Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2001-01-09
2003-10-07
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077070, C360S077080, C360S051000
Reexamination Certificate
active
06631046
ABSTRACT:
FIELD OF THE INVENTION
This application relates generally to disc drive data storage devices and more particularly to an apparatus and method of writing servo track information thereon.
BACKGROUND OF THE INVENTION
Disc drives are the most common means of storing electronic information in use today. Ordinary disc drives are typically constructed with the following internal components: one or more magnetic media discs attached to a spindle; a spindle motor that rotates the spindle and the attached discs at a constant high speed; an actuator assembly, located adjacent to the discs, with a plurality of actuator arms that extend over the discs, each with one or more flexures extending from the end of each actuator arm, and with a read/write head mounted at the distal end of each flexure; and a servo positioner that rotates the actuator assembly about a bearing shaft assembly positioned adjacent to the discs such that the read/write heads radially traverse the disc surface (i.e., move back and forth the between the inner and outer diameters of the disc).
Information is stored on and retrieved from a magnetizable material on the disc's surface. To facilitate information storage and retrieval, discs are radially divided in concentric circles known as “servo tracks” or “tracks”. The tracks are given a track number so that the servo positioner can locate a specific track. The servo positioner, upon receiving a control command, aligns the read/write head over the desired track. Information can be stored or retrieved from the disc once the read/write head is in the correct position. The process of switching between different tracks is called “seeking”, whereas remaining over a single track while information is stored or retrieved is called “following”.
Each track is subdivided into pie-shaped sections, called “segments” or “sectors”. The two most common types of sectors are informational data sectors and servo data sectors. In a typical disc drive, the informational data sectors usually contain information generated or stored by the user such as programs files, application files, or database files. There may be ten to a hundred, or even more, informational data sectors dispersed around a single track.
The servo data sectors, on the other hand, contain information that is used by the servo positioner to determine the radial position of the head relative to the disc surface and relative to the track center. Servo sectors typically consist of a Grey code field, which provides coarse position information such as the track and cylinder number, and a servo burst field, which provides fine position information such as tie relative position of the head to the track center. Generally speaking, the burst field creates a signal with a specific voltage magnitude when the read head is not aligned over the track centerline. The signal is decoded to pinpoint the read head's location and the read head is moved directly over the centerline by positioning the read head such that the sum of the burst field voltages equal zero.
Servo sectors are usually placed between adjacent informational data sectors on the same track. A clock signal mechanism is used to insure that data intended to be stored in a servo sector does not overwrite data in an information sector (and vice versa).
During the servo writing process, a timing pulse from the clock signal mechanism notifies the servo positioner when the head is over a servo sector (as opposed to over an information sector). The write enable signal is turned on and information is written to the servo sector. The timing pulse also notifies the servo positioner when the head is over an information sector. The write enable signal is turned off and servo information is not stored in the informational data sector during the servo writing process.
In contrast during normal disc drive operation, the timing pulse notifies the servo positioner when the head is over an information sector (as opposed to a servo sector). The write enable signal is turned on and data is written to the information sector. The timing pulse also notifies the servo positioner when the head is over a servo sector. The write enable signal is turned off and user data is not stored in the servo sector during normal disc drive operation.
Information is transferred to and from the tracks by the read/write heads attached to the flexures at the end of the actuator arms. Each head includes an air bearing slider that enables the head to fly on a cushion of air in close proximity to the corresponding surface of the associated disc. Most heads have a write element and a read element. The write element is used to store information to the disc, whereas the read element is used to retrieve information from the disc.
The number of tracks located within a specific area of the disc is called the “track density”. The greater the number of tracks per area, the greater the track density. The track density may vary as the disc is radially traversed. Disc manufacturers attempt to increase track density in order to place more information on a constant size disc. Track density may be increased by either decreasing the track width or by decreasing the spacing between adjacent tracks.
An increase in track density necessitates increased positioning accuracy of the read/write elements in order to prevent data from being read from or written to the wrong track. Manufacturers attempt to fly the read/write head elements directly over the center of the desired track when the read/write operation occurs to insure that the information is being read from and written to the correct track. Hitting the track center target at high track densities requires that the tracks be as close to perfectly circular as possible when written to the disc surface.
Tracks are usually written on the disc during manufacturing using one of two means: 1) a servowriting machine, or 2) self-propagated servo writing. In both methods, a timing clock is used to notify the servo positioner when the head is over an area where a servo sector is to be written. A write enable signal is activated and servo information is written when the timing pulse indicates that the head is located over a servo sector. The write enable signal is de-activated and information is not written once the head exits the area where a servo sector is to be written.
A servowriting machine is a large piece of external equipment that writes servo tracks on a disc drive. The servowriting machine uses a very accurate lead screw and laser displacement measurement feedback device to precisely align a write element. The write element, which is attached to an external head/arm positioner, is aligned relative to where the desired track is to be written on the disc surface. A track is written on the disc once the write element is correctly aligned. The head/arm positioner then moves the write element a predetermined distance to the next desired track location. The head/arm positioner, therefore, controls both the track placement and track-to-track spacing.
A servowriter, however, has several drawbacks. First, a typical disc may contain more than 60,000 servo tracks. The process of aligning and writing each track on the disc is very time consuming and expensive. Second, although very accurate at lower track densities, the servowriter cannot meet the accuracy requirements dictated by higher track densities. Finally, the procedure must be completed in a clean room because the disc components are exposed during servowriting; again adding expense to the servowriting procedure.
The second means of writing tracks on a disc is called self-propagating servo writing. Oliver et al first described this method of servo track writing in U.S. Pat. No. 4,414,589. Several other patents have disclosed slight variations in the Oliver patent, but the same basic approach is used. Under the basic method, the drive's actuator arm is positioned at one of its travel range limit stops. A first reference track is written with the write head element. The first reference track is then read with the read element as t
Ang ChiapHeok
Belser Karl A.
Szita Gabor
Seagate Technology LLC
Sniezek Andrew L.
LandOfFree
Servo track writing using extended copying with head offset does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Servo track writing using extended copying with head offset, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Servo track writing using extended copying with head offset will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3119566