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: An acoustic emission sensor is mounted on a flying slider opposed to a rotating recording medium, for example. The acoustic emission sensor outputs a detection signal in response to the sound of collision. When a protrusion exists on the recording medium, the flying slider is expected to collide against the protrusion at a predetermined fixed angular position. A variation is induced in the detection signal based on the collision between the flying slider and the protrusion in synchronization with the rotation of the recording medium. Specifically, when a variation is synchronized with the angular position signal of the recording medium, the variation should correspond to a protrusion existing on the surface of the recording medium. If the component corresponding to the variation is extracted out of the detection signal, a protrusion on the recording medium can be determined at a higher accuracy.

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

Abstract: Friction existing between any two surfaces having relative motion is nonlinear, multiform, and is difficult to model. Nonlinear friction in the actuator pivot of a hard disk drive (HDD) limits the low frequency gain, which prevents the system positioning accuracy from further improvement. This problem is much more pronounced for the severe nonlinearity at the micrometer level. The conventional two-mode proximate time optimal servomechanism (PTOS) is inadequate for immediate future hard disk drives because of the existence of restrictions in the particular design approach. A triple-mode control scheme, and its variations, as presented herein, include (a) a proximate time-optimal controller (PTOC) having a relatively large output is used for track seeking, (b) a robust compensator having a relatively small output is used for track following to compensate for friction and other nonlinearities, and (c) a bridging (connection) control to guarantee the continuity of the control signals.

Abstract: An apparatus and method of controlling an actuator of a data storage device detect and/or correct narrowband mechanical excitations such as due to spindle bearing defects through sensing and/or rejecting disturbance frequencies associated with such narrowband mechanical excitations in an actuator control signal generated by a data storage device controller. A narrowband filter may be used to reject, from an actuator control signal generated by a data storage device controller, a disturbance frequency associated with a spindle bearing defect in a data storage device, and disposed in proximity to a zero crossover frequency associated with the data storage device controller. In addition, a peak filter disposed in a control loop of a data storage device controller may be configured to detect a spindle bearing defect in a data storage device by detecting an amplitude of a control signal in the control loop in proximity to a disturbance frequency associated with the spindle bearing defect.

Abstract: An information recording system includes a storage medium, such as a magnetic or an optical medium, that is formed to have a plurality of adjacent tracks. Each track includes a plurality of storage elements that are arranged substantially along the track in a regular manner. A head disposed in proximity to the storage medium and has a width that spans at least two adjacent tracks. The storage elements are further arranged substantially along first and second axes, such that the first and second axes are substantially perpendicular to each other and are each substantially oriented 45° from an along-track direction associated with a track. The head reads and/or writes information from at least two adjacent tracks spanned by the head.

Abstract: A hard disk drive that has a reaction mass and a transducer that can be used to move and/or sense the acceleration of an actuator arm of the drive. The transducer is coupled to a disk controller that can provide output signals which induce a movement of the reaction mass. Movement of the reaction mass will cause a responsive movement of a head(s) coupled to the actuator arm. The transducer can also provide input signals to the controller that correspond to an acceleration of the actuator arm. The acceleration signal can provide force feedback for a servo system of the drive.

Abstract: A disk drive includes a head stack assembly having a storage disk, a data transducer, an actuator pivot center and a positioner. The positioner includes a magnet assembly, a primary coil array that generates a first rotational displacement of the data transducer, and a secondary coil array that generates a second rotational displacement of the data transducer. The absolute value of the ratio of the first rotational displacement to the second rotational displacement is at least approximately 1.5:1. The primary coil array generates a first vibration displacement that causes the data transducer to move off track, and the secondary coil array generates a second vibration displacement that is out of phase from the first vibration displacement. The absolute value of the sum of the first and second vibration displacements is less than the absolute value of the first vibration displacement.

Abstract: A method and apparatus for improving the settle time and thus, the transition from seek control to track following control in a disc drive system are provided. With the apparatus and method, two counters are provided—a consecutive counter and a non-consecutive counter. The consecutive counter counts consecutive samples that meet threshold requirements. The non-consecutive counter counts non-consecutive groups of consecutive samples that meet threshold requirements. When the consecutive counter reaches a first predetermined value, the non-consecutive counter is incremented and the consecutive counter is reset to zero. When the non-consecutive counter reaches a second predetermined value, a track following control mechanism is initiated to thereby transition from a seek control operation to a transitional control operation and finally a track following control operation.

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 disturbance compensation signal is produced by estimating the magnitude of disturbance acting upon an actuator based on a driving signal and a voltage signal generated when driving the actuator. A control signal is produced by multiplying the disturbance compensation signal by a gain adjustment coefficient. A head position error signal is produced based on the target position of a magnetic head and the current position of the magnetic head that is detected based on servo information recorded in advance on a magnetic disk. A gain adjuster obtains the driving signal by adding together the control signal and a position control signal. The actuator is driven with the driving signal output from the gain adjuster.

Abstract: A method for improving the performance of a rotary actuator in a disk drive, the rotary actuator comprises a voice coil motor (VCM) characterized by a torque parameter, the disk drive comprises a servo control system having a motor driver circuit for receiving a series of command effort signals (CEFs) transmitted based on a first seek profile, and for providing an operating current to VCM based on the CEFs for causing a movement of the actuator from a first radial location to a target radial location. The method includes recording the transmitted CEFs, and while actuator is moving: adjusting each recorded CEF to account for a disk drive influence on actuator movement; storing adjusted CEFs; monitoring velocity of moving actuator; calculating an acceleration value corresponding to moving actuator from the stored CEFs and monitored velocity; and adjusting the acceleration value to account for a radial torque parameter variation.

Abstract: A magnetic disc storage apparatus including a magnetic head for reading information from a storage track on a magnetic storage disc driven to spin, a voice coil motor for moving the magnetic head above the disc, and a magnetic head drive system for executing a position control of the magnetic head by controlling driving current of the voice coil motor by a feedback control while monitoring a state of reading the magnetic head in which the magnetic head drive system includes multi-mode driving means for executing a linear drive mode for controlling, as an analog amount, the driving current of the voice coil motor when an amount of driving to move the magnetic head is small and executing a pulse drive mode for controlling, as a digital amount, the driving current of the voice coil motor when the amount of driving to move the magnetic head is large.

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

Abstract: A disk drive (HDD) (and method) subject to linear and rotational vibration, includes an independent sensing unit for sensing a rotational velocity component of the rotational vibration in a predetermined frequency range, and an optimal filter combination for receiving an output from the sensing unit.

Abstract: A position control system for a magnetic head improves servo tracking characteristics in a low frequency range without impairing the stability of seek operations. The position control system is equipped with two integrators: a first integrator 43 and second integrator 45. The gain K3? of the second integrator 45 is set larger than the gain K3 of the first integrator 43. The first integrator 43 plays the role of offsetting the bias force acting on the magnetic head while the second integrator 45 plays the role of improving the servo tracking characteristics in the low frequency range.

Abstract: A method for writing streaming audiovisual data to a disk drive is performed by organizing the data into clusters and commencing writing the clusters to the first physical sector encountered after the read/write head has settled to the desired track on the rotating disk. A cluster contains a number of data blocks corresponding to the number of physical sectors in an integer number of tracks on the disk, so that the writing of a single cluster is the writing to an integer number of full tracks on the disk. Even though the disk drive may have a physical index to identify the first physical sector in all the tracks, the writing of cluster data takes place without regard to index position.

Abstract: The magnetic disk apparatus includes a magnetic disk for storing thereinto information; a head equipped with a recording conversion element for writing information into the magnetic disk and a reproducing conversion element for reading information from the magnetic disk; an actuator arranged by a suspension for supporting the head so as to move the head on the magnetic disk, and also a drive apparatus for driving the suspension; and a stopper for limiting a movable range of the actuator, whereby a distance between a reproduction element and a recording element is measured and also a track width of the magnetic disk is measured in order to execute a self-servo write operation.

Abstract: A detector detects, in read data, a servo address mark of a type indicated by a register. Every time a SAM is detected during a self servo process, a CPU carries out tracking control in accordance with corresponding servo data. The CPU causes a head to write a corresponding type of additional servo data item in a disk at a position offset from the position of servo data containing the detected SAM, by a predetermined distance in a circumferential direction of the disk. Every time sets of servo data, each consisting of various types of data items, are written in the disk, the head is moved by a predetermined pitch in a radial direction of the disk.

Abstract: A skip mask mechanism is implemented in a disc drive in order to increase performance by minimizing the number of necessary disc rotations required while executing a set of pseudo-sequential commands. The drive includes an interface between the host computer and the drive, a read/write channel between the interface and the transducer/head, a formatter between the interface and the read/write channel for timing when data is transferred between the interface and the read/write channel, and a skip mask mechanism interposed between a target calculator and the formatter that provides a masked input to the formatter for controlling passage of data between the interface and the read/write channel.

Abstract: A magnetic disk drive that drives and positions an actuator using a voice coil motor, includes a current sensing resistor connected in series to a terminal on current input side of the voice coil motor, a first operational amplifier and a second operational amplifier. The magnetic disk drive further includes one of a third operational amplifier and a microcomputer.

Abstract: Position error values are obtained from a transducer head while following a plurality of servo tracks with a servo loop that band-blocks a frequency range that includes F, a nominal rotation frequency. An estimated difference distribution is derived from the position error values, the difference distribution having a first frequency component at a positive frequency ?2*F. A scalar track squeeze magnitude indicator is derived from the estimated difference distribution so that the indicator to be transmitted depends on the frequency component.

Abstract: A device for generating synchronous numeric signals, including a first signal generator which supplies a numeric reference signal having a first frequency and a first period; and a second signal generator which generates an internal numeric signal having a second frequency and a second period, and a synchronized numeric signal. In addition, the second signal generator includes a predictor which generates, with a third period and a third frequency higher than the first frequency and the second frequency, estimated samples correlated to a current sample and to a predetermined number of former samples of the internal numeric signal. The predictor, in turn, includes a selection circuit controlled by the first signal generator for selecting one among the estimated samples in each reference period, the synchronized numeric signal being formed by the selected estimated samples.

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 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 split actuator comprising two spring coupled actuators that share a common pivot bearing. The two reduced inertia actuators permit overlapping motions during a seek operation thereby reducing dead times in transfer of data between disk and transducers disposed on the actuators. A spring member that spring couples the two actuators boosts relative motions by storing and releasing spring potential energy selectively. The spring member is also configured so as to substantially restrict the relative motions of the two actuators to rotational motions about a common axis of the common pivot bearing. Rigidity of the spring member to non-rotational relative motions, as well as tuning of the spring member to provide a rigid response to selected frequencies, the spring member in conjunction with the common pivot bearing result in mechanical disturbance being substantially common to the two actuators, thereby allowing predictable and manageable disturbance corrections.

Abstract: A nested transimpedance amplifier (TIA) circuit includes a zero-order TIA having an input and an output. A first operational amplifier (opamp) has an input that communicates with the output of the zero-order TIA and an output. A first feedback resistor has one end that communicates with the input of the zero-order TIA and an opposite end that communicates with the output of the first opamp. A capacitor has one end that communicates with the input of the zero-order TIA. The gain-bandwidth product of the nested TIA is increased. Differential mode TIAs also have increased gain-bandwidth products.

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: 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 servo control circuit provides seamless transition between seek and track modes while enabling both rapid seek mode operation and accurate tracking. The control circuit includes an analog-to-digital converter having a non-linear characteristic. The non-linear characteristic provides disproportionately large control voltages to derive speed and settling in the seek mode and essentially linear control voltages in the track mode to provide low noise and accurate tracking operation.

Abstract: A disk apparatus includes: an actuator 7; a driver 10; a voltage detector 11 for outputting first voltage signal Ed which is produced in a driving coil 5 of the actuator 7; a voltage signal adjuster 16 for outputting pseudo disturbance signal ur and generating second voltage signal Ed+ from pseudo disturbance signal ur, driving signal u, first voltage signal Ed, and disturbance estimation signal &tgr;dest; a disturbance estimator 12 for estimating the magnitude of disturbance load &tgr;d applied to a magnetic head 2 from driving signal u and second voltage signal Ed+ to output disturbance estimation signal &tgr;dest; a position detector 13 for generating position error signal e which corresponds to a current position of the magnetic head 2; a position controller 14 for generating control signal c from position error signal e; and a corrector 15 for generating driving signal u from disturbance estimation signal &tgr;dest and position control signal c.

Abstract: A method is disclosed for recursively 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, resonant filter values for developing RRO cancellation values are iteratively learned and updated after each disk rotation during track following operations on a predetermined track until a threshold, such as a particular number of disk rotations, is obtained.

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 phase lock loop to control phase error including a first phase error detector to detect the phase error in a first mode, a first loop filter to filter a first phase error by using a first factor, a second phase error detector to detect a second phase error in a second mode, a second loop filter to filter a second phase error by using a second factor, and a circuit to select either the first phase error or the second phase error in accordance with the first or second mode.

Abstract: An apparatus and method for removing mechanical resonance in a disc drive using an adaptive notch filter. Mechanical resonance harmful to a system is removed by a notch filter that adaptively varies the frequency characteristics of the filter with respect to the mechanical resonance frequency existing in the system.

Abstract: A method of testing a performance of an HGA including 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: A magnetic read/write apparatus comprises: a recording medium; and a head for writing/reading data to/from each sector on the recording medium; wherein the magnetic read/write apparatus further comprises: a write inhibit slice setting circuit for, when data is written to the recording medium, setting a write inhibit slice for each sector based on the recording state of each sector on the recording medium.

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 method of expanding the on-track operational range of a disk drive based upon detection of an external vibration condition. The method involves detecting that a vibration state exists and, while the existence of the vibration state is detected, modifying the default on-track-declaration algorithm such that a data transfer operation can be completed in less time than if the default on-track-declaration algorithm was in use.

Abstract: A piezo actuator drive circuit (40) adapted to operate in both a charge mode and a voltage mode. A low frequency compensation loop (44) is formed from a piezo actuator output (OUT6XP) of a driver (42) to the input thereof. The resulting closed loop system produces charge mode operation within a bandpass that can be tuned for desired operation. Below the bandpass turn on frequency (Fh) the closed loop system restores the piezo output (OUT6XP) to a defined DC voltage and compensates for any wandering effects, such as DC current mismatches in the closed loop configuration, such that the piezo output is centered around the desired DC operating point. The circuit is further provided with a DC restore feature in combination with the feedback which allows for a low frequency DC coupled path and thus allows for the DC positioning of the piezo in the charge mode to be changed. The DC restoring amplifier is used to compensate for offsets in the amplifier chain.

Abstract: Apparatus and method for enhancing disc drive reliability by applying reduced read bias levels to read elements of a disc drive during an idle mode of operation. A preamplifier driver circuit applies an operational read bias signal of selected, nonzero magnitude to the read element to transduce data from a recording surface during an active mode. Once a predetermined period of inactivity occurs during which host data transfer commands are not processed, the disc drive enters the idle mode and the preamplifier reduces the read bias signal magnitude. The reduced bias level during the idle mode reduces thermal stress and electromigration within the read element while still allowing data to be transduced from the recording surface as the drive performs a dithering operation to move the head to different tracks on the recording surface.

Abstract: Method and apparatus for improving data transfer rate performance of a disc drive data handling system having a plurality of transducing heads adjacent a corresponding plurality of data recording surfaces. Concentric tracks on each of the recording surfaces are provided with a physical track address determined by servo data written to each track. Logical track addresses are assigned to the tracks by positioning a first head adjacent a selected location on the corresponding recording surface, measuring a head offset value for each of the remaining heads, and assigning the logical track addresses on each data recording surface in relation to the measured head offset values. The logical cylinders include tracks with different physical track addresses, and the tracks in each logical cylinder are nominally aligned with the heads. This reduces the need for corrective seeks after head switching within the same logical cylinder.

Abstract: A disk drive comprises an actuator servo control system including at least one disk, an actuator structure comprising at least transducer head for writing and/or reading data from the disk and providing a transducer head position error signal (PES), and a servo compensator applying a servo control algorithm to the PES to produce a servo control signal. An adaptive elliptic notch filter controller is adapted to analyze the PES for a transducer head at a disk track radii, identify resonant disturbances present in the PES, select two adjacent resonant disturbances having first and second frequencies, ascertain coefficients of at least a fourth-order elliptic notch filter transfer function having first and second zero-notches with frequencies substantially at the first and second resonant frequencies, apply the at least fourth-order elliptic notch filter transfer function with the ascertained coefficients in the servo system to thereby substantially attenuate the selected adjacent resonant disturbances.

Abstract: Apparatus and method for reducing nonlinearities in a position error signal (PES) of a disc drive data handling system. The disc drive data handling system includes a disc recording surface having a number of tracks and a controllably positionable read/write head. A servo circuit generates a sequence of PES samples indicative of head position with respect to a selected track using servo position data samples transduced from the selected track and a first set of compensation values selected to reduce nonlinearities in said PES samples. The PES samples are combined with the first set of compensation values to generate an updated set of compensation values. This process is preferably repeated a number of iterations to converge to a final set of compensation values which provide a substantially linear PES across the radial width of each track.

Abstract: A positioner (20) for a disk drive (10) that includes a magnet assembly (52), a conductor assembly (54), and a control system (22) is provided herein. The magnet assembly (52) includes a pair of magnet arrays (56A) (56B) and a pair of spaced apart flux return plates (75A) (75B). The conductor assembly (54) includes at least a first coil array (80) and a second coil array (82) that are substantially co-planar. The control system (22) directs current to electrically excite the coil arrays (80) (82) to maintain a data transducer (50) on a target track (32) of a storage disk (28).

Abstract: An attenuating filter for the servo control processor of a disc drive data storage device. The filter is constructed by determining the peak resonance in the structure frequency response above a preselected magnitude and computing a digital notch filter to attenuate that peak resonance. The notch filter domain is then summed with the structure frequency response to derive a modified structure frequency response. The modified structure frequency response is substituted for the unfiltered structure frequency response and again the peak resonance in the modified structure frequency response above a preselected magnitude is determined and a notch filter is computed as necessary. This process of summing the structure frequency response with the latest computed notch filter domain to derive a modified structure frequency response continues until the peak resonance of the latest modified structure frequency response is less than the preselected magnitude.

Abstract: A nested transimpedance amplifier (TIA) circuit includes a zero-order TIA having an input and an output. A first operational amplifier (opamp) has an input that communicates with the output of the zero-order TIA and an output. A first feedback resistor has one end that communicates with the input of the zero-order TIA and an opposite end that communicates with the output of the first opamp. A capacitor has one end that communicates with the input of the zero-order TIA. The gain-bandwidth product of the nested TIA is increased. Differential mode TIAs also have increased gain-bandwidth products.