Position sensorless control of permanent magnet motor

• US 8,179,065 B2
• Filed: 04/30/2008
• Issued: 05/15/2012
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Matsuo, Takayoshi
• Primary Examiner(s): Ro, Bentsu
• Assistant Examiner(s): DINH, THAI T
• Application Number:
  US12/113,148
• Publication Number:
  US 20090273308A1
• Time in Patent Office: 1,476 Days
• Field of Search: 318/400.01, 318/400.02, 318/400.04, 318/400.06, 318/400.32, 318/700, 318/705, 318/722
• US Class Current: 318/400.1
• CPC Class Codes: H02P 21/0003 Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
• CPC Class Codes: H02P 25/024 controlled by supply frequency

Abstract

Systems and methods of controlling a permanent magnet motor without a mechanical position sensor are provided. In accordance with one embodiment, a motor control system includes an inverter configured to receive direct current (DC) power and output a power waveform to a permanent magnet motor, driver circuitry configured to receive control signals and drive the inverter based upon the control signals, a current sensor configured to determine a sampled current value associated with the power waveform, and control circuitry configured to generate the control signals based at least in part upon a comparison of a flux-producing component of the sampled current value and a flux-producing component of a command reference current value.

Claims

1. A motor control system comprising:

control circuitry configured to generate control signals to control a permanent magnet motor based at least in part upon a comparison of a flux-producing current component of a power waveform supplied to the permanent magnet motor and a flux-producing component of a command reference current value and to determine the angular position of the stator magneto-motive force based at least in part on a comparison of a torque-producing current component of the power waveform and a torque-producing component of the command reference current value.

2. The system of claim 1, wherein the control circuitry is configured to determine a stator frequency based at least in part on the comparison of the torque-producing current component of the power waveform and the torque-producing component of the command reference current value and wherein the control circuitry is configured to determine the stator magneto-motive force based at least in part on the stator frequency.

3. The system of claim 1, wherein the control circuitry is configured to determine a torque-producing correction voltage based on the comparison of the flux-producing current component of the power waveform and the flux-producing component of the command reference current value.

4. The system of claim 3, wherein the control circuitry is configured to generate the control signals based at least in part upon a summation of the torque-producing correction voltage and a torque-producing command voltage.

5. The system of claim 4, wherein the control circuitry is configured to determine the torque-producing command voltage based at least in part upon a stator frequency and a torque-producing component of the command reference current value.

6. The system of claim 1, wherein the control circuitry is configured to generate the control signals based at least in part upon the following relationships, where V_ds^e* represents a flux-producing command voltage, V_qs—

<sub>ω

e</sub>^e* represents a component of a torque-producing command voltage based on stator frequency, i_qs^e* represents the torque-producing component of the command reference current value, i_ds^e* represents the flux-producing component of the command reference current value, r_s represents stator resistance, L_sq* represents torque-producing stator inductance, λ

_fs^e* represents a coefficient of electromotive force (EMF) due to magnetic fields associated with permanent magnets of the permanent magnet motor, and ω

_e* represents stator frequency;

V<sub>qs—

ω

e</sub>^e*=r_s·

i_qs^e*+ω

_e*·

λ

_fs^e* 

 

(1)

V_ds^e*=r_s·

i_ds^e*−

L_qs*·

i_qs^e*. 

 

(2)

7. The system of claim 6, wherein the control circuitry is configured to generate the control signals based at least in part upon the following relationship, where V_qs^e* represents a torque-producing command voltage, V_qs—

<sub>ω

e</sub>^e* represents the component of a torque-producing command voltage based on stator frequency, and V<sub>qs—

id</sub>^e* represents a component of the torque-producing command voltage based on the comparison of the flux-producing component of the sampled current value and the flux-producing component of the command reference current value;

V_qs^e*=V<sub>qs—

ω

e</sub>^e*+V<sub>qs—

id</sub>^e*.

8. A method of controlling a permanent magnet motor comprising:

causing an inverter to output a voltage waveform to a permanent magnet motor;

sensing a current associated with the voltage waveform;

determining a flux-producing component of the current based at least in part on an angular position of a stator magneto-motive force;

causing the inverter to output a corrected voltage waveform based at least in part upon a comparison of the flux-producing component of the current and a flux-producing component of a command reference current; and

determining the angular position of the stator magneto-motive force based at least in part upon the a comparison of a torque-producing current component of the power waveform and a torque-producing component of the command reference current.

9. The method of claim 8, wherein the inverter is caused to output a corrected voltage waveform based at least in part upon a torque-producing correction voltage based on the comparison of the flux-producing component of the current and the flux-producing component of the command reference current.

10. The method of claim 9, wherein the inverter is caused to output a corrected voltage waveform based at least in part upon a summation of the torque-producing correction voltage and a torque-producing command voltage.

11. The method of claim 10, wherein the torque-producing command voltage is based at least in part upon a stator frequency and a torque-producing component of the command reference current value.

12. The method of claim 8, wherein the inverter is caused to output a corrected voltage waveform based at least in part upon the following relationships, where V_ds^e* represents a flux-producing command voltage, V_qs—

<sub>ω

e</sub>^e* represents a component of a torque-producing command voltage based on stator frequency, i_qs^e* represents the torque-producing component of the command reference current, i_ds^e* represents the flux-producing component of the command reference current value, r_s represents stator resistance, L_sq* represents torque-producing stator inductance, λ

_fs^e* represents a coefficient of electromotive force (EMF) due to magnetic fields associated with permanent magnets of the permanent magnet motor, and ω

_e* represents stator frequency;

V<sub>qs—

ω

e</sub>^e*=r_s·

i_qs^e*+ω

_e*·

λ

_fs^e* 

 

(1)

V_ds^e*=r_s·

i_ds^e*−

L_qs*·

i_qs^e*. 

 

(2)

13. The method of claim 12, wherein the inverter is caused to output a corrected voltage waveform based at least in part upon the following relationship, where V_qs^e* represents a torque-producing command voltage, V_qs—

<sub>ω

e</sub>^e* represents the component of a torque-producing command voltage based on stator frequency, and V<sub>qs—

id</sub>^e* represents a component of the torque-producing command voltage based on the comparison of the flux-producing component of the sampled current value and the flux-producing component of the command reference current value;

V_qs^e*=V<sub>qs—

ω

e</sub>^e*+V<sub>qs—

id</sub>^e*.

14. A method of controlling a motor comprising:

receiving a current reference value;

sampling a power waveform supplied to a permanent magnet motor to obtain a feedback current value;

determining a torque-producing correction voltage based at least in part on a comparison of a flux-producing component of the feedback current value and a flux-producing component of the command reference current value;

determining a command voltage value based at least in part on the torque-producing correction voltage; and

determining an angular position of a stator magneto-motive force of the permanent magnet motor based at least in part on a comparison of a torque-producing current component of the power waveform and a torque-producing component of the command reference current value.

15. The method of claim 14, wherein sampling the power waveform comprises sampling the power waveform supplied to a surface permanent magnet motor.

16. The method of claim 14, wherein the method does not involve high frequency injection in the power waveform supplied to the permanent magnet motor.

17. The method of claim 14, wherein the method does not involve injection of back electromotive force (EMF) into the permanent magnet motor.

18. A motor control system comprising:

control circuitry configured to generate control signals for controlling a permanent magnet motor without the use of a motor position sensor and without regard to a saliency of the permanent magnet motor, wherein the control signals are based at least in part upon feedback from a power waveform supplied to the permanent magnet motor, wherein the control circuitry is configured to determine a position of the permanent magnet motor based at least in part on a comparison of a torque-producing component of the current reference value and a torque-producing component of the feedback from the power waveform.

19. The system of claim 18, wherein the control circuitry is configured to generate the control signals without high frequency injection.

20. The system of claim 18, wherein the permanent magnet motor is a surface permanent magnet motor.

21. The system of claim 18, wherein the permanent magnet motor is an interior permanent magnet motor.

22. The system of claim 18, wherein the control circuitry is configured to generate the control signals without involving back electromotive force (EMF) into the permanent magnet motor.

23. A machine readable storage medium tangibly embodying a sequence of instructions executable by the machine to perform a method, the method comprising:

receiving a current reference value;

receiving a feedback current value; and

determining a position of the permanent magnet motor without the use of a mechanical position sensor based at least in part on a comparison of a torque-producing component of the current reference value and a torque-producing component of the feedback current value.

24. The machine readable storage medium of claim 23, wherein the method comprises determining the position of the permanent magnet motor based at least in part on a stator frequency determined by processing the comparison of the torque-producing component of the current reference value and the torque-producing component of the feedback current value in a proportional and integral regulator.

25. The machine readable storage medium of claim 23, wherein the method comprises determining the position of the permanent magnet motor without regard to a saliency of the motor.