Sensorless lost/found rotor detection for permanent magnet motors
View Patent ↗Various methods of detecting a found rotor, a lost rotor, a locked rotor and a caught rotor after a power disruption using flux estimates are disclosed. Also disclosed are permanent magnet motor controllers and assemblies suitable for performing one or more of these methods.
1. A method of controlling a permanent magnet motor, the method comprising:
estimating flux of the motor;
determining whether the estimated flux has substantially converged toward an actual flux of the motor including estimating a value of another motor operating parameter in a reference frame using the estimated flux, and comparing the estimate of said motor operating parameter with a measured value of said motor operating parameter in said reference frame including producing an error signal from the estimated and measured values of said motor operating parameter and processing the error signal to determine whether the estimated flux has substantially converged toward the actual flux; and
in response to determining the estimated flux has substantially converged toward the actual flux, using the estimated flux to control the motor.
2. The method of claim 1 wherein said motor operating parameter is current flow.
3. The method of claim 1 wherein estimating includes using the error signal to improve a next estimate of the motor flux.
4. The method of claim 1 wherein processing includes producing statistical information for the error signal.
5. The method of claim 4 wherein the statistical information includes mean, variance and/or standard deviation.
6. The method of claim 4 wherein processing includes processing the error signal with a digital filter to produce the statistical information.
7. The method of claim 6 wherein processing includes incrementing and/or decrementing a counter according to an output of the digital filter.
8. The method of claim 7 wherein the output of the digital filter is a recursive rolling mean for the error signal.
9. The method of claim 7 wherein processing includes incrementing and/or decrementing the counter according to a set of counter rules and the output of the digital filter.
10. The method of claim 9 wherein the counter rules depend on the operating state of the motor.
11. The method of claim 1 wherein flux includes magnet flux and flux linkage terms.
12. The method of claim 1 wherein estimating includes estimating the flux value using an observer.
13. The method of claim 1 wherein the motor does not include a rotor position sensor.
14. The method of claim 1 wherein using includes estimating a value of another motor operating parameter using the estimated flux, and using the estimated value of said motor operating parameter to control the motor.
15. The method of claim 14 wherein said motor operating parameter is electrical angle or speed.
16. The method of claim 1 wherein using includes using the estimated flux to control motor current or motor flux.
17. The method of claim 1 wherein estimating includes estimating the flux using measured or demanded phase currents and/or phase voltages of the motor.
18. The method of claim 1 further comprising transitioning from a first control mode to a second control mode in response to determining the estimated flux has substantially converged toward the actual flux.
19. The method of claim 18 wherein the first control mode is an open loop control mode and the second control mode is a closed loop control mode.
20. The method of claim 19 wherein the closed loop control mode is a closed loop sensorless control mode.
21. The method of claim 1 wherein determining includes determining whether the estimated flux has substantially converged toward the actual flux during start-up of the motor.
22. The method of claim 21 wherein using includes using the estimated flux to control the motor immediately after determining the estimated flux has substantially converged toward the actual flux.
23. A controller for a permanent magnet motor, the controller configured to perform the method of claim 1 .
24. An assembly comprising a permanent magnet motor and the controller of claim 23 .
25. A method of controlling a permanent magnet motor, the method comprising:
estimating flux of the motor;
determining whether the estimated flux has substantially converged toward an actual flux of the motor;
in response to determining the estimated flux has substantially converged toward the actual flux, transitioning from a first control mode to a second control mode and using the estimated flux to control the motor.
26. The method of claim 25 wherein determining includes estimating a value of another motor operating parameter in a reference frame using the estimated flux, and comparing the estimate of said motor operating parameter with a measured value of said motor operating parameter in said reference frame.
27. The method of claim 25 wherein the first control mode is an open loop control mode and the second control mode is a closed loop control mode.
28. The method of claim 27 wherein the closed loop control mode is a closed loop sensorless control mode.
29. The method of claim 25 wherein the first control mode is one of a speed control mode and a torque control mode and wherein the second control mode is the other of said one of a speed control mode and a torque control mode.