Bi-Stable, Sub-Commutated, Direct-Drive, Sinusoidal Motor Controller for Precision Position Control

• US 20140312815A1
• Filed: 02/12/2014
• Published: 10/23/2014
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: Aerovironment
• Original Assignee: Aerovironment
• Inventors: Nicoloff, William, Leonardi, Michael
• Granted Patent: US 11,264,925 B2
• Time in Patent Office: Days
• US Class Current: 318/400.04
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 2200/10 Air crafts
• CPC Class Codes: B60L 2220/16 DC brushless machines
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2260/32 Auto pilot mode
• CPC Class Codes: H02P 6/10 Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

An electric motor controller system for modulating requested motor torque via oscillating the instantaneous torque, including a bi-stable torque controller; a proportional-integral (PI) velocity controller a proportional-integral-differential (PID) position controller; and sinusoidal zero-velocity table mapping.

Claims

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 requested instantaneous torque is based on a sinusoidal reference.

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 reference 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.

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 9 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.

26. An unmanned aerial vehicle (UAV) sensor apparatus, comprising:

a UAV;

a direct-drive motor coupled to the UAV; and

a sensor coupled to the direct-drive motor, the direct-drive motor configured to angularly drive the sensor.

27. The apparatus of claim 28, wherein the direct-drive motor is coupled to the UAV through a support.