Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-11-06
2002-04-30
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S053000, C360S077120, C369S043000
Reexamination Certificate
active
06381088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to using information about errors for improving extracted data sensed from stored data and more specifically relates to apparatus for using information about the extent of errors wherein a transducer is used to sense stored data having at least one constraint from predetermined storage locations. The transducer generates a signal containing at least one constraint and any errors introduced into the sensed data during the sensing. An input device, which in the preferred embodiment is a detector, is responsive to the signal from the sensor to generate a control signal containing information about the extent of errors and extracts a data signal. An output device is responsive to the control signal to perform a control function to effectively improve the extracted data signal as a function of the extent of errors in the sensed data. In addition, the transducer may have at least two sensors or two transducers may be used to produce a first signal and second signal which is applied to the input device to extract a first data signal and a second data signal wherein the output device is responsive to the control signal and to the first data signal and second data signal to derive a data signal therefrom having the least number of errors.
The apparatus accomplishes this control function by: (i) using the control signal to produce a dynamic servo signal , which in the preferred embodiment is in the form of a substantially continuous servo signal, to adjust a transducer or transducers position to improve alignment of the first transducer relative to predetermined storage locations, which in the preferred embodiment is a track; (ii) deriving, from data signals extracted from signals sensed from two or more transducers or sensors, a data signal having the least number of errors; or (iii) a combination of producing a dynamic servo signal and deriving a data signal having the least number of errors.
In the preferred embodiment, the input device or detector generates a position error signal from the signal received from the transducer and that position error signal is used as a servo signal for adjusting the transducer position to improve alignment of the transducer relative to the predetermined storage locations.
This invention also relates to a method for using information about errors for performing a control function to improve the extracted data from the stored data in the predetermined storage locations as a function of the extent of errors in the sensed data.
In the preferred embodiment, the invention relates to the field of reading or reproducing from and writing data to mass storage devices, such as magnetic discs.
Also, in the preferred embodiment, the apparatus and method improves the extracted data that is read or reproduced by deriving from among two or more data signals by deriving therefrom the data signal having the least number of errors, or from a combination thereof. This invention is based on the principle that when at least one constraint is added to the data, this constitutes prior knowledge of the expected data signal in the absence of noise or other impairments. Such knowledge can be exploited, such as for example, by making a computation or comparison between the expected data signal including the at least one constraint and the observed data signal including the at least one constraint, to develop a control signal representing the extent of errors introduced into the signal sensed from the predetermined storage locations by the transducer, transducers or sensors. The so developed control signal can be used to develop a dynamic servo signal in the form of a substantially continuous position error signal which is used to improve head/track alignment using conventional apparatus and methods.
In another embodiment of this invention, by reading and calculating the position error signal on a substantially continuous basis, an effective servo sampling rate is achieved that is much higher than the sampling rates of the state-of-the art apparatus and method.
In the writing mode using a magnetic head, the recorded data is read and the head position is adjusted using the servo system up to the instant the head begins to write thereby improving the quality of the written data on a track.
In yet another embodiment of the present invention, the magnetic head or transducer may contain more than one read sensor. By using the teachings of this invention, the signal representing the extent of errors may be used to derive a data signal containing the least number of errors from the more than one data signals.
In a further embodiment of this invention, deriving the data signal which contains the least number of errors and adjusting the head position to improve alignment with the predetermined storage locations in response to a control signal representing the extent of information about errors may be used in combination to improve the extracted data signal.
2. Description of the Prior Art
It is well known in the art that magnetic discs operate by providing a surface capable of being magnetized in individualized storage locations or in predetermined storage locations. One or more read/write heads are used for interacting with or transducing with the predetermined storage locations for sensing data store at the predetermined storage locations. The magnetized surface is rotated at relatively high speed, thus presenting each predetermined storage location on the surface to the read/write heads or transducers. The use of and operation of transducers for recording and reproducing data from predetermined storage locations from mass storage devices, such as for example a rotating magnetic disc memory system, optical memories, magnetic tape and the like is well known in the art.
It is also known in the art to record or store at predetermined storage locations data or information on rotating surfaces, such as for example, magnetic discs and optical discs. The term “predetermined storage locations” as used herein means the individualized area on a surface, such as for example a predetermined or addressable location on a treated surface area in a rotating memory storage device, which contains or stores data or information. In a rotating memory storage device, which utilizes magnetic media as a magnetic recording surface, the data or information is stored as a series of magnetic field transitions on the magnetic recording surface. Such series of magnetic transitions are included in the term “predetermined storage locations”. The predetermined storage locations are generally recorded or stored in tracks on magnetic media.
Data is read from the predetermined storage locations on the magnetic media using a transducer that interacts with the recording media as a write transducer interacted with the magnetic media when the data or information was recorded or stored. In reading or sensing previously written data from a discrete storage location, the transducer, which functions as a read sensor, must be positioned over or aligned with the tracks on the recording surface where the writing transducer has written or stored the data. Typically, the width allocated to a track of recorded or stored data is wider than the width of the actually recorded predetermined storage locations. Further, the width of the sensor used for reading or sensing the stored data has a width that is less than the width of both the track and of the discrete storage location.
In magnetic discs, data is generally disposed on generally circular tracks, each on the surface of the disc and oriented with its center coaxial with the physical disc. The read/write heads, sometimes referred to as read/write transducers, are disposed in a head/arm assembly so as to be adapted to be moved to a selected track, under control of a disc servo controller.
The state-of-the-art rotating memory systems store as much data as possible on the magnetic disc. This, in turn, requires that the individuated locations or predetermined storage locations of data or information be
Despain Alvin M.
Gaines R. Stockton
Acorn Technologies, Inc.
Davidson Dan I.
Hogan & Hartson L.L.P.
Hudspeth David
LandOfFree
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