Variable stopwrite threshold with variable smoothing factor

Patent metadata

Field	Value
Publication number	US-9263065-B2
Application number	US-201414563851-A
Country	US
Kind code	B2
Filing date	Dec 8, 2014
Priority date	Jul 20, 2012
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

In one embodiment, a method includes determining a stopwrite threshold based on a standard deviation or a variance at a current position error signal sample, and determining whether the current position error signal sample exceeds the stopwrite threshold. Writing is disabled in response to determining that the current position error signal sample exceeds the stopwrite threshold. Writing is enabled in response to determining that the current position error signal sample does not exceed the stopwrite threshold.

First claim

What is claimed is:

1. A system, comprising:
a controller; and
logic encoded in and/or available to the controller, the logic being configured to:
determine a stopwrite threshold based on a standard deviation or a variance at a current position error signal sample;
determine whether the current position error signal sample exceeds the stopwrite threshold;
disable writing in response to determining that the current position error signal sample exceeds the stopwrite threshold; and
enable writing in response to determining that the current position error signal sample does not exceed the stopwrite threshold.

2. A system as recited in claim 1 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the logic for periodically determining the stopwrite threshold includes:
logic encoded in or available to the controller for updating the standard deviation or the variance based on position error signal samples and the altered smoothing factor;
logic encoded in or available to the controller for determining whether the standard deviation or the variance exceeds a predetermined threshold; and
logic encoded in or available to the controller for determining the stopwrite threshold based on the standard deviation or the variance when the standard deviation or the variance exceeds the predetermined threshold.

3. A system as recited in claim 2 , comprising:
logic encoded in or available to the controller for comparing the current position error signal to a second value calculated using the standard deviation or the variance when the standard deviation or the variance does not exceed the predetermined threshold;
logic encoded in or available to the controller for disabling writing when the current position error signal sample exceeds the second value; and
logic encoded in or available to the controller for enabling writing when the current position error signal sample does not exceed the second value.

4. A system as recited in claim 2 , comprising logic encoded in or available to the controller for updating a truncated value using a current position error signal value when writing is enabled, wherein the truncated value is not updated when writing is disabled; and logic encoded in or available to the controller for comparing the truncated value to the predetermined threshold.

5. A system as recited in claim 2 , wherein the stopwrite threshold is determined by selecting a stopwrite value preassociated with the standard deviation or the variance.

6. A system as recited in claim 1 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the smoothing factor is altered to slow a change in the standard deviation or the variance in the subsequent calculation thereof when the standard deviation or the variance at the current position error signal sample is below a specified value.

7. A system as recited in claim 1 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the smoothing factor is altered to accelerate a change in the standard deviation or the variance in the subsequent calculation thereof when the standard deviation or the variance at the current position error signal sample is above a specified value.

8. A system as recited in claim 1 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the smoothing factor is altered after each calculation of the standard deviation or the variance.

9. A system as recited in claim 1 , wherein the logic is executed at intervals of less than 1 millisecond.

10. A system as recited in claim 1 , comprising a magnetic head electrically coupled to the controller.

11. A method, comprising:
determining a stopwrite threshold based on a standard deviation or a variance at a current position error signal sample;
determining whether the current position error signal sample exceeds the stopwrite threshold;
disabling writing in response to determining that the current position error signal sample exceeds the stopwrite threshold; and
enabling writing in response to determining that the current position error signal sample does not exceed the stopwrite threshold.

12. A method as recited in claim 11 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the determining the stopwrite threshold includes:
updating the standard deviation or the variance based on the current position error signal sample and the altered smoothing factor;
determining whether the standard deviation or the variance exceeds a predetermined threshold; and
determining the stopwrite threshold based on the standard deviation or the variance when the standard deviation or the variance exceeds the predetermined threshold.

13. A method as recited in claim 11 , comprising:
comparing the current position error signal to a second value calculated using the standard deviation or the variance when the standard deviation or the variance does not exceed a predetermined threshold;
disabling writing when the current position error signal sample exceeds the second value; and
enabling writing when the current position error signal sample does not exceed the second value.

14. A method as recited in claim 11 , comprising updating a truncated value using a current position error signal value when writing is enabled, wherein the truncated value is not updated when writing is disabled; and comparing the truncated value to a predetermined threshold.

15. A method as recited in claim 11 , wherein the stopwrite threshold is determined by selecting a stopwrite value preassociated with the standard deviation or the variance.

16. A method as recited in claim 11 , wherein the method is executed at intervals of less than 1 millisecond.

17. A method as recited in claim 11 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the smoothing factor is altered to slow a change in the standard deviation or the variance in the subsequent calculation thereof when the standard deviation or the variance at the current position error signal sample is below a specified value.

18. A method as recited in claim 11 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of the standard deviation or the variance, wherein the smoothing factor is altered to accelerate a change in the standard deviation or the variance in the subsequent calculation thereof when the standard deviation or the variance at the current position error signal sample is above a specified value.

19. A method as recited in claim 11 , wherein a smoothing factor applied to a subsequent calculation of the standard deviation or variance is altered based at least in part on a current magnitude of th

Assignees

• IBM

Inventors

• Bui Nhan X
• Judd Kevin B
• Taketomi Tomoko

Classifications

• G11B5/0083 Primary

  for parallel information processing, e.g. PCM recording · CPC title

• G11B5/09

  Digital recording · CPC title

• G11B5/584

  for track following on tapes · CPC title

• G11B27/36

  Monitoring, i.e. supervising the progress of recording or reproducing {(for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06)} · CPC title

• G11B20/10388

  control of the read or write heads, e.g. tracking errors, defocus or tilt compensation · CPC title