Abstract: When a head passes over a track with a projected item in a seek operation, the CPU delays a seek start time to conduct the seek by changing a period of time from a seek start position to a position of the track with a projected item. Or, the CPU conducts seek control by changing a speed table. Or, the CPU changes a sequence of items of a tag queue to obtain a seek locus not passing the projected item. By the control operation, a seek error due to thermal asperity is prevented and the head is not damaged. This also prevents appearance of a new projected item produced by contact between the magneto-resistive head and the projected item on the recording medium.

Abstract: There is disclosed a disk drive using a disk medium in which a non-servo range exists. In order to position a head at a target track, a CPU executes a seek operation by normal velocity control using servo data. At this positioning, when the head passes the non-servo range from which no servo data can be obtained, the CPU executes a seek operation by special velocity control to move the head at a velocity calculated based on a moving distance of the non-servo range.

Abstract: Provided are a method, system, and program for initializing a storage device. A pulse response profile is determined for a storage system in response to a series of signals generated to seek to a location in the storage system. A determination is made of a desired response trajectory for the storage system that optimizes seek performance. An adjustment vector is calculated based on the pulse and step response profiles and the desired response trajectory to optimize the pulse response profile. The adjustment vector is stored in the storage device for use during storage device operations to apply to control signals generated to perform one seek operation.

Abstract: Systems and methods in a disc drive improve data transfer performance by interrupting disc write operations to service read commands.

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: In a positioning control device for a two-stage actuator having a coarse-movement actuator and a fine-movement actuator, a notch filter having a cutoff frequency fn is provided to a coarse-movement control loop, and the fine-movement actuator is driven by a sine wave of the frequency fn. At the frequency fn, a head position signal becomes identical with an output signal of the fine-movement actuator, by which the gain of the fine-movement actuator can be estimated by an adaptive identification unit with high accuracy based on the control input to the fine-movement actuator and the head position signal.

Abstract: A magnetic recording disk drive can prevent the deterioration of the head off-track characteristics and the reduction of the drive performance even when an erase band asymmetry resulting from a skew angle exists. A write inhibit slice value for an inner peripheral side offset is made smaller than a write inhibit slice value for an outer peripheral side offset at a position where an erase band on the inner peripheral side is greater than an erase band on the outer peripheral side, so that the adjacent track on the outer peripheral side cannot easily erase a data track. On the contrary, the inner periphery and the outer periphery are paraphrased at a position where the erase band on the outer peripheral side is greater than the erase band on the inner peripheral side.

Abstract: Method and apparatus for moving a control object, such as a data transducing head in a data storage device, from an initial position to a destination position. A base generation term describes a normalized trajectory (acceleration, velocity, displacement) of the control object away from the initial position and toward the destination position. A control profile is determined in relation to the base generation term as well as in relation to an acceleration distance and an acceleration time, respectively characterized as a displacement distance and an elapsed time during which the control object is accelerated. The control object is then moved in relation to the control profile. The base generation term is preferably stored in a table which is accessed and scaled in relation to the displacement distance (seek length) for the control object.

Abstract: A method for positioning a control object using an optimum jerk profile to reduce excitation of mechanical resonances. A base set of control profiles is selected to describe jerk, acceleration, velocity and displacement of the control object during a seek. Notch functions are applied to the base jerk profile to provide a modified jerk profile having a value of zero at selected times during which maximum current is to be applied to move the control object. Normalized control profiles describing acceleration, velocity and displacement are generated from the modified jerk profile and thereafter used to move the control object. To suppress specific resonant frequencies of interest, the elapsed time of the seek is selected to coincide with a time at which a combination of the excitation energies associated with the resonant frequencies is at a minimum.

Abstract: An apparatus and associated method are disclosed for compensating for repeated servo runout error in a disc drive. The disc drive includes a disc on which servo information is arranged as a plurality of servo fields which define tracks on the disc. An actuator assembly is provided adjacent the disc and includes a head which accesses the servo fields and an actuator motor which moves the head relative to the disc. A servo circuit controls radial location of the head by applying current to the actuator motor in response to the servo information. The repeated servo runout error, caused by errors in the radial location of the servo fields on the disc, is compensated by the servo circuit through the use of compensation values which are stored in compensation fields of the servo fields.

Abstract: A control arrangement having a feedforward system and a feedback system, a control model for generating reference position data from a feedforward control signal is separated into an original control model and a compensation filter. Gain of the feedforward control signal is compensated by a gain compensation circuit to form a feedforward control signal after compensation. The reference position data is input to a feedback controller, and a feedback control signal and feedforward control signal are input to a control object. Coefficients of the compensation filter and the gain compensation circuit are compensated on the basis of a head position trajectory obtained by actual seek operation.

Abstract: There is disclosed a disk drive using a disk medium in which a non-servo range exists. In order to position a head at a target track, a CPU executes a seek operation by normal velocity control using servo data. At this positioning, when the head passes the non-servo range from which no servo data can be obtained, the CPU executes a seek operation by special velocity control to move the head at a velocity calculated based on a moving distance of the non-servo range.

Abstract: An adaptive maximum seek velocity clipping technique is employed in a disk drive to reduce head movement power requirements. Separate maximum seek velocities are established for respective categories of access commands, where the categories are defined by seek distance and estimated extra latency. The maximum seek velocity established for each category of access commands reflects actual experience in executing access commands of the given category. The maximum seek velocity values for the various categories are stored in a maximum seek velocity table, which is referred to upon execution of access commands. The inventive power-saving technique may be advantageously applied in conjunction with a probability-based shortest access time first (SATF) command queue ordering algorithm.

Abstract: A position of an object is controlled based on a distance YS until the object is stopped, a target velocity VS of the object, acceleration time ta for accelerating the object, deceleration time td for decelerating the object, velocity variation &Dgr;Va within the acceleration time, and velocity variation &Dgr;Vd within the deceleration time, and a deceleration-start distance YSd. The distance YSd is a distance from where the object is made to start deceleration. The distance YSd is a sum of an integer part YSdq and a decimal part YSdr of the deceleration-start distance. Thus, management of decimal fractions is performed with respect to a pulse generation unit that outputs an output pulse corresponding to the velocity instruction.

Abstract: A method, apparatus and computer program for performing a servo seek according to a voltage-constrained sinusoidal acceleration trajectory. In one embodiment, the apparatus comprises a hard disk drive which has a disk with a surface, spin motor, transducer, and an actuator arm to move a transducer across the surface of the disk. The apparatus further includes a controller that controls the actuator arm and to perform a seek having a length. The actuator arm moves the transducer across the surface of the disk with an essentially sinusoidal acceleration trajectory using a substantially constant voltage. In another embodiment, the substantially constant voltage is based on the maximum voltage from a power supply.

Abstract: A controller for a disk drive that accesses a look up table having a plurality of thermally characterized values corresponding to a plurality of seek operations. For each seek operation, the corresponding value is added to a register. The controller decrements the register at a rate that is determined using servo interrupts occurring as a result of the rotation of the disk. When the value of the register exceeds a threshold, the controller adjusts the subsequent seek operation so as to inhibit damage to the voice coil as a result of overheating.

Abstract: A method and apparatus position a plurality of data heads relative to a plurality of surfaces of at least one disc in a disc drive. One of the plurality of data heads corresponds to each of the plurality of surfaces. The data heads are provided for writing information to the surfaces and reading information from the surfaces. Each of the data heads may be simultaneously positioned relative to the corresponding surfaces using the embedded servo information. Information can be simultaneously transferred relative to the corresponding surfaces using the plurality of data heads. Uninterrupted sequential data transfers may also be executed without servo overhead. Further, an apparatus is provided for accomplishing such servo control, as is a method of accomplishing model-based servo control.

Abstract: A method and apparatus for controlling acoustic noise generated by a seek operation in a disc drive by using a feedback control system to control the seek operation. The feedback control system is excited by a feed-forward signal during execution of the seek operation. An acoustic factor, which defines a seek operation noise level, is selected. The feed-forward signal is generated based, at least in part, upon the selected acoustic factor. The feed-forward signal has a first derivative having a maximum value. The selected acoustic factor is used to select the maximum value of the first derivative of the feed-forward signal.

Abstract: Methods and systems in a data storage device selectively employ a seek time array and/or a seek time list to accurately predict a time required for a seek operation to move a transducer in the data storage device a given seek distance. The seek time list and/or seek time profiles are automatically compiled in the data storage device based on seek time entries located in a servo data table located in the data storage device.

Abstract: A method, apparatus, and computer program product for a hard disk drive servomechanism. In one embodiment, the apparatus comprises a disk which has a surface, a spindle motor that rotates the disk, a transducer which can write information onto the disk and read information from the disk, and an actuator arm that can move the transducer across the surface of the disk. The apparatus further includes a controller. The controller can determine a seek length from a first track to a second track, determine a seek time based on the seek length, scale the seek time in response to a velocity error between a calculated velocity and a design velocity for the seek length, and control the actuator arm to move the transducer across the disk surface from the first track to the second track using an acceleration trajectory.

Abstract: A disk drive control system that compensates for mechanical bias torques present in disk drives. A transducer, commonly referred to as a head, is attached to an actuator arm that is subjected to mechanical bias torques, including flex bias torque and bearing friction. The net bias torque has a mechanical memory that is manifested as hysteresis whose magnitude depends on the size of the stroke length between inflection points of the transducer in seek operations. The dependence of the net bias torque includes location of the transducer, direction of the seek, and the history of previous seeks. The dependence may further include operating temperature of the disk drive. The disk control system determines and applies these corrections to the disk drive to enhance the seek performance.

Abstract: The present invention relates to a head positioning method and device for positioning a head to read information from disk media at prescribed positions using a rotary actuator, in which eccentricity errors of the rotary actuator are corrected. In a disk device having disk media, a head, a rotary actuator, and a control circuit, memory is provided to store eccentricity correction information for each region of a disk divided in the radial direction. Eccentricity correction information corresponding to the head position is read, and eccentricity correction signals are created. Optimal eccentricity correction corresponding to the position of the head on the disk is made possible, and rapid seeking is enabled.

Abstract: A disk drive and methods for preventing a coil in a voice coil motor from overheating due to the application of excess current. The disk drive comprises a servo control system. The servo control system is adapted for applying a current to a coil of the voice coil motor thereby causing the voice coil motor to move the head according to a seek distance. The servo control system generates a plurality of seek profiles for each of a plurality of seek distances and a plurality of current limits for the plurality of seek profiles. Each of the plurality of seek profiles defines a plan for controlling the current to be applied to the coil while the voice coil motor is operated over the seek distance. The plurality of current limits each define a maximum current allowed while controlling the current to be applied to the coil.

Abstract: Method and apparatus for moving a control object, such as a data transducing head in a data storage device, from an initial position to a destination position. A base generation term describes a normalized trajectory (acceleration, velocity, displacement) of the control object away from the initial position and toward the destination position. A control profile is determined in relation to the base generation term as well as in relation to an acceleration distance and an acceleration time, respectively characterized as a displacement distance and an elapsed time during which the control object is accelerated. The control object is then moved in relation to the control profile. The base generation term is preferably stored in a table which is accessed and scaled in relation to the displacement distance (seek length) for the control object.

Abstract: A method of implementing an automatic acoustic management feature for a disc drive includes receiving an acoustic/performance compromising factor from a host, tuning disc drive performance by applying the factor to a control parameter to generate a modified control parameter, and executing a loop for controlling a disc drive operation using the modified control parameter. In another embodiment, a disc drive has a base, a rotatable disc, an actuator assembly with an arm for carrying a head in transducing relation to the disc in response to a control signal, a receiver for receiving an acoustic/performance compromising factor, and a controller that monitors the position of the arm and generates the control signal. The controller executes a seeking control loop having a control parameter modified by applying a compromising factor to the parameter to tune the acoustic performance of the drive.

Abstract: A hard disk controller (HDC) receives a request an operation to retrieve, read, or write data using a magnetic disk. An MPU determines the contents of the received request, and transfers to an IC such as a head IC (HDIC), a PRML read channel process (RDC), a servo-demodulator (SV-DEMO), etc. set values of minimal parameters to control the parameters whose settings are to be changed to control the operations of a storage device to perform the processes for the request.

Abstract: A disk drive uses seek profile manipulation to provide enhanced transducer fly height control. The maximum seek velocity that is used during a seek operation is made dependent upon, among other things, the direction associated with the seek operation (i.e., either radially inward or radially outward with respect to the disk). In a preferred embodiment, the maximum seek velocity in a direction that normally results in a fly height loss is made less than the maximum seek velocity in the opposite direction. Thus, a minimum transducer fly height can be maintained with minimal effect on average seek time in the disk drive. In one approach, the maximum seek velocity values are stored within a lookup table within the disk drive.

Abstract: A method and apparatus for normalizing the acceleration constant used by a servo control system in a disc drive are disclosed. The method and apparatus involve performing a test seek and summing the position error measured at sample periods during the deceleration phase of the test seek. A correction factor applied to the acceleration constant is adjusted if the sum of the position errors differs from the sum of position errors measured from a nominal seek. Adjusting the correction factor to cause a position error sum that is close or equal to the sum from the nominal seek provides a relatively symmetrical seek arrival without additional correction factor offsets or gain variances.

Abstract: A method of tuning a servo control system in a disk drive that implements seeks using a the feed-forward command effort signal uffwd and a PES reference signal r that were designed to be compatible with one another on the basis of a modeled frequency response G0(z) that is different from an actual frequency response G(z).

Abstract: A learning control unit is provided between a feedback calculating unit and a driving unit. When a period for one medium rotation period is assumed to be TL, an unknown drive current function Irepeat(t) which repeats for a period of time from a start time t=0 for one medium rotation period to an end time t=TL is obtained by a learning algorithm as an approximated function I{circumflex over ( )}repeat(t) that is approximately presumed by a set of the heights Ci of N rectangular functions having interval numbers i=0˜ (N−1) whose time widths are obtained by dividing the period for one medium rotation period into N intervals. After the learning, a learning control signal I{circumflex over ( )}repeat is outputted synchronously with the medium rotation and a feed-forward control is performed.

Abstract: Method for performing seek operations in a disk drive including at least one data disk having multiple concentric data tracks thereon, and a transducer radially moveable relative to said data tracks by an actuator during a seek operation from a starting track to a destination track. Upon receiving a request for a seek from starting track to a destination track, a seek profile is obtained to control application of current to the actuator based on the seek profile, wherein the seek profile includes actuator current level and transducer target velocity control values for the seek operation based on said starting and destination tracks, to achieve a desirable acoustic output. Actuator current is applied to the actuator as a function of the control to perform the seek operation.

Abstract: An adaptive maximum seek velocity clipping technique is employed in a disk drive to reduce head movement power requirements. Separate maximum seek velocities are established for respective categories of access commands, where the categories are defined by seek distance and estimated extra latency. The maximum seek velocity established for each category of access commands reflects actual experience in executing access commands of the given category. The maximum seek velocity values for the various categories are stored in a maximum seek velocity table, which is referred to upon execution of access commands. The inventive power-saving technique may be advantageously applied in conjunction with a probability-based shortest access time first (SATF) command queue ordering algorithm.

Abstract: An active noise canceller outputs a noise pattern learning request signal to a hard disk drive causing the hard disk drive to perform a predetermined operation, receives noise at this moment through a sound-receiving unit, and stores, in a nonvolatile memory unit, a relationship between the noise and a head operation data signal output from the hard disk drive. Based on the operation data signal outputted from the hard disk drive, the active noise canceller generates a noise-canceling sound while making a reference to the above relationship stored in the nonvolatile memory unit. Therefore, the signal processing needs a low degree of response for operating the noise-canceling sound.

Abstract: To provide a disk unit wherein a prompt search is enabled even if the recorded time of one track is long, if the total recorded time of one track is below five minutes, a search mode is set to a small jump mode in which a search is performed at a short step. If the total recorded time of one track is over 5 minutes, thirty minutes or below thirty minutes for example, a search mode is set to an intermediate jump mode in which a search is performed at an intermediate step and the small jump mode. In case the total recorded time of one track exceeds thirty minutes for example, a search mode is set to a time jump mode in which a jump by input time is performed, the intermediate jump mode and the small jump mode.

Abstract: A method for adapting a control system governing the swing of an actuator arm to the actual deceleration capacity of an attached servomechanism, comprising: maximally accelerating the actuator arm; measuring the actual acceleration; calculating the ratio between the actual acceleration and nominal acceleration; multiplying an actual distance parameter by the ratio before indexing into a velocity profile to retrieve a target velocity; and multiplying a feedforward signal by the ratio prior to feeding it into a control loop.

Abstract: Disclosed is a method of access control for a disk drive whereby an access operation for, particularly, sequentially and alternately executing accesses is supported. A CPU of the present disk drive sequentially and alternately executes accesses to a plurality of data tracks on a disk in response to an access request generated from a host system. During the access operation, the CPU secures time for a look-ahead operation, the time corresponding to the difference between transfer rates. Thus, sequential and alternate access operation in which the number of seek operations can be reduced can be realized.

Abstract: An apparatus and method for tracking radially-dependent repeatable run-out in a disc drive having a servo loop for positioning a head over a rotating disc is provided. The disc includes multiple tracks. Radially-dependent repeatable run-out control components for at least a subset of the multiple tracks are first determined. Data representative of the radially-dependent repeatable run-out control components for the subset of the multiple tracks is then stored. The stored data representative of the radially-dependent repeatable run-out control components is retrieved before settling on the target track, and subsequently used to follow the selected track.

Abstract: A servo system and method position a head laterally with respect to magnetic tape longitudinal defined servo bands arranged in a longitudinally shifted pattern for identification, and separated by data tracks. A servo controller responds to a loss of lateral position, sensing an estimated longitudinal position of the magnetic tape. If the estimated longitudinal position is within a predetermined distance of an end of the tape, the servo controller operates a drive to continuously move the tape away from the sensed end. The servo controller senses a home lateral position sensor to determine whether a compound actuator is within a predetermined distance of the edge of the magnetic tape. If so, it operates the coarse actuator portion of the compound actuator to move laterally away from the edge of the magnetic tape; else, to move toward the edge.

Abstract: The present invention may be regarded as a data storage system and a method of controlling the acoustic noise generated by a storage drive of a data storage system. The data storage system includes a storage drive adapted to operate in a selected operational state of a plurality of operational states. Each operational state generates a corresponding acoustic noise level and operates at a corresponding performance level. The data storage system further includes a system controller coupled to the storage drive, the system controller including a system profile. The system controller is adapted to: (a) receive at least one variable parameter; (b) use the at least one variable parameter as an index to the system profile to autonomously select one of the plurality of operational states as the selected operational state; and (c) transmit a control signal to the storage drive.

Abstract: Techniques are provided herein for reducing vibrations in various modes of a dynamic system. One such technique comprises incorporating vibration limiting and sensitivity constraints into a partial fraction expansion equation model of the system so as to reduce vibrations to specific levels. Another technique comprises shaping a command determined using the partial fraction expansion equation model to produce a desired output. The entire command may be shaped or only selected portions thereof which produce vibrations. Another technique involves commanding in current to produce saturation in voltage. By doing this, it is possible to command voltage switches. The times at which the switches occur can be set to reduce system vibrations. Other techniques are also provided. These include varying transient portions at the beginning, middle and/or end of a move and using Posicast inputs, among others.

Abstract: A technique for adaptively and stably updating the feed forward value required to drive the head of a rotational recording apparatus. A trajectory of a target position is generated for each seek command by using a compound function comprising a ramp function and a sine-wave function. The sine-wave element of the target position is transmitted to an adaptive filter for updating coefficients of the compound formula. All elements other than the sine-wave element are removed to provide a smooth update of the compound function's coefficients.

Abstract: A method and apparatus for moving a transducer across a disk surface in accordance with generalized Fourier seek trajectories for position, velocity, and acceleration control. The generalized Fourier acceleration trajectory includes one or more sine functions with the coefficients determined using a least-mean-square-error technique, which optimizes the selection of the trajectory. The corresponding velocity and position trajectories are derived based on the selected acceleration trajectory. The generalized Fourier seek method and apparatus provides improved performance and robustness of hard disk drive servomechanism, including shorter seek time. Additionally, the hard disk drive is more immune to external disturbances, and the acoustic noise caused by seeking is reduced. Using the generalized Fourier seek method, the duration of acceleration and deceleration modes may be equal or different.

Abstract: Method and apparatus for moving a head of a disc drive from an initial position to a destination position on a recording surface of a rotatable disc by generating and applying a model reference current to an actuator motor. A servo circuit includes a current profile generator which generates a baseline reference current profile. A gain calculator calculates first and second gain factors in relation to an initial velocity of the head. A gain block generates the model reference current by applying the first gain factor to a first portion of the baseline reference current profile used to accelerate the head and subsequently applying the second gain factor to a second portion of the baseline reference current profile used to decelerate the head, wherein the first and second gain factors have different respective magnitudes to compensate for a nonzero initial velocity of the head.

Abstract: During a sampling interval, a disk-drive seek controller receives a digital sample of actuator drive current and a head-assembly position signal from a drive system and estimates a one-sample future value of remaining seek distance to a target track and a one-sample future value of head-assembly's velocity. Two-sample future values of remaining seek distance and velocity are then estimated from the estimated one-sample future values and a calculated control current. A target velocity value is read from a memory corresponding to the estimated two-sample future remaining seek distance value and a difference between the estimated two-sample future velocity value and the target velocity value is detected. From the difference, an incremental value of control current is determined and summed with a previous value of control current to produce an accumulated control current value.

Abstract: Disk drive access times are reduced by including at least one cancellation impulse in a voice coil motor input signal to effectively cancel oscillations caused by natural resonances in an actuator assembly during a seek operation. Each cancellation impulse has an amplitude and application time that is tailored for optimal cancellation of oscillations. The amplitude and application time are calculated based upon known or estimated characteristics of the natural resonance within the actuator assembly.

Abstract: A seek-servo apparatus and method used by a hard disk drive is capable of making the actual position of a head correctly follow the target position of the head irrespective of time delay. The seek-servo apparatus of a hard disk drive is capable of moving a head to a desired track location, and includes an actuator which moves the head to the desired track location in response to an acceleration command having a target acceleration, which leads a target velocity and a target position by a predetermined time. Therefore, the head can be correctly positioned at a desired location on a desired track in real time, and the time for the head to read/write information can be significantly shortened.

Abstract: Apparatus and method for optimizing a gain of a disc drive servo circuit, the gain used to control the magnitude of current applied by the servo circuit to a voice coil motor to position a head adjacent tracks of a disc. The servo circuit includes a servo processor which selects an initial value of the gain, and then proceeds to perform a gain convergence operation wherein the head is repeatedly moved across the disc over a number of passes and position error is accumulated during each pass. The accumulated position error is used along with a scale factor to converge the gain from an initial gain value to a final, optimal gain value. The scale factor is variable and is also converged over the successive number of passes from an initial value to a final, nominal value, in order to decrease the time required to obtain the final, optimal gain value.

Abstract: Apparatus and method which provide accelerated servo control value calculations for a control processor controlling an actuator maintaining a head adjacent a rotatable disc f a disc drive. A dedicated multiply-accumulate hardware core of a servo micro engine calculates sum-of-products terms common in servo control loops. The multiply-accumulate hardware core uses a pipeline with stages for fetch, read, multiply, accumulate, and write-back as an arithmetic core to fully utilize all of the hardware during every servo interval. Feeding this arithmetic core is a dedicated state memory, from which a first signed servo state and a second signed servo state are read and where calculation results may be optionally written. Another, independent, coefficient memory provides predetermined coefficients used in resolving servo control loop algorithms. A final dedicated instruction memory provides shifter control values and the addresses of the states and coefficients.

Abstract: A method and apparatus are provided for positioning a head over a disc in a disc drive while maintaining servo loop stability. The apparatus includes an actuator-head assembly having a large-scale actuator and a micro-actuator that are both able to move the head over the disc. A saturation adjustment component detects when a micro-actuator controller is producing a micro-actuator control value that will saturate the micro-actuator. Using the micro-actuator control value, the saturation adjustment component generates a saturation error value. An adaptive anti-windup circuit transfers control to the large-scale actuator when the saturation error value is generated by the saturation adjustment component.

Abstract: Method and apparatus for reducing repeatable runout signals in a servo position error (SPE) signal of a disc drive actuator. During track following, a measurement estimate is obtained through the sampling and accumulating of data from the SPE over a mechanical revolution of the drive, the measurement estimate providing a characterization of the repeatable runout signal in the servo position error signal. A correction estimate is updated by the measurement estimate, and the correction estimate is added to the servo position error signal to provide an adjusted servo position error signal. The disc drive uses the adjusted servo position error signal to generate a correction signal for adjusting the position of the actuator. The measurement estimate is reset after each update of the correction estimate and a new measurement estimate is generated during each subsequent rotation of the disc drive during track following mode.