head alignment | DataRecoveryUnion.com

Magnetic disc drives for recording digital data are well known to the art. In such drives it is desirable to achieve the highest recording density possible, such recording density being a function of both the number of annular tracks per radial inch of disc surface and the number of bits per inch along each track. The optimum number of tracks on the individual discs is dependent on the precision of the head positioning system and on the precision in the alignment of the various read/write heads in the disc drive. The system of the present invention provides for the precise alignment of each of the read/write heads in the disc drive so that an optimum number of tracks per radial inch of the individual discs may be achieved.

The discs incorporated into present-day disc drives are usually referred to as a disc pack, and these discs are stacked one above the other to be sensed by a plurality of magnetic read/write heads mounted in vertical alignment and positioned by a single actuator. In one type of present-day head positioning system used in disc drives, one of the heads (servo disc surface) and one disc surface are dedicated to the generation of debit position signals for an associated servo system. A plurality of servo tracks are recorded in concentric circles on the dedicated servo disc surface, and the servo head produces the debit signals which are indicative of the relative position of the servo head and the servo tracks.

For interchangeability of the disc packs, the various tracks recorded on each of the disc surfaces must be closely aligned with the pre-recorded servo tracks on the dedicated servo disc surface so that the read back of the data from each disc pack is possible on recorders other than the one on which the data was recorded.

When the servo head is held in registry with the servo tracks on the dedicated servo disc surface, and the remaining read/write heads are aligned with the servo head, the remaining heads will be properly positioned over the corresponding data tracks on other disc surfaces. As mentioned above, an objective of the present invention is to provide a system which enables the remaining magnetic heads to be precisely aligned with the servo head, so that they will all be properly positioned with respect to the data tracks on the other disc surfaces.

The normal procedure for assuring that the read/write heads are in vertical alignment is to place a disc pack into the disc drive which has pre-recorded and precisely positioned servo tracks on all the disc surfaces. Such pre-recorded servo disc packs are commercially available for use in head alignment and are usually referred to as “CE” (Customer Engineer) packs. By reading the signals from the individual heads, as the heads read the various servo tracks, and by feeding such signals to a display device, each head can be adjusted until it is in precise tracking engagement with the tracks on the surface of the corresponding disc.

The present invention, as mentioned above, provides a system for reading debit signals generated by the various heads of a disc drive, as these heads read the various servo tracks on the pre-recorded servo disc pack, and it provides digital outputs representative of any misalignments of the various heads. Each head can then be adjusted to a position at which the digital output signal for that head indicates precise alignment.

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Magnetic disc drive head alignment system

DATARECOVERYUNION.COM16 years ago4 years ago06 mins

1. In a disc drive which includes a plurality of read/write magnetic heads and a servo magnetic head mounted for simultaneous movement by an actuator in response to a servo signal from the servo head, and in which the positions of the read/write heads are individually adjustable with respect to the servo head, a system for indicating any misalignment of the individual read/write heads as the particular head produces a cyclic position signal in response to position signals pre-recorded on alignment tracks of an alignment disc, each cycle of said cyclic position signal having a first segment with positive and negative peak amplitudes and a second segment with positive and negative peak amplitudes, the positive and negative peak amplitudes of said first and second segments being equal when the particular head is in registry with the corresponding alignment track, and the positive and negative peak amplitudes of one or the other segments decreasing when the particular head moves out of registry with the alignment rack to one side or the other thereof; said system including balanced gating circuitry having four output circuits for respectively producing four gating signals respectively timed to occur in time coincidence with respective ones of the positive and negative peak amplitudes of said first and second segments; a balanced input circuit connected to the particular head and including first and second outputs respectively applying the cyclic position signal and its complement to said gating circuitry to cause said gating circuitry to cause said gating circuitry to produce said four gating signals at the respective output circuits thereof; peak detector circuitry including four peak detector circuits respectively connected to said four output circuits of said gating circuitry to be individually gated by respective ones of said four gating signals, means connecting two of said peak detector circuits to the first output of said balanced input circuit and further means connecting the other two of said peak detector circuits to the second output of said balanced input circuit, said four peak detector circuits collectively detecting the positive and negative peak amplitudes of each of the two segments of each cycle of said position signal and providing four analog outputs corresponding thereto; and output circuitry connected to the outputs of said four peak detector circuits in said peak detector circuitry for producing an analog output signal having an amplitude corresponding to the difference between the algebraic sum of the positive and negative peak amplitudes of the first segment and the algebraic sum of the positive and negative peak amplitudes of the second segment.

2. The system defined in claim 1, in which said balanced input circuit includes a linear amplifier, and in which said system includes a summing circuit connected to said four peak detectors in said peak detector circuitry for producing an output signal representing the algebraic sum of the outputs of the four peak detector circuits, and an automatic gain control circuit connected to said summing circuit and responsive to the output thereof for producing an automatic gain control signal for said linear amplifier.

3. The system defined in claim 1, in which said gating circuitry contains a frequency-independent phase-shifting circuit so that the system may be used with a wide variety of recorded signals without adjustment.

4. The system defined in claim 1, and which includes circuitry connected to said peak detector circuitry for limiting the analog outputs thereof to a predetermined maximum.

5. The system defined in claim 1, and which includes an analog/digital converter coupled to the output of said output circuitry to convert the analog output signal therefrom into a corresponding digital signal; and a digital display device coupled to the output of the analog/digital converter.

6. The system defined in claim 1, in which said gating circuitry includes first and second comparators interconnected to provide a quadrature shift to the cyclic position signal from said balanced input circuit which is independent of frequency.

Background of the Magnetic disc drive head alignment system Invention

Magnetic disc drive head alignment system