Seagate Technology Incorporated

Dustin Mark Cvancara

John Christopher Morris

Wenzhong Zhu

Timothy Francis Ellis

Kenneth A Haapala

Jason Wayne Riddering

Reed David Hanson

Raye Abdoulie Sosseh

Tao Zhang

Nathaniel Boyd Wilson

Bin Huang

Yi-Ping Hsin

Eric John McCalla

A clearance heater of a write head is engaged with a boosted current that exceeds a steady-state current. The steady-state current causes the write head to maintain a desired clearance over a disk during writing, the boosted current being applied before a start of the writing. The boosted current is monotonically decreased before the start of the writing and the steady-state current is applied to the heater after the start of the writing.

Boosted preheat trajectory to obtain desired clearance before writing to disk

An apparatus and method of maintaining stability in a servo loop of a disc drive is provided. A dither signal (a single frequency sine wave or a multi-frequency signal) is injected into the servo loop. A servo loop gain error signal is obtained in response to the injected dither signal. A gain of the servo loop is adjusted as a function of the servo loop gain error signal in real-time.

Apparatus and method for maintaining stability in a disc drive servo loop

An apparatus and method for compensating for variation in sample rate in a disc drive having a rotating disc and a head that is positioned over the rotating disc is provided. The disc includes at least one track that has multiple consecutive sectors. A sample rate value between timing marks of each pair of consecutive sectors of the multiple consecutive sectors is computed to obtain a sequence of sample rate values. A sequence of timing error values is computed as a function of the sequence of sample rate values and a nominal sample rate value. Data related to the sequence of timing error values is utilized to compensate for variation in sample rate values.

Compensation for timing variation in disc drives employing servo tracking systems

A disc storage system performing an in-situ test on a MEMS accelerometer, in a disc drive. The circuit includes a control circuit that establishes a desired self test condition conducive to the in-situ test during a self test interval. The circuit includes a stored reference representing at least one characteristic limit of an integrity output of the, MEMS accelerometer. The circuit includes a test circuit that receives the integrity output value and the stored reference during the in-situ test interval and that generates an in-situ test output representative of integrity of the MEMS accelerometer. Damaged or degraded MEMS accelerometers can be diagnosed in-situ.

In-situ testing of a MEMS accelerometer in a disc storage system

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

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.

Rotational acceleration correction in a disc drive

A method and apparatus are provided for positioning a head based on a control signal and a cancellation signal. In the method and apparatus, a sensor located in the disc drive is capable of generating sensor data samples at a sensor data rate that is different from a servo data rate. A data enlarger inserts additional data samples between the sensor data samples to produce enlarged data that is filtered to produce filtered data, which is decimated to form decimated sensor data at the servo data rate. A cancellation component converts the decimated sensor data into a cancellation signal that may be combined with a control signal to control the actuator. A sensor chip is also provided that includes a sensing element and a sigma-delta circuit that cooperate to generate sensor samples at a sensor data rate and a buffer that stores sensor samples at the sensor data rate.

Method and apparatus for servo data synchronization in a disc drive

A sensor chip is provided that includes a sensing element and a sigma-delta circuit that cooperate to generate sensor samples at a sensor data rate and a buffer that stores sensor samples at the sensor data rate. Although the buffer stores the samples at the sensor data rate, it is capable of providing the samples to an external circuit at a higher data rate. In one embodiment, the sensor chip is able to provide the stored sensor samples to an off-chip component at a rate set by the off-chip component.

Growing community of inventors

Saint Paul, MN, United States of America

Dustin Mark Cvancara