Samsung Electronics Co., Ltd.

Quantum Corporation

Kwong Tat Chan

Linh Nguyen

Nikolay Ivanov

Stanley H Shepherd

John J Kardash

Joe Bragg

Bipinchandra V Gami

A method for writing servo onto a disk of a hard disk drive with a servo writer. The method includes writing a plurality of spiral servo signals onto a disk. The spiral servo signals include a plurality of short spirals separated by unequal distances. The short spirals are detected by determining the unequal distances and used to write a plurality of servo patterns. The unequal distances provide information of the short spirals at different quadrants of the disk. The distances between a bank of odd short spirals is different than a bank of even short spirals which allows the servo writer to determine whether the bank is odd or even without switching banks. Either the even or odd bank of short spirals can be used to locate a starting reference point from which the servo writer can count spirals and write A, B, C and D servo bursts.

Method to identify short spirals

A method for writing servo information onto a disk of a hard disk drive with a servo writer. The disk has a circumferential index and a band of servo reference tracks. The circumferential index is detected from a clock signal generated from a clock track of the disk. The reference tracks include radial indices. A spiral servo pattern is written upon the detection of the circumferential index and a radial index. The servo writer includes a phase detector that detects changes in the relative position of the circumferential and radial indices and a delay circuit that delays the clock signal to offset such changes.

Delay clock track read back data to compensate time variance due to disk thermal expansion in spiral servo track writing

A method for writing servo information onto a disk of a hard disk drive. The method includes writing a reference servo pattern onto a track of a disk with an off-line servo track writer. The reference servo pattern has less servo bits than the final pattern allowing the off-line writer to write in a single pass. The disk is then assembled into a hard disk drive assembly and a final servo pattern is written onto the track. The final pattern can also be written with two passes. The single pass writing process reduces the time required to write the servo information. Additionally, the off-line servo track writer can write servo on a plurality of disk at the same time, further reducing the process time for writing servo and mass producing hard disk drives.

Use of offline servo track writer together with single pass servo writing process

A method and apparatus for driving a decelerating a multi-phase wound electric motor having a rotor and multiple phase coils arranged as a stator, wherein each phase coil has a first terminal and a second terminal, and the first terminals of the phase coils are connected together at a center tap. Commutation signals in response to BEMF voltages in the phase coils select a first and a second coil in each commutation state, such that when energized the first and second coils are capable of providing forward torque to the rotor based on the rotational position of the rotor relative to the phase coils. In each commutation state, the second terminal of the first is electrically connected to an upper voltage supply. For applying forward torque to the rotor, the second coil is electrically connecting the second terminal of the second coil to a lower voltage supply, wherein the upper voltage supply is at a higher voltage than the lower voltage supply. Otherwise, to apply reverse torque to the rotor to decelerate the rotor, the second terminal of the second coil is electrically connected to the upper voltage supply during at least a portion of each commutation state, causing a reverse current to flow in the first and second coils to provide reverse torque to the rotor. During each commutation state when the second terminal of the first coil is electrically connected to the upper voltage supply and the second terminal of the second coil is electrically connected to the lower voltage supply, forward current flows in a direction from the first coil to the second coil, inducing forward torque on the rotor. Further, when the second terminals of the first and the second coils are electrically connected to the upper voltage supply during at least a portion of each commutation state, reverse current flows in a direction from the second coil to the first coil, inducing reverse torque on the rotor.

Growing community of inventors

Pleasanton, CA, United States of America

Kwong Tat Chan