Bi-stable, sub-commutated, direct-drive, sinusoidal motor controller for precision position control

1. An electric motor controller system for modulating requested motor torque via oscillating the requested instantaneous torque, the system comprising:

a bi-stable torque controller comprising a sinusoidal drive table having at least three phases, wherein the bi-stable torque controller generates the requested instantaneous torque based on the sinusoidal drive table.

2. The electric motor controller system of claim 1 further comprising:

a brushless electric motor, in communication with the torque drive oscillating circuit, the brushless electric motor comprising:

a rotor having three or more multi-turn coils, each multi-turn coil disposed about an associated armature of the rotor; and

a stator having circumferentially distributed magnetic elements.

3. The electric motor controller system of claim 2 further comprising:

a motor torque feedback path;

a motor velocity feedback path; and

an encoder angle feedback path.

4. The electric motor controller system of claim 3 wherein the sinusoidal drive table is a sinusoidal zero-velocity table mapping, and the bi-stable torque controller is configured to draw from the sinusoidal zero-velocity table mapping to energize a brushless motor phase through the stator of the brushless motor, detect a static condition, and yield a symmetrical three-phase sinusoidal drive table for the brushless motor.

5. An electric motor controller for achieving sub-degree pointing accuracy of a brushless direct current (DC) motor comprising:

a proportional-integral-differential (PID) position controller;

a proportional-integral (PI) velocity controller in communication with the PID position controller;

a bi-stable torque controller in communication with the PI velocity controller; and

sinusoidal zero-velocity table mapping in communication with the bi-stable torque controller to reduce torque ripple.

6. The electric motor controller of claim 5 wherein the brushless DC motor is sub-commutated greater than one hundred times within one electrical commutation cycle.

7. The electric motor controller of claim 6 wherein the bi-stable torque controller is configured to oscillate about a request to yield a modulated torque value to average a total torque requested of the brushless DC motor.

8. The electric motor controller of claim 7 further comprising a current sensor configured to detect a current through the brushless DC motor.

9. The electric motor controller of claim 8 wherein the bi-stable torque controller is configured to receive feedback input through a slow varying filter measured from an input of the current sensor.

10. The electric motor controller of claim 7 wherein the bi-stable torque controller is further configured to restrict a change in torque to a small fraction of torque change per second.

11. The electric motor controller of claim 7 wherein the bi-stable torque controller is further configured to adjust a delta torque more positive than negative to achieve a gradually modulated torque value when a forward position is requested.

12. The electric motor controller of claim 7 wherein the bi-stable torque controller is further configured to draw values from the sinusoidal zero-velocity table mapping.

13. The electric motor controller of claim 12 wherein the sinusoidal zero-velocity table mapping is configured to use three phases simultaneously to reduce torque ripple.

14. The electric motor controller of claim 12 wherein the sinusoidal zero-velocity table mapping is configured to use at least four phases simultaneously to reduce torque ripple.

15. The electric motor controller of claim 6 wherein the proportional-integral (PI) velocity controller is configured to output a result based on a velocity bias and a feedback of the brushless DC motor velocity.

16. The electric motor controller of claim 15 wherein the proportional-integral (PI) velocity controller is configured to output the result to the bi-stable torque controller.

17. The electric motor controller of claim 15 wherein the proportional-integral (PI) velocity controller is configured to receive an input frequency of 5 kHz.

18. The electric motor controller of claim 17 wherein the input frequency of 5 kHz is infinite impulse response (IIR) filtered with 3 db attenuation and a cut-off frequency of 1.5 kHz.

19. The electric motor controller of claim 6 wherein the proportional-integral-differential (PID) position controller is configured to output a result based on a pointing routine and an angle measurement feedback.

20. The electric motor controller of claim 19 wherein the proportional-integral-differential (PID) position controller is configured to sample directly from an encoder.

21. The electric motor controller of claim 20 wherein an input frequency to the proportional-integral-differential (PID) position controller from the encoder is 5 kHz 16-Tap finite impulse response (FIR) filter with 3 db attenuation and a cut-off frequency of 300 Hz.

22. The electric motor controller of claim 19 wherein the proportional-integral-differential (PID) position controller is configured to output the result to the proportional-integral (PI) velocity controller.

23. The electric motor controller of claim 6 wherein the sinusoidal zero-velocity table mapping is configured to advance or retard θ AR electrical degrees to yield a consistent torque curve over all positions within the brushless DC motor.

24. The electric motor controller of claim 6 wherein the sinusoidal zero-velocity table mapping is implemented via a look-up table.

25. The electric motor controller of claim 6 wherein the sinusoidal zero-velocity table mapping is implemented in microcode.