Seagate Technology Incorporated

YangQuan Chen

KianKeong Ooi

MingZhong Ding

Ricky Wei Watt Yeo

ShuangQuan Min

Qiang Bi

LeeLing Tan

Louis Seng Hong Pang

Beng Wee Quak

Kian Keong Ooi

BengWee Quak

WeiSung Lee

Xiong Liu

Kevin Arthur Gomez

ChoonKiat Lim

WingKong Chiang

Ming Zhong Ding

Jack Ming Teng

Wing Kong Chiang

KianKeon Ooi

SiokYin Tan

Lincheng Xiu

LinCheng Xiu

KokHiang Cheong

Written-in runout due to vibration of the cage of a spindle motor of a disc drive is detected by identifying an initial cage frequency value of the motor. A written-in magnitude of successive servo burst closures, D(n ), is read over a plurality of tracks, and a maximum servo burst closure D(n ) is identified from the plurality of read servo bursts. A magnitude of the cage frequency at a servo sector n is calculated based on a difference between the read magnitudes of the servo burst closures at servo sectors n and n , and a phase of the cage frequency is calculated based on the magnitude of the written-in cage frequency at servo sector n . The profile, in the form of cage frequency, maximum servo burst closure magnitude, and initial phase, is stored in a memory or table for each of a plurality of radial zones of tracks. The profile is combined with a position error signal and applied to the controller in a feed forward scheme to adjust the position of the head based on the written-in runout.

Identification and cancellation of cage frequency in a hard disc drive

A method of implementing an automatic acoustic management feature for a disc drive includes receiving an acoustic/performance compromising factor from a host, tuning disc drive performance by applying the factor to a control parameter to generate a modified control parameter, and executing a loop for controlling a disc drive operation using the modified control parameter. In another embodiment, a disc drive has a base, a rotatable disc, an actuator assembly with an arm for carrying a head in transducing relation to the disc in response to a control signal, a receiver for receiving an acoustic/performance compromising factor, and a controller that monitors the position of the arm and generates the control signal. The controller executes a seeking control loop having a control parameter modified by applying a compromising factor to the parameter to tune the acoustic performance of the drive.

Automatic acoustic management system for a disc drive

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

A method and storage device are provided for initializing a polynomial linearizer in the storage device. The linearizer is initialized by identifying the coefficients of the linearizer polynomial. To reduce the computational intensity of this process, orthogonal-type coefficients for at least two orthogonal polynomials are identified, where the linearizer polynomial is formed as the sum of the orthogonal polynomials. The orthogonal-type coefficients are then combined to identify linearizer coefficients for the linearizer polynomial.

Method and apparatus for determining high order polynomials for linearization of position signals

A disc drive device includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The actuator assembly includes an actuator arm and a transducer head in a transducing relationship with respect to the disc. The transducer is attached to the actuator arm. A method of screening disc drives for harmonic resonant frequencies includes sampling the position error signal at a track location in the disc drive, and determining the velocity of the position error signal from the sample of the position error signal. The velocity of the position error signal sample is divided by the position error signal to produce a quotient. The quotient is compared to a selected quotient threshold value to determine the type of a harmonic in the disc drive.

Method for harmonic frequency identification in a disc drive

A method of producing a modified control signal to an actuator arm assembly of a disc drive to reduce RRO includes the step of generating a correction signal corresponding to a position error signal of a current track. Then to determine a high pass filter transfer function of a high pass filter to decrease a gain of an unwanted frequency generated when increasing a learning gain of the correction signal to achieve a faster convergence without any loss of performance in the disc drive. Then to determine filter parameters from the high pass filter transfer function, and to filter the correction signal by passing the correction signal through the high pass filter to generate a modified control signal to the actuator arm assembly of the disc drive using the filtered correction signal to remove the RRO on a next track.

Enhanced adaptive feedforward control to cancel once-per-revolution disturbance by shaping the internal mode

Steps for isolating and correcting total written-in repeatable run-out error written into servo sectors of a disc drive include, determining a total repeatable run-out error value for each servo sector, isolating a repeatable error value component of the total written-in repeatable run-out error value for each servo sector, removing the repeatable error value component from total written-in repeatable run-out error value to provide a non-repeatable error value component of the total written-in repeatable run-out error value for each servo sector, providing both the repeatable and non-repeatable error value components to a processor for generation of compensation signals, and applying the compensation signals into a servo control circuit of control loop of the disc drive using compensation circuits to compensate for each component of the total written-in repeatable run-out error.

Repeatable run-out error compensation method for a disc drive

According to one embodiment of the present invention, a disc drive includes a disc and a transducer supported by an actuator assembly that is accelerated by controlling current in a voice coil. The disc drive controls a position of the transducer over a present track on the disc in a track-and-follow mode, generates an estimated bias current to be applied to the voice coil to balance a bias on the actuator assembly when the transducer is over the present track, starts a movement of the transducer toward a target track in a seek mode, enters the estimated bias current into a bias table if an immediately preceding movement of the transducer in the seek mode was longer than a seek length boundary such that nonlinear friction in a pivot in the actuator assembly is less substantial, and applies a bias current to the voice coil calculated based on a bias current entry in the bias table during the seek mode.

Seek in a disc drive with nonlinear pivot friction

A repetitive learning compensator for a servo system of a disc drive includes a memory buffer having a length N/m where N is the number of servo sectors in a track, m is a parsing factor greater than 1 and N/m is an integer. A down sampler supplies servo signals containing error signals to the repetitive learning compensator at a frequency of f /m, where f is a sampling frequency based on N and a fundamental frequency f of the spindle motor. An up sampler supplies filtered signals from the repetitive learning compensator to the actuator assembly at the sampling frequency f . One aspect of the disclosure includes tuning the repetitive learning compensator with a phase advance represented by N and a cutoff frequency f , where N and f are selected as a pair to provide the greatest transfer function amplitude at the harmonic frequencies for the repetitive learning compensator.

Optimally designed parsimonious repetitive learning compensator for hard disc drives having high track density

A disc storage system is provided which includes a servo control loop for compensating for repeatable runout. Repeatable runout is compensated using table entries of the form Comp Value(k&plus;1)&equals;Comp Value(k)&plus;K&PHgr;(z)RRO(k), where K is a learning rate; k is iteration number &PHgr;(z) is a filter and RRO(k) is the repeatable runout error. Further, &rgr;(j&ohgr;)&equals;&verbar;1&minus;K&PHgr;(j&ohgr;)/(1&plus;PC(j&ohgr;)&verbar;<1 needs to be satisfied, where PC(j&ohgr;) is an open loop frequency response of the servo loop. The filter can comprise a order filter.

Repeatable runout compensation using iterative learning control in a disc storage system

A method and apparatus for compensating for written-in repeatable runout in a disc drive is provided. Compensation values are determined through an iterative learning process in which parameters of the learning process such as learning gain, servo loop gain, etc. are functions of the iteration number. The learning process also employs a nominal double integrator model of an actuator of the disc storage system. The learning process is also a function of a zero-phase low-pass filter.

Repeatable runout compensation using a learning algorithm with scheduled parameters

A method of characterizing and screening a disc drive based on a voice coil motor pivot friction developed during a low velocity seek operation consists of determining estimated drive level bias values required by the voice coil motor to move an actuator arm assembly during a fast seek, then determining a low velocity drive level bias values required by the voice coil motor to move an actuator arm assembly during a slow seek, then computing a difference between the estimate drive level bias values and the low velocity drive level bias values, then determining a hit counter value based on comparing the computed difference with a predetermined threshold value, and then characterizing the disc drive based on the hit counter value.

Growing community of inventors

Singapore, Singapore

YangQuan Chen