Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A disk drive, such as a magnetic recording hard disk drive, has a head positioning servo control system that includes an improved repetitive controller included with the conventional feedback controller for suppressing periodic disturbances. The repetitive controller includes a low-pass filter (LPF) and a time-delay memory with a time delay matched to the period of the periodic disturbance. In a digital implementation, where the head position error signal (PES) is sampled, the time delay is the time for N samples. A subsequent PES sample is summed with the time-delay input sample from N samples earlier and this summed value is input to the LPF. The output of the LPF is added to the subsequent PES sample and the added value is input to the feedback controller. The value of N is adjustable, so the repetitive controller is adaptable to changes in frequency of the periodic disturbance.

Abstract: A magnetic recording disk drive has a patterned magnetic recording disk with data blocks of magnetizable material separated by nonmagnetic regions, a write-clock-generation circuit for timing write pulses to the write head, and a rotational vibration sensor that adjusts the timing of the write pulses to correct for errors caused by rotational disturbances to the disk drive. The write-clock-generation circuit receives a reference clock signal synchronized to disk rotation and multiplies it to generate a higher-frequency write-clock signal. The write-clock-generation circuit includes a phase detector that compares the phase of the reference clock signal and the write-clock signal and provides an error signal. The output of the rotational vibration sensor is summed with the phase detector error signal to compensate for disk rotation speed changes caused by rotational disturbances.

Abstract: In conventional magnetic disk drives where stream data are treated, seek operations are performed at unnecessarily high speeds. This put the magnetic disk drives at a disadvantage in suppressing noise, reducing power consumption, and lowering the costs of actuator components. In one embodiment of the invention, a magnetic disk drive comprises a magnetic disk medium; a magnetic head; a head actuator to move the magnetic head relative to the magnetic disk medium; and a controller configured to control the head actuator to move the magnetic head to record data to and reproduce data from the magnetic disk medium. The controller is configured to control the magnetic head to record stream data on the magnetic disk medium in such a manner that the stream data is recognizable as stream data. The controller is configured to detect a situation in which two or more stream data are to be recorded or reproduced concurrently so as to set a slower seek operation mode.

Abstract: A magnetic recording disk drive has a patterned magnetic recording disk with data blocks of magnetizable material separated by nonmagnetic regions, a write-clock-generation circuit for timing write pulses to the write head, and a rotational vibration sensor that adjusts the timing of the write pulses to correct for errors caused by rotational disturbances to the disk drive. The write-clock-generation circuit receives a reference clock signal synchronized to disk rotation and multiplies it to generate a higher-frequency write-clock signal. The write-clock-generation circuit includes a phase detector that compares the phase of the reference clock signal and the write-clock signal and provides an error signal. The output of the rotational vibration sensor is summed with the phase detector error signal to compensate for disk rotation speed changes caused by rotational disturbances.

Abstract: In seek control for a head of a rotary recorder/reproducer, the seek time is reduced with noise reduced while utilizing a driving force of an actuator effectively. In one embodiment, when a microprocessor generates a control signal for a drive current given to an actuator for head seek, a signal generator generates a prespecified acceleration allowing for the allowable maximum acceleration when the actuator is accelerated, a prespecified deceleration signal allowing for the allowable maximum deceleration when the actuator is decelerated, and a zero level signal when the actuator is settled. Switching from deceleration to settling is performed at a point of time computed by the microprocessor as a time point when settling is to be started so that the head may reach a target position within the shortest period of time.

Abstract: 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.

Abstract: 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.

Abstract: 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.