Abstract: According to one embodiment, a magnetic disk device comprises a feedforward control unit, which includes a plant model processing unit including a plurality of submodel processing units. Each of the submodel processing units generates a submodel output value that is an output value for an input value to be input, and the feedforward control unit generates the output value based on a plurality of the submodel output values.

Abstract: A data storage device includes a data storage disc, an arm, a head, a rotary actuator, and an elevator. The disc has a read/write surface defining an x-y plane. The arm includes a load beam. The head is supported by the load beam, and the head is configured to interact with the read/write surface. The rotary actuator is configured to move a first portion of the arm about a first pivot axis in the x-y plane. The elevator is configured to move the arm in a z direction relative to a vertical surface and is configured to frictionally engage the vertical surface to hold the arm at a z direction position while allowing the rotary actuator to move the first portion of the arm about the first pivot axis. In another aspect, an apparatus includes a stack block, first and second clamp arm assemblies, and first and second piezoelectric actuators.

Abstract: A method for offset calibration of a rotation rate sensor signal of a rotation rate sensor. In a first step, an ascertainment is made that the rotation rate sensor is in an idle state. In a second step, after the first step, a filter parameter is determined as a function of the measured rotation rate sensor values, measured in the idle state, of the rotation rate sensor. In a third step, after the second step, a filtered measured rotation rate sensor value is determined with the aid of the filter parameter. An offset is determined with the aid of the filtered measured rotation rate sensor value.

Abstract: A data storage device is disclosed comprising a first plurality of heads actuated over a first subset of disk surfaces by a first servo control loop comprising a first coarse actuator and a first fine actuator, and a second plurality of heads actuated over a second subset of the disk surfaces by a second servo control loop comprising a second coarse actuator and a second fine actuator. A plurality of access commands are received, wherein each access command is associated with one of the heads. While executing a first access command using the first servo control loop, a disturbance is ramped while injecting the disturbance into the second servo control loop, and the second fine actuator is calibrated based on the disturbance.

Abstract: Systems and methods are disclosed for calibrating actuators in a multi-stage servo system. In certain embodiments, a method may comprise performing a calibration process on a multi-stage actuated servo system, including: seeking the multi-stage actuated servo system to a selected location, via a first stage actuator; providing a first voltage injection to a first microactuator of the multi-stage actuated servo system; measuring a first position error signal (PES) of the multi-stage actuated servo system; determining a first gain for the first microactuator based on the first PES, without adding a signal injection to the first PES; and applying the first gain to the first microactuator.

Abstract: A data storage device is disclosed comprising a first head connected to a distal end of a first actuator arm, a second head connected to a distal end of second first actuator arm, a first coupler configured to couple the first actuator arm to an actuator, and a second coupler configured to couple the second actuator arm to the actuator. Access commands stored in a command queue are sorted into an execution order based on a selective coupling of the first and second actuator arms to the actuator. At least one of the access commands is executed based on the execution order in order to access at least one of a first and second disk surfaces using at least one of the first and second heads.

Abstract: A data storage device is disclosed comprising a first disk surface, a first actuator arm, a first head connected to a distal end of the first actuator arm, an actuator, and a first coupler configured to couple the first actuator arm to the actuator. The first coupler is actuated in order to couple the first actuator arm to the actuator during at least part of a seek interval, and while the first actuator arm is coupled to the actuator, the actuator is moved in order to seek the first head over the first disk surface.

Abstract: Systems and methods are provided for designing a compensator for controlling a plant and to control systems for such plants. In one embodiment, a compensator may be designed by introducing a predetermined input into the plant; measuring an impulse response of the plant responding to the predetermined input; determining a mathematical model for the plant based at least in part on the impulse response of the plant, the model comprising a first ratio of polynomials (the plant model) including a first set of coefficients; and determining a second ratio of polynomials including a second set of coefficients (the compensator) based at least in part on the first set of coefficients to operate the compensator such that the compensator produces a series of plant inputs to move the plant towards a setpoint according to a predetermined plant output.

Abstract: A head suspension assembly for supporting a read/write head of a disk drive located on a rotatable drive actuator arm is disclosed. The head suspension assembly includes a baseplate end proximate to and operatively connected to a first microactuator pair, the first microactuator pair communicatively coupled to a controller. The head suspension assembly also includes a load beam movably connecting the first microactuator pair to a second microactuator pair. The head suspension assembly also includes a head transducer end proximate to and operatively connected to the second microactuator pair, the second microactuator pair communicatively coupled to the controller. The read/write head is located proximate to the head transducer end, the read/write head being flexibly connected to the load beam, and the controller is configured to selectably transmit control signals to the first and second microactuator pairs in order to improve tracking control of the read/write head.

Abstract: A device is provided for controlling a piezoelectric actuator able to combine two types of piezoelectric actuator control, namely voltage control and charge control. Switching between charge control and voltage control takes place automatically, without added switching elements, according to the nature of the voltage applied to the input of the setup.

Abstract: A data storage device is disclosed comprising a head actuated over a disk surface comprising a plurality of servo sectors, wherein each servo sector comprises a servo burst field. Across a first radial band of servo tracks, the servo burst field comprises a first length, and across a second radial band of servo tracks, the servo burst field comprises a second length longer than the first length. When the head is over the first radial band of the servo tracks, the head is servoed over the disk surface based on the first read element reading a first servo sector and the second read element concurrently reading a second servo sector different from the first servo sector. When the head is over the second radial band of the servo tracks, the head is servoed over the disk surface based on the first read element reading a third servo sector.

Abstract: Implementations disclosed herein include a method to synthesize the controller of a multi-stage servo control system with multiple actuators in a hard disk drive by dividing controller synthesis into multiple dual-stage steps. The method includes measuring a first output of a first plant corresponding to a first actuator, measuring a second output of a second plant corresponding to a second actuator, designing a first controller responsive to the first output, designing a second controller responsive to the second output, and combining the first output and the second output to obtain a first combined output in a first dual-stage. The method also includes designing a third controller responsive to the first combined output, measuring a third output from a third plant corresponding to a third actuator, designing a fourth controller responsive to the third output, and combining the first combined output and the third output to obtain a second combined output.

Abstract: An apparatus includes voice coil motor (VCM) control circuitry and microactuator control circuitry. The VCM control circuitry includes a VCM disturbance observer configured to generate a VCM disturbance compensation signal. The microactuator control circuitry includes a microactuator disturbance observer configured to generate a microactuator disturbance compensation signal. The VCM disturbance observer and the microactuator disturbance observer are decoupled from each other.

Abstract: Systems and methods for compensating for hysteresis in a disc drive are described. In one embodiment, a method may use an inverse hysteresis model to linearize effects of hysteresis of a microactuator in the disc drive. The hysteresis model may be a Coleman-Hodgdon hysteresis model. The hysteresis of the microactuator may be characterized, and the inverse hysteresis model may be based at least in part on the characterization. The inverse hysteresis model may be used to implement a digital filter. The digital filter may be employed in series with the microactuator to linearize the effects of hysteresis.

Abstract: Embodiments of the invention provide a device for measuring pitch and roll torques. The device comprises a sensor plate having a horizontal cross member, a vertical cross member and a surrounding member connecting ends of the horizontal and vertical cross members, wherein the horizontal cross member and the vertical cross member intersect each other at a centre region of the sensor plate; a VCM coil attached to the sensor plate and configured to generate a pitch and a roll torque when an electrical current is applied to the VCM coil; a first strain gauge attached to a surface of the horizontal cross member and configured to detect a horizontal strain caused by the pitch and roll torques; and a second strain gauge attached to a surface of the vertical cross member and configured to detect a vertical strain caused by the pitch and roll torques.

Abstract: Disturbance rejection in a closed loop multi-actuator system. In some embodiments, a first disturbance observer (DOB) circuit is configured to inject a first disturbance rejection signal into an input control signal of a first stage of a multi-stage actuator. A second DOB circuit is configured to concurrently inject a second disturbance rejection signal into an input control signal of a second stage of the multi-stage actuator. Each of the first and second DOB circuits includes a band pass filter and an energy reducing filter. In some embodiments, the energy reducing filter has at least one notch filter and at least one anti-notch filter. In other embodiments, the energy reducing filter is a low-pass filter (LPF).

Abstract: An apparatus and associated method are provided whereby first and second spindles operably rotate first and second overlapping storage discs, respectively. First and second data transfer members are operably disposed adjacent storage areas of the respective storage discs. An edge of the first disc moves in a prescribed close spatial separation from a rotating surface of the second spindle so that the second spindle strips windage, generated by the rotation of the first disc, away from the second data transfer member.

Abstract: An offset compensation method of a current sensor is provided for determining whether an offset compensation of the current sensor is abnormal, and a motor driving system includes the current sensor. The offset compensation method includes: compensating for an offset of the current sensor, and determining whether the offset compensation of the current sensor is abnormal.

Abstract: In response to positioning a read/write head of a hard drive, a voice coil motor (VCM) input signal is applied to a voice coil motor and a microactuator (PZT) input signal is applied to a microactuator. A position signal is determined in response to positioning the read/write head. A PZT component is decoupled from the position signal to determine an estimated VCM response. The estimated VCM response used to determine an estimated VCM disturbance. A VCM component is decoupled from the position signal to determine an estimated PZT response. The estimated PZT response used to determine an estimated PZT disturbance. The VCM input signal and the PZT input signal are modified respectively to compensate for the estimated VCM disturbance and the estimated PZT disturbance.

Abstract: Provided herein are devices, systems, and methods for electrically-augmented damping of an actuator and associated devices. In particular, electrically-augmented damping derived from measurement of voltage across an actuator and current flowing through an actuator is provided.

Abstract: A magnetic recording system includes an array of analog inputs operable to receive analog signals retrieved from a magnetic storage medium, a modulator operable to combine the analog signals to yield a frequency division multiplexed signal, a demodulator operable to yield a plurality of demodulated signals from the frequency division multiplexed signal corresponding to each channel of the array, and a joint equalizer operable to filter the plurality of demodulated signals to yield an equalized output.

Abstract: A magnetic recording system includes an array of analog inputs operable to receive analog signals retrieved from a magnetic storage medium, a quadrature amplitude modulator operable to combine the analog signals to yield a quadrature amplitude modulated signal, a quadrature amplitude demodulator operable to yield a plurality of demodulated signals from the quadrature amplitude modulated signal corresponding to each channel of the array, and a joint equalizer operable to filter the plurality of demodulated signals to yield an equalized output.

Abstract: An apparatus includes a feedback controller receiving feedback from a position error signal of a hard drive read/write head. The feedback controller provides respective voice coil motor and microactuator control signals to a voice coil and microactuator that together position the hard drive read/write head in response to a position control signal. A rotational vibration feed-forward compensator receives vibration measurements via a sensor and providing a rotational vibration compensation signal in response thereto. A dynamic control allocator is coupled to the feedback controller and the rotational vibration feed-forward compensator. The dynamic control allocator is configured to combine a high frequency component of the rotational vibration compensation signal with the microactuator control signal; and to combine a low frequency component of the rotational vibration compensation signal with the voice coil motor control signal.

Abstract: Methods and apparatus concern testing a disk drive suspension. Testing includes moving a first portion of a suspension relative to a second portion. A pair of motors is mounted on the suspension. The testing further includes measuring an electrical signal that is intrinsically produced by the motors, combined in a circuit, in response to the relative movement. The testing further includes identifying a characteristic of the electrical signal and determining whether an orientation of one or both of the motors is reversed relative to an intended motor orientation based on the characteristic of the electrical signal. The testing can determine whether the orientation of both motors matches the intended motor orientation, whether the orientation of one motor is reversed in a same polarity condition, whether the orientations of both motors are reversed in a mutual reverse polarity condition, or whether the suspension has a mechanical or electrical defect.

Abstract: A disk drive is disclosed comprising a servo control system configured to control an actuator for actuating a head over a disk. Servo sectors are sampled at a servo sample frequency fs to generate a position error signal PES(k) that is filtered with a compensator to generate a first control signal u1(k). A first discrete-time sinusoid comprising a sinusoid frequency of fs+?f is added to the first control signal u1(k) to generate a second control signal u2(k). The second control signal u2(k) is applied to the actuator, and a frequency response of the actuator is determined at the frequency |?f|. The frequency response of the actuator is determined at the frequency fs+?f based at least in part on the frequency response of the actuator at the frequency |?f| and a measured signal of the servo control system when applying the second control signal u2(k) to the actuator.

Abstract: A disk drive is disclosed comprising a voice coil motor (VCM) configured to actuate a head over a disk. The VCM is controlled to seek the head over the disk during a first seek, and a back electromotive force (BEMF) voltage generated by the VCM during the first seek is measured. Feed-forward compensation is generated based on the measured BEMF voltage, and the VCM is controlled to seek the head over the disk during a second seek using the feed-forward compensation while writing servo data to the disk.

Abstract: In certain embodiments, an apparatus includes a first piezoelectric (PZT) element poled in the same direction as a second PZT element. The first and second PZT elements are configured to be driven while simultaneously sensing motion. The apparatus further includes a circuit configured to add outputs of the first and second PZT elements, extract the sensed motion, and detect off-track motion from the extracted sensed motion.

Abstract: A disk drive is disclosed comprising, a head, a disk surface, and a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop comprising a VCM and a microactuator servo loop comprising a microactuator operable to actuate the head over the disk surface. A frequency component of a servo signal in the DSA servo loop is evaluated, wherein the frequency component is based on a peak frequency of an error rejection curve of the DSA servo loop. A degradation of the microactuator is detected based on the frequency component of the servo signal.

Abstract: A data storage device is disclosed comprising a disk, a head, and a microactuator configured to actuate the head over the disk. The data storage device further comprises control circuitry comprising a digital-to-analog converter (DAC) configured to generate a control signal applied to the microactuator. The control circuitry measures an operating temperature and then adjusts a range of the DAC based on the measured operating temperature.

Abstract: A disk drive is disclosed comprising a disk media, a head stack assembly (HSA) having a head coupled to its distal end, a microactuator used to provide fine position of the head and a voice coil motor (VCM) configured to actuate the HSA over the disk media, and control circuitry. The control circuitry may be configured to move the HSA in an alternating manner across the disk media while actuating the microactuator. One or more performance characteristics of the microactuator may be measured before and after the actuation of the microactuator, and failure may be detected based on the absolute or relative change of the one or more performance characteristics.

Abstract: Apparatus and method for mitigating impedance changes in a microactuator conductive joint. In accordance with some embodiments, a microactuating element has a conductive input junction, the junction having dissimilar metals in contact with one another. The microactuating element is adapted to mechanically deform to displace a control object responsive to a micractuation control signal that is applied to the junction. A control circuit applies a bi-directional transition signal to the conductive input junction to reduce an increased impedance of the junction.

Abstract: A magnetic disk device according to one embodiment includes: a disturbance vibration detector; a movement position controller; and a disturbance compensation module. The disturbance vibration detector detects a disturbance vibration component with respect to a fine-movement actuator. The movement position controller drives each of the fine-movement actuator and a coarse-movement actuator to control a movement position of a magnetic head. The disturbance compensation module corrects the movement position so as to suppress the disturbance vibration component detected by the disturbance vibration detector.

Abstract: Methods, systems, and computer program products for compensating unstable linear time-invariant due to input nonlinearities are described. In one implementation, compensating a controlled device may include controlling the controlled device using feedforward control. In another implementation, compensating the controlled device may include controlling the controlled device using feedback control.

Abstract: A disk drive is disclosed comprising a head, a disk surface, and a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop comprising a VCM and a microactuator servo loop comprising a microactuator operable to actuate the head over the disk surface. A microactuator compensator processes a position error signal (PES) to generate a first control signal, and a disturbance sinusoid is injected into the first control signal to generate a second control signal, wherein the microactuator is controlled in response to the second control signal. Feed-forward compensation is generated corresponding to the injected disturbance sinusoid, and a third control signal is generated in response to the PES and the feed-forward compensation, wherein the VCM is controlled in response to the third control signal. A gain of the microactuator is estimated in response to the feed-forward compensation.

Abstract: A method of evaluating a dual stage actuator (DSA) servo loop in a disk drive is disclosed. The disk drive comprises a dual stage actuator (DSA) servo loop operable to actuate a head over a disk surface. A first sinusoidal signal A1 is added to a VCM control signal B1 generated by a VCM servo loop. A response of the VCM control signal B1 to the first sinusoidal signal A1 is measured, and a closed loop response of the VCM servo loop is computed in response to A1 and B1. A second sinusoidal signal A2 is added to a microactuator control signal B2 generated by a microactuator servo loop. A response of the microactuator control signal B2 to the second sinusoidal signal A2 is measured, and a closed loop response of the microactuator servo loop is computed in response to A2 and B2.

Abstract: A magnetic head drive device including a suspension for supporting a magnetic head, and a main actuator that produces rotary movement of the magnetic head by applying current to a coil. The main actuator includes end arms each comprising a single micro-actuator, and an intermediate arm comprising two micro-actuators. The micro-actuators of the end arms are driven in the same direction, and the micro-actuators of the intermediate arm are driven in the opposite direction to the drive direction of the micro-actuators of said the arms.

Abstract: A disk drive is disclosed comprising a head, a disk surface, and a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop and a microactuator servo loop operable to actuate the head over the disk surface. A microactuator compensator in the microactuator servo loop is disabled, a sinusoid is injected into a control signal applied to the microactuator, and coefficients of a corresponding sinusoidal response in a DSA error signal of the DSA servo loop is measured. The sinusoid is injected into a model of the microactuator to generate a compensation signal. A gain of the microactuator is adjusted based on a VCM error signal and the coefficients of the sinusoidal response in the DSA error signal.

Abstract: A disk drive is disclosed comprising a head, a disk surface, and a voice coil motor (VCM) and a microactuator operable to actuate the head over the disk surface. A sensitivity of the microactuator is periodically measured over a lifetime of the microactuator. Each measured sensitivity is stored in a timeline log, wherein the timeline log represents a degradation curve of the microactuator over the lifetime of the microactuator.

Abstract: A disk drive is disclosed comprising a disk surface comprising a plurality of tracks, each track comprising a plurality of servo sectors. The disk drive further comprises a head coupled to a distal end of an actuator arm, and a voice coil motor (VCM) and a microactuator operable to actuate the head over the disk surface. The head is first servoed in response to the servo sectors, and after first servoing the head, a manufacturing procedure is executed by controlling the VCM and the microactuator to servo the head while accessing the disk surface. After executing the manufacturing procedure, the head is second servoed in response to the servo sectors, and the microactuator is evaluated in response to the first and second servoing.

Abstract: A multi-stage tracking control system includes at least a main actuator and a microactuator. The tracking control system is switched to a single-stage mode so that the main actuator alone provides tracking. A disturbance signal is applied to the microactuator while in the single-stage mode, and a failure condition of the microactuator is determined based on a position error generated in response to the disturbance signal.

Abstract: In inspection for a magnetic head having a built-in fine-motion actuator, stable servo control is realized without an effect of thermal drift or thermal expansion. A magnetic head inspection apparatus includes a fine-motion stage, a data process circuit, and a servo control circuit. The fine-motion stage performs positioning of a magnetic head in a predetermined position on a magnetic disk. The data process circuit measures the movement characteristic of the fine-motion actuator. The servo control circuit controls the magnetic head to track the servo track on the magnetic disk based on a measurement result of the data process circuit. The servo control circuit drives the fine-motion stage, and controls the magnetic head to move in a manner that the value of movement of the fine-motion actuator remains within an acceptable range.

Abstract: According to one embodiment, a magnetic disk drive includes a detector and a servo controller. The detector detects, as actual timestamps, time intervals at which a head reads servo sync marks recorded on a disk at predetermined intervals. The servo controller controls a VCM actuator and a microactuator with feedback control in order to position the head at a target position. The servo controller comprises a feedforward controller configured to compensate for disturbance. The feedforward controller comprises a difference detector and an integrator. The difference detector detects a deviation of the actual timestamps from target timestamps as a timestamp difference. The integrator configured to convert the detected timestamp difference into displacement of the microactuator by integrating the detected timestamp difference.

Abstract: According to one embodiment, a servo controller of a magnetic disk drive includes a microactuator (MA) estimator, VCM actuator (VCMA) controller, a filter and an adder. The MA estimator estimates a first displacement of an MA from a control input to be provided to the MA. The VCMA controller controls a VCMA based on a positioning error between a target track and a first position of the VCMA. The first position is estimated from a position of a head and the first displacement. The filter estimates a second position of the VCMA corresponding to a delay in a displacement of the MA caused by hysteresis of the MA, from a state of the VCMA in a seek operation, and estimates a second displacement that is the delayed displacement of the MA, from the second position. The adder adds the second displacement to an input to the MA controller.

Abstract: A disk drive is disclosed comprising a first disk surface, a first head coupled to a distal end of an actuator arm, and a voice coil motor (VCM) and a first microactuator operable to actuate the first head over the first disk surface. A servo loop for servoing the head in response to the servo sectors is disabled, and after disabling the servo loop, the first microactuator is excited with a control signal at a test frequency in order to accentuate a crack in the first microactuator. After exciting the first microactuator, the servo loop is enabled, and after enabling the servo loop, the first microactuator is evaluated to detect the crack in the first microactuator.

Abstract: A disk drive is disclosed comprising a disk surface, a head coupled to a distal end of an actuator arm, and a dual stage actuator (DSA) servo loop comprising a voice coil motor (VCM) servo loop and a microactuator servo loop operable to actuate the head over the disk surface. The microactuator servo loop is disabled, and after disabling the microactuator servo loop a sinusoid is injected into the VCM servo loop, wherein the sinusoid comprises a target frequency. A first open loop response of the VCM servo loop is computed. The microactuator servo loop is enabled, and after enabling the microactuator servo loop the sinusoid is injected into the DSA servo loop. A second open loop response of the DSA servo loop is computed. A microactuator servo loop gain and a VCM servo loop gain are tuned in response to the first and second open loop responses.

Abstract: A magnetic head-positioning servo system is provided to accurately test a magnetic disk with a track written in advance, by providing two fine actuators. The second fine actuator, to which a magnetic head is attached, is mounted on the first fine actuator. The second fine actuator has a larger generating displacement than a generating displacement of the first fine actuator, and lets the magnetic disk to follow the eccentricity of the track. In this way, the positioning accuracy can be increased.

Abstract: An information recording and reproducing apparatus 1 having a high efficiency of information transfer includes one or more recording media forming a plurality of recording surfaces, a plurality of heads respectively disposed on the recording surfaces, a first actuator for supporting the heads and moving the heads uniformly, a plurality of second actuators provided one for an associated one of the heads, the second actuators moving the heads independently relative to the first actuator, recording processing circuits for simultaneously outputting recording signals, and reproducing processing circuits simultaneously supplied with reproduced signals read out by the heads to reproduce information from the reproduced signals.

Abstract: An apparatus and a method for improving bandwidth of a fine positioning mechanism in data storage manufacturing and test equipment that require fine positioning of a head on or about a track. The method comprises the steps of sensing separate sources of mechanical disturbance that mis-position the head with one or more non-contact position sensors, generating a compensating position control signal from one or more input signals, and positioning the head with a fine positioning mechanism and position control signal. The apparatus uses a shear mode micro-actuator as a fine positioning mechanism.

Abstract: A method for detecting head-disc contact is disclosed. The method comprises locating a head including a head positioning microactuator and at least one of a read transducer and a write transducer adjacent to a disc such that the head is in communication with the disc, monitoring an output signal from the head positioning microactuator of the head, and evaluating the output signal to determine if the head contacts the disc.

Abstract: A mark information is recorded in an area which is on a circumference of a magnetic disk corresponding to a last track in which a servo information write is ended or a track, which is one or two in front of the last track in which servo information is not written and the mark information is detected by returning a magnetic head in a radial direction of the magnetic disk by a fine movement stage after the magnetic head is moved to a next aimed track by a coarse movement stage. The servo information write position is detected by the magnetic head and the servo information is written in a servo information write position of a next track by positioning the magnetic head therein by using the fine movement stage.