Seagate Technology Incorporated

Yi-Ping Hsin

John Christopher Morris

Dustin Mark Cvancara

Samir Mittal

An equalization filter for counteracting the effects of unwanted resonance modes and noise in the VCM plant. The filter comprises a transfer function derived from a function of the actual VCM plant response and an ideal response, for which the servo controller is designed. The response of the combined equalization filter and the actual VCM plant response substantially adheres to the ideal response. The disc drive includes firmware operable to generate one or more equalization filters for each of one or more heads.

Automatic model regulation in a disc drive servo system using model reference inverse

A repeatable runout (RRO) identification device for use with a disc drive having a rotatable disc is provided. The RRO identification device determines RRO values for servo fields of a first track of the disc as a function of received position error signal (PES) values for the servo fields independent of averaging the PES values for each servo field. The RRO identification device compares, in real-time, each determined RRO value for each servo field with a threshold repeatable runout value.

Repeatable runout identification device and method

An apparatus and method of correcting for written-in repeatable run-out in a disc drive having a servo loop for positioning a head over a rotating disc is provided. The rotating disc has at least one data track and servo information recorded in a plurality of servo fields along the data track. An initial written-in repeatable run-out compensation value for each servo field is computed as a function of a position error signal generated for each servo field during a first revolution of the disc. The initial written-in repeatable run-out compensation value for each servo field is then injected into the servo loop during another revolution of the disc. A compensated position error signal for each servo field is computed as a function of the initial written-in repeatable run-out compensation value for each servo field. A refined written-in repeatable run-out compensation value for each servo field is then computed as a function of the compensated position error signal for each servo field.

Written-in repeatable run-out compensation in embedded servo disc drives

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.

Plant variation compensation for piezoelectric microactuator in dual-stage servo of disc drives

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.

Disturbance rejection for disc drives using adaptive accelerometer feedforward servo

Method and apparatus for suppressing seek-induced vibration in a disc drive

The present invention incorporates an add-on adaptive feedforward controller into the existent track-following servomechanism of a dual-actuator disc drive to suppress the disturbance caused by mechanical interaction of the two actuator assemblies to thereby enhance the positioning accuracy at track following. The control signal fed into the power amplifier of one actuator is also used as the input signal of an adaptive controller in the other one. In an illustrative embodiment, the information is fed into an adaptive LMS filter. The output of the adaptive filter is then used as a feedforward signal to coordinate the head position with the desired track position. By matching the unknown disturbance dynamics with a filtered-x LMS (least mean square) adaptation algorithm, the output of the feedforward controller is able to cancel the disturbance from mechanical interaction, and thereby realizes the necessary fast, accurate head positioning.

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Burnsville, MN, United States of America

Yi-Ping Hsin