Hitachi Global Storage Technologies Netherlands B.v.

Matthew Taylor White

Tetsuo Semba

Toshiki Hirano

Satoshi Yamamoto

Fu-Ying Huang

Kevin Tzou

Eric Baugh

Wayne Isami Imaino

Hiroshi Uchida

Michael Anthony Moser

Jiann-Chang Lo

Gary Allan Herbst

Jong-Ming Lin

A method for repairing at least one defective servo segment of a servo sector having at least one defective servo track written on a magnetic recording media. The method comprises mapping the magnetic recording media for locations of the defective servo segment of the servo sector. A non-defective segment of the servo sector is replicated at least once on the magnetic recording media in a customer data zone, thereby creating at least one good servo segment copy of the servo sector. The good servo segment copy is propagated through the customer data zone associated with the defective servo segment. The good servo segment copy is copied onto the magnetic recording media previously occupied by the defective servo segment of the servo sector.

Repair of defective servo tracks

A data recording disk drive has one or more capacitive sensors for sensing out-of-plane vibration of the disk or disks. The sensors are attached to a support structure that is attached to the disk drive housing. Each sensor is associated with a disk and faces a surface of the disk near the outer perimeter of the disk and close to the recording head. The support structure can be made of a metal or a high-strength plastic and can be a separate structure mounted to the housing, or integrated as part of the single-piece housing casting. If it is metallic, as would be the case if it were integrated with the housing, then layers of insulating material separate the sensors from the support structure. A support structure that serves other functions in the disk drive, such as a support for air dams that extend between the disks, can also function as the support structure for the capacitive sensors.

Disk drive with support structure for air dams and disk-vibration capacitive sensors

A data recording disk drive has one or more capacitive sensors for sensing out-of-plane vibration of the disk or disks. The sensors are attached to a support structure that is attached to the disk drive housing. Each sensor is associated with a disk and faces a surface of the disk near the outer perimeter of the disk and close to the recording head. The support structure can be made of a metal or a high-strength plastic and can be a separate structure mounted to the housing, or integrated as part of the single-piece housing casting. If it is metallic, as would be the case if it were integrated with the housing, then layers of insulating material separate the sensors from the support structure. A support structure that serves other functions in the disk drive, such as support for disk damping plates, can also function as the support structure for the capacitive sensors.

Disk drive with support structure for damping plates and disk-vibration capacitive sensors

Methods and systems for reducing read/write head track misregistration are described. According to one embodiment, a first signal is received from a first capacitive sensor that faces a surface of a disk associated with a disk drive. A second signal is received from a second capacitive sensor that faces the surface of the disk. A determination is made as to whether the disk is being moved along its axis of rotation or whether the disk is tilting. Read/write head track misregistration is reduced based on the determination of whether the disk drive is being moved along an axis of rotation or whether the disk is tilting.

Reducing read/write head track misregistration

A disk drive has multiple feedforward controllers for handling external disturbances, such as rotational vibration (RV), that have different external disturbance frequency spectra. Each feedforward controller is designed to be optimal for a canceling a specific associated RV spectrum. The actual RV spectrum acting on the disk drive is determined and the proper feedforward controller is then selected and used to generate a compensation signal for canceling the RV. Each feedforward controller may be tested when the disk drive is experiencing the RV, and the resulting compensation signal and PES measured. The feedforward controller that produces the best external disturbance cancellation is then selected as the feedforward controller. A signal from a RV sensor may be used to detect the peak frequency of the actual RV spectrum. This detected peak frequency is then matched to a peak frequency in a plurality of peak frequencies in a lookup table, and the feedforward controller associated with the matching peak frequency is selected as the feedforward controller.

Magnetic recording disk drive with multiple feedforward controllers for rotational vibration cancellation

A magnetic recording disk drive has a disturbance sensor and a disturbance frequency identifier that are used to adjust the frequency of a peak filter as the disturbance frequency changes. The sensor and the frequency identifier are separate from the servo control loop and thus do not rely on the head position error signal (PES) to predict the disturbance frequency. The adjustable peak filter is coupled in parallel with the servo feedback controller. The peak filter modifies the open loop transfer function and the error rejection function of the servo control loop to provide a higher rejection at the identified frequency. The peak filter may be switched out of or uncoupled from the servo feedback controller during track-seeking or as desired, depending on the amplitude of the sensor signal or the amplitude of the PES.

Disk drive using a disturbance sensor for disturbance frequency-identification and suppression

A data recording disk drive has one or more capacitive sensors for sensing out-of-plane vibration of the disk or disks. The sensors are attached to a support structure that is attached to the disk drive housing. Each sensor is associated with a disk and faces a surface of the disk near the outer perimeter of the disk and close to the recording head. The support structure can be made of a metal or a high-strength plastic and can be a separate structure mounted to the housing, or integrated as part of the single-piece housing casting. If it is metallic, as would be the case if it were integrated with the housing, then layers of insulating material separate the sensors from the support structure. A support structure that serves other functions in the disk drive can also function as the support structure for the capacitive sensors.

Disk drive with support structure for disk-vibration capacitive sensors

A dual-stage actuator disk drive has both a rotary primary actuator and a rotary secondary actuator. When the primary actuator initiates a seek there are two torque components acting on the center of mass of the secondary actuator's moving portion. The center of rotation of the moving portion is located at an optimal location relative to the center of mass of the moving portion, which results in cancellation of the two torque components and a secondary actuator that has essentially no resonant frequency in response to a seek by the primary actuator. If the optimal location can not be achieved because of assembly tolerances, then the center of rotation is placed at a distance at least as great as the assembly tolerance from the optimal location.

Dual-stage actuator disk drive with optimal location of the movable portion of the secondary actuator

Embodiments of the present invention provide a way to modify the controller of a HDD head actuator to increase the error rejection capability and suppress the wideband vibration that affects the head motion. In one embodiment, a system to suppress influence of an external disturbance to an actuator comprises a controller providing a controller output as an actuator input to drive an actuator; a feedback loop to feed a head signal at an output of the actuator back as an input to the controller to produce an error signal; and a plurality of peak filters coupled to the controller and having different peak frequencies. Each peak filter has a peak filter input including the error signal, and has a peak filter output. A supervisor module is coupled with the peak filters to selectively add or delete the peak filter output of each peak filter to the actuator input to drive the actuator.

Vibration suppression for servo control

A method and apparatus for compensating for head-to-disk contact-induced disturbances in a hard disk drive is disclosed. The method includes determining topographical variations across a surface of a disk during the manufacturing or operation of the hard disk drive. Error signal variations that occur as a result of head-to-disk contact-induced disturbances resulting from the topographical variations are recorded. Current to a voice coil motor in the hard disk drive is varied to correct for the contact-induced disturbances before they occur.

Method and apparatus for rejecting contact-induced disturbances

Embodiments of the present invention provide a method and a system for generating optimal feedforward signal for the seek control to suppress the RTV (Random Transient Vibrations) and the seek acoustic noise. One aspect is directed to a method of providing a revised feedforward signal using an adaptive filter in a feedforward control system for controlling an actuator to move a head to seek a track and settle on the track of a disk in a disk drive apparatus. The method comprises performing a seek operation of the head using an initial feedforward signal; obtaining an error signal at settling after performing the seek operation; determining filter characteristics of the adaptive filter to minimize the error signal; and implementing the adaptive filter having the determined filter characteristics in the feedforward control system to produce a revised feedforward signal for controlling the actuator for moving the head in the disk drive apparatus.

Seek trajectory generation using adaptive filtering

A magnetic recording disk drive with rotational vibration (RV) cancellation uses the position error signal (PES) and the signal from a RV sensor to determine when to enable and disable RV cancellation. An RV feedforward compensation signal to be summed with the VCM control signal is 'switchable', meaning that it can be enabled or disabled by the disk drive servo control processor. The determination to enable or disable is made from a comparison of the PES with a threshold PES, which may be an estimate of the off-track position of the head calculated from the RV sensor signal. The estimated off-track is compared to the absolute value of the actual or measured PES. If the estimated off-track is smaller than the actual PES, then the state of the RV cancellation is switched, i.e., if it is enabled it is disabled and if it is disabled it is enabled.

Magnetic recording disk drive with switchable rotational vibration cancellation

A method for secondary-actuator failure-detection and recovery in a dual-stage actuator disk drive includes running a calibration test by the servo control processor and measuring the position of the secondary actuator relative to its neutral position in response to the calibration test. The secondary-actuator failure detection and calibration test can be performed on a regular schedule or at selected times, such as at disk drive start-up. With the primary actuator biased at a test location, such as a crash stop or a load/unload ramp, the servo control processor generates a test signal to the secondary actuator and receives a relative-position signal (RPS) from the relative-position sensor in response to the test signal. The test comprises two measurements: a measurement of the secondary actuator static characteristics, and a measurement of the secondary actuator dynamic characteristics.

Method for secondary-actuator failure detection and recovery in a dual-stage actuator disk drive

A method for secondary-actuator failure-detection and recovery in a dual-stage actuator disk drive includes running a calibration test by the servo control processor and measuring the position of the secondary actuator relative to its neutral position in response to the calibration test. The secondary-actuator failure detection and calibration test can be performed on a regular schedule or at selected times, such as at disk drive start-up. With the primary actuator maintaining the read/write head on a data track in track-following mode, the servo control processor generates a test signal to the secondary actuator and receives a relative-position signal (RPS) from the relative-position sensor in response to the test signal. The test comprises two measurements: a measurement of the secondary actuator static characteristics, and a measurement of the secondary actuator dynamic characteristics.

Dual-stage actuator disk drive with method for secondary-actuator failure detection and recovery using a relative-position sensor while track following

A method in a dual-stage actuator disk drive tests if the secondary actuator has failed while the disk drive is in its normal track-following operating mode. The secondary actuator is removed from the control loop and the primary actuator maintains the read/write head on a data track in the track-following mode. The servo control processor generates a test signal to the secondary actuator and receives the position error signal (PES) as the read head detects the PES bursts in the data track being followed. The servo control processor calculates the response of the secondary actuator to the test signal by deconvolving the motion of the primary actuator from the PES. The calculated response is then compared with an expected response to determine if the secondary actuator has failed. The coherence function can be calculated to measure the statistical validity of the calculated secondary-actuator frequency response.

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Mountain View, CA, United States of America

Matthew Taylor White