Balanced delay and resolution for high density servo systems

Patent metadata

Field	Value
Publication number	US-10102873-B2
Application number	US-201715439790-A
Country	US
Kind code	B2
Filing date	Feb 22, 2017
Priority date	Feb 22, 2017
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

A tape drive-implemented method, according to another embodiment, includes: determining a length of a window of a servo pattern to use for calculating a lateral position estimate, determining a number of the windows of the servo pattern to use for calculating a lateral position value, receiving signals corresponding to each of the number of the windows of the servo pattern from a single servo channel, calculating a lateral position estimate for each of the number of the windows of the servo pattern, calculating the lateral position value by using the lateral position estimates, and using the lateral position value to control a tape head actuator. Other systems, methods, and computer program products are described in additional embodiments.

First claim

What is claimed is:

1. A tape drive-implemented method, comprising:
determining a length of a window of a servo pattern to use for calculating a lateral position estimate;
determining a number of the windows of the servo pattern to use for calculating a lateral position value;
receiving signals corresponding to each of the number of the windows of the servo pattern from a single servo channel;
calculating a lateral position estimate for each of the number of the windows of the servo pattern;
calculating the lateral position value by using the lateral position estimates; and
using the lateral position value to control a tape head actuator.

2. The tape drive-implemented method as presented in claim 1 , comprising:
determining a current speed of a magnetic tape,
wherein determining the number of the windows of the servo pattern is based on the current speed of the magnetic tape.

3. The tape drive-implemented method as presented in claim 2 , wherein the number of the windows of the servo pattern is also based on at least one parameter selected from a group of parameters consisting of: a vibration condition, media type, and an environmental condition.

4. The tape drive-implemented method as presented in claim 1 ,
wherein the servo pattern is a high density servo track on a magnetic tape.

5. The tape drive-implemented method as presented in claim 4 , comprising:
storing at least some of the lateral position estimates in memory; and
retrieving the stored lateral position estimates from the memory to calculate the lateral position value.

6. The tape drive-implemented method as presented in claim 1 , comprising:
receiving signals corresponding to windows of a second servo pattern from a second servo channel;
calculating a lateral position estimate for each of a second number of the windows of the second servo pattern, the second number of the windows of the second servo pattern according to the number of the windows of the servo pattern;
calculating a second lateral position value using the lateral position estimates for the second number of the windows, wherein the servo pattern is a high density servo track on a magnetic tape, wherein the second servo pattern is a respective high density servo track on the magnetic tape; and
using the second lateral position value along with the lateral position value to control the tape head actuator.

7. The tape drive-implemented method as presented in claim 1 , comprising:
calculating an operating frequency of a track-following control loop using a current speed of a magnetic tape and the length of the window; and
applying the operating frequency to the track-following control loop.

8. The tape drive-implemented method as presented in claim 1 , comprising:
receiving additional estimates from the servo channel;
calculating a supplemental value using the received additional estimates; and
using the supplemental value to control a tape head actuator,
wherein the supplemental value is selected from a group consisting of: a current speed of a magnetic tape, and a magnetic tape skew value.

9. The tape drive-implemented method as presented in claim 1 , wherein calculating the lateral position value includes: calculating an arithmetic mean of the lateral position estimates, or calculating a weighted average of the lateral position estimates.

10. A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to:
determine, by the processor, a length of a window of a servo pattern to use for calculating a lateral position estimate;
determine, by the processor, a number of the windows of the servo pattern to use for calculating a lateral position value;
receive, by the processor, signals corresponding to each of the number of the windows of the servo pattern from a single servo channel;
calculate, by the processor, a lateral position estimate for each of the number of the windows of the servo pattern;
calculate, by the processor, the lateral position value by using the lateral position estimates; and
use, by the processor, the lateral position value to control a tape head actuator.

11. The computer program product as presented in claim 10 , the program instructions executable by the processor to cause the processor to:
determine, by the processor, a current speed of a magnetic tape,
wherein determining the number of the windows of the servo pattern is based on the current speed of the magnetic tape.

12. The computer program product as presented in claim 11 , wherein the number of the windows of the servo pattern is also based on at least one parameter selected from a group of parameters consisting of: a vibration condition, media type, and an environmental condition.

13. The computer program product as presented in claim 10 , wherein the servo pattern is a high density servo track on a magnetic tape.

14. The computer program product as presented in claim 13 , the program instructions executable by the processor to cause the processor to:
store, by the processor, at least some of the lateral position estimates in memory; and
retrieve, by the processor, the stored lateral position estimates from the memory to calculate the lateral position value.

15. The computer program product as presented in claim 10 , the program instructions executable by the processor to cause the processor to:
receive, by the processor, signals corresponding to windows of a second servo pattern from a second servo channel;
calculate, by the processor, a lateral position estimate for each of a second number of the windows of the second servo pattern, the second number of the windows of the second servo pattern according to the number of the windows of the servo pattern;
calculate, by the processor, a second lateral position value using the lateral position estimates for the second number of the windows, wherein the servo pattern is a high density servo track on a magnetic tape, wherein the second servo pattern is a respective high density servo track on the magnetic tape; and
use, by the processor, the second lateral position value along with the lateral position value to control the tape head actuator.

16. The computer program product as presented in claim 15 , the program instructions executable by the processor to cause the processor to:
receive, by the processor, signals corresponding to windows of a third servo pattern from a third servo channel;
calculate, by the processor, a lateral position estimate for each of a third number of the windows of the third servo pattern, the third number of the windows of the third servo pattern according to the number of the windows of the servo pattern;
calculate, by the processor, a third lateral position value using the lateral position estimates for the third number of the windows, wherein the third servo pattern is a respective high density servo track on the magnetic tape; and
use, by the processor, the third lateral position value along with the lateral position value and the second lateral position value to control the tape head actuator.

17. The computer program product as presented in claim 10 , the program instructions executable by the processor to cause the processor to:
calculate, by the processor, an operating frequency of a track-following control loop using a current speed of a magnetic tape and the length of the window; and
apply, by the processor, the operating frequency to the track-following control loop.

18. The c

Assignees

• IBM

Inventors

• Bui Nhan X
• Cherubini Giovanni
• Furrer Simeon
• Lantz Mark A

Classifications

• G11B5/5926 Primary

  recorded in separate tracks, e.g. servo tracks · CPC title

• G11B5/584 Primary

  for track following on tapes · CPC title