Western Digital Technologies, Inc.

Jern Khang Tan

Shuyu Cao

Jie Wan

Guoxiao Guo

Wei Xi

Jianghong Ding

Boworn Panyavoravaj

Xiaotian Xu

Zhou Yong

Amar Nath

An apparatus includes: a disk; a spindle motor configured to rotate the disk; and control circuitry with a spindle motor control loop, coupled to the spindle motor, the control circuitry configured to: inject a bandwidth test frequency into the spindle motor control loop, measure an open loop gain of the spindle motor control loop, calculate, using coordinate transformations, an estimated loop bandwidth of the spindle motor control loop based at least on one iteration of the bandwidth test frequency injection and the open loop gain measurement, and generate optimum loop parameters of the spindle motor control loop.

Electronic system with a method of motor spindle bandwidth estimation and calibration thereof

A method is disclosed for selecting a rotation speed when servo writing a disk of a disk drive. A gas is injected into a head disk assembly (HDA) comprising the disk. The disk is rotated while reading data from the disk using a head to generate a read signal. A fly height modulation (FHM) of the head is measured in response to the read signal. When the FHM exceeds a threshold, the rotation speed is adjusted. The disk is servo written at the adjusted rotation speed. After servo writing the disk and evacuating the gas from the HDA, the disk is rotated at a normal rotation speed lower than the adjusted rotation speed used to servo write the disk, and manufacturing data is written to the disk at the normal rotation speed.

Adjusting rotation speed of disk to reduce fly height modulation when servo writing in gas

A disk drive is disclosed comprising a head and a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors. The disk drive further comprises control circuitry comprising a servo control system operable to actuate the head over the disk in response to the servo sectors. The disk is rotated at a first speed and the servo sectors are read at a first servo sample frequency to generate first servo samples. The disk is rotated at a second speed different from the first speed and the servo sectors are read at a second servo sample frequency to generate second servo samples. The second servo samples are processed to measure a frequency response of the servo control system proximate the first servo sample frequency.

Disk drive adjusting rotation speed of disk to compensate for blind area when measuring frequency response of servo control system

Growing community of inventors

Muar, Malaysia

Jern Khang Tan