JPS5822819B2 - Recording media skew correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides mechanically readable and writable information on a magnetic tape in which magnetic regions are arranged to form information tracks extending transversely to the longitudinal direction of the magnetic tape. The present invention relates to a magnetic tape unit that records and reproduces information using a rotary head that is moved while maintaining a magnetic transduction relationship with respect to a strip-shaped medium such as the above.

Various rotating head magnetic tape units are already widely known.

In one type of unit, a cylindrical core or guide called a drum encloses a rotating head wheel equipped with one or more read-write heads.

The magnetic tape is in contact with the cylinder at a location on the cylinder, is helically wrapped around at least a portion of the cylinder, and is spaced axially and circumferentially of the cylinder from the contact initiation point. Leave the cylinder at another position.

The angle of helical winding varies according to design choices, but is typically between 180° and 360°.

The head wheel rotates so that one or more heads sweep diagonally across the tape.

The angle at which the head enters and exits the tape may vary from slightly less than 90 degrees to as little as 15 degrees, for example, depending on design choices.

Other types of tape units have a head wheel coupled to a tape guide mechanism that bends the tape laterally in an arc to conform to the outer circumference of the head wheel. .

In this unit, the tape advances linearly past the head wheel and is laterally bent by the associated guide mechanism as it enters the head wheel area.

Although the present invention can be utilized and applied to any of the above-mentioned types of units, it has been found particularly useful in spirally wound units.

The primary problem encountered in each of the units described above is maintaining precise positional alignment between the trajectory of the head wheel carrying the transducer head and the diagonal data tracks on the tape so that they do not become misaligned. That's a problem.

The above-described distortion and skew problems are particularly pronounced when data tracks are written on one tape unit and subsequently read on another tape unit.

This phenomenon of skew, or misalignment, occurs between tapes being written to or read by different tape units. This stems from the fact that the data track is accessed from different angles.

Another source of skew problems is media distortion.

In general, the media used for data recording are flexible and are sensitive to changes in temperature, humidity, atmospheric pressure, and the passage of time.
Even if the recording angle of the track is within the expected range at the time of recording, fluctuations in the above parameters (temperature, etc.) tend to deform the medium (expand or contract), and the initial data
Vary the angle at which the track is recorded.

If the recording angle changes, the head will not be able to follow this distorted data track when reproducing recorded data, and information will be lost.

As a means of dealing with skew, it is often required that recording media be stored in a rigid environment.

For example, it is often necessary to store the media in a predetermined temperature and humidity controlled area.3 Additionally, storage media are sometimes given a useful lifespan, at which point the data recorded thereon may be It may also be transferred to another medium or re-recorded on the same medium.

These requirements require customers to pay significantly higher maintenance costs and sometimes fail to guarantee accurate data playback capabilities.

Other methods performed in the prior art to solve the above skew problem are dynamic methods and symmetric static methods.

Generally speaking, in prior art rotary head devices, the media was guided toward and away from the rotary head by inlet and outlet guides.

Traditionally, skew correction has been accomplished by manually adjusting one or a combination of the rotating head, inlet guide, outlet guide.

This adjustment effectively changes the angle at which the rotating head accesses tracks on the media and serves the purpose of skew adjustment to the extent that it does so.

The problem with this type of skew adjustment is that it must be done at the factory before shipping or requires the work of a skilled technician.

A detailed description of a manual skew adjustment device can be found in US Pat. No. 3,697,676.

In other types of static methods in the prior art, the means for shifting the head wheel or tape guide is automatic.

In this type of device, adjustments are made without external or manual intervention.

Although this scheme is a considerable improvement over the conventional manual skew adjustment methods described above, its drawback is that it may not be possible to recover skewed data.

For example, when a data track is severely skewed, resulting in a bowed trajectory in the middle of the diagonal track.

In such a case, skewed data cannot be retrieved using conventional adjustment methods because the adjustment is made before the head trajectory begins.

The main drawback of conventional static skew correction devices, whether manual or automatic, may be that their movable guides are difficult to control, thus adding complexity and cost to the recording device.

This may be due to the considerable amount of time required to move the inherent mass of the guide device and head wheel.

In the present invention, skew between a recording track on a magnetic recording medium and a transducing head is dynamically corrected in a closed-loop controlled servo manner.

More specifically, this control servo device's stop and
The lock counter is inserted an offset number when the transducing head is not in translating relation to the media.

The stop lock counter generates a series of pulses while decreasing its offset number towards zero.

This pulse is converted to an analog voltage, which energizes a motor that rotates a take-up reel (cubstan) that winds the media through the head.

When the stoplock count value is zero, the head (
a transducer) is positioned in line with the selected data track on the medium.

In another form of the invention, a relatively low value number, e.g., u, I+, is placed in the stop lock counter when the head is in translation relationship with the media.

In a similar manner, the number of times this operation process (entering/decrementing numbers) is selected, in which this °゛1' is reduced to zero;
Or it continues until the head is removed from the medium.

While counting and decrementing the stop lock counter, pulses are output that control the take-up reel motor to continuously step the media in fixed length increments.
This continuously changes the effective angle at which data is transformed on the medium.

This continuous motion creates a new head/media trajectory that causes the head to match the skewed track on the media.

Figure 1 shows a dynamic rotating head device with spiral winding type.
The invention for skew correction is shown implemented.

This type of device is also shown in more detail in US Pat. No. 3,845,500.

The rotary head tape apparatus has a tape processing section 10 in the form of a two-part core 11 having a rotary head wheel 12 therebetween, which is moved by a transducing head 13. It has become.

Although only one head is shown in this figure, more than one head can also be used with the present invention.

A length of flexible media 14 is wound helically around the center of core 11, and head 13 passes over a path or track transverse to the length of the media.

A supply reel 15 has a tape supply source.

The reel beam C is controlled by a motor 16. After the media leaves reel 15, a certain length is retained by vacuum column 17.

This vacuum column maintains one end of the media in the processing section under constant tension.

Media loop 18 in vacuum column 17 is connected to loop position servo 19
monitoring and control.

This servo controls the drive of the motor 16 and the tape,
Maintain optimal loop length within the vacuum column.

Loop position sensors are disclosed, for example, in U.S. Pat. No. 3,122,333.
The one described in No. 2 may be used, but the motor 16 can be biased with variable strength in both directions, and the loop 18 can be maintained at an optimum position no matter which direction the tape moves relative to the reel 15.

The other end of the tape 14 passes through the processing section 10 and winds up at the winding loop 20.
The tension is maintained by a reel motor 21.

An entrance guide 30 and an exit guide 3 are provided for guiding the medium 140.
2 are placed at the entry and exit points of the processing section 10, respectively.

The function of both of these guides is to isolate tape disturbances from the processing section.

Although the present invention is described with respect to a rotary head apparatus, it is not limited to such applications as it relates to a rotary head, as it has applicability in any other case where a transducing means is matched to a track on a flexible medium. should not be done.

In FIG. 1, head wheel 12 is driven by drive means 27. In FIG.

In this embodiment, this driving means is a beam C and a motor.

When the head 13 is rotated by the head wheel 12, the trajectory of the head is divided into two parts.

That is, arc A (shown as a dotted line) and arc B (shown as a solid line).

When the head 13 travels along the arc A, it is in a transforming relationship with the medium.

In other words, when head 13 travels arc A, it faces the medium.

The conversion relationship is when the head writes data to the medium,
It means reading and scales.

When running over arc B, the head is not in a translating relationship with the media.

As will be explained below, the time elapsed while the head travels through arcs A and B is used to condition the media for recovery of data from skewed data tracks on the media.

A timing means called a tachometer 28 is attached to the shaft of the drive means 27 to determine the speed and direction in which the head wheel 12 rotates.

Tachometer 28 provides position signal pulses on conductor 34.

This pulse is sent to a head-to-track alignment device 36.

The pulse on the conductor 23, C, energizes the motor 21,
Rotate clockwise or counterclockwise.

The rotation of the motor is transmitted to the take-up wheel 20, which provides a step drive to the media 14 in the present invention.

The stepping motion of the media sets a new head track trajectory that allows recovery of skewed data.

The movement of D, C, motors 21 are all monitored by tachometer 25, which provides feedback pulses to terminal 26.

This feedback pulse is sent to positioning device 36.

C, a closed-loop servo that controls motor 21 along with control pulses on conductor 34 as described below.

The skew correction method of the present invention is defined.

To start the skew correction circuit, a control signal is applied to terminal 38 prior to activation of this circuit.3 Referring now to FIG. 2, a diagram of the tape skew data track and servo format is shown here. ing.

Data tracks 36 and 40 in this figure are normal (no skew).

In this arrangement, head 13 is shown moving in the direction of arrow 34 along an ideal trajectory shown by dotted line 35.

This head path is ideal because it coincides with the center of data track 36.

As the head 13 then travels along the path 35, the data contained in the track 36 is accurately converted.

In order for the head 13 to select the ideal path, previously recorded information is read from the servo tracks 42 and 44.

This servo information is utilized by a head controller (not shown) for accurate head track positioning.

A more detailed explanation of the positioning means is provided in U.S. Pat.
No. 845500.

In FIG. 3, previously described parts are designated by the same numbers, but this figure shows an unskewed track 36 and a skewed track 36'.

In the normal case (no skew), the head 13 passes through the ideal head circuit 35 and correctly reproduces the information on the non-skewed data track 36.

However, without the present invention, if track 36 becomes skewed into track 36', a head following ideal path 35 will not be able to reproduce data.

However, using the mechanism of the present invention, head 13 deviates from ideal path 35 by an offset distance 116 and follows a new trajectory designated head path 35'.

When the head 13 passes through the trajectory 35', the data on the skewed track 36' is reproduced.

The skewed track 36' is shown to be on the left side of the non-skewed track 36, but of course the skewed track can also be on the right side, and the present invention is also effective in recovering skewed data. It is.

FIG. 4 shows the active portion of the tape sandwiched by the inlet and outlet guides 30,32.

In this figure, the tape is shown uncoiled from the core.

A tension indicated by arrow 50 is provided by vacuum column 17.

Furthermore, the ideal head path 35 and the skewed path 35
'It is shown.

As mentioned above, skew can occur to the right or left.

In accordance with the present invention, the positioning of the head 13 on a skewed path 35 to recover the skewed data details the apparatus 36.

When the winding wheel 20 is driven once, the C motor (Fig. 1,
(Fig. 4) is controlled by a closed-loop servo system, and the control information for this servo system is such that the head 13 is brought into contact with the medium, and the deskew (skew correction, return) on the motor 27 and the conductor 52 is controlled. Obtained from the command signal.

As described below, activation of the deskew command signal activates the deskew device, ie, the circuit of the present invention.

More specifically, with reference to FIGS. 4, 1, and 3, the tape drive utilizes servo information to position head 13 on ideal path 35. Referring to FIGS.

The command signal on conductor 52 is output after several times when head 13 is unable to recover the data on ideal path 35 due to skew.

This signal enables the positioning device (FIG. 1), the details of its skew correction operation being shown in FIG.

In addition to the deskew command signal, the position of head 13 relative to media 14 is verified.

This is done via the tachometer 28.

The tachometer 28 (Fig. 1) is a conventional translucent type.
includes an optical disk having one or more optical tracks.

The illuminating device, the light receiving device, and the head wheel 1 are mounted on this disc.
20A circuit is attached that outputs a signal indicating the direction and magnitude of the rotation.

Specifically, the disc of tachometer 28 has two tracks.

One of these tracks produces a signal when the head 13 is at arc B of the trajectory in FIG.

This signal, known as the beta angle signal, appears on conductor 54 in FIG. 4 and is illustrated by curve A in FIG.

The other track generates multiple pulses known as digital gain control (DGC) pulses, which are the fourth
Appears on conductor 56 in the figure.

DGC pulses are generated when the head is in a transducing relationship to the media (ie, running along arc A in Figure 1).

The signals output on conductors 54 and 56 and shown by curves A and B in FIG. be.

The β angle signal is sent to the conductor 54, and the deskew command signal is sent to the conductor 52.
, the first AND circuit 58 is activated.

When this occurs, a load offset signal appears on conductor 60.

A load offset signal is applied to conductor 60 and an increase/decrease counter (UDC) 62 is loaded with a value.

This UDC is a conventional increase/decrease counter and is under the control of counter controller 64.

The combination of UDC 62 and controller 64 is referred to as a stop lock counter device 66.

A stop lock counter device 66 generates a control pulse on conductor 68 which is connected to a digital to analog converter (
DAC) 70.

The DAC 70 converts the digital pulses into analog pulses or analog voltages and connects them to the power amplification device 7 via a conductor 74.
Send to 2.

This analog voltage is amplified by the gain of a power amplifier and is applied to motor 21 via conductor 76.

The sign of these analog voltages is either positive or negative.

This analog voltage turns clockwise or counterclockwise depending on the sign supplied to the DAC 70 from the counter controller 64 by conductor 78, causing the motor 21 to turn.

Of course, the code beam generated by the device 64, C, and the motor 2
1 depends on the clockwise or counterclockwise direction in which it is turned.

In FIG. 4, the stop lock counter device 66 is
When the value of DC62 is ``zero''.

C, DAC 7 so that the motor 21 is stopped (stationary)
0 and the width increaser 72.

D. C. Rotation of motor 21 (in either direction) causes stop lock counter device 66 to control the motor so that the count value of UDC 62 becomes zero.

Additionally, counter controller 64 controls UDC 62 to prevent it from counting down past zero.

Counter controller 64 controls the stop signal appearing on conductor 78.
It generates a lock code and addition and subtraction pulses appearing on conductors 80, 82, respectively.

Add and subtract pulses indicate when UDC 62 is increased or decreased.

It also generates a signal on conductor 84 when the content of UDC 62 is approximately zero.

The signal on conductor 84 informs counter controller 64 that the counter is now in equilibrium.

As previously discussed, when a load offset signal appears on conductor 60, a load offset number is loaded onto UDC 62.

In one embodiment of the invention, the number 9 is loaded into a counter.

However, the present invention is not limited to this value.

In short, a wide range of numbers can be loaded onto the counter.

However, the only condition is that the number that can be entered into the counter is
It is a value of magnitude such that it is reduced to approximately zero by the time the head 13 is running arc B in FIG.

In other words, the total time for this number to be reduced to zero must be less than or equal to the time it takes for the head 13 to pass through the β angle.

Of course, this depends on the rotational speed of the head wheel.

It is within the ordinary skill of those skilled in the art to create a system and a circuit for automatically determining the numerical value to be loaded on the UDC.

For this automatic method, the magnitude of the number is, of course, related to the skew angle of the media.

In one embodiment of the invention, the head wheel is approximately 25.4
It rotates at a peripheral speed of m/s.

The media is operated in step mode, ie, the media is stationary while the head is running the trajectory.

At the above speed, it takes about 1177 ZS (milliseconds) for the head to pass through one path.

Of the 11 m5, 8 mS is spent by the head running the data track in the media, and 3 mS is spent passing through the β angle (Figure 1, arc B).

In this case, the number put into UDC62 is about 3ms
It must be thrown with something that can be reduced to 0 within the same time period.

Upon entering the selected value into UDC 62, a signal is generated on conductor 86.

This signal from conductor 86 is routed through impark 90 to the third
It is used to de-energize the AND circuit 88 of.

The third AND circuit 88 is inhibited when a number is entered into the UDC 62, thereby preventing any signal in the C motor 21 feedback loop from changing the value of the counter.

As mentioned above, this system is in equilibrium when the UDC 62 count is zero and the D, C, and motors 21 are stopped.

If the count of UDC62 is thicker than zero, conductor 7
An analog voltage is applied to the motor 21 via C and C.

This voltage rotates the motor clockwise or counterclockwise depending on its polarity.

When the motor rotates, the conventional tachometer 25 is connected to the conductor 9.
Two-phase signals of θ1 and θ2 are output to terminals 2 and 94, respectively.

A direction sensing device 96 receives the θ1 and θ2 pulses and generates forward and backward pulses appearing on conductors 100 and 98, respectively.

These pulses, along with the output pulses from the OR circuit 102 on conductor 104, control the counter controller 64.
In the figure, the direction sensing device converts a tachometer signal into a pulse indicating a unit of displacement in the forward or backward direction.

This direction detection device is, for example, IBM TDB Volume 14
The format described in No. 2, May 1972, page 3672 may be used.

The forward and backward pulses of conductors 98, 100 are used to energize a second OR circuit 106, which also
generates a feedback signal on conductor 108 as it rotates.

FIG. 5 shows waveforms at various points when a control signal is applied to the circuit of FIG. 4.

Also shown are the analog voltages applied to the D, C and motors and the head path.

The head path is generated as a result of the adjustments provided to the media via the take-up reel C and motor 21 by the deskew circuit of the present invention.

As described above, the dynamic skew correction method of the present invention can perform skew correction within a short period of time (at least one head rotation).

Of course, this dynamic skew correction scheme is used less frequently than head rotation.

Curve A in FIG. 5 shows the time for one revolution of the head.

In the lowered part 110, the head 13 runs along the arc A (Fig. 1,
period (in a transformation relationship with the medium).

During this period, conductor 54 (FIG. 4) is in a down state (inactive).

The ascending portion 112 of curve A indicates the period in which the head is running arc B, or angle β, and is not in transducing relation to the tape.

During this period, conductor 54 is active (ON: at UDC 62
can be loaded with numbers.

Curve C shows the analog voltage applied to motor 21 by conductor 76.

Portion 114 of curve C shows the analog voltage applied when the head is at angle β.

This voltage suddenly reaches a maximum peak or decreases to near zero.

As described below, when the β angle signal is on, the motor begins to move clockwise or counterclockwise and tachometer 25 begins to send subtraction pulses via the feedback loop described above with respect to FIG. The number is subtracted to 0.

When the head exits the β angle and enters the conversion relationship with the tape, the DGC
A pulse (FIG. 5, curve B) appears on conductor 56 (FIG. 4).

For each DGC pulse appearing on conductor 56, a corresponding low value, e.g. 1'', is loaded into UDC 62.

For each of these 1'', a corresponding analog voltage is applied to conductor 76.
As a result, C is applied to the motor 21.

These analog voltages are shown in section 115 of curve C in FIG.

When these voltages, C, are applied to the motor 21, the motor starts to move.

A signal is fed back from the tachometer 25 to zero the counter.

This process (entering a small number and decreasing to zero) is repeated until the head leaves the tape.

In other words, each time a DGC pulse appears on conductor 56 (
Curve B), corresponding analog voltage rise, C, motor 21
(section 115 of curve C).

Here the voltage becomes zero due to the decrease in the number in the UDC.

This process of loading and decreasing continues until the head detaches from the tape.
It is done many times.

Of course, this process may be performed only once when the head is traveling through arc A (FIG. 1), and this also falls within the scope of the invention.

Each time a DGC pulse appears on conductor 56, D, C.

Motor 21 rotates a fixed distance (clockwise or counterclockwise), resulting in advancement of media 14.

Associating the curves A, B, and C in FIG. 5 with the head paths shown in FIGS. 3 and 4, when a portion 112 of curve A is applied to the motor 21 and the tape steps, an offset distance 116 occurs. be done.

Head path 35' is connected to C
, occurs when applied to the motor 21.

Head path 35', seen in FIG. 3, is an electrical model of the head path.

However, due to mechanical delays in mechanical components, such as the motor in FIG.
becomes round like the curve in Figure 5.

In other words, the head path tends to form a circle connecting the peaks of the curved electrical response.

When activating the automatic skew control scheme of the present invention, a command signal is applied to conductor 38.

This signal resets UDC 62 to zero.

In other words, this signal triggers the deskew circuit.

During normal operation, the tape drive is in read mode;
The data of the already recorded track of the medium 14 is read.

If the track is skewed as shown in FIG. 3, the tape drive will make several attempts to read the data.

If, after a predetermined number of attempts, the tape drive is unable to read the data, a tape drive controller (not shown) provides a deskew signal on conductor 52.

When this signal is input and the head is at the β angle, the conductor 5
A signal is generated at 4.

When signals are received on conductors 54 and 52, AND circuit 58 is activated and the offset number is placed in UDC 62.

At the same time, a signal is applied to conductor 86 to suppress the feedback loop of the dynamic deskew circuit.

In other words, as soon as a number is placed in the UDC 62, a feedback loop is castrated to prevent the number from changing too quickly.

When a number is entered in UDC62, a digital pulse is sent to conductor 6.
Go out on 8th.

This pulse is converted to an analog voltage by a DAC 70 and supplied to a power amplifier 72.

This voltage is amplified by the gain of amplifier 72 and conductor 76
Therefore, C is applied to the motor 21.

This voltage rise causes the motor 21 to rotate clockwise or counterclockwise.

When the D, C, and motors 21 start moving, pulses from the tacho make 25 are fed back through the conductor 92.94.

These pulses are applied to direction sensing device 96, which generates output pulses on conductor 98100 indicating forward or backward movement.

These forward or backward pulses are sent to a counter controller 64 which generates pulses that decrease the number in UDC 62.

Unit 64 also generates the sign bit to the DAC.

As the motor continues to turn, the pulses on conductor 98 or 100 continue to subtract the number that was on UDC 62 until it becomes zero.

At this point, the motor should be stationary.

Within this time period, the media is offset distance 116 (third
(Fig.) is shifted by a distance approximately equal to that shown in Fig.

As a result of the media movement, the head 13 is aligned with the deskew head path 35.

At this point, head 13 should be at the beginning of new head path 35'.

Additionally, the head should be nearly ready to convert data from media 14.

At this point, DGC pulses begin to appear on conductor 56, with the first pulse on conductor 56 and the deskew command signal on, energizing the second AND circuit 118 and outputting a signal on conductor 120, which outputs a low value on UDC 62. Enter the number of

According to the load/subtraction method described above, the low value in UDC 62 generates a voltage, which in turn turns C and motor 21.

A feedback signal is generated to subtract the counter to zero.

This steps the tape a step distance.

The load/subtraction operation is repeated a predetermined number of times, and at the end, the third
A new head path is generated as shown by line 35' or the curved line in FIG.

This new head path 35' allows skewed data to be read by the tape drive.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a rotary head magnetic tape drive used in the present invention; FIG. 2 is a diagram of the longitudinal servo track and lateral data track pattern on the tape; and FIG. 3 is a diagram of the skewed data track. 4 is a schematic diagram of the present invention for handling skewed data tracks, and FIG. 5 is a waveform diagram of various parts of the present invention during one revolution of the head.

Claims (1)

[Claims] 1. A recording medium skew correction device including a recording medium drive device and a rotary head device and for aligning the rotary head with a data track on the medium in a skewed state, wherein the rotary head performs a conversion operation with the track. a device for generating a first control signal while the rotary head is in a position in which it does not perform a conversion operation; a device for generating a second control signal while the rotary head is in a position in which it performs a transducing operation with the track; A device that generates a numerical value corresponding to the amount of movement of the medium to be corrected when starting the conversion operation between the two; a device that stores the numerical value and generates an output corresponding to the numerical value; apparatus for moving the medium within the period of the first control signal to correct skew in response to an output, and reducing the stored value to zero when the medium is moved by the amount of movement; and a device that responds to the second control signal to set a numerical value that is sufficiently lower than the numerical value over the period of the second control signal so that the sum thereof becomes equal to the numerical value corresponding to the movement amount. a device for sequentially supplying the medium; and a device for storing the sequentially supplied low numerical values, moving to correct the skew of the medium in response to the numerical values, subtracting the stored numerical values according to the amount of movement, and storing the low numerical values sequentially supplied. and a device for repeating increment and subtraction within the period of the second control signal.