Motor state counting

• US 20060261807A1
• Filed: 04/28/2006
• Published: 11/23/2006
• Est. Priority Date: 01/09/2004
• Status: Active Grant

• Current Assignee: HR Textron, Inc.
• Original Assignee: HR Textron, Inc.
• Inventors: Chung, Estella C., Liu, Raymond Y., Morita, William K. Jr.
• Granted Patent: US 7,230,422 B2
• Time in Patent Office: Days
• US Class Current: 324/251
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position

Abstract

Systems, methods, and computer-readable media are disclosed for error-compensated counting of Hall states for motor position feedback and/or commutation. An indicated Hall state is detected by digital Hall state sensors and a duration of the Hall state is compared to a specified time period. When the duration exceeds the specified time period, the indicated Hall state is compared to one or more valid Hall states and a position counter is changed for valid states. When the indicated Hall state is invalid, the position counter is not changed. The Hall state sensors may be connected to logic means and may detect the position of a rotor of a permanent magnet motor relative to a stator. When noise induces a change in an indicated Hall state, corresponding noise-induced effects on the position counter may be may be removed through error-compensated counting.

Claims

1. A method of error-compensated counting of Hall states for position feedback, wherein compensation is made for noise-induced Hall state changes.

2. The method of claim 1, further comprising the step of comparing a duration of an indicated Hall state to a specified or threshold time period.

3. The method of claim 2, further comprising the step of comparing said indicated Hall state to one or more valid Hall states when said duration is greater than said specified or threshold time period.

4. The method of claim 3, further comprising the step of generating a Hall state change pulse.

5. The method of claim 4, further comprising the step of changing a position counter.

6. The method of claim 3, further comprising the step of determining a first direction associated with said indicated Hall state.

7. A method of incrementing a position counter comprising the steps of:

detecting an indicated Hall state from a plurality of Hall effect sensors;

detecting a duration of said indicated Hall state;

comparing said duration to a specified time period;

comparing said indicated Hall state to one or more valid Hall states, in the event that said duration is greater than said specified time period;

determining whether said indicated Hall state corresponds to a valid Hall state;

determining whether said indicated Hall state corresponds to first direction or second direction relative to a previous Hall state;

changing a position counter in response to determining that said indicated Hall state corresponds to said first direction or said second direction; and

ignoring said Hall state, in the event that said indicated Hall state corresponds to an invalid Hall position or said duration is less than said specified time period.

8. The method of claim 7, wherein said step of changing a position counter further comprises generating a state change pulse.

9. The method of claim 7, wherein said step of changing a position counter comprises incrementing said position counter.

10. The method of claim 7, wherein said step of changing a position counter comprises decrementing said position counter.

11. The method of claim 7, wherein said step of changing a position counter is in response to a clockwise direction of a rotor.

12. The method of claim 7, wherein said step of changing a position counter is in response to a counter clockwise direction of a rotor.

13. The method of claim 7, wherein said step of comparing said duration to a specified time period includes comparing said duration to a specified time period of about 500 nanoseconds.

14. The method of claim 7, wherein said step of detecting an indicated Hall state comprises the step of detecting an indicated Hall state that corresponds to a position of a rotor relative to a stator.

15. A computer-readable medium having computer-executable instructions stored thereon to perform the steps of:

detecting an indicated Hall state from a plurality of Hall effect sensors;

detecting a duration of said indicated Hall state;

comparing said duration to a specified time period;

comparing said indicated Hall state to one or more valid Hall states, in the event that said duration is greater than said specified time period;

determining whether said indicated Hall state corresponds to a valid Hall state;

determining whether said indicated Hall state corresponds to a first direction or a second direction relative to a previous Hall state;

changing a position counter in response to determining that said indicated Hall state corresponds to said first direction or said second direction; and

ignoring said Hall state, in the event that said indicated Hall state corresponds to an invalid Hall position or said duration is less than said specified time period.

16. The computer-readable medium of claim 15, wherein said computer-readable instructions to perform the step of changing a position counter further include instructions for incrementing said position counter.

17. The computer-readable medium of claim 15, wherein said computer-readable instructions to perform the step of changing a position counter further include instructions for decrementing said position counter.

18. The computer-readable medium of claim 15, wherein said computer-readable instructions to perform the step of changing a position counter include instructions for changing said position counter in response to a clockwise direction of a rotor.

19. The computer-readable medium of claim 15, wherein said computer-readable instructions to perform the step of changing a position counter include instructions for changing said position counter in response to a counter clockwise direction of a rotor.

20. The computer-readable medium of claim 15, wherein said computer-readable instructions to perform the step of comparing said duration to a specified time period include instructions for comparing said duration to a specified time period of about 500 nanoseconds.

21. The computer-readable medium of claim 15, wherein said computer-readable instructions to perform the step of changing a position counter include instructions for changing a position counter indicating a position of a rotor relative to a stator.

22. A system for incrementing a position counter comprising:

a plurality of Hall state sensors, each Hall state sensor operable to produce at least one binary value; and

logic means for determining a valid Hall state made up of said at least one binary value and for changing a position counter.

23. The system of claim 22, wherein said logic means is operable to (a) receive said at least one binary value from said plurality of Hall state sensors, (b) detect an indicated Hall state, (c) detect a duration of said indicated Hall state (d) compare said duration to a specified time period, (e) compare said indicated Hall state to one or more valid Hall states, (e) determine whether said indicated Hall state corresponds to a valid Hall state, (f) determine whether said indicated Hall state indicates a first direction or a second direction relative to a previous Hall state, (g) change a position counter in response to determining said indicated Hall state indicates said first direction or said second direction, and (i) ignore said indicated Hall state in the event that said indicated Hall state corresponds to an invalid Hall position or said duration is less than said specified time period.

24. The system of claim 22, further comprising a position counter connected to said logic means.

25. The system of claim 22, further comprising a brushless DC motor including a permanent magnet rotor, wherein said plurality of Hall state sensors are arranged to detect motion of magnetic fields of said permanent magnet rotor.

26. The system of claim 25, wherein said brushless DC motor has an even number of magnetic poles.

27. The system of claim 26, wherein said brushless DC motor is selected from the group consisting of a 2-pole motor, a 4-pole motor, a 6-pole motor, an 8-pole motor, a 10-pole motor, and a 12-pole motor.

28. The system of claim 27, wherein said brushless DC motor is an 8-pole brushless DC motor.

29. The system of claim 25, wherein said plurality of Hall state sensors comprise three Hall state sensors.

30. The system of claim 29, wherein said Hall state sensors are arranged 30, 60, or 120 degrees apart from one another relative to a said rotor.

31. The system of claim 25, wherein said Hall sensors are connected to a stator of said brushless DC motor.

39. The system of claim 22, wherein said logic means comprise a programmable logic controller (PLC).

40. The system of claim 22, wherein said logic means comprise a field programmable gate array (FPGA).

41. The system of claim 22, wherein said logic means comprise a central processing unit (CPU).

42. The system of claim 22, wherein each of said plurality of Hall state sensors comprises a Schmitt trigger.

43. The system of claim 22, wherein each of said plurality of Hall state sensors comprises a Schmitt inverter.

44. The system of claim 22, wherein each of said plurality of Hall state sensors comprises a low noise, high input impedance differential amplifier.

32. The system of 22, further comprising a Hall sensor interface circuit connected to each of said plurality of Hall state sensors.

33. The system of claim 32, wherein each said Hall sensor interface circuit comprises a low-pass filter.

34. The system of claim 32, wherein each said Hall sensor interface circuit comprises a voltage divider circuit.

35. The system of claim 32, wherein each said Hall sensor interface circuit comprises a Hall sensor output transistor.

36. The system of claim 35, wherein said Hall sensor output transistor is a current-sinking NPN type transistor.

37. The system of claim 35, wherein said output transistor is configured as an open collector transistor.

38. The system of claim 32, wherein said low-pass filter has a corner frequency of about 11.37 kHz.