Method for controlling the lateral position of a tape head of a magnetic tape drive

• US 9,564,161 B1
• Filed: 11/10/2015
• Issued: 02/07/2017
• Est. Priority Date: 11/10/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Cherubini, Giovanni, Furrer, Simeon, Lantz, Mark A., Pantazi, Angeliki
• Primary Examiner(s): Wong, K.
• Application Number:
  US14/937,028
• Time in Patent Office: 455 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 5/584 for track following on tapes
• CPC Class Codes: G11B 5/588 by controlling the position of the rotating heads by controlling the speed of the record carrier G11B15/467; by controlling speed of the heads G11B15/473; by moving the transducing part of the head relative to the headwheel, in the direction of the scanning movement G11B15/1841

Abstract

Embodiments include methods, systems and computer program products for controlling a lateral position of a tape head of a magnetic tape drive. Aspects include determining a first servo signal by reading position marks from a first servo band on a magnetic tape using a first sensor and determining a second servo signal by reading position marks from a second servo band on the magnetic tape using a second sensor. Aspects also include delaying the first servo signal relative to the second servo signal by a delay and calculating an average signal based on the first and the delayed second servo signal. Aspects further include determining servo information from the average signal indicative of a deviation of the lateral position of the tape head from an ideal lateral position of the tape head and controlling the tape head to adjust its lateral position such that the deviation is decreased.

Claims

1. A method for controlling a lateral position of a tape head of a magnetic tape drive, the method comprising:

determining a first servo signal by reading position marks from a first servo band on a magnetic tape using a first sensor,

determining a second servo signal by reading position marks from a second servo band on the magnetic tape using a second sensor,

delaying the first servo signal relative to the second servo signal by a delay to create a delayed second servo signal, wherein the delay is based on the frequency (f) of a longitudinal oscillation of the magnetic tape,

calculating an average signal based on the first servo signal and the delayed second servo signal,

determining a servo information from the average signal, the servo information being indicative of a deviation of the lateral position of the tape head from an ideal lateral position of the tape head relative to the magnetic tape, and

controlling the tape head to adjust its lateral position such that the deviation is decreased.

2. The method of claim 1, the delay (Δ

t) is chosen such that

3. The method of claim 1, wherein the delay Δ

t is

4. The method of claim 1, wherein the delay Δ

t is caused by a relative spatial displacement Δ

s of one of the sensors with respect to the other sensor in longitudinal direction of the magnetic tape.

5. The method of claim 4 further comprising:

determining the longitudinal velocity of the magnetic tape; and

determining the spatial displacement Δ

s as a function of the delay Δ

t and the determined longitudinal velocity of the magnetic tape.

6. The method of claim 4, wherein the spatial displacement Δ

s is caused by a tilting of the tape head by an angle ψ

around an axis, the axis being perpendicular to the plane of the magnetic tape.

7. The method of claim 6 further comprising:

determining the longitudinal velocity of the magnetic tape; and

determining the angle γ

as a function of the delay Δ

t, the lateral distance between the first and second servo sensor, and the determined longitudinal velocity of the magnetic tape.

8. The method of claim 1, wherein the delay Δ

t is caused by introducing a delay in the second servo signal after determination of the second servo signal.

9. The method of claim 1, wherein the magnetic tape drive is in communication with to a data storage unit, the data storage unit comprising a look-up table comprising the delays Δ

t for a predefined number of media types, the determination of the delay Δ

t comprising accessing the look-up table and determining the delay Δ

t from the entry of the look-up table corresponding to the determined media type.

10. The method of claim 5, wherein the magnetic tape drive is in communication with to a data storage unit, the data storage unit comprising a look-up table comprising the spatial displacement Δ

s for a predefined number of longitudinal velocities of the magnetic tape and media type, the determination of the spatial displacement Δ

s comprising accessing the look-up table and determining the spatial displacement Δ

s from the entry of the look-up table corresponding to the determined longitudinal velocity of the magnetic tape and media type.

11. The method of claim 7, wherein the magnetic tape drive is in communication with to a data storage unit, the data storage unit comprising a look-up table comprising the angle ψ

for a predefined number of longitudinal velocities of the magnetic tape and media type, the determination of the angle ψ

comprising accessing the look-up table and determining the angle ψ

from the entry of the look-up table corresponding to the determined longitudinal velocity of the magnetic tape and media type.

12. A computer program product for controlling a lateral position of a tape head of a magnetic tape drive, the computer program product comprising:

a non-transitory storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

determining a first servo signal by reading position marks from a first servo band on a magnetic tape using a first sensor,

determining a second servo signal by reading position marks from a second servo band on the magnetic tape using a second sensor,

delaying the first servo signal relative to the second servo signal by a delay to create a delayed second servo signal, wherein the delay is based on the frequency (f) of a longitudinal oscillation of the magnetic tape,

calculating an average signal based on the first servo signal and the delayed second servo signal,

determining a servo information from the average signal, the servo information being indicative of a deviation of the lateral position of the tape head from an ideal lateral position of the tape head relative to the magnetic tape, and

controlling the tape head to adjust its lateral position such that the deviation is decreased.

13. The computer program product of claim 12, the delay (Δ

t) is chosen such that

14. The computer program product of claim 12, wherein the delay Δ

t is

15. The computer program product of claim 12, wherein the delay Δ

t is caused by a relative spatial displacement Δ

s of one of the sensors with respect to the other sensor in longitudinal direction of the magnetic tape.

16. The computer program product of claim 15 further comprising:

determining the longitudinal velocity of the magnetic tape; and

determining the spatial displacement Δ

s as a function of the delay Δ

t and the determined longitudinal velocity of the magnetic tape.

17. The computer program product of claim 15, wherein the spatial displacement Δ

s is caused by a tilting of the tape head by an angle ψ

around an axis, the axis being perpendicular to the plane of the magnetic tape.

18. The computer program product of claim 17 further comprising:

determining the longitudinal velocity of the magnetic tape; and

determining the angle ψ

as a function of the delay Δ

t, the lateral distance between the first and second servo sensor, and the determined longitudinal velocity of the magnetic tape.

19. The computer program product of claim 12, wherein the delay Δ

t is caused by introducing a delay in the second servo signal after determination of the second servo signal.

20. A magnetic tape drive for reading data from a magnetic tape using a tape head, the tape head comprising at least two sensors adapted to determine a signal from a magnetic tape, the magnetic tape comprising at least two servo bands, the servo bands comprising position marks indicative of a lateral position of the tape head relative to the magnetic tape, the position marks providing identical lateral position information for each servo band of the magnetic tape, the tape head being in physical contact with the magnetic tape, the physical contact causing a longitudinal oscillation of the magnetic tape in case the magnetic tape is passing the tape head with a velocity which is non-zero, the oscillation having a frequency f, the magnetic tape drive being adapted to:

determine a first servo signal by reading the position marks from a first servo band using a first sensor,

determine a second servo signal by reading the position marks from a second servo band using a second sensor,

delay the first servo signal relative to the second servo signal by a delay, the delaying resulting in a delayed second servo signal, the delay depending on the frequency f of the longitudinal oscillation of the magnetic tape,

determine the average signal of the first servo signal and the delayed second servo signal,

determine a servo information from the average signal, the servo information being indicative of a deviation of the lateral position of the tape head from an ideal lateral position of the tape head relative to the magnetic tape, and

re-adjust the lateral position of the tape head such that the determined deviation is decreased.