Abstract: To increase the number of CSI-RSs for interference measurement to improve interference measurement accuracy, a first reference signal for channel state measurement and a second reference signal for interference measurement are assigned to reference signal resources defined for transmission of the first reference signal, and a mobile terminal apparatus that supports both the first reference signal and the second reference signal is notified of pattern information to identify an assignment pattern of the first reference signal and the second reference signal. A second mobile terminal apparatus that supports the first reference signal and that does not support the second reference signal is notified of pattern information to identify an assignment pattern of the first reference signal, and of assignment information indicating that resources assigned the second reference signal are assigned a third reference signal of zero power for channel state measurement.

Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of tracks defined by servo sectors, wherein each servo sector comprises a plurality of servo bursts and the servo sectors define a plurality of servo wedges. A first write operation is executed to a first track and a first absolute position for the head is generated corresponding to a first servo wedge. A second write operation is executed to a second track and a second absolute position for the head is generated corresponding to the first servo wedge. An off-track write condition is detected when executing the second write operation based on the first absolute position and the second absolute position. The first absolute position comprises a track address of the first track and a position error measurement based on the servo bursts in the first servo wedge.

Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising tracks defined by servo sectors. A location of the head is generated based on the servo sectors, and a position error signal (PES) representing a difference between a target location for the head and the measured location for the head is generated. An actuator control signal (ACS) is generated in response to the PES, a disturbance compensation signal (DCS) is generated based on the PES and the ACS, and the DCS is filtered with a disturbance observer filter. The DCS is filtered with a plurality of band-pass filters, and an output of one of the band-pass filters is filtered with a peak detection filter configured to detect a peak frequency corresponding to a peak in a frequency response of the band-pass filter, wherein the disturbance observer filter is adjusted based on the peak frequency.

Abstract: A data storage device is disclosed comprising a first disk surface comprising servo data defining servo tracks at a first radial density, a first head, and a voice coil motor (VCM) configured to actuate the first head over the first disk surface using a servo control system. A load operation is executed to load the first head over the first disk surface, and a back electromotive force (BEMF) voltage generated by the VCM during the load operation is evaluated to generate an estimated distance traveled. The servo data on the first disk surface is detected, and an initial servo track during the load operation based on the detected servo data to generate a measured distance traveled. A gain of the servo control system is configured based on the estimated distance traveled and the measured distance traveled.

Abstract: A data storage device is disclosed comprising a microactuator configured to actuate a head over a disk. A control signal applied to the microactuator is generated based on an input sequence u(k). A Preisach bit map bj is updated based on the input sequence u(k), wherein the Preisach bit map bj corresponds to a Preisach plane modeling a hysteretic response of the microactuator. A current compensation value yi is generated based on an update value generated based on: ? j ? h ? ( j ) ? b ^ j where hj represents a slice of the Preisach plane and {circumflex over (b)}j is an update bit map based on at least part of the Preisach bit map bj. The current input ui and the current compensation value yi are combined to generate the control signal applied to the microactuator.

Abstract: A disk drive is disclosed comprising a head, a disk surface comprising servo information, 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 position error signal (PES) is generated based on the servo information, and a first control signal is generated based on the PES. The first control signal is adjusted based on a function of the first control signal to generate a second control signal that compensates for a gain variation of the microactuator, and the microactuator is controlled based on the second control signal.

Abstract: A data storage device is disclosed comprising a head actuated over a disk and a vibration detector configured to generate a vibration signal in response to a vibration affecting the data storage device. A timing loop is configured to generate a disk-locked clock substantially synchronized to a rotation frequency of the disk. An adaptation control signal is generated based on the vibration signal and an error signal of the timing loop. An adaptive filter is adapted based on the adaptation control signal, wherein the adaptive filter filters the vibration signal to generate feed-forward compensation values. The feed-forward compensation values are applied to the timing loop to compensate for the vibration.

Abstract: A disk drive is disclosed comprising a servo control system operable to actuate a head over a disk. A sensor signal is filtered with a first filter comprising a frequency response, and the filtered sensor signal is filtered to generate a compensated sensor signal. An error signal is filtered with a second filter comprising the frequency response, and an adaptation control signal is generated based on the compensated sensor signal and the filtered error signal. An adaptive filter is adapted in response to the adaptation control signal, wherein the adaptive filter filters the sensor signal to generate feed-forward compensation values. The feed-forward compensation values are applied to the servo control system to compensate for the disturbance. A disturbance signal that represents the disturbance is generated, and the frequency response of the first and second filters is optimized based on the sensor signal and the disturbance signal.

Abstract: A data storage device is disclosed comprising a head actuated over a disk comprising tracks defined by servo sectors. A location of the head over the disk is measured based on the servo sectors, and a position error signal (PES) is generated representing a difference between a target location for the head and the measured location for the head. An actuator control signal (ACS) is generated in response to the PES, a disturbance compensation signal (DCS) is generated based on the PES and the ACS, and the DCS is filtered with a disturbance observer filter. The ACS is adjusted based on an output of the disturbance observer filter, and the head is actuated over the disk based on the adjusted ACS. The DCS is filtered with a plurality of band-pass filters, and the disturbance observer filter is adjusted based on the plurality of band-pass filters.

Abstract: A disk drive is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors, a head actuated over the disk, and control circuitry comprising a servo control system operable to servo the head over the disk. A plurality of data tracks are defined relative to the servo tracks, and a first data track is accessed while servoing the head over the first data track based on a position error signal Xn?1(k) generated at each servo sector of the first data track. Feed-forward compensation values are generated based on Xn?1(k), and a second, consecutive data track is accessed while servoing the head over the second data track based on a position error signal Xn(k) generated at each servo sector of the second data track and based on the feed-forward compensation values.

Abstract: A data storage device is disclosed comprising a disk, a head, and a microactuator configured to actuate the head over the disk. An input signal to a compensator is generated, wherein the compensator is configured to generate a microactuator control signal. A slew rate signal representing a slew rate of the microactuator control signal is generated and applied to a first saturator configured to generate a saturated slew rate signal. The input signal is adjusted based on the slew rate saturation signal, and the microactuator is controlled based on the microactuator control signal.

Abstract: A disk drive is disclosed comprising a disk comprising tracks defined by servo sectors, a head, and control circuitry comprising a servo control system operable to actuate the head over the disk in response to the servo sectors. The servo control system is configured into a first state, and a position error signal (PES) representing a difference between a target location for the head and a measured location for the head is generated. An actuator control signal is generated in response to the PES, a feed-forward control signal is adapted in response to the servo sectors, and the actuator control signal is adjusted using the feed-forward control signal. The servo control system is configured from the first state to a second state, and a phase of the adaptation of the feed-forward control signal is adjusted based on the second state.

Abstract: A disk drive is disclosed comprising a disk, a head, and control circuitry comprising a servo control system operable to actuate the head over the disk. A plurality of disturbance signals is generated in response to a vibration. A plurality of correlations is generated in response to each disturbance signal and an error signal of the servo control system. At least one of the disturbance signals is selected in response to the correlations. A feed-forward compensation value is generated in response to the selected disturbance signal, and the feed-forward compensation value is applied to the servo control system to compensate for the vibration.

Abstract: A disk drive is disclosed comprising a servo control system operable to actuate a head over a disk. A disturbance signal is generated in response to a vibration, and the disturbance signal is filtered with a first filter comprising a frequency response to generate a filtered disturbance signal. The filtered disturbance signal is filtered with a model of the servo control system to generate a compensated disturbance signal. An error signal of the servo control system is filtered with a second filter comprising the frequency response to generate a filtered error signal. An adaptation control signal is generated in response to the compensated disturbance signal and the filtered error signal, and an adaptive filter is adapted in response to the adaptation control signal, wherein the adaptive filter filters the disturbance signal to generate feed-forward compensation values applied to the servo control system to compensate for the vibration.

Abstract: A disk drive is disclosed comprising a disk comprising servo data, and a head actuated over the disk. An offset r0 representing a difference between an axial rotation of the disk and an axial rotation of the servo data is estimated, and radial dependent timing compensation values are generated in response to the estimated r0. A phase error is generated in response to the servo data, and a control signal is generated in response to the phase error and the radial dependent timing compensation values. A frequency of an oscillator is adjusted in response to the control signal.

Abstract: A disk drive is disclosed comprising a head actuated over a disk having a plurality of data tracks. A vibration is detected, and a write operation is configured to write a first plurality of blocks and a second plurality of blocks to a target data track based on the detected vibration. The first plurality of blocks are written to the target data track during a first revolution of the disk, and the second plurality of blocks are written to the target data track during a second revolution of the disk.

Abstract: To increase the number of CSI-RSs for interference measurement to improve interference measurement accuracy, a first reference signal for channel state measurement and a second reference signal for interference measurement are assigned to reference signal resources defined for transmission of the first reference signal, and a mobile terminal apparatus that supports both the first reference signal and the second reference signal is notified of pattern information to identify an assignment pattern of the first reference signal and the second reference signal. A second mobile terminal apparatus that supports the first reference signal and that does not support the second reference signal is notified of pattern information to identify an assignment pattern of the first reference signal, and of assignment information indicating that resources assigned the second reference signal are assigned a third reference signal of zero power for channel state measurement.

Abstract: A disk drive is disclosed comprising a head and a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors. The disk drive further comprises control circuitry comprising a servo control system operable to actuate the head over the disk in response to the servo sectors. The disk is rotated at a first speed and the servo sectors are read at a first servo sample frequency to generate first servo samples. The disk is rotated at a second speed different from the first speed and the servo sectors are read at a second servo sample frequency to generate second servo samples. The second servo samples are processed to measure a frequency response of the servo control system proximate the first servo sample frequency.

Abstract: A disk drive is disclosed comprising a disk, a head, and control circuitry comprising a servo control system operable to actuate the head over the disk. A plurality of disturbance signals is generated in response to a vibration. A plurality of correlations is generated in response to each disturbance signal and an error signal of the servo control system. At least one of the disturbance signals is selected in response to the correlations. A feed-forward compensation value is generated in response to the selected disturbance signal, and the feed-forward compensation value is applied to the servo control system to compensate for the vibration.

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.