Granted Patent B2

US 7,705,555 · App. 11/959,057 · Granted Apr 27, 2010

Abstract

Claims (41)

1. A method for detecting a stall condition in a stepping motor, the stepping motor having two coils and a rotor, the stepping motor being micro-stepped by substantially continuously driving both of the two coils with out-of-phase time varying voltages, the method comprising:

stepping the stepping motor to a next micro-step;

determining that a predetermined motor parameter of a first coil of the two coils is to be sampled;

opening the first coil for a predetermined period, wherein the predetermined period is less than or equal to a micro-step;

sampling the predetermined motor parameter of the first coil during the predetermined period;

closing the first coil; and

detecting if a stall condition exists.

2. The method of claim 1 , wherein determining that a predetermined motor parameter of a first coil of the two coils is to be sampled further comprises determining that one of either a back electro-magnetic force (BEMF) or a flyback voltage of the first coil is to be sampled.

3. The method of claim 1 , wherein detecting if a stall condition exists further comprises:

integrating the predetermined motor parameter; and

comparing the integrated predetermined parameter to a threshold to produce a comparison result.

4. The method of claim 3 , further comprising using the comparison result to determine if a stall condition exists.

5. The method of claim 3 , further comprising incrementing or decrementing a value in an accumulator register based on the comparison result.

6. The method of claim 5 , further comprising loading the accumulator register with a preset value based on a sampling rate of the predetermined motor parameter.

7. The method of claim 6 , wherein the preset value is stored in a look-up table of a plurality of preset values, wherein each value of the plurality of preset values corresponds to one of a plurality of sampling rates.

8. The method of claim 6 , wherein the sampling rate is determined by a frequency of a clock signal.

9. The method of claim 1 , wherein determining that a predetermined motor parameter of a first coil of the two coils is to be sampled further comprises determining that one of either a motor flux of the first coil or energy of the first coil is to be sampled.

10. A method for detecting a stall condition in a stepping motor, the stepping motor having two coils and a rotor, the stepping motor being micro-stepped by substantially continuously driving both of the two coils with out-of-phase time varying voltages, the method comprising:

stepping the stepping motor to a next micro-step;

determining that a predetermined motor parameter of a first coil of the two coils is to be sampled;

opening the first coil for a predetermined period, wherein the predetermined period is less than or equal to a micro-step;

sampling the predetermined motor parameter of the first coil during the predetermined period;

closing the first coil;

integrating the predetermined motor parameter; and

comparing the integrated predetermined parameter to a threshold to produce a comparison result; and

using the comparison result to determine if a stall condition exists.

11. The method of claim 10 , wherein determining that a predetermined motor parameter of a first coil of the two coils is to be sampled further comprises determining that one of either a back electro-magnetic force (BEMF) or a flyback voltage of the first coil is to be sampled.

12. The method of claim 10 , wherein determining that a predetermined motor parameter of a first coil of the two coils is to be sampled further comprises determining that one of either a motor flux of the first coil or energy of the first coil is to be sampled.

13. The method of claim 10 , further comprising using the comparison result to determine if a stall condition exists.

14. The method of claim 10 , further comprising incrementing or decrementing a value in an accumulator register based on the comparison result.

15. The method of claim 14 , further comprising loading the accumulator register with a preset value based on a sampling rate of the predetermined motor parameter.

16. The method of claim 15 , wherein the preset value is stored in a look-up table of a plurality of preset values, wherein each value of the plurality of preset values corresponds to one of a plurality of sampling rates.

17. The method of claim 15 , wherein the sampling rate is determined by a frequency of a clock signal.

18. A motor controller, comprising:

a coil driving circuit for driving a first coil and a second coil of a stepper motor;

a control circuit, coupled to the coil driving circuit, for causing the coil driving circuit to micro-step the stepper motor by supplying each of the first and second coils with substantially continuous out-of-phase time varying voltages, and the control circuit for causing either the first coil or the second coil to periodically open during a micro-step; and

a stall detection circuit, coupled to the coil driving circuit, for sampling a predetermined motor parameter of one of either the first coil or the second coil during the micro-step when the one of either the first coil or the second coil is open, to determine if the stepper motor has stalled.

19. The motor controller of claim 18 , wherein the predetermined motor parameter is one of either a back electro-magnetic force (BEMF) or a flyback voltage.

20. The motor controller of claim 18 , wherein the stall detection circuit comprises:

an integrator for integrating the predetermined motor parameter; and

a comparator for comparing the predetermined motor parameter with a threshold voltage to detect a stall condition of the stepper motor.

Assignments (22)