Absolute position magnetic encoder with binary and decimal output

• US 7,999,536 B2
• Filed: 10/15/2008
• Issued: 08/16/2011
• Est. Priority Date: 10/22/2007
• Status: Active Grant

• Current Assignee: The Timken Company
• Original Assignee: The Timken Company
• Inventors: Santos, Alfred John, Pride, Bruce M.
• Primary Examiner(s): Patel; Paresh
• Application Number:
  US12/252,083
• Publication Number:
  US 20090102461A1
• Time in Patent Office: 1,035 Days
• Field of Search: None
• US Class Current: 324/207.2
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

An absolute position magnetic encoder includes a first magnetic track configured for a binary output, a second magnetic track configured for a decimal output, a first magnetic sensor positioned proximate the first magnetic track to detect the magnetic field of the first magnetic track, and a second magnetic sensor positioned proximate the second magnetic track to detect the magnetic field of the second magnetic track. The encoder is selectively operable to provide one of the binary output and the decimal output.

Claims

1. An absolute position magnetic encoder comprising:

a first magnetic track configured for a binary output;

a second magnetic track configured for a decimal output;

a first magnetic sensor positioned proximate the first magnetic track to detect the magnetic field of the first magnetic track;

a second magnetic sensor positioned proximate the second magnetic track to detect the magnetic field of the second magnetic track;

a third magnetic track including a single North/South pole pair; and

a plurality of Hall-effect devices positioned proximate the third magnetic track to detect the magnetic field of the third magnetic track;

wherein the encoder is selectively operable to provide one of the binary output and the decimal output.

2. The absolute position magnetic encoder of claim 1, wherein the single pole pair includes a North pole and a South pole, and wherein the Hall-effect devices fit within the circumferential length of one of the North pole and the South pole.

3. The absolute position magnetic encoder of claim 2, wherein the Hall-effect devices fit within the circumferential length of the North pole and the circumferential length of the South pole.

4. The absolute position magnetic encoder of claim 1, further comprising a target wheel supporting the first, second, and third magnetic tracks.

5. The absolute position magnetic encoder of claim 1, further comprising a logic module in communication with the first and second magnetic sensors and the plurality of Hall-effect devices.

6. The absolute position magnetic encoder of claim 5, wherein the logic module is configured to record the output of one of the first and second magnetic sensors into a first array layer, and wherein the logic module is configured to record the output of the plurality of Hall-effect devices into a second array layer having the same number of rows and columns as the first array layer.

7. The absolute position magnetic encoder of claim 1, wherein the first magnetic track includes a first number of North/South pole pairs conducive to provide the binary output, and wherein the second magnetic track includes a second number of North/South pole pairs conducive to provide the decimal output.

8. The absolute position magnetic encoder of claim 7, wherein the first number of North/South pole pairs includes one of 32 North/South pole pairs and a whole number multiple thereof, and wherein the second number of North/South pole pairs includes one of 25 North/South pole pairs and a whole number multiple thereof.

9. The absolute position magnetic encoder of claim 1, wherein at least one of the first and second magnetic sensors includes a microchip having a Hall string multiplying sensor.

10. A method of calculating an absolute position of an encoder, the method comprising:

providing a first magnetic track configured for a binary output;

providing a second magnetic track configured for a decimal output;

detecting a first count value from the first magnetic track;

detecting a second count value from the second magnetic track substantially simultaneously with the first count value;

calculating a third count value indicative of the absolute position of the encoder using the first and second count values, the third count value conducive to provide one of the binary output and the decimal output;

providing a third magnetic track including a single North/South pole pair; and

detecting a change in magnetic polarity between a North pole and a South pole of the single pole pair.

11. The method of claim 10, further comprising positioning a plurality of Hall-effect devices proximate the third magnetic track, wherein detecting a change in magnetic polarity between the North pole and the South pole of the single pole pair includes detecting a junction between the North pole and the South pole with each of the Hall-effect devices.

12. The method of claim 11, further comprising:

creating an array having a number of rows equal to a number of pole pairs in one of the first and second magnetic tracks, and a number of columns equal to a resolution of a magnetic sensor positioned proximate the one of the first and second magnetic tracks; and

recording the count value detected from the other of the first and second magnetic tracks into the array.

13. The method of claim 12, wherein creating the array includes creating a first array layer into which the count value detected from the other of the first and second magnetic tracks is recorded, and wherein creating the array includes creating a second array layer into which the output of the Hall-effect devices is recorded.

14. The method of claim 13, wherein creating the second array layer includes

associating a sequence of on/off states of the Hall-effect devices with a position number;

and

recording the position number in the second array layer.

15. The method of claim 13, wherein creating the first and second array layers includes creating the second array layer with an equal number of rows and an equal number of columns as the first array layer.

16. The method of claim 10, further comprising:

coupling the first magnetic track, in a circular arrangement, to a target wheel; and

coupling the second magnetic track, in a circular arrangement and concentric with the first magnetic track, to the target wheel.

17. The method of claim 10, wherein providing the first magnetic track includes providing a first number of North/South pole pairs conducive to provide the binary output, and wherein providing the second magnetic track includes providing a second number of North/South pole pairs conducive to provide the decimal output.

18. The method of claim 17, wherein providing the first number of North/South pole pairs includes providing one of 32 North/South pole pairs and a whole number multiple thereof, and wherein providing the second number of North/South pole pairs includes providing one of 25 North/South pole pairs and a whole number multiple thereof.

19. The method of claim 10, further comprising providing the binary output and the decimal output of the absolute position of the encoder substantially concurrently.

20. The method of claim 10, further comprising pulse-width modulating the one of the binary output and the decimal output of the absolute position of the encoder over a range of pulse widths between about 10% duty cycle and about 90% duty cycle, wherein pulse-width modulating the one of the binary output and the decimal output of the absolute position of the encoder outside the range of pulse widths between about 10% duty cycle and about 90% duty cycle provides at least one of diagnostic information, alarm information, and digital date information.

21. The method of claim 10, further comprising providing at least one of a U, V, W commutation signal and a reference pulse based upon the one of the binary output and the decimal output of the absolute position of the encoder.

22. An absolute position magnetic encoder comprising:

a first magnetic track including a first number of North/South pole pairs conducive to provide a binary output;

a second magnetic track including a second number of North/South pole pairs conducive to provide a decimal output;

a first magnetic sensor positioned proximate the first magnetic track to detect the magnetic field of the first magnetic track;

a second magnetic sensor positioned proximate the second magnetic track to detect the magnetic field of the second magnetic track;

wherein the encoder is selectively operable to provide one of the binary output and the decimal output.

23. The absolute position magnetic encoder of claim 22, further comprising:

a third magnetic track including a single North/South pole pair; and

a plurality of Hall-effect devices positioned proximate the third magnetic track to detect the magnetic field of the third magnetic track.

24. The absolute position magnetic encoder of claim 23, wherein the single pole pair includes a North pole and a South pole, and wherein the Hall-effect devices fit within the circumferential length of one of the North pole and the South pole.

25. The absolute position magnetic encoder of claim 24, wherein the Hall-effect devices fit within the circumferential length of the North pole and the circumferential length of the South pole.

26. The absolute position magnetic encoder of claim 23, further comprising a target wheel supporting the first, second, and third magnetic tracks.

27. The absolute position magnetic encoder of claim 23, further comprising a logic module in communication with the first and second magnetic sensors and the plurality of Hall-effect devices.

28. The absolute position magnetic encoder of claim 27, wherein the logic module is configured to record the output of one of the first and second magnetic sensors into a first array layer, and wherein the logic module is configured to record the output of the plurality of Hall-effect devices into a second array layer having the same number of rows and columns as the first array layer.

29. The absolute position magnetic encoder of claim 22, wherein the first number of North/South pole pairs includes one of 32 North/South pole pairs and a whole number multiple thereof, and wherein the second number of North/South pole pairs includes one of 25 North/South pole pairs and a whole number multiple thereof.

30. The absolute position magnetic encoder of claim 22, wherein at least one of the first and second magnetic sensors includes a microchip having a Hall string multiplying sensor.

31. A method of calculating an absolute position of an encoder, the method comprising:

providing a first magnetic track including a first number of North/South pole pairs conducive to provide a binary output;

providing a second magnetic track including a second number of North/South pole pairs conducive to provide a decimal output;

detecting a first count value from the first magnetic track;

detecting a second count value from the second magnetic track substantially simultaneously with the first count value; and

calculating a third count value indicative of the absolute position of the encoder using the first and second count values, the third count value conducive to provide one of the binary output and the decimal output.

32. The method of claim 31, further comprising:

providing a third magnetic track including a single North/South pole pair; and

detecting a change in magnetic polarity between a North pole and a South pole of the single pole pair.

33. The method of claim 32, further comprising positioning a plurality of Hall-effect devices proximate the third magnetic track, wherein detecting a change in magnetic polarity between the North pole and the South pole of the single pole pair includes detecting a junction between the North pole and the South pole with each of the Hall-effect devices.

34. The method of claim 33, further comprising:

creating an array having a number of rows equal to a number of pole pairs in one of the first and second magnetic tracks, and a number of columns equal to a resolution of a magnetic sensor positioned proximate the one of the first and second magnetic tracks; and

recording the count value detected from the other of the first and second magnetic tracks into the array.

35. The method of claim 34, wherein creating the array includes creating a first array layer into which the count value detected from the other of the first and second magnetic tracks is recorded, and wherein creating the array includes creating a second array layer into which the output of the Hall-effect devices is recorded.

36. The method of claim 35, wherein creating the second array layer includes

associating a sequence of on/off states of the Hall-effect devices with a position number;

and

recording the position number in the second array layer.

37. The method of claim 35, wherein creating the first and second array layers includes creating the second array layer with an equal number of rows and an equal number of columns as the first array layer.

38. The method of claim 31, further comprising:

coupling the first magnetic track, in a circular arrangement, to a target wheel; and

coupling the second magnetic track, in a circular arrangement and concentric with the first magnetic track, to the target wheel.

39. The method of claim 31, wherein providing the first number of North/South pole pairs includes providing one of 32 North/South pole pairs and a whole number multiple thereof, and wherein providing the second number of North/South pole pairs includes providing one of 25 North/South pole pairs and a whole number multiple thereof.

40. The method of claim 31, further comprising providing the binary output and the decimal output of the absolute position of the encoder substantially concurrently.

41. The method of claim 31, further comprising pulse-width modulating the one of the binary output and the decimal output of the absolute position of the encoder over a range of pulse widths between about 10% duty cycle and about 90% duty cycle, wherein pulse-width modulating the one of the binary output and the decimal output of the absolute position of the encoder outside the range of pulse widths between about 10% duty cycle and about 90% duty cycle provides at least one of diagnostic information, alarm information, and digital date information.

42. The method of claim 31, further comprising providing at least one of a U, V, W commutation signal and a reference pulse based upon the one of the binary output and the decimal output of the absolute position of the encoder.