Method and apparatus for motor lock or stall detection

Patent metadata

Field	Value
Publication number	US-10075107-B2
Application number	US-201514930904-A
Country	US
Kind code	B2
Filing date	Nov 3, 2015
Priority date	Nov 3, 2015
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A method and apparatus are provided for detecting a rotor lock condition in a sensorless permanent magnet synchronous motor. A BEMF observer determines an estimated rotor speed {circumflex over (ω)} and a first BEMF voltage value in an estimated rotor-related γ,δ reference frame. In addition, a second estimated BEMF voltage value is calculated in a rotor-related d,q reference frame based on at least a first motor constant and an estimated rotor speed {circumflex over (ω)}. After generating a BEMF error filter value from the first and second estimated BEMF voltage values and calculating a BEMF error threshold value as a function of the estimated rotor speed {circumflex over (ω)} that is subject to a minimum threshold BEMF value, a rotor lock condition is detected based on at least the BEMF error filter value and the BEMF error threshold value.

First claim

What is claimed is:

1. A method for detecting a rotor lock condition in a sensorless permanent magnet synchronous motor, comprising:
determining a first estimated back electromotive force (BEMF) voltage value in an estimated rotor-related reference frame using a Luenberger-based BEMF observer;
calculating a second estimated BEMF voltage value in a rotor-related reference frame based on at least a first motor constant and an estimated rotor speed {circumflex over (ω)};
generating a BEMF error filter value from the first and second estimated BEMF voltage values;
generating a BEMF error threshold value by calculating a product of a BEMF threshold coefficient (C BEMFThresholdCoef ) and an absolute value of the estimated rotor speed {circumflex over (ω)}, subject to the minimum threshold BEMF value;
detecting a rotor lock condition in the sensorless permanent magnet synchronous motor based on at least the BEMF error filter value and the BEMF error threshold value; and
discontinuing application of power to the sensorless permanent magnet synchronous motor upon detecting the rotor lock condition.

2. The method of claim 1 , where determining the first estimated BEMF voltage value comprises computing a first estimated BEMF voltage value ê δ as a δ coordinate in virtual rotating reference frame (γ,δ).

3. The method of claim 1 , where calculating the second estimated BEMF voltage value comprises calculating a second estimated BEMF voltage value ê q =+c BemfCoef ·{circumflex over (ω)}+c BemfOffset ·sgn({circumflex over (ω)}) as a q coordinate in rotating reference frame (d,q), where c BemfCoef is a first BEMF coefficient term defined from a measurement on the motor, where C BemfOffset is a second BEMF offset coefficient defined from a measurement on the motor, and where the sgn({circumflex over (ω)}) term represents a sign function having a first output if {circumflex over (ω)}>0 and having a second output if {circumflex over (ω)}<0.

4. The method of claim 1 , where generating the BEMF error filter value comprises filtering an absolute value of a difference between the first and second estimated BEMF voltage values.

5. The method of claim 4 , where detecting the rotor lock condition comprises determining if an absolute value of the BEMF error filter value exceeds the BEMF error threshold value.

6. The method of claim 1 , where generating the BEMF error filter value comprises filtering a difference between the first and second estimated BEMF voltage values.

7. The method of claim 6 , where detecting the rotor lock condition comprises determining if an absolute value of the BEMF error filter value exceeds the BEMF error threshold value.

8. The method of claim 1 , where generating the BEMF error filter value comprises filtering a squared difference between the first and second estimated BEMF voltage values.

9. The method of claim 8 , where detecting the rotor lock condition comprises squaring the BEMF error threshold value to generate a squared BEMF error threshold value and determining if the BEMF error filter value exceeds the squared BEMF error threshold value.

10. The method of claim 1 , where generating the BEMF error filter value comprises filtering a difference between the first and second estimated BEMF voltage values which is normalized by multiplying by a nonlinear scaling function before filtering.

11. The method of claim 10 , where detecting the rotor lock condition comprises determining if an absolute value of the BEMF error filter value exceeds the BEMF error threshold value.

12. The method of claim 1 , where generating the BEMF error filter value comprises filtering a squared difference between the first and second estimated BEMF voltage values which is normalized by multiplying by a nonlinear scaling function before power by two calculation.

13. The method of claim 12 , where detecting the rotor lock condition comprises squaring the BEMF error threshold value to generate a squared BEMF error threshold value and determining if the BEMF error filter value exceeds the squared BEMF error threshold value.

14. The method of claim 1 , where detecting the rotor lock condition comprises detecting if an absolute value of the estimated rotor speed value {circumflex over (ω)} falls below a minimum stall speed (ω StallMin ).

15. An electric motor controller comprising:
a Luenberger-based back electromotive force (BEMF) observer for determining a first estimated BEMF voltage value in an estimated rotor-related reference frame and for determining an estimated rotor speed {circumflex over (ω)};
a processor coupled to the Luenberger-based BEMF EMF observer to calculate:
a second estimated BEMF voltage value in a rotor-related reference frame based on at least a first motor constant and the estimated rotor speed {circumflex over (ω)},
a BEMF error filter value based on a difference between the first and second estimated BEMF voltage values, and
a BEMF error threshold value {circumflex over (ω)} by calculating a product of a BEMF threshold coefficient (C BEMFThresholdCoef ) and an absolute value of the estimated rotor speed {circumflex over (ω)}, subject to the minimum threshold BEMF value; and
an electric motor driver circuit coupled to the processor for providing drive signals for controlling delivery of power to an electric motor;
where the processor is configured to detect if a rotor lock condition exists at the electric motor based on at least the BEMF error filter value and the BEMF error threshold value; and
wherein the processor is configured to cause the electric motor driver circuit to discontinue application of power to the electric motor upon detecting a rotor lock condition.

16. The electric motor controller of claim 15 , wherein the Luenberger-based BEMF observer is configured to generate the first estimated BEMF voltage value by computing a first estimated BEMF voltage value ê δ as a δ coordinate in virtual rotating reference frame (γ,δ).

17. The electric motor controller of claim 15 , wherein the processor is configured to calculate the second estimated BEMF voltage value by calculating a second estimated BEMF voltage value ê q =+c BemfCoef ·{circumflex over (ω)}+c BemfOffset ·sgn({circumflex over (ω)}) as a q coordinate in rotating reference frame (d, q), where c BemfCoef is a first BEMF coefficient term defined from a measurement on the motor, where C BemfOffset is a second BEMF offset coefficient defined from a measurement on the motor, and where the sgn({circumflex over (ω)}) term represents a sign function based on whether the {circumflex over (ω)} is positive or negative.

18. The electric motor controller of claim 15 , wherein the processor is configured to calculate the BEMF error filter value by filtering an absolute value of a difference between the first and second estimated BEMF voltage values.

19. The electric motor controller of claim 15 , wherein the processor is configured to calculate the BEMF error filter value by filtering a difference between the first and second estimated BEMF voltage values.

20. The electric motor controller of claim 15 , wherein the processor is configured to calculate the BEMF error filter value by filtering a squared difference between the first and second estimated BEMF voltage values.

21. A system for detecting locked rotor in a sensorless permanent magnet synchronous motor, comprising:
a Luenberger-based back electromotive force (BEMF) device for producing an estimated rotor speed {circumflex over (ω)} and a first estimated BEMF voltage value ê δ

Assignees

• Freescale Semiconductor Inc
• Nxp Usa Inc

Inventors

• Lepka Jaroslav
• Prokop Libor

Classifications

• H02P29/0241

  the fault being an overvoltage · CPC title

• H02P29/024

  Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load · CPC title

• H02P6/12 Primary

  Monitoring commutation; Providing indication of commutation failure · CPC title

• H02P6/18

  without separate position detecting elements · CPC title

• H02P29/021

  Electricity · mapped topic