Motor drive with velocity-second compensation

• US 7,109,670 B1
• Filed: 05/25/2005
• Issued: 09/19/2006
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Rehm, Thomas J.
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): HORN, ROBERT WAYNE
• Application Number:
  US11/138,534
• Time in Patent Office: 482 Days
• Field of Search: None
• US Class Current: 318/68
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/41148 Model, from position, speed, acceleration derive compensation
• CPC Class Codes: G05B 2219/43018 Compensation, correction of acceleration, deceleration time

Abstract

An apparatus for use with a signal generator and a motor controller includes a velocity compensator, an adjustor, and a velocity regulator. The signal generator provides a reference velocity signal, and the motor controller receives an output signal and uses the output signal to control a torque input signal applied to the motor. The velocity compensator is operable to receive the reference velocity signal, determine a derivative of the reference velocity signal, and generate a velocity compensation signal based on the derivative. The adjustor is operable to adjust the reference velocity signal as a function of the velocity compensation signal. The velocity regulator is operable to compare the adjusted reference velocity signal to a feedback velocity signal and generate the output signal received by the motor controller for adjusting the torque input signal based on the comparison.

Claims

1. An apparatus for use with a signal generator and a motor controller, where the signal generator provides a reference velocity signal, and the motor controller receives an output signal and uses the output signal to control a torque input signal applied to the motor, comprising:

a velocity compensator operable to receive the reference velocity signal, determine a derivative of the reference velocity signal, and generate a velocity compensation signal based on the derivative;

an adjustor operable to adjust the reference velocity signal as a function of the velocity compensation signal; and

a velocity regulator operable to compare the adjusted reference velocity signal to a feedback velocity signal and generate the output signal received by the motor controller for adjusting the torque input signal based on the comparison.

2. The apparatus of claim 1, further comprising a velocity filter coupled to receive a position feedback signal and operable to filter the position feedback signal over a predetermined number of samples to generate the feedback velocity signal, wherein the velocity compensation unit is operable to multiply the derivative by a velocity compensation gain factor generated based on the predetermined number of samples to generate the velocity compensation signal.

3. The apparatus of claim 2, wherein the velocity filter comprises a finite impulse response filter.

4. The apparatus of claim 3, wherein the finite impulse response filter has a transfer function comprising:

$G<br><br>\left(Z\right)=\frac{1-Z^{-N}}{T_v<br><br>N},$

where N equals a number of taps, T_v is a sample time of the velocity filter, and Z=exp(sT_v).

5. The apparatus of claim 2, wherein the velocity filter includes a velocity averaging stage and a velocity error stage.

6. The apparatus of claim 5, wherein the velocity averaging stage comprises a finite impulse response filter, and the velocity error stage further comprises an infinite impulse response filter.

7. The apparatus of claim 1, wherein the velocity regulator is operable based on a velocity sampling time, and the velocity compensation unit is operable to multiply the derivative by the velocity sampling time to generate the velocity compensation signal.

8. The apparatus of claim 7, further comprising a position regulator operable based on a position sampling time to compare a reference position signal to a feedback position signal to generate a position error signal, wherein the adjustor is further operable to adjust the reference velocity signal based on the velocity compensation signal and the position error signal, and the velocity compensation unit is operable to multiply the product of the derivative and the velocity sampling time by a velocity compensation gain factor generated based on the velocity sampling time and the position sampling time to generate the velocity compensation signal.

9. The apparatus of claim 8, further comprising a velocity filter coupled to receive a position feedback signal and operable to filter the position feedback signal over a predetermined number of samples to generate the feedback velocity signal, wherein the velocity compensation gain factor is generated based on the velocity sampling time, T_v, the position sampling time, T_x, and the predetermined number of samples, N, to generate the velocity compensation signal.

10. The apparatus of claim 9, wherein the velocity regulator operates at a velocity sampling time occurring after a corresponding position sampling time of the position regulator and the velocity compensation unit is operable to generate the velocity compensation gain factor using the equation:

$\mathrm{Vcomp\_gain}=1-\left[\frac{T_v}{T_x}·<br><br>\frac{\left(N+1\right)}{2}\right].$

11. The apparatus of claim 9, wherein the velocity regulator operates at a velocity sampling time occurring before a corresponding position sampling time of the position regulator and the velocity compensation unit is operable to generate the velocity compensation gain factor using the equation:

$\mathrm{Vcomp\_gain}=1-\left[\frac{T_v}{T_x}·<br><br>\frac{\left(N-1\right)}{2}\right].$

12. An electronic line shaft, comprising:

a signal source operable to generate a reference velocity signal;

a master drive unit operable to receive the reference velocity signal, comprising;

a motor;

a motor controller operable to provide a torque input signal to the motor;

a velocity compensator operable to receive the reference velocity signal, determine a derivative of the reference velocity signal, and generate a velocity compensation signal based on the derivative;

an adjustor operable to adjust the reference velocity signal as a function of the velocity compensation signal; and

a velocity regulator operable to compare the adjusted reference velocity signal to a feedback velocity signal and provide an output signal to the motor controller for adjusting the torque input signal based on the comparison.

13. The electronic line shaft of claim 12, further comprising a virtual encoder operable to receive the reference velocity signal and generate a reference position signal based thereon, wherein the master drive unit is operable to receive the reference position signal.

14. The electronic line shaft of claim 13, further comprising at least one slave drive unit operable to receive the reference velocity and reference position signals in a synchronous manner with respect to the master drive unit.

15. The electronic line shaft of claim 12, wherein the master drive unit further comprises a velocity filter coupled to receive a position feedback signal and operable to filter the position feedback signal over a predetermined number of samples to generate the feedback velocity signal, wherein the velocity compensation unit is operable to multiply the derivative by a velocity compensation gain factor generated based on the predetermined number of samples to generate the velocity compensation signal.

16. The electronic line shaft of claim 15, wherein the velocity filter comprises a finite impulse response filter.

17. The electronic line shaft of claim 16, wherein the finite impulse response filter has a transfer function comprising:

$G<br><br>\left(Z\right)=\frac{1-Z^{-N}}{T_v<br><br>N},$

where N equals a number of taps, T_v is a sample time of the velocity filter, and Z=exp(sT_v).

18. The electronic line shaft of claim 15, wherein the velocity filter includes a velocity averaging stage and a velocity error stage.

19. The electronic line shaft of claim 18, wherein the velocity averaging stage comprises a finite impulse response filter, and the velocity error stage further comprises an infinite impulse response filter.

20. The electronic line shaft of claim 12, wherein the velocity regulator is operable based on a velocity sampling time, and the velocity compensation unit is operable to multiply the derivative by the velocity sampling time to generate the velocity compensation signal.

21. The electronic line shaft of claim 20, further comprising a position regulator operable based on a position sampling time to compare a reference position signal to a feedback position signal to generate a position error signal, wherein the adjustor is further operable to adjust the reference velocity signal based on the velocity compensation signal and the position error signal, and the velocity compensation unit is operable to multiply the product of the derivative and the velocity sampling time by a velocity compensation gain factor generated based on the velocity sampling time and the position sampling time to generate the velocity compensation signal.

22. The electronic line shaft of claim 21, wherein the master drive unit further comprises a velocity filter coupled to receive a position feedback signal and operable to filter the position feedback signal over a predetermined number of samples to generate the feedback velocity signal, wherein the velocity compensation gain factor is generated based on the velocity sampling time, T_v, the position sampling time, T_x, and the predetermined number of samples, N, to generate the velocity compensation signal.

23. The electronic line shaft of claim 22, wherein the velocity regulator operates at a velocity sampling time occurring before a corresponding position sampling time of the position regulator and the velocity compensation unit is operable to generate the velocity compensation gain factor using the equation:

$\mathrm{Vcomp\_gain}=1-\left[\frac{T_v}{T_x}·<br><br>\frac{\left(N-1\right)}{2}\right].$

24. The electronic line shaft of claim 22, wherein the velocity regulator operates at a velocity sampling time occurring after a corresponding position sampling time of the position regulator and the velocity compensation unit is operable to generate the velocity compensation gain factor using the equation:

$\mathrm{Vcomp\_gain}=1-\left[\frac{T_v}{T_x}·<br><br>\frac{\left(N+1\right)}{2}\right].$

25. A method for controlling a motor, comprising:

providing a torque input signal to the motor;

generating a reference velocity signal;

generating a velocity compensation signal based on a derivative of the reference velocity signal;

adjusting the reference velocity signal based on the velocity compensation signal; and

comparing the adjusted reference velocity signal to a feedback velocity signal; and

adjusting the torque input signal based on the comparison.

26. A printing system including a plurality of printing stations for processing a web, comprising:

a signal source operable to generate a reference velocity signal; and

a plurality of drive units for moving the web through the printing stations in accordance with the reference velocity signal, each of the drive units comprising;

a motor;

a motor controller operable to provide a torque input signal to the motor;

a velocity compensator operable to receive the reference velocity signal, determine a derivative of the reference velocity signal, and generate a velocity compensation signal based on the derivative;

an adjustor operable to adjust the reference velocity signal as a function of the velocity compensation signal; and

a velocity regulator operable to compare the adjusted reference velocity signal to a feedback velocity signal and provide an output signal to the motor controller for adjusting the torque input signal based on the comparison.

27. The printing system of claim 26, wherein one of the plurality of drive units is designated as a master drive unit, and the remaining drive units are designated as slave drive units, further comprising a synchronization unit operable to receive the reference velocity signal and distribute the reference velocity signal to at least the slave drive units, the slave drive units being operable to process the reference velocity signal synchronously with respect to the master drive unit.