Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
2001-01-29
2004-08-10
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
C360S002000, C360S075000, C235S493000
Reexamination Certificate
active
06775080
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to systems and method for reading data from and writing data to data storage medium by employing the magnetic or optical recording technology. More particularly, this invention is related to a data access system implemented with stepping motors using open and closed control loops to position a flat medium with data stored in discrete stepwise curved segments accessed by a rotational pickup head controlled with servo data feedback from each stepwise discrete segment.
2. Description of the Prior Art
Conventional methods of reading data from and writing data to data-storage tracks with these tracks formed either as circular tracks or separate segments as parts of a circular track present technical difficulties when stepping motors are employed for moving the pickup head to access high density data tracks. Due to these technical difficulties, stepping motors moved in discrete stepwise movements and controlled with open-loop control schemes, are typically implemented in data-access operations of lower data density. In a data track, typically a circular track, that has a lower data storage density the spot size for data-bit storage is large enough to accommodate a larger tolerance of radius variations as the disk rotates over a pickup head for accessing data stored in the data tracks. For this reason, an open-loop control would be sufficient for carrying out the data access functions by moving a data disk or a pickup head in a stepwise manner to a particular track on a relatively low track density device such as a conventional floppy disk. And, the pickup head is applied to read or write data on that track without further position control of the data access functions. It is expected that the circular track or arc segment(s) prescribed by the pickup head would match the data-storage track formed either as a circular track or circular segment.
Based on these operational principles, there are many prior art disclosures for data recording and access systems implemented with group of concentric circular data tracks. Prior art patents disclose the storage and data access technologies in U.S. Pat. No. 3,596,061 issued on Oct. 14, 1968 to Pasini, U.S. Pat. No. 5,526,328 issued on Jun. 11, 1996 to Oshima et al., and U.S. Pat. No. 6,052,347 issued on Apr. 18, 2000 to Miyata et al. In addition to the concentric circular data tracks, continuous circular or linear segments employed for data storage and access are also known in many prior art disclosures. These disclosures provide group of data tracks as circular arcs or linear line segments to store and retrieve data on a flat media. The prior art patents include U.S. Pat. No. 3,716,678 issued on Nov, 9, 1970 to Starr, U.S. Pat. No. 3,598,965 issued on Aug. 10, 1971 to Nagata et al., U.S. Pat. No. 5,107,099 issued on Apr. 21, 1992 to Smith, U.S. Pat. No. 5,963,513 issued on Oct. 5, 1999 to Lemelson, U.S. Pat. No. 6,016,959 issued on Jun. 25, 2000 to Kamo et al., U.S. Pat. No. 5,521,774 issued on May 28, 1996 to Parks et al., U.S. Pat. No. 6,084,850 issued on Jul. 4, 2000 to Gudesen et al., U.S. Pat. No. 5,045,676 issued on Sep. 3, 1991 to Kime, U.S. Pat. No. 4014604 issued on Mar. 29, 1997 to Schwartz, U.S. Pat. No. 5,059,774 issued on Oct., 9, 1991 to Kubo et al.
These earlier teachings use oscillating pivot rotating arms or oscillating flat media to access such plurality of data tracks. Smith (U.S. Pat. No. 5,107,099) teaches a method of rotating flat media and a fixed head mechanics to produce and retrieve such plurality of data arc tracks in the circular arc forms in additional to the mechanics of oscillating pivoted rotating head arm to a fixed flat media. Gudesen (U.S. Pat. No. 6,084,850) further extended such rotating media arrangement. Smith (U.S. Pat. No. 5,107,099) failed to teach the using of full rotational head mechanics to a flat media. Kamo (U.S. Pat. No. 6,016,959) recognized the full rotational head mechanics to produce and retrieve such plurality of data tracks in the circular arc forms. Kamo insists such mechanics requiring one or multiple pair of such rotational heads together to achieve such result even only one or more head is active for data access, one or more dummy head must be used to pair odd number of active heads. Kamo also teaches the loading of flat media to the mechanic in static mode that engage to pickup head at the placement of flat media to the device and disengage the pickup head at the removal of the flat media from the device.
For data retrieval and recording access, some of prior art teachings apply open loop to place the signal pickup head to desired data tracks under a relative low track density arrangement and expect the prescribed arc segment by the pickup head matches the recorded data circular arc. When the data track density becomes relative high, prior teachings use closed loop design or servo method to place the signal pick head to the desired data area that follows the profiles of recorded track. The track profile is expected to be a continuous circular arc or line. When a stepper motor is applied into track following, the motion of a stepper motor is discrete. The continuous track following of data segments becomes very difficult and almost impossible. Usually the radius of rotating head of servo writer is different from a drive, the continuous track following by the drive head along a servo written track is physically impossible by a stepper motor access mechanism that can only provide discrete motions.
Specifically, when the data-storage density is increased and a stepping motor is employed, technical difficulties arise due to the discrete and open loop features of the stepping motor movements. A continuous circular movement of the pickup head rotating over the data storage medium may not precisely track the profile of the actual locations of the stored data written onto the data storage medium. The difficulties of continuous track following of the data segments or a circular track can be clearly appreciated because the radius of the rotating head of a servo writer is different from that of a data drive. In addition to the difference in radiuses between that of the servo drive from that of a data drive in reading or writing the data, there are also differences of radius between every two drives used in writing and reading a data card. When the density of data storage becomes higher and the tolerance of data track following is reduced, implementation of stepping motor to adjust a relative position between a pickup head and a circular track or circular segments becomes impractical. For these reasons, the conventional circular track or arc segments as part of a circular track are no longer suitable.
In addition to the above difficulties, the rotational head data recording and retrieving system as that disclosed in a co-pending patent application is implemented to resolve the difficulties of the conventional technology. Specifically, in conventional data storage systems, the reading and writing of data are performed on concentric circular data tracks. The concentric data track configuration often presents a problem that the data-bit density varies between the outer tracks and the inner tracks. The variable bit density in data storage is due to a geometrical factor that the outer data tracks are much longer in length than the inner tracks. A common practice is to form the inner tracks with a capacity to store the data bit at a higher bit density. A more complicate servo control system implemented with more complex signal-processing algorithms is required due to the variations of data storage density between different data tracks. Additionally, by varying the data storage density from the inner tracks toward the outside tracks, the data transfer rate is also changed in accessing data from the inner tracks then outside tracks. Such variation may also cause difficulties and complications in processing the data. Higher error rates may incur due to these variations between the inner tracks and the outer tracks.
There
King Francis K.
Liu Jeffrey F.
Davidson Dan I
DCARD, Inc.
Hudspeth David
Lin Bo-In
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