Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2002-03-22
2004-05-18
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06738215
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority from Japanese Patent Applications No. 2001-084325, filed on Mar. 23, 2001, and No. 2001-275592, filed Sep. 11, 2001. Each of these applications is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a magnetic disk drive apparatus having a servo system and methods for writing servo data therein. More particularly, it relates to apparatus and methods for performing self-servo writing based on reference servo data (servo patterns) being preliminarily written in a disk medium.
2. Description of the Related Art
Conventionally, in order to write and read data on and from a target track on a recording surface of a data storage disk medium (hereinafter referred to as a “disk”‘), a magnetic disk drive apparatus, such as a hard disk drive apparatus, (hereinafter simply referred to as a “disk drive”) includes a servo system for moving and positioning magnetic head elements onto a target track. The servo system includes a servo controller for controlling a drive on a rotary actuator so as to carry the head elements onto a target track by using reference servo data (servo patterns) on a recording surface of a disk. The reference servo patterns are preliminarily provided at servo areas on a recording surface of a disk at a predetermined interval. The servo controller includes a microprocessor (CPU) for mainly controlling a disk drive and a voice coil motor (VCM) driver for driving a rotary actuator under control of the CPU. The reference servo patterns include track address signals and servo burst signals. Track address signals detect track positions and servo burst signals detect a position in a particular track on the recording surface of a disk.
Conventionally, the reference servo patterns are written in servo areas on each recording surface of a disk by using a specialized instrument for a servo track writer. Thus, there is a need for manufacturing a disk drive that includes a process for writing reference servo patterns on both sides of a disk.
The specialized servo track writer instrument includes a head positioning control system (hereinafter referred to as a “positioner”) in order to drive a rotary actuator in the disk drive before the servo writing process. In order to write servo patterns onto a disk, the disk drive itself is temporarily fixed in the specialized servo writer instrument so as to synchronize each movement of the positioner and a rotary actuator. Thus, the positioner determines a head position by controlling an amount of movement of the rotary actuator as a preceding process for the servo pattern writing operation. The positioner includes a positioning controller for inputting a target position as an absolute position.
The operation for writing servo patterns is performed through a head element of the disk drive. When a target position is inputted, the positioning controller determines an error between a present position of the positioner and a target position. Based on a remaining distance of the target position, the positioning controller calculates an operation amount C(z) for driving a motor in the positioner by a rotation angle M(s). Thus, the positioner is moved by an amount P(s).
The positioner further includes an encoder for measuring a feedback moving amount E(s) of a target position to the positioning controller as an absolute position of the positioner. During the feedback operation, the moving amount E(s) may be affected by noises. The positioner further includes a pushpin that is coupled to a rotary actuator so as to move the actuator by an amount R(s) in accordance with the movement amount P(s). Based on the rotary actuator movement amount R(s), a head slider moves by an amount H(s). Thus, an actual position for writing the servo pattern can be determined. After the servo pattern writing position is determined, there is a possibility for the servo pattern writing position to be influenced by vibrations of a spindle motor (SPM) of the disk drive. The vibrations of the SPM produces an error for the servo pattern writing position.
Further, the servo track writer instrument includes a clock head for writing a clock pattern during a rotation of the disk by the SPM. The servo track writer instrument determines a specific time for writing (writing time) servo pattern along a rotational direction of a disk by reading the clock pattern through the clock head. The servo track writer instrument executes the servo pattern writing operation by using the writing head of the magnetic head element based on the clock timing detected by the clock head. Thus, when the head positioning operation is completed, the servo track writer instrument instructs the writing head to write servo patterns in a target track.
When the servo pattern writing operation for one track circle has completed, the positioner moves to a next position of another target track circle. By repeating the same servo pattern writing operations on succeeding positions on a target track circle, the servo patterns are written on one surface of the disk. Since a disk has two surfaces, the same operation for writing the servo patterns is performed on a second surface of the disk.
In order to accurately write the servo patterns, as explained above, measurements are determined for a relative position between a head position and a disk surface. However, even if the position of the positioner is controlled with high accuracy, it does not mean the relative position error between the head position and the disk surface is reduced since the disk is a rotating body connected to a spindle motor (SPM). Thus, in order to improve the accuracy of the servo pattern writing, there is a need to accurately follow the head position in responding to position variations due to the SPM.
Since the conventional operation for writing servo patterns on a disk is performed by removing a top cover of a disk drive, i.e., both disk surfaces and magnetic head elements are exposed, the servo pattern writing operation must be performed in a clean room environment.
A recent increase of recording density in a disk surface, i.e., a higher track pitch, increases the number of tracks for writing the servo patterns. As a result, an operation time for writing the servo patterns per one disk drive is also increased. So far, it takes more than twenty minutes for writing the servo patterns per one disk drive including a disk that has formed thereon more than ten thousand tracks on one surface. Thus, the servo writer instrument is occupied by one disk drive until completing the servo pattern writing operation on both surfaces of the disk. Therefore, an increase of the track density is expected. Under these circumstances, there is a need to install an increased number of servo writer instruments in an enlarged clean room environment.
When the servo pattern writing operation on both surfaces of a disk have completed, the disk drive is removed from the servo writer instrument, the disk drive is covered with a top cover and is brought to a functional verification process for the disk drive by attaching a circuit board module.
However, the conventional apparatus and methods for writing servo patterns using a specialized servo track writer instrument have serious deficiencies, in particular manufacturing costs and a writing accuracy of the servo patterns.
As explained above, a conventional servo track writer instrument drives a rotary actuator based on movement of the positioner. During driving of the rotary actuator, a relative error between a present position of the positioner and a feedback of a target position is supplied to the position controller as a control amount. As a result, when the positioner reaches a position of a target track, it is assumed that a writing head element on the rotary actuator also reached the position of the target track. Then the position controller calculates an operation amount in order to reduce the relative error between the present position of the positioner
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hudspeth David
Kabushiki Kaisha Toshiba
Tzeng Fred F.
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