Abstract: A system and method for attenuating the effect of rotational vibration on the positioning of the read/write head in a disc drive. The rotational acceleration of the disc drive body is sensed and applied to an adaptive filter that produces a feedforward signal designed to offset the effects of the rotational vibration. The adaptive filter adjusts its parameters based on the rotational acceleration signal, the position error signal of the servo system, and a transfer function relating the actual position signal to the feedforward signal. The plant estimate of the transfer function relating the actual position signal to the feedforward signal is determined off-line and stored for use by the adaptive filter in adjusting its parameters during operation.

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: An apparatus and method optimizing a model reference generator of a servo circuit to substantially mimic actual read/write head positions are disclosed. The servo circuit includes a microprocessor with associated random access memory storing a current profile and a set of optimized filter coefficients. The coefficients optimize a delay length of a finite impulse response filter, which delays passage of the current profile to a double integrator embedded in the microprocessor. The double integrator generates the substantially mimicked head positions.

Abstract: A method and apparatus are disclosed for improving seek performance of a disc drive through adaptive servo gain adjustment. The disc drive comprises a head adjacent a rotatable disc and a servo circuit which controllably positions the head adjacent tracks defined on the disc. During a seek operation in which the servo circuit moves the head from an initial track to a destination track, the servo circuit accumulates a velocity error as a sum of a series of velocity errors each obtained as a difference between an actual velocity of the head and a corresponding desired velocity over a selected radial distance of the disc. The servo circuit additionally measures an elapsed time for the head to pass over a second selected radial distance of the disc as the head is decelerated toward the destination track. Thereafter, the servo circuit adjusts a gain of the servo circuit in relation to the accumulated velocity error and the measured elapsed time.

Abstract: A positioning control apparatus for a magnetic disk apparatus. Internal models and a trajectory generation section are constructed in a control program. Based on generated position trajectory and velocity trajectory and an internal model position and velocity, a model control section outputs a first operation signal Umf for a fixed sample time Tu and then outputs a second operation signal Ums for Tu. The model control section calculates Umf and Ums so as to cause a position Pm and a velocity Vm output by an internal model 2 Tu seconds later to coincide with the generated position trajectory and velocity trajectory. When a detector has detected a voice coil saturation current for head movement, a signal obtained by subtracting a position feedback signal Uh from a detected voice coil current is used as an internal model input to thereby cause the model to track a control subject.

Abstract: The fundamental vibration or butterfly mode sensitivity of a hard disk drive,is significantly dependent on the operating temperature of the drive. The temperature of the drive is readily determined via measurement with a thermal or coil resistance sensor. The sensor provides the drive's servo controller with the drive temperature. The current operating temperature of the disk drive, in combination with its modal sensitivity to thermal changes, are used to regularly update the servo controller. With this information, the servo controller calculates new butterfly mode characteristics as the operating temperature changes in order to actively compensate for the mode, and thus increase the performance of the disk drive.

Abstract: Herein is disclosed a method and apparatus for controlling the excitation of a servomechanism in a disc drive with a low frequency stimulus, yet necessitating the control system to include only a model of the servomechanism's response to having been excited by a high frequency stimulus (square-wave). The invention uses a square wave as a feedforward input signal. This feedforward input signal is low-pass filtered and used as a stimulus to excite the servomechansim, during seek operations. The response of the servomechanism is measured at intervals. The response of the servomechanism is predicted, by a servomechanism model, as if the servomechanism had been excited by the feedforward square-wave signal, rather than its filtered counterpart. The predicted response of the servomechanism is then filtered, using a similar low-pass filter. The difference between filtered modeled responses and the measured responses are used to subsequently adjust the signal that stimulates the servomechanism.

Abstract: The present invention includes a servo control system for controlling a dual stage actuator in a disc drive. The disc drive includes a data head for accessing information on a disc surface, and the dual stage actuator includes a coarse actuator and at least one fine actuator. The control system includes a fine actuator driver and a coarse actuator driver for driving the fine and coarse actuators, respectively. The control system also includes an observer which receives the coarse and fine actuator input signals and estimates a response of the coarse and fine actuators.

Abstract: A filter for attenuating a resonance mode without substantial phase margin loss. The filter comprises a transfer function having an additional pole, such that the phase of the input signal is advanced. The phase-advanced filter substantially attenuates all frequencies above a selected center frequency while avoiding substantial phase margin loss.

Abstract: A method is provided for identifying a transfer function used to regulate a response of a positioning system. The method includes identifying data representing a desired frequency response for a transfer function. A first function of one order is generated based on the identified data. A second function of a larger order than the order of the first function is also generated based on the identified data. A transfer function based on one of the first function or second function is then selected and used to regulate the response of the positioning system.

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: Methods and systems for detecting and correcting for undesirable vibrations impacting the servo systems in data storage devices. A detection technique is provided wherein a detection filter is configured to scan a position signal of the servo system across a range of frequencies, and, at each respective scanned frequency, record an amplitude associated therewith. The recorded amplitudes are examined to determine whether any exceed a threshold, thereby locating a peak frequency of the vibration. Using the detected peak frequency of the vibration, a corrective filter is configured to operate about the peak frequency of vibration, thereby reducing its impact on the position signal in the servo system.

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

Abstract: An apparatus and method optimizing a model reference generator of a servo circuit to substantially mimic actual read/write head positions are disclosed. The servo circuit includes a microprocessor with associated random access memory storing a current profile and a set of optimized filter coefficients. The coefficients optimize a delay length of a finite impulse response filter, which delays passage of the current profile to a double integrator embedded in the microprocessor. The double integrator generates the substantially mimicked head positions.

Abstract: In summary, preferred embodiments disclose a system, method, and program for determining a value for non-mechanical noise within a disk drive system. The non-mechanical noise is likely related to instability in a head which reads data from a magnetic surface within the disk drive system. First, a sample of position error signals (PES) indicating non-repeatable runouts (NRRO) is provided from read operations within the disk drive system. Spectral analysis is then performed on the provided samples to calculate non-filtered power values for the NRRO values at different frequencies. A filtered power spectrum is determined within a frequency range excluding mechanical noise. A filtered power value is calculated from the determined filtered power spectrum within the frequency range excluding mechanical noise.

Abstract: A method and apparatus for providing feedforward control of two interacting actuators to compensate for interaction there between is disclosed. State models for each actuator that processes acceleration for each actuator provide an estimate of head acceleration for each of the actuators and to provide feedforward control signals to the actuators for controlling the positioning of the heads based upon the estimates of head acceleration for each of the actuators.

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: According to one embodiment of the present invention, a fly height of a read/write head in a disc drive is actively controlled as the read/write head is positioned over a rotating disc with a patterned media. The patterned media includes ridges and grooves in servo wedges in the patterned media. According to another embodiment of the present invention, an estimated fly height of the read/write head is compared with a desired fly height to generate a control signal. The control signal is used to apply a voltage difference across a piezoelectric layer joining the read/write head to a slider to move the read/write head relative to the slider and adjust the fly height of the read/write head. According to another embodiment of the present invention, a map of ridges and grooves in the patterned media is generated and the fly height of the read/write head is actively controlled based on information in the map.

Abstract: A disk drive with the capability to prevent off-track writing with reduced false triggering is described. An improved method of predicting the position of a head is used to determine whether the head is on or off-track. A position error signal at an nth servo position Pn and a velocity Vn at the nth servo position (Vn=Pn−Pn−1) are calculated using values read at the nth and n−1 head positions. Based on these Pn and Vn and on the output of the servo controller at the nth servo position Un, the predicted PESn+1 is calculated as: Predicted PESn+1=Pn+Vn+kUn where k is a constant.

Abstract: To improve the positioning accuracy which has been limited so far due to a vibration mode of an actuator for positioning a head and increase the capacity of an apparatus by raising the density of tracks for recording or reproducing information.

Abstract: Apparatus and method for generating control inputs for a disc drive dual stage actuator having primary and secondary actuator motors used to maintain a head adjacent a rotatable disc surface. An h-infinity hardware controller generates the control inputs in relation to an actual position signal, a desired position signal and a unique set of coefficients for each selected head. The coefficients are selected by obtaining an output response for each head, selecting the coefficients in relation to the output response for each head, and storing the coefficients in a nonvolatile memory location of the disc drive. The appropriate set of coefficients are thereafter loaded as each head is selected in turn during normal drive operation.

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: 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: A method and system for providing plant variation compensation for a microactuator in a dual-stage servomechanism of a disc drive. The method includes performing indirect adaptive filtering to identify plant variation in the microactuator, and tuning a compensator for the microactuator based on the plant variation. The indirect adaptive filtering can be performed using a two-stage process, including a first stage of adaptive modeling for the dual-stage servomechanism and a second stage of generating an indirect mode-reference inverse for the microactuator. A combined process can alternatively be employed. The microactuator can be a piezoelectric microactuator which forms a PZT system. The dual-stage servomechanism also includes a coarse actuator such as a voice coil motor.

Abstract: In control means having a feedforward system and a feedback system, a control model for generating reference position data yr from feedforward control signal Uff0 is separated into an original control model 22 and a compensation filter 23. Gain of feedforward control signal Uff0 is compensated by gain compensation means 24 to form feedforward control signal Uff after compensation. Data yr is input to a feedback controller 25, and feedback control signal Ufb and Uff are input to a control object 26. Coefficients of the compensation filter 23 and the gain compensation means 24 are compensated on the basis of a head position trajectory obtained by actual seek operation.

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: A signal reproducing method reproduces servo information recorded on a recording medium by use of a head. A current calculation related to a current and an observer calculation related to a position and a velocity of the head are made based on reproduced servo information, and a current value for driving the head is calculated based on the above calculation result. Only computations which require a demodulation result of a present sample are made during a first time after demodulation of the position of the head to a time when the current value is output, and computations which require a demodulation result of a past sample are made during a second time other than the first time.

Abstract: A hard disk drive which moves a transducer across a disk surface so that the transducer has an essentially sinusoidal acceleration trajectory. The transducer may be integrated into a slider that is incorporated into a head gimbal assembly. The head gimbal assembly may be mounted to an actuator arm which can move the transducer across the disk surface. The movement of the actuator arm and the transducer may be controlled by a controller. The controller may move the transducer from a first track to a new track in accordance with a seek routine and a servo control routine. During the seek routine the controller may move the transducer in accordance with a sinusoidal acceleration trajectory. The sinusoidal trajectory may reduce the high harmonics found in square waveforms of the prior art, and thus minimize the acoustic noise of the head gimbal assembly and reduce the settling time of the transducer for reducing the duration of the seek routine.

Abstract: Disclosed herein is a head actuator for a head provided so as to accessible to a disk-shaped recording medium rotating above a base. The head actuator includes a main actuator driven so as to rotate above the base, and a microactuator driven so as to swing relative to the main actuator. The head is mounted on the microactuator. The main actuator and the microactuator are controlled so that the head is moved in a substantially radial direction of the recording medium and positioned over a desired track of the recording medium. A primary resonant frequency of mechanical characteristics of the main actuator is set to 100 Hz or higher. This setting may be achieved by increasing a preload in a ball bearing of the main actuator, for example, to thereby increase the rigidity of a nonlinear spring of the ball bearing. In the case that a disturbance acts on the main actuator, the above setting allows a reduction in displacement of the microactuator required for positioning of the head over the desired track.

Abstract: A method, apparatus, or product for a rotating disk storage device. In one embodiment, the apparatus includes a disk, a spindle motor that rotates the disk, a transducer, an actuator arm that can move the transducer, and a controller. The controller can control the movement of the actuator arm to move the transducer across the disk surface from a first track to a second track, and determine a position error signal (PES) at one or more positions between the first and second tracks, where the PES includes a non-repeatable disturbance signal. The controller can iteratively generate a disturbance correction signal at the one or more positions based on the PES, combine the disturbance correction signal with the PES to minimize the non-repeatable disturbance signal to provide a corrected PES, and vary, at the one or more positions, the movement of the transducer as a function of the corrected PES.

Abstract: This invention comprises a head 3 for reading information from a disk storage medium 2, an actuator 5 for moving the head 3, and a control circuit 8 for calculating a control signal from the position signal, that was read by the head, using an eccentricity observer 21. The control circuit 8 selects a first eccentricity estimation gain during seek control and selects a second eccentricity estimation gain during following control. This makes it possible to perform seek control that is not affected by the eccentricity error.

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

Abstract: A scheme for management of uncertainty in control systems that require adaptation is described. The scheme removes as much uncertainty as possible at design time and manufacturing time by taking advantage of available compute resources in pre-computing a large set of robustness-performance tradeoff based model controllers at different operating conditions for different values of uncertainty parameters that occur in-use and in manufacturing. A group of control models, and corresponding model controllers with an uncertainty bound larger than the best-tuned controller, are generated. A subset of the model controllers is implemented in the system at manufacturing time based on characterization of the system. The subset of model controllers is switched at run time based on transient information received during operation of the system.

Abstract: Method and apparatus for evaluating programming used by a programmable processor device in a disc drive to carry out servo control of a head with respect to a rotatable disc. The programming is first generated as a series of instructions executable by the programmable processor device. Processor emulation software is used to simulate execution of the instructions in a computer. A dynamic model of electrical and mechanical portions of the disc drive is generated using plant simulation software. A dynamic linking program is configured to synchronize and transfer data between the processor emulation software and the plant simulation software. All three programs are thereafter simultaneously executed in the computer to evaluate realtime operation of the programming.

Abstract: A method for controlling the current applied to a voice coil motor (VCM) prevents overheating of a coil in the VCM. The method includes the steps of defining an acceleration interval for measuring the distance traveled by a head moved by the VCM. The method also defines a distance traveled during the acceleration interval which can be used as a reference for indicating that the coil is being overheated. The VCM is driven for the acceleration interval and the distance traveled during the interval is measured and compared to the reference distance. If the difference exceeds a threshold, then the current being applied to the coil is controlled to maintain the coil temperature within a limit. If, however, the difference does not exceed the threshold, the current being applied to the coil is controlled to meet a performance requirement.

Abstract: A method and storage device are provided for initializing a polynomial linearizer in the storage device. The linearizer is initialized by identifying the coefficients of the linearizer polynomial. To reduce the computational intensity of this process, orthogonal-type coefficients for at least two orthogonal polynomials are identified, where the linearizer polynomial is formed as the sum of the orthogonal polynomials. The orthogonal-type coefficients are then combined to identify linearizer coefficients for the linearizer polynomial.

Abstract: Steps for isolating and correcting total written-in repeatable run-out error written into servo sectors of a disc drive include, determining a total repeatable run-out error value for each servo sector, isolating a repeatable error value component of the total written-in repeatable run-out error value for each servo sector, removing the repeatable error value component from total written-in repeatable run-out error value to provide a non-repeatable error value component of the total written-in repeatable run-out error value for each servo sector, providing both the repeatable and non-repeatable error value components to a processor for generation of compensation signals, and applying the compensation signals into a servo control circuit of control loop of the disc drive using compensation circuits to compensate for each component of the total written-in repeatable run-out error.

Abstract: Linearizing hysteresis of a microactuator for a disc drive by modeling the microactuator with a first polynomial equation to provide a linear displacement response of the microactuator responding to an applied voltage, deriving a set of constants from a plurality of burst patterns for use with the first polynomial equation to provide a set of variables for use in resolving the second polynomial equation to provide a set of equations from which a set of constants can be derived for use by the second polynomial equation to provide a voltage to the microactuator to displace the microactuator by a predetermined incremental distance.

Abstract: A hard disk drive device (11) includes an actuator (16) controlling movement of read/write heads (20) relative to a stack (12) of rotating disks. A control arrangement (30) for controlling the actuator includes a control loop (50) using a model reference control portion (68, 76) to generate a first digital positioning signal component (72), and using a further control portion (66, 60, 62, 64) to generate a second digital positioning signal component. Two low-precision digital-to-analog converters (54, 56) respectively convert the first and second digital positioning signal components to respective analog positioning signal components (61, 59). A summing junction (57) combines the analog positioning signal components in a manner giving one greater weight than the other in a resulting analog positioning signal (48), which is applied to the actuator.

Abstract: The invention is a servo compensation method and system for use in a disk storage system. The disk storage system experiences error that causes a head to become mis-aligned with the disk. The error comprises multiple spin-frequency harmonic run-out error and other servo position errors. During follow mode, a digital filter processes a position error signal to generate a compensation signal. The position error signal is comprised of components representative of the multiple spin-frequency harmonic run-out error and the other servo position errors. The compensation signal is comprised of components that cause the servo positioning system to compensate for the multiple spin-frequency harmonic run-out error and the other servo position errors. The digital filter also operates as an oscillator that provides an oscillating signal at multiples of the spin frequency of the disk during seek mode.

Abstract: A hard disk has a servo loop and a rotating storage medium. The rotating storage medium has one or more significant flutter modes at frequencies below a zero cross frequency of a rejection transfer function of the servo loop. The effect of the forgoing is to allow the servo loop to better track a rotating medium that is subject to significant flutter. Peak filters with frequency bands that substantially overlap frequency bands of the significant flutter modes can also be added to the servo loop to further improve tracking. Multiple narrow band filters with frequency bands overlap can be used to cover the spectrum of a single flutter mode. Two lag-lead filters, the frequency responses of which overlap can be used to cover two adjacent significant flutter modes. At frequencies intermediate to the two adjacent flutter, modes, the lead caused by one filter, will be cancelled by the lag caused by the second.

Abstract: A feedback control system applicable to a magnetic disk unit is capable of improving the accuracy of positioning at a low sampling frequency.

Abstract: According to one embodiment of the invention, a method of moving a device from a first position to a second position by an actuation system includes moving the device in response to providing a control signal having a first amplitude for a first time period. The method also includes, immediately after the first time period, moving the device in response to providing a control signal having a second amplitude for a second time period, the device having a nonzero velocity after the second time period. The nonzero velocity has a magnitude that allows the device to coast to, and stop at, the second position after the second time period without receiving a control signal.

Abstract: In a disk drive system, a servo controller is operative to perform a process of inhibiting write operations for writing data to tracks of a disk during a head settling period following a track seek operation. During each of a first plurality of sampling intervals transpiring during a first time period, the servo controller determines a present position value indicative of the position of the head during the present sampling interval, and also determines a predicted position value indicative of the position of the head during a subsequent sampling interval. Also during each of the first plurality of sampling intervals, the servo controller determines: whether the present position value is within a first error margin from the center of a target track; and whether the predicted position value is within the first error margin. If the present position value and the predicted position value are both within the first error margin, the servo controller enables write operations.

Abstract: A method of controlling an actuator in a disc drive to perform a seek operation prior to a read operation is disclosed. A radial distance between the initial track and the target track is determined. A rotational distance between the initial head rotational position and the target rotational position is also determined. The magnitude of the performance benefit to be gained by reading pre-fetch and post-fetch data is estimated. Then a seek velocity profile is selected based on the radial distance, the rotational distance and the estimated magnitude of the performance benefit that would be gained by reading pre-fetch and post-fetch data. The actuator then is controlled using the selected seek profile. A disc drive for implementing this method is also provided.

Abstract: A disc drive controller corrects for rotational vibration disturbances of a head position. The controller includes multiple sets of adjustable controller gains. The controller compares an accelerometer output to an acceleration threshold and generates conditional branches as a function of the comparison. The controller updates one set of the adjustable controller gains within a computational time limit after a first conditional branching. The controller updates a second set of the adjustable controller gains within the computational time limit after a second conditional branching.

Abstract: Disclosed is a calibration method for an acceleration sensor in a storage device for calibrating and a storage device, an enclosure for calibrating the acceleration sensor for compensating a vibration of an enclosure in a state of its being mounted in a storage drive. The calibration method and mode comprises a step of exciting a actuator of the drive by flowing a drive current having a predetermined current value, a step of calculating the acceleration of the enclosure of the drive from the predetermined current value and a mechanical transfer function of the storage device, a step of detecting a measured value of the acceleration sensor, and a step of calculating a sensitivity of the acceleration sensor from the calculated acceleration and from the detected measured value. The acceleration sensor is calibrated in the state of its being mounted in the disk drive, and hence the sensitivity can be precisely calibrated.

Abstract: A method for determining servo loop gain of a servo loop in a disc drive includes performing a plurality of seek operations, each seek operation moving a head in a disc drive across a plurality of tracks on the disc. Afterwards, the head is settled over a radial position on a track and a signal is injected into the servo loop at the first frequency. At least two values generated by portions of the servo loop are measured to determine a servo loop gain.

Abstract: There is provided a positioning control method of magnetic disc apparatus which can permit fast and stable settling to a target position without overshoot or undershoot in connection with a moving distance of one track seek to about 16-track seek for which positioning must be determined within a moving time corresponding to a resonance frequency of a mechanical system. (1) a method of generating a position/velocity orbit for reducing power at a specified frequency, (2) a method of generating acceleration feed-forward compensation which can permit a head to accurately reach the target position even when the feedback system does not function under a condition that external disturbance does not act and (3) a method of generating a position orbit corrected by a controlled object model accurately modeling resonance oscillation up to a moving frequency band are used in combination.