Abstract: An apparatus, method, and system for providing a fine adjustment for transducing head positioning in a hard disk drive (HDD). The apparatus, method, and system include reading a positioning error field wherein the resulting signal is a substantially sinusoidal position error signal (PES), filtering the PES to remove low frequencies and attenuate high frequencies, sample the filtered PES at a multiple of the channel frequency, filter the higher frequency harmonics, down sample the PES, and provide a signal proportional to the amplitude of the down sampled PES. This signal is the reference signal to the head positioning servo.

Abstract: A method used in a disk drive system for compensating a frequency component affecting servo control performance. The method includes detecting a frequency component affecting a servo control output in a disk drive/head during a manufacturing process and storing the detected frequency component in a nonvolatile memory device. A frequency component is read from a nonvolatile memory device corresponding to a selected head each time the disk drive is turned on by a user. A parameter value of a filter is determined by using a servo control circuit of the disk drive to suppress the read frequency component.

Abstract: A method of determining frequency bands of a data storage system and an apparatus using the same are provided. More particularly, a method of determining frequencies used for reading and writing data from and to a disk drive while avoiding frequencies that have adverse effects on a system and a disk drive using the same are provided. A method of determining read and write frequencies of the data storage system may include determining frequencies that have adverse effects on functions of the data storage system; selecting frequencies to be used when reading and writing data to and from a disk drive while avoiding the frequencies determined to have adverse effects on the functions of the data storage system.

Abstract: A disk drive uses a hybrid analog-digital acceleration feedforward control system and method for cancellation of rotational disturbances. A rotational vibration (RV) sensor is used with an analog circuit to generate an analog feedforward signal that is summed with the analog actuator control signal from the servo control processor. The analog feedforward signal is also converted to a digital feedforward signal and input to the processor. When the actuator gain deviates from its design value, the processor retrieves the appropriate actuator gain value from a lookup table. The processor uses the actuator gain value and the digital feedforward signal to calculate a modified feedforward signal, which is a fraction of the digital feedforward signal. The processor also calculates a feedback control value from the servo positioning information and a feedback controller.

Abstract: Embodiments in accordance with the present invention relate to a positioning control system of a magnetic disk drive. Even if there is no phase correlation in a specific vibration component before and after a seek operation of a magnetic head, a resonance filter in accordance with an embodiment of the present invention follows the vibration at the frequency at high speed. A frequency showing a periodic disturbance is selected as a target frequency Ft[Hz]. A resonance filter showing a peak gain at a frequency Ft is designed. For an input to the resonance filter, a time-variable gain K(t) is used that varies depending on the time lapsed after the completion of a seek operation. This time-variable gain K(t) takes a value larger than 1 when the resonance filter starts operating, and after the lapse of a fixed length of time, the value becomes 1 by degrees.

Abstract: A terminal voltage of an actuator motor is measured while the actuator motor is in a high impedance state. An internal voltage of the actuator motor is measured, and a back-EMF voltage of the actuator motor is estimated in response to the terminal voltage of the actuator motor and the internal voltage of the actuator motor. A drive current supplied to the actuator motor is controlled in response to the estimated back-EMF.

Abstract: Embodiments in accordance with the present invention provide a disk drive capable of verifying whether the speed of an actuator is true or not, the speed being detected while the actuator is being moved between a retracted position and a recording surface of a magnetic disk, and to provide a control method for controlling the disk drive. In a particular embodiment, a hard disk drive (HDD) comprises: a head for accessing a disk; an actuator for supporting the head, the actuator being driven by a voice coil motor (VCM); a speed monitor for, on the basis of a cylinder ID written to the disk, monitoring the speed of the actuator while the actuator is being moved between a ramp which is provided outside a data area of the disk and the data area; and a speed verifier for, if an abnormal speed condition of the actuator is detected by the speed monitor, verifying the abnormal speed condition on the basis of the counter electromotive voltage of the VCM.

Abstract: Embodiments of the invention provide a servo information write method that makes it possible to properly locate the last-written servo information even when old servo information is overwritten by new servo information. In one embodiment, a servo track writer controller, which is within a servo track writer, reads a serial number (S/N) from a HDD (step 101), and acquires a magnetic disk drive servo information write count (P-ID) from a manufacturing process host (step 102). The next step (step 103) is then performed to control a positioner and a read/write channel so as to start writing servo information onto a magnetic disk. Servo information is sequentially written until the last track is written into (step 104). When the Nth servo information is to be written, a P-ID (N) is written subsequently to a burst signal (step 105). When the last track is written into in step 104, step 106 is performed to notify the manufacturing process host that the Nth servo information write is performed.

Abstract: Embodiments of the invention provide a magnetic disk drive and its control method capable of effectively using the unrecordable area which is caused due to the composite magnetic head's gap between the read head and the write head. In one embodiment, a disk drive comprises a composite magnetic head structured in such a manner that during write the write head WH reaches each servo area earlier than the read head RH, and a read write control unit to control the write and read done by the composite magnetic head. On the disk, common servo data SP to be used both during read and during write, write servo data SW to be used during write and read servo data SR to be used during read are recorded in this order in each servo area. During write, the read write control unit starts the write head recording data at the timing when reading write servo data SW from the servo area is completed.

Abstract: A rate of occurrence of off-track write events is determined. A seek function control parameter for a head is adaptively adjusted based on the determined rate of occurrence of the off-track write events. Related circuits and devices are also discussed.

Abstract: A synchronization system includes a signal generating module that generates a signal comprising modulated waveforms and a timing window generator that generates a timing window. A proportional integral controller (a) divides the timing window into a first half window and a second half window, (b) demodulates the digital signal in the first half window and the second half window, (c) compares an amplitude of demodulated signal in the first half window to an amplitude of demodulated signal in the second half window, (d) calculates a new location for the timing window, and (e) repeats (b), (c), and (d) until the amplitude in the first half window equals the amplitude in the second half window.

Abstract: Provided is a method of compensating for a bias for efficient servo control of a hard disk drive, and optimally compensating for bias force based on the elapsed usage time of a hard disk drive, and a bias force profile generation method, recording media, and a hard disk drive appropriate to the bias compensation method. The bias compensation method for compensating for a bias force applied to a magnetic head of a hard disk drive includes: measuring the bias force at the current position of a head; selecting a bias force profile having a bias force similar to the bias force measured at the current position of the head, from among a plurality of bias force profiles that are obtained by measuring bias forces of a disc from based on the elapsed usage time of the hard disk drive; and compensating for the bias force according to the selected bias force profile.

Abstract: Embodiments in accordance with the present invention provide a magnetic disk drive with sufficiently low noise. A digital/analog converter supplies to a voice coil motor (VCM) driver a control voltage comprising a first preset voltage value, a second preset voltage value, and a transition voltage value of a substantially cosine wave that interconnects the first preset voltage value and the second preset voltage value. A driving current is supplied from the VCM driver to a voice coil of an actuator assembly. Since a current not containing higher-harmonic components in a transition period flows as a VCM current that flows into the voice coil, vibromotive force can be easily suppressed by shifting a structural resonance point of the entire disk drive including the actuator assembly.

Abstract: A microactuator reference limit used to prevent over-accumulation of internal states may be set based on the microactuator's mechanical properties and is applied at the reference point to the microactuator servo subsystem. A microactuator variable input limit to prevent over-accumulation of internal states may be dynamically determined based on the difference between a signal corresponding to the maximum physical stroke of the microactuator and an estimated motion of the microactuator. Either configuration of servo system automatically ensures that all the internal states of the microactuator controller will not over-react and cause excessive overshoot, sluggish response, and/or saturation.

Abstract: An acceleration sensor outputs a signal in accordance with acceleration. A differentiator outputs a differential signal of the output signal. A comparator inverts the state of an output when the differential signal goes beyond a threshold. A monostable multivibrator maintains the state-inverted signal of the output for a predetermined period of time. An integrator integrates the acceleration detection signal. A comparator inverts the state of an output signal when an integrated signal goes beyond a threshold. A fall determination processor outputs a signal out indicating that a fall has been detected in a situation in which, when the output of the monostable multivibrator is active, the state of the output of the comparator is inverted.

Abstract: A seek control unit moves a head to the vicinity of a target track of a storage medium by coarse control, then switches it to fine control, and positions the head to the target track. A rotation disturbance compensation control unit applies a rotation disturbance vibration detection signal based on acceleration velocity sensors to the seek control unit as a compensation signal so as to cancel out rotation disturbance vibration components. A compensation control switching unit sets the rotation disturbance compensation control unit to be either on or off and, when a coarse seek error in which it is out of a fine switch error range upon coarse control by the seek control unit is finished is determined, switches the rotation disturbance compensation control unit to an opposite setting state and causes the seek control unit to perform seek again.

Abstract: A seek-information storing unit stores seek information including a correlation between a seek distance indicating a shift distance from a current track to a target track where a target frame for a data input/out is located and a seek time indicating a shifting time that takes for a head to shift from the current track to the target track, based on an actual measurement. A head-shift control unit controls a shift of the head based on an estimated time obtained by adding a rotational delay time that takes until the target frame arrives at the head position after the head arrives at the target track to the seek time acquired from the seek information.

Abstract: Embodiments of the present invention allow for controlling a microactuator based at least in part on an output of a temperature sensor. Also, embodiments of the present invention allow for adjusting a control of a microactuator so as to compensate for changes in a gain of the microactuator due to changes in temperature.

Abstract: Various embodiments of the present invention are generally directed to using a transducer to transfer data during a transducer displacement operation at a time during such operation when the transducer is substantially stationary.

Abstract: Embodiments in accordance with the present invention erase a desired area on a recording surface of disk or disk drive apparatus. According to an embodiment, a hard disk drive (HDD) performs erase on a recording surface by moving a head element unit at one-half a servo track pitch with reference to a servo address. Before actual erase is started on the recording surface, the HDD generates a management table configured based on servo addresses from a management table configured based on data tracks. At an erase process, the HDD sets parameters in accordance with the zone and skips a management area with reference to this management table based on the servo addresses.

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: A disk drive controller including a differential voice coil motor control function is disclosed. The differential voice coil motor control function includes an on-chip compensation network for the inner control loop, including a resistor formed of one or more MOS transistors connected in series. The gate of the MOS transistors in the compensation network is driven with a bias voltage based on a tuning current, where the tuning current is derived so that it varies with process and temperature variations of the integrated circuit, for example with variations in an on-chip capacitor. The on-chip compensation network can be tuned with sufficient precision to properly compensate the inner control loop to provide the desired frequency response in driving the voice coil motor in the disk drive.

Abstract: Stable recording and reproduction of data onto and from a recording medium that requires precise tracking is provided by using a simple head tracking mechanism. In a hard disk drive (200), a piece of sector data to be written or read is pre-associated with a sector number of a sector where the piece of sector data is to be written or read. A seek control unit (260) corrects first-order run-out relative to a revolution axis of a DTM magnetic disk (100) and permits second-and-higher order run-out relative to the revolution axis, and moves a read/write head (122, 124) gradually in one radial direction of the DTM magnetic disk at a shift pitch smaller than the track pitch for each revolution in accordance with the sector numbers of the sectors where pieces of sector data are to be written or read, within a range of tracks containing the sector numbers of the sectors where the pieces of sector data are to be written or read.

Abstract: An actuator supports a head at one end of a rotatably supported shaft unit and supports a coil of a voice coil motor at the other end, and moves the head to an arbitrary track position of a recording medium. A sensor, attached to a coil support unit of the actuator, detects the coil vibration and outputs a vibration detected signal. A control unit controls the actuator to reduce a head position error signal based on the vibration detected signal of the sensor in time of seek and in time of settling of moving the head to a target track position on the medium through drive of the actuator and drawing the same. The vibration detected signal of the sensor includes bending vibration component of the coil and the twisting vibration component of the coil when the actuator is driven.

Abstract: The present invention provides a positioning control device and a disk device for shortening a calculation delay time. Upon detection of a position signal from a demodulation circuit, an MCU of the disk device calculates a position error, and following calculation of a control amount, executes determination and correction processing. A variable value prior to the start of calculation is stored in a save area of a memory (or a save memory) such that when the variable value is to be reset as a result of the determination and correction processing, the variable value is read from the save area, the reset variable value is stored in an overwrite area of the memory (or an overwrite memory), and calculation of the control amount is re-executed.

Abstract: Methods and devices are shown that identify suitable second data operations after experiencing an off track event in a first data operation and perform the second data operations before correcting an off track event. Methods and device as shown provide increased efficiency in a hard disk drive. Time that normally would be wasted waiting for the read/write head to spin around for another try to correct an off track error is used to complete other nearby operations.

Abstract: A method and apparatus for controlling movement of a transducer to limit its stopping time at a certain position of a disk regardless of whether the disk drive performs a read/write operation, an etching or clustering effect of a lube layer coated on the disk is prevented, thereby preventing performance degradation of the disk drive.

Abstract: A method of controlling recording and a hard disk drive (HDD) using the same. The HDD has heads in which a write head and a read head are spaced apart from each other by a predetermined gap in a track direction, and the method includes: reading a table having a head gap time corresponding to the gap between the write head and the read head and a disk linear velocity; and beginning a write operation by delaying the write operation by the head gap time from a data sector pulse. Accordingly, since a gap between a servo sector and a data sector and between data sectors can be reduced by the length corresponding to a head gap time, the usage efficiency of a data area can be increased.

Abstract: In a hard disk drive (HDD), biases are measured across all zones of a disk, and nonlinear bias components are extracted. Upon a change in operational condition of the HDD, biases are measured at two reference positions on the disk so as to estimate a corresponding change in a linear bias component across all zones of the disk. The bias at a given position of the disk is then calculated based on the estimated linear bias component and the extracted nonlinear bias component.

Abstract: A method of providing a control output by selecting a controller to an actuator is discussed. A first controller having an estimator-compensator architecture is selected if the actuator is in a settle stage. A second controller having an architecture other than that of the first controller is selected when the actuator is in a track follow stage. The control output is provided from the selected controller to the actuator. The control output is indicative of the control signal.

Abstract: In a magnetic disk device, a magnetic head protrudes when a write current is applied to a write element, and the protrusion amount is controlled using a heat generating element provided on the magnetic head. During read operations, power equal to the sum of a first power value and a second power value is supplied to the heat generating element of the magnetic head, and during write operations, power equal to the first power value is supplied to the heat generating element in addition to the write power. In this manner, protrusion can be controlled to compensate for scattering among the heads and changes in ambient conditions, so that overwrite characteristics can be improved, and read characteristics can also be improved.

Abstract: The delay time from the rotation start of a magnetic disk medium (M) to a servo pattern being read is obtained with respect to a radial position from the phase delay that the trajectory of a magnetic head (H) by a rotary actuator causes with respect to the radial direction axis of the medium (M), and is reflected to the generation delay time of a servo gate signal used at servo reading.

Abstract: A disk drive is disclosed employing a VCM control loop comprising a voltage detector operable to detect a back EMF voltage across a voice coil of a voice coil motor, a current detector operable to detect a current flowing through the voice coil, and a control voltage generator, responsive to a command input and the detected back EMF voltage, operable to generate a control voltage applied to the voice coil. Control circuitry within the disk drive (a) initializes the control voltage; (b) injects a transient into the VCM control loop and detects a corresponding current flowing through the voice coil; (c) adjusts the control voltage in response to a polarity of the detected current; (d) repeats elements (b) and (c) at least once; and (e) stores an offset value in response to the adjusted control voltage.

Abstract: A method of determining a correction factor for a voice coil motor of a disk drive device is performed by driving a relatively low current through the voice coil motor during a seek operation. Actuator velocity is then measured. A correction factor is calculated as a function of the actuator velocity to allow estimation of velocity as a function of back EMF.

Abstract: A magnetic disk device includes a position and velocity demodulating circuit. In the position and velocity demodulating circuit, a difference calculating unit demodulates a moving velocity of a magnetic head based on a phase difference in servo signals as servo data in the same sector. An overflow detecting unit detects an overflow of the demodulated moving velocity and calculates a correction value for the overflow. The overflow is corrected based on the correction value. The corrected overflow is further corrected by a correction value of a repeatable velocity error for the demodulated velocity to output an accurate demodulated velocity.

Abstract: A reduced hardware control circuit device includes a current loop for broad band Hard Disk Drive applications. The current loop detects the value of the current flowing on the coils of a voice coil electric motor incorporated in the Hard Disk Drive. A sensing resistance is connected in series with the motor and at least a driving driver for a relative motor coil. Advantageously the current loop is a transconductance loop with a first transconductance amplifier associated with the sensing resistance. A second transconductance amplifier is provided for fixing the current value to be applied to the motor. The circuit device advantageously is deprived of a local compensation in correspondence with the first transconductance amplifier.

Abstract: In a settling judgment method for judging whether an object is settled in a target position, the settlement is judged accurately at high-speed. In a positioning device for controlling a position of an object using a position error between a target position and a current position, a plurality of judgment blocks, each of which has a different judgment slice value and continuous sample count, are created in a settling judgment block for judging whether the object is settled within the positioning accuracy range of the target position, the judgment value of the position error computed by the judgment formula is judged in each judgment block each having a different judgment slice value and continuous sample count respectively, and OR of the judgment results is output. According to the settling judgment formula, settling can be judged accurately at high-speed, and both improvement of positioning accuracy and high-speed judgment can be implemented.

Abstract: A feedforward compensator for induced vibration is disclosed. Controlled motions in an actuator induce mechanical disturbances in a surrounding cabinet. The feedforward compensator allows such disturbances to be compensated for without the need of a vibration sensor. The compensator provides a feedforward compensation signal configured to compensate for a mechanical disturbance predicted to be induced by a controlled motion of the actuator, and applies the feedforward compensation signal to a signal that controls the motion of the actuator.

Abstract: In a seek control device based on a current observer control which performs two degree of freedom control, a current step difference to be generated when seek control is switched to following control is prevented. When seek control is switched to following control, a current step difference cancellation trajectory generation section calculates a current value Udiff for the amount of the step difference based on a difference between current values u(n) and u(n?1), and supplies a target position trajectory r?(n) (or target current trajectory) for offsetting this calculated value to a following controller. Therefore the current step difference of the output current is cancelled.

Abstract: A method is disclosed for determining fundamental-frequency repeatable runout (1FRRO) coefficients in a disk drive. The disk drive includes a transducer head, a rotating magnetic disk having a plurality of concentric data tracks defined by embedded servo wedges that provide position information, and an actuator coupled to the head. In the method, the head is caused to move in a substantially constant velocity motion across a selected portion of the tracks of the rotating magnetic disk in response to a control signal. The position information is read from the embedded servo wedges as the head moves across of the selected portion of the tracks. The 1FRRO coefficients are determined based on the position information read as the head moved in a substantially constant velocity motion across the selected portion of the tracks.

Abstract: In an integrated free-fall detection device for a portable apparatus an acceleration sensor generates acceleration signals correlated to the components of the acceleration of the portable apparatus along three detection axes. A dedicated purely hardware circuit connected to the acceleration sensor generates a free-fall detection signal in a continuous way and in real-time. The free-fall detection signal has a first logic value in the event that the acceleration signals are simultaneously lower than a respective acceleration threshold, and is sent to a processor unit of the portable apparatus as an interrupt signal to activate appropriate actions of protection for the portable apparatus. Preferably, the acceleration sensor and the dedicated purely hardware circuit are integrated in a single chip and the acceleration sensor is made as a MEMS.

Abstract: A disk drive is disclosed including a disk having a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors forming N servo wedges, and a wedge time period (WTP) occurs between each servo wedge. A VCM control signal is generated by generating an estimated WTP by detecting the servo sectors, estimating a pivot velocity in response to the estimated WTP, the pivot velocity representing a velocity of an actuator arm about a pivot, generating a pivot friction compensation in response to the estimated pivot velocity, and generating the VCM control signal in response to the pivot friction compensation.

Abstract: A loading/unloading type magnetic disk unit includes a magnetic disk that is rotated or driven by a motor, and a head slider bearing a magnetic head and being movable above the magnetic disk owing to a driving mechanism. Herein, at least one projection made of a highly conductive material is formed on the surface of the head slider opposed to the magnetic disk. When the magnetic disk unit is in operation, conduction to the spindle motor is discontinued after the elapse of a predetermined time. Thus, the height by which the head slider floats is decreased so that the projections come into contact with the magnetic disk. Consequently, a charge on the magnetic disk escapes through the housing of the magnetic disk unit via the head slider. Thus, when the loading/unloading type magnetic disk unit is in operation, a charge on the magnetic disk can be removed.

Abstract: Embodiments of the invention provide a data storage device and its control method that are capable of minimizing the possibility of head deterioration while maintaining the minimum required sustained data rate. In one embodiment, each track is divided into three areas (A, B, and C). When a ? track is accessed, the head is changed to access a ? track on the next recording surface. In this instance, LBAs are assigned to disks so that heads Hd0 through Hd4, which access both surfaces of disks 0 and 1, are selected for accessing purposes in the Hd0, Hd1, Hd2, Hd3, Hd0, and Hd1 order while an area selection is made in the area A, area B, and area C order.

Abstract: A data storage device executes sector guarantee processing at an unexpected power supply disconnection. The sector guarantee processing can be accurately performed even if the fluctuation of power supply voltage during normal operation is high. The voltage of the power supply is monitored via an A/D converter. The control unit calculates a voltage change value, which is a relative value of the detected voltage of the power supply, and judges power supply disconnection by the level of the voltage change value, to perform sector guarantee processing. The voltage fluctuation during normal operation and the voltage fluctuation at power supply disconnection can be distinguished, power supply disconnection can be accurately detected, and write disable status can be judged.

Abstract: A head control device for controlling, through thermal expansion of a heater, a position of a head for reading and writing data from and to a storage medium, includes a heater control unit that increases a current supplied to the heater stepwise; and an external-force sample retrieving unit that retrieves sampling values of signals each indicating a magnitude of an external force acting on the head in a moving direction of a head support mechanism. The head control device also includes an external-force evaluating unit that calculates a representative value of the sampling values retrieved by the external-force sample retrieving unit to evaluate the magnitude of the external force every time the heater control unit increases the current; and a contact detecting unit that detects contact between the head and the storage medium by comparing each evaluation result by the external-force evaluating unit with a predetermined threshold value.

Abstract: A servo control method of controlling a plant to track a reference trajectory with enhanced accuracy using a reference signal and its derivative signals, an apparatus and a recording medium suitable for same. The servo control method includes: determining a polynomial indicating a reference trajectory desired by a plant and derivatives of the polynomial; sampling a plant output with respect to a plant input; generating a reference signal and its derivative signals with reference to a time between samples (a relative time); and determining a plant input at a sampling time using the generated reference signal and its derivative signals, a delayed plant input and a delayed plant output. Accordingly, a plant is controlled to track a reference trajectory with enhanced accuracy using a reference signal and its derivative signals.

Abstract: In a settling judgment method for judging whether an object is settled at a target position, a margin for settling judgment is expanded, and settling is judged accurately. As the settling judgment formula of the settling judgment block, both the position error and the added value of the position errors of a plurality of samples are used. Particularly for the vibration in the low frequency area, the margin for settling judgment increases. Therefore even if vibration exists in the low frequency area, judging as deviation from the settling judgment conditions by mistake can be decreased, and operations (e.g. read/write operation) can be continued.

Abstract: A seek control apparatus for performing a seek control of a head comprises an MCU that acquires control information corresponding to the externally indicated data length out of the control information stored in a storage section storing the control information for seek control for each of a plurality of data length ranges and performs a seek control according to the acquired control information.

Abstract: According to embodiments of the present invention, tracks can be formed on a magnetic recording medium on a zonal area at intervals of either a first track pitch or a second track pitch, both of which differ from each other. For a reference track defined in each zonal area, regardless of whether tracks are formed with the first track pitch or the second track pitch, the first track pitch and the second track pitch are specified so that a head position at the time of writing or reading information to or from the reference track, is common to both of the first track pitch and the second track pitch.