Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2001-01-30
2004-04-20
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078080
Reexamination Certificate
active
06724558
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to writing servo track information on magnetic disc drives, and more specifically to propagating servo tracks using an actuator assembly with substantially identical data transducers.
BACKGROUND OF THE INVENTION
Disc drives are among 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 transducer head (also referred to as a “head,” “read/write head,” or “slider”) 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 transducer 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. Typically, both the top and bottom surfaces of each disc are utilized to store and retrieve information. Information is transferred to and from a disc surface by a transducer head attached to a flexure at the end of the actuator arm. Each transducer head normally includes an air-bearing slider that enables the transducer to fly on a cushion of air in close proximity to the corresponding surface of the associated disc. Most transducers have a write transducer element and a read transducer element. The write element is used to store information to the disc, whereas the read element is used to retrieve information from the disc.
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 transducer head over the desired track. Information can be stored or retrieved from the disc once the transducer 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 as few as ten or as many as thousands of 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 the relative position of the transducer head to the track center. Generally the burst fields are used to create a positive voltage on one side of the track centerline and a negative voltage on the other side of the track centerline. A read element on the transducer head can be aligned directly over the centerline by positioning the read element 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).
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 transducer elements in order to prevent data from being read from or written to the wrong track. Manufacturers attempt to position the read/write transducer elements directly over the center of the desired track (sometimes referred to as the “null error position”) when a read/write operation occurs to insure that the information is being read from and written to the correct track. Closely following the track center position 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 transducer 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 piece of external equipment that writes servo tracks on a disc drive. The servowriting machine uses a relatively large, very accurate and relatively expensive positioning system which connects to the actuator assembly within the disc drive to precisely align a write element in the drive. The write element is aligned to where the desired track is to be written on the disc surface. A track is written on the disc once the write transducer element is correctly aligned. The servowriter positioning system then moves the write element a predetermined distance to the next desired track location. The servowriter positioning system, therefore, controls both the track placement and track-to-track spacing. There may be several actuator arms with several heads and several write elements attached which will write several tracks at each track location. In this case each track would be written on one side of each of several discs thereby writing a group of tracks or a cylinder of tracks at one time.
Utilizing a conventional servowriter for writing servo tracks has several drawbacks. First, a typical disc may contain tens or hundreds of thousands of 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 ever increasing track densities. Finally, the servowriting procedure must be completed in a clean room because internal disc drive components are exposed during servowriting, again adding expense to the procedure.
A 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 mechanical travel range limit stops. A first reference track is written with the write transducer element. The first reference track is then read with the read transducer element as the transducer is radially displaced from the first reference track. When a distance is reached such that the read element senses a predetermined percentage of the first reference t
Belser Karl Arnold
Bryant Lawrence Matthias
Murphy Robert Dale
Hudspeth David
JPMorgan Chase Bank
Merchant & Gould P,C,
Wong K.
LandOfFree
Servo writing in a disc drive with substantially identical... 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 writing in a disc drive with substantially identical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Servo writing in a disc drive with substantially identical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3233309