of a track switch operation. The system compares the two time durations to determine whether head switching or track switching should be utilized within a zone of tracks on the surface of the data disc. Track switch time durations and head switch time durations may be averaged within a zone and the averages compared to determine whether to use head switching or track switching.

Abstract: A method for improving disk drive performance by adaptively calculating skew values for each drive. During a production phase of the disk drive manufacturing process, skew values are calculated using measured seek times, then implemented to each drive. The calculation scheme permits slipped revolutions to occur during a percentage of the time so that skew values are not so high as to hinder high performance.

Abstract: A method of storing data on a surface of a storage disk, the data being capable of verifying an identity of the surface, includes determining first check data from first alignment correction data associated with a first storage surface. The method also includes determining second check data from second alignment correction data associated with a second storage surface such that the second check data is different from the first check data if the first and second alignment correction data are identical. The method further includes writing the first and second check data to the first and second storage surfaces in association with the first and second alignment correction data, respectively.