Method for tuning a motor drive using frequency response

Patent metadata

Field	Value
Publication number	US-10033319-B2
Application number	US-201514842495-A
Country	US
Kind code	B2
Filing date	Sep 1, 2015
Priority date	Sep 1, 2015
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

An improved system for tuning a motor controller is disclosed. The controller gains are initially set based on the measured frequency response for the controlled system. A desired level of performance is defined by setting a desired phase margin and a desired gain margin to be observed in the frequency response. An improved method of determining the frequency response provides for a reduced computational intensity. The initial tuning routine uses the frequency response to set not only controller gains, but also settings for filters in the control module. Having obtained the desired level of performance from the initial tuning, the motor drive executes an adaptive tuning routine while controlling the motor. The adaptive tuning routine tracks changes in the operating performance and adjusts the filter settings or the controller gains to return operation to within the desired level of performance while the motor continues to operate.

First claim

We claim:

1. A method for tuning performance of a motor drive during operation of a motor operatively connected to the motor drive, wherein the motor controls motion of a mechanical load coupled to the motor, the method comprising the steps of:
measuring a first feedback signal generated by at least one current sensor, wherein the first feedback signal corresponds to a current present on one phase of the output of the motor drive;
measuring a second feedback signal generated by a position feedback device connected to the motor;
measuring a command signal provided to a control loop in the motor drive, wherein the command signal corresponds to a desired operation of the motor during operation of the motor;
storing a plurality of values of the command signal in a memory device of the motor drive;
generating a response signal with a control module in the motor drive corresponding to operation of the motor during operation of the motor, wherein: the control module includes the control loop and at least one notch filter, each notch filter includes a notch filter frequency, and the response signal is generated as a function of one of the first feedback signal and the second feedback signal;
storing a plurality of values of the response signal in the memory device of the motor drive;
generating a first frequency response within the motor drive as a function of the plurality of values of the response signal;
generating a second frequency response within the motor drive as a function of the plurality of values of the command signal;
identifying a resonant frequency in the first frequency response having a magnitude greater than the magnitude of the other frequencies in the first frequency response;
identifying a commanded frequency in the second frequency response having a magnitude greater than the magnitude of the other frequencies in the second frequency response;
comparing the resonant frequency to the commanded frequency;
comparing a magnitude of the resonant frequency against a first threshold when the resonant frequency does not match the commanded frequency; and
setting the notch filter frequency of the notch filter in the control loop equal to the resonant frequency when the magnitude of the resonant frequency is greater than the first threshold to attenuate the magnitude of the identified resonant frequency.

2. The method of claim 1 wherein:
each of the first and the second frequency responses is determined for a predefined array of frequencies,
the step of generating the first frequency response further comprises the steps of:
reading the predefined array of frequencies from the memory device in the motor drive; and
determining a magnitude and a phase for each frequency in the predefined array of frequencies as a function of the plurality of values of the response signal; and

the step of generating the second frequency response further comprises the steps of:
reading the predefined array of frequencies from the memory device in the motor drive; and

determining a magnitude and a phase for each frequency in the predefined array of frequencies as a function of the plurality of values of the command signal.

3. The method of claim 1 further comprising the steps of:
determining one of a plurality of frequency ranges in which the resonant frequency exists when the resonant frequency does not match the commanded frequency, wherein the notch filter frequency is set equal to the resonant frequency when the resonant frequency is in a first frequency range; and
setting a low pass filter frequency of a low pass filter in the control module equal to or less than the resonant frequency to attenuate the magnitude of the resonant frequency when the resonant frequency is in a second frequency range and the second frequency range is greater than the first frequency range.

4. The method of claim 3 , further comprising the step of adjusting at least one gain in the at least one control loop for the control module of the motor drive when the resonant frequency is in a third frequency range and the third frequency range is less than the first frequency range.

5. The method of claim 4 wherein the step of adjusting at least one gain further comprises the steps of:
comparing the magnitude of the resonant frequency to an upper limit;
adjusting the at least one gain to reduce the magnitude of the resonant frequency when the magnitude of the resonant frequency is greater than the upper limit;
comparing the magnitude of the resonant frequency to a lower limit; and
adjusting the at least one gain to increase the magnitude of the resonant frequency when the magnitude of the resonant frequency is less than the lower limit.

6. A method for tuning performance of a motor drive, wherein the motor drive controls operation of a motor and wherein operation of the motor controls motion of a mechanical load coupled to the motor, the method comprising the steps of:
measuring a first feedback signal generated by at least one current sensor, wherein the first feedback signal corresponds to a current present on one phase of the output of the motor drive;
measuring a second feedback signal generated by a position feedback device connected to the motor;
providing a command signal to a control loop in the motor drive corresponding to a desired operation of the mechanical load;
generating a response signal with a control module in the motor drive, wherein: the control module includes the control loon and at least one notch filter, each notch filter includes a notch filter frequency, and the response signal is generated as a function of one of the first feedback signal and the second feedback signal;
storing a plurality of values of the response signal in a memory device of the motor drive;
generating a first frequency response within the motor drive as a function of the plurality of values of the response signal, wherein the first frequency response is determined for a predefined array of frequencies;
identifying a resonant frequency from the first frequency response;
comparing a magnitude of the resonant frequency to a first threshold;
when the magnitude of the resonant frequency is greater than the predefined threshold, determining one of a plurality of frequency ranges in which the resonant frequency exists;
adjusting a gain for the control loop to reduce the magnitude of the resonant frequency when the identified resonant frequency is in a first frequency range, selected from the plurality of frequency ranges;
adjusting a low pass filter bandwidth of a low pass filter in the control module to reduce the magnitude of the resonant frequency when the identified resonant frequency is in a second frequency range, selected from the plurality of frequency ranges; and
adjusting the notch filter frequency of one of the at least one notch filters to reduce the magnitude of the resonant frequency when the identified resonant frequency is in a third frequency range, selected from the plurality of frequency ranges.

7. The method of claim 6 further comprising the steps of:
storing a plurality of values of the command signal in the memory device of the motor drive;
generating a second frequency response within the motor drive as a function of the plurality of values of the command signal, wherein the second frequency response sequence is determined for the predefined array of frequencies;
comparing the identified resonant frequency to the second frequency response; and
not performing each of the adjusting steps when the identified resonant frequency corresponds to a frequency in the second frequency response.

8. The method of claim 7 wherein the command signal is selected from one of an input to the control module and a feed forward signal determined from

Assignees

• Rockwell Automation Tech Inc

Inventors

• Da Silva Aderiano M
• Fast Brian
• Miklosovic Robert J
• Holt Michelle E

Classifications

• H02P23/14 Primary

  Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage · CPC title

• G05B13/02

  electric · CPC title

• H02P23/0004 Primary

  Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control · CPC title