Seagate Technology Incorporated

Wing Kong Chiang

Kian Keong Ooi

Ricky Wei Watt Yeo

Beng Wee Quak

Ming Zhong Ding

Jack Ming Teng

KianKeong Ooi

MingZhong Ding

Choon Kiat Lim

YangQuan Chen

BengWee Quak

LeeLing Tan

Louis Seng Hong Pang

Lee Ling Tan

Kok Hiang Cheong

Yang Quan Chen

Siok Yin Tan

A method of handling resonance effects on disc drives includes the steps of monitoring a position error signal (PES) for an actuator arm of a disc drive, generating a feedforward compensation signal from the PES using a bandpass filter, and applying the compensation signal to a servo control signal. The bandpass filter has a center frequency set to a known resonance frequency. A disc drive includes an actuator assembly including an arm for carrying a head in a transducing relation with respect to a disc in response to a control signal, and a controller that monitors a PES for the arm and generates the control signal. The controller includes a servo controller that generates a servo control signal from the PES, and a feedforward compensation element which bandpass filters the PES to generate a compensation signal which is combined with the servo control signal to generate the control signal.

Method and apparatus for handling resonance effects in disc drives using active damping

An information handling system, such as a disc drive, includes a base, a disc stack rotatably attached to the base, and an actuator assembly movably attached to the base. A region of the disc stack is identified as a parking band, and when power is not provided to the disc drive, the actuator assembly is held in a parked position within the parking band by an actuator latch. The actuator latch and actuator assembly have different resonant frequencies based on several environmental elements near the actuator assembly, including the temperature of the environment in the disc enclosure. The actuator assembly is unlatched by measuring the environmental element near the actuator assembly and applying an alternating current to a voice coil coupled to the actuator. The frequency of the alternating current applied to the actuator assembly during the unlatching procedure is near the resonant frequency of the actuator assembly in the measured environment.

Adaptive temperature compensated AC unlatch algorithm

A method of handling multiple resonance frequencies in a disc drive includes monitoring a position error signal (PES) for an actuator arm, generating a plurality of feedforward compensation signals from the PES using a plurality of bandpass filters, and applying the compensation signals to a servo control signal. Each filter has a center frequency that is set to a problematic resonance frequency. The method may also include identifying the problematic frequencies by, for example, commanding a movement of the actuator arm, collecting data points for the PES that are associated with the movement, and performing a digital fourier transform of the data points to identify resonant frequencies. Other methods of identifying problematic frequencies include analyzing PES zero-crossing data, or using principal component analysis.

Method and apparatus for handling multiple resonance frequencies in disc drives using active damping

The present invention provides a method to screen tracks on a magnetic disc in a disc drive for harmonic resonance. There are several algorithms in the method performing different functions at various stages of the method. At any point in time, only one track is subjected to test by the method. The first stage of the method has one algorithm performing the function of obtaining a summation of all the absolute Position Error Signal (PES) velocities on a single track. Another algorithm performs the function of obtaining the average PES velocity with the summation of the absolute PES velocities. At the subsequent stage, another algorithm performs the function of obtaining the average PES velocity of a number of revolutions. An algorithm at the final stage performs the function of comparing the average PES velocity to a preset standard criterion, which is determined empirically in a separate algorithm. The track would be failed if the average PES velocity exceeds the preset standard criterion value.

Method for screening oscillatory PES with 1.7 kHz harmonic resonance

A method and disc drive system identify defective servo information elements on a disc. Servo information elements are read from the track on the disc to receive first servo data status values associated with the servo information elements. If the first servo data status value associated with a first servo information element fails to satisfy a first predetermined criterion, the first servo information element is identified as a suspected servo information element. Location and error type information associated with the suspected servo information element is recorded in a hit table. The servo information elements from the track on the disc are reread with a second servo information element masked, and second servo data status values for the servo information elements are received. If the second servo data status value associated with the suspected servo information element satisfies the first predetermined criterion, the second servo information element is identified as the defective servo information element. A read head reads servo information elements from the track on the disc. A test module identifies suspected servo information elements. A hit table stores location and error type information associated with the suspected servo information elements.

Identification of defective servo information elements in a disc drive system

A method and apparatus for releasing an actuator from a latched position. A voice coil motor is operably coupled to the actuator which is held by a latch in a latched position. The voice coil motor is provided with a first current signal of increasing magnitude alternating with a second current signal out of phase with the first current signal. The first current signal causes the voice coil motor to urge the actuator away from the latched position, and the second current signal causes the voice coil motor to urge the actuator towards the latched position.

Method and apparatus for unlatching an actuator

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Singapore, Singapore

Wing Kong Chiang