Granted Patent B2

US 7,684,141 · App. 12/040,419 · Granted Mar 23, 2010

Abstract

Claims (64)

1. A computer-implemented method, comprising:

calculating an estimate of an interval to degrees translation factor that represents a measurement angle interval divided by a first pulse count, wherein the first pulse count represents magnetic format transitions counted during an angular measurement interval, wherein a servo format is formed by the magnetic format transitions written on a tape medium, wherein the measurement angle interval is determined with a reference angle sensor; and

determining a reel motor angle using the estimate by:

receiving an indication that a rotating reference point has crossed a stationary reference point, wherein the indication is recognized as indicating that an angle between a motor rotor and a motor stator is a reference angle;

determining a second pulse count, wherein the second pulse count represents magnetic format transitions counted since the indication was received to a given point in time; and

at the given point in time,

multiplying the second pulse count by the estimate to generate a first value; and

adding the reference angle to the first value to generate the reel motor angle.

2. The method of claim 1 , farther comprising:

calculating the estimate and determining the reel motor angle in parallel, wherein the reel motor angle is determined using a best available estimate.

3. The method of claim 1 , wherein the measurement angle interval is some angle in degrees among possible angles formed between one or more rotating reference points that are fixed in angular position relative to the motor rotor, wherein the one or more rotating reference points are sensed by a sensor at the stationary reference point that is fixed in angular position relative to the motor stator.

4. The method of claim 1 , wherein calculating the estimate further comprises:

detecting a beginning of the angular measurement interval;

resetting an interval pulse train counter;

starting to count pulses by updating the interval pulse train counter with a number of magnetic format transitions that occur since the beginning of the angular measurement interval;

detecting an end of the angular measurement interval; and

recording the first pulse count in the interval pulse train counter.

5. The method of claim 1 , further comprising:

determining the angular measurement interval in response to receiving an indication from a sensor of a beginning and an end of the angular measurement interval.

6. The method of claim 1 , wherein determining a second pulse count further comprises:

receiving pulses from a servo channel that detects a magnetic format transition.

7. A computer program product comprising a computer-readable storage medium storing a computer readable program, wherein the computer readable program when executed by a processor on a computer causes the computer to:

calculate an estimate of an interval to degrees translation factor that represents a measurement angle interval divided by a first pulse count, wherein the first pulse count represents magnetic format transitions counted during an angular measurement interval, wherein a servo format is formed by the magnetic format transitions written on a tape medium, wherein the measurement angle interval is determined with a reference angle sensor; and

determine a reel motor angle using the estimate by:

receiving an indication that a rotating reference point has crossed a stationary reference point, wherein the indication is recognized as indicating that an angle between a motor rotor and a motor stator is a reference angle;

determining a second pulse count, wherein the second pulse count represents magnetic format transitions counted since the indication was received to a given point in time; and

at the given point in time,

multiplying the second pulse count by the estimate to generate a first value; and

adding the reference angle to the first value to generate the reel motor angle.

8. The computer program product of claim 7 , wherein the computer readable program when executed on a computer causes the computer to:

calculate the estimate and determining the reel motor angle in parallel, wherein the reel motor angle is determined using a best available estimate.

9. The computer program product of claim 7 , wherein the measurement angle interval is some angle in degrees among possible angles formed between one or more rotating reference points that are fixed in angular position relative to the motor rotor, wherein the one or more rotating reference points are sensed by a sensor at the stationary reference point that is fixed in angular position relative to the motor stator.

10. The computer program product of claim 7 , wherein the computer readable program when executed on a computer causes the computer to calculate the estimate by:

detecting a beginning of the angular measurement interval;

resetting an interval pulse train counter;

starting to count pulses by updating the interval pulse train counter with a number of magnetic format transitions that occur since the beginning of the angular measurement interval;

detecting an end of the angular measurement interval; and

recording the first pulse count in the interval pulse train counter.

11. The computer program product of claim 7 , wherein the computer readable program when executed on a computer causes the computer to:

determine the angular measurement interval in response to receiving an indication from a sensor of a beginning and an end of the angular measurement interval.

12. The computer program product of claim 7 , wherein the computer readable program when executed on a computer causes the computer to determine a second pulse count by:

receiving pulses from a servo channel that detects a magnetic format transition.

13. A system, comprising:

a processor; and

an integrated circuit performing operations, the operations comprising:

calculating an estimate of an interval to degrees translation factor that represents a angle interval divided by a first pulse count, wherein the first pulse count represents magnetic format transitions counted during an angular measurement interval, wherein a servo format is formed by the magnetic format transitions written on a tape medium, wherein the measurement angle interval is determined with a reference angle sensor; and

determining a reel motor angle using the estimate by:

receiving an indication that a rotating reference point has crossed a stationary reference point, wherein the indication is recognized as indicating that an angle between a motor rotor and a motor stator is a reference angle;

determining a second pulse count, wherein the second pulse count represents magnetic format transitions counted since the indication was received to a given point in time; and

at the given point in time,

multiplying the second pulse count by the estimate to generate a first value; and

adding the reference angle to the first value to generate the reel motor angle.

14. The system of claim 13 , wherein the operations further comprise: calculating the estimate and determining the reel motor angle in parallel, wherein the reel motor angle is determined using a best available estimate.

15. The system of claim 13 , wherein the measurement angle interval is some angle in degrees among possible angles formed between one or more rotating reference points that are fixed in angular position relative to the motor rotor, wherein the one or more rotating reference points are sensed by a sensor at the stationary reference point that is fixed in angular position relative to the motor stator.

16. The system of claim 13 , wherein operations for calculating the estimate further comprise:

detecting a beginning of the angular measurement interval;

resetting an interval pulse train counter;

starting to count pulses by updating the interval pulse train counter with a number of magnetic format transitions that occur since the beginning of the angular measurement interval;

detecting an end of the angular measurement interval; and

recording the first pulse count in the interval pulse train counter.

17. The system of claim 13 , wherein the operations further comprise:

determining the angular measurement interval in response to receiving an indication from a sensor of a beginning and an end of the angular measurement interval.

18. The system of claim 13 , wherein operations for determining a second pulse count further comprise:

receiving pulses from a servo channel that detects a magnetic format transition.

Assignments (8)