Method and system for vibration avoidance for automated machinery

• US 7,613,540 B2
• Filed: 05/04/2007
• Issued: 11/03/2009
• Est. Priority Date: 05/04/2007
• Status: Active Grant

• Current Assignee: Teknic, Inc.
• Original Assignee: Teknic, Inc.
• Inventors: Testa, Francis Joseph
• Primary Examiner(s): Hartman, Jr.; Ronald D
• Application Number:
  US11/744,425
• Publication Number:
  US 20080275574A1
• Time in Patent Office: 914 Days
• Field of Search: 735/70, 318/570, 318/573, 700/186, 700/187, 700/188, 700/189, 700/280
• US Class Current: 700/187
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/41117 Cancel vibration during positioning of slide
• CPC Class Codes: G05B 2219/49054 Active damping of tool vibration

Abstract

A method for vibration avoidance in automated machinery produces actuator space-time contours that meet design objectives of the machinery while suppressing energy content at frequencies in the space-time contour, by concatenating multiple space-time contour segments together in such a way as to be mostly free of energy at the frequencies of interest while meeting other specified design goals. The segments used to construct these frequency-optimized-contours are a series of concatenated polynomial segments, the independent variable t being time. These segments can define the variable to be controlled (e.g. speed or distance) versus time, or define one of the controlled variable'"'"'s time-derivatives (e.g., the slope of the speed vs. time, etc.). When these frequency-optimized-contours are fed as a command to a machine controller through an actuator or actuators, the energy at the frequencies of interest is low enough to avoid deleterious vibration from occurring while still meeting the machine performance objectives.

Claims

1. A method of producing a space-time contour to be followed by at least one actuator forcing at least one machine element, based upon a series of concatenated polynomial segments that are functions of time where their dependent variable is a time-derivative of at least the first order of a physical variable to be controlled, each polynomial segment comprising a duration and at least one coefficient;

the method comprising;

a) optimizing the durations and coefficients of the series of concatenated polynomial segments, such that the following constraints are met;

i) energy that would be introduced into at least one machine element by an actuator following a space-time contour created by time-integrating the series of concatenated polynomial segments, is suppressed for at least one frequency, and

ii) a space-time contour created by time-integrating the series of concatenated polynomial segments, is constrained within at least one limitation of the physical variable; and

b) time-integrating, at least once, the series of concatenated polynomial segments to form a space-time contour in the physical variable to be controlled;

c) commanding an actuator to follow the space-time contour.

2. The method of claim 1 in which the optimization step a further comprises the step of adding or subtracting segments from the series of concatenated polynomial segments.

3. The method of claim 1, wherein said constraints in step a further include:

iii) a space-time contour created by time-integrating the series of concatenated polynomial segments will be at one or more points in a controlled variable space at selected points in time.

4. The method of claim 1, wherein said constraints in step a) further include:

iv) the sum of durations of the concatenated segments of the series of concatenated polynomial segments is minimized.

5. The method of claim 1, wherein said constraints in step a) further include:

v) energy dissipated by the at least one actuator following a space-time contour created by time-integrating the series of concatenated polynomial segments is minimized.

6. The method of claim 1, wherein the optimizing step a) utilizes a search method.

7. The method of claim 6, wherein the search method comprises the steps of:

i) using at least one capability of the actuator as a constraint, forming a prototype set from at least one series of concatenated polynomial segments;

ii) calculating for each series of concatenated polynomial segments in the prototype set, the energy at a set of frequencies that would be introduced into at least one machine element by an actuator following a space-time contour created by time-integrating each series of concatenated polynomial segments;

iii) assigning a quality rating to each series of concatenated polynomial segments within the prototype set using the energy calculated in step b, the quality rating being related to the suppression of energy at the at least one frequency;

iv) perturbing at least one of the series of concatenated polynomial segments within the prototype set to produce a new prototype set; and

v) iteratively repeating steps ii, iii, and iv, until the best quality rating for the series of concatenated polynomial segments within the prototype set approaches a determined value, then

vi) selecting the series of concatenated polynomial segments within the prototype set with the best quality rating.

8. The method of claim 7, wherein the quality rating assigned in step iii is also related to the sum of durations of the concatenated segments of the series of concatenated polynomial segments.

9. The method of claim 7, wherein the quality rating assigned in step iii is also related to a capability of an actuator to follow the space-time contour.

10. The method of claim 7, wherein step ii uses a time-frequency transform process to calculate the energy at the set of frequencies.

11. The method of claim 7, wherein the quality rating assigned in step iii is also related to a total energy dissipated by an actuator when forcing a machine element to follow the space-time contour.

12. A method of producing a space-time contour to be followed by at least one actuator forcing at least one machine element, based upon a series of concatenated polynomial segments that are functions of time, in which a dependent variable of each segment is a physical variable to be controlled, and each polynomial segment comprises a duration and a coefficient, forming a space-time contour in the physical variable, the method comprising:

a) optimizing the durations and coefficients of the series of concatenated polynomial segments such that the following constraints are met;

i) the energy that would be introduced into at least one machine element by an actuator following the space-time contour is suppressed for at least one frequency, and

ii) the space-time contour is constrained within at least one limitation of the physical variable; and

c) commanding an actuator to follow the space-time contour.

13. The method of claim 12 in which the optimization step a further comprises the step of adding or subtracting segments from the series of concatenated polynomial segments.

14. The method of claim 12, wherein said constraints in step a further include:

iii) that the space-time contour will be at one or more points in a controlled variable space at selected points in time.

15. The method of claim 12, wherein said constraints in step a further include:

iv) the sum of durations of the concatenated segments of the series of concatenated polynomial segments is minimized.

16. The method of claim 12, wherein said constraints in step a further include:

v) energy dissipated by the at least one actuator following the space-time contour is minimized.

17. The method of claim 12, wherein the optimizing step a utilizes a search method.

18. The method of claim 17, wherein the search method comprises the steps of:

i) using at least one capability of the actuator as a constraint, forming a prototype set from at least one series of concatenated polynomial segments;

ii) calculating for each series of concatenated polynomial segments in the prototype set, the energy at a set of frequencies that would be introduced into at least one machine element by an actuator following each space-time contour of concatenated polynomial segments;

iii) assigning a quality rating to each series of concatenated polynomial segments within the prototype set using the energy calculated in step ii, the quality rating being related to the suppression of energy at the at least one frequency;

iv) perturbing at least one of the series of concatenated polynomial segments within the prototype set to produce a new prototype set; and

v) iteratively repeating steps ii, iii, and iv, until the quality rating approaches a determined value, then

vi) selecting the series of concatenated polynomial segments within the prototype set with the best quality rating.

19. The method of claim 18, wherein the quality rating assigned in step iii is also related to the sum of durations of the concatenated segments of the series of concatenated polynomial segments.

20. The method of claim 18, wherein the quality rating assigned in step iii is also related to a capability of an actuator to follow the space-time contour.

21. The method of claim 18, wherein step ii uses a time-frequency transform process to calculate the energy at the set of frequencies.

22. The method of claim 18, wherein the quality rating assigned in step iii is also related to a total energy dissipated by an actuator when forcing a machine element to follow the space-time contour.