Digital control servo system

• US 7,200,464 B2
• Filed: 09/21/2001
• Issued: 04/03/2007
• Est. Priority Date: 09/21/2000
• Status: Expired due to Fees

• Current Assignee: Novanta Corporation (Novanta Inc.)
• Original Assignee: GSI Group Corporation (Novanta Inc.)
• Inventors: Nussbaum, Michael B, Shannon, Michael R, Stewart, Fredrick A
• Primary Examiner(s): Chang; Jungwon
• Application Number:
  US09/957,788
• Publication Number:
  US 20020049513A1
• Time in Patent Office: 2,020 Days
• Field of Search: 359/213, 356/141.4, 399/81, 700/83, 700/186, 700/56, 318/600, 346/107.4
• US Class Current: 700/186
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03

Abstract

An improved servo system for galvanometers, scanners and similar devices which uses digital processing to increase the dynamic range and provide greater effective resolution. The system provides digital control of a reference point that directly influences the excitation, which in turn directly influences the gain of the circuit. A high and low resolution switching path is provided to optimize dynamic range. Wide angle torque compensation improves uniformity of response at large angular deflections from zero. Improved thermal protection allows safe operation near system thermal limits. A graphical user interface allows adjustments and changes response on the fly for tuning due to input conditions or user control.

Claims

1. A galvanometer optical scanning system comprising:

a galvanometer scanner adapted for directing an energy beam to at least one location within a field of view;

a digital controlled servo system adapted for controlling motion of the galvanometer scanner in accordance with a servo command waveform said command waveform including at least a first portion and a second portion; and

a digital processor for providing a first set of closed-loop control parameters for use during the first portion of said command waveform in conformance with which said first portion of said command waveform will be employed to control motion of the galvanometer, and for providing a second set of closed-loop control parameters for use during the second portion of said command waveform in conformance with which said second portion of said command waveform will be employed to control motion of the galvanometer.

2. The system of claim 1, wherein each set of closed-loop control parameters includes at least two of a proportional coefficient, an integral coefficient, a derivative coefficient, a system gain, an offset coefficient, and a bandwidth filter.

3. The system of claim 1, wherein the first set of closed-loop control parameters includes a high bandpass filter, and the second set of closed-loop control parameters includes a low bandpass filter.

4. The system of claim 1, further comprising a graphical user interface, which is operatively coupled with the digital processor, and is adapted to allow a user to provide input for the first and second sets of closed-loop control parameters.

5. The system of claim 4, wherein the graphical user interface is adapted to permit simulated analog control inputs in real-time for one or more servo system closed-loop control parameters.

6. The system of claim 4, wherein the graphical user interface is adapted to permit real-time tuning of the digital controlled servo system.

7. The system of claim 4, wherein the graphical user interface is adapted to display at least one of servo system closed-loop control parameter values and states.

8. The system of claim 4, wherein the graphical user interface runs on a computer that is adapted to interface with the digital processor, and provides a set-up tool for programming servo system operation.

9. The system of claim 4, wherein the graphical user interface includes one or more sliders that control servo system closed-loop control parameters.

10. The system of claim 9, wherein the servo system closed-loop control parameters include at least one of command feedforward, position proportional, error proportional, integrated error, velocity damping, filter damping, field of view, amplifier offset, and amplifier gain.

11. The system of claim 4, wherein the graphical user interface includes a filter tuner that allows a user to visually design a filter in the frequency domain.

12. The system of claim 4, wherein the graphical user interface includes one or more boxes that can be checked to enable servo system features.

13. The system of claim 12, wherein the servo system features include at least one of a notch filter, notch filter model, wide angle compensation, and zoom.

14. The system of claim 4, wherein the graphical user interface allows a user to select at least one of a second and third order servo algorithm.

15. The system of claim 4, wherein the graphical user interface includes an expert configuration having options for a second order tune algorithm.

16. The system of claim 4, wherein the graphical user interface includes a restricted configuration where certain options have been at least one of modified, dimmed, and eliminated for simplicity.

17. The system of claim 4, wherein the graphical user interface enables a user to program executable sets of closed-loop control parameters that are available for automated sequencing during subsequent operations.

18. The system of claim 1, wherein each set of closed-loop control parameters is associated with at least a portion of a forward scan.

19. The system of claim 1, wherein the digital processor is adapted to switch from one set of closed-loop control parameters to another set of closed-loop control parameters in real-time in response to at least one of internal states and external commands.

20. The system of claim 1, wherein the first set of closed-loop control parameters is for a first bandwidth application and the second set of closed-loop control parameters is for a second bandwidth application.

21. The system of claim 20, wherein the first bandwidth application is for a first scan period and the second bandwidth application is for a second scan period, the second bandwidth application having a bandwidth less than the first bandwidth application, and for free scan control relative to the first bandwidth application.

22. The system of claim 1, wherein the scanning system is employed in a laser marking application, and the first set of closed-loop control parameters is used for marking and the second set of closed-loop control parameters is used for jumps between marks.

23. The system of claim 1, wherein the scanning system is employed in a laser marking application, and the first set of closed-loop control parameters is used for marking outlines and the second set of closed-loop control parameters is used for filling outlines.

24. The system of claim 1, wherein the scanning system is employed in a laser marking application, and the first set of closed-loop control parameters is used for marking outlines, the second set of closed-loop control parameters is used for jumps between outlines, and a third set of closed-loop control parameters is used for filling outlines.

25. The system of claim 1, wherein the digital processor is embedded in the digital controlled servo system.

26. A method for laser marking using an optical scanning system including a servo controller, the method comprising the steps of:

providing a first bandwidth closed-loop control parameter for use during a first scan period of a marking application; and

providing a second bandwidth closed-loop control parameter for use during a second scan period of the marking application;

wherein each bandwidth closed-loop control parameter includes servo closed-loop control parameters that can be adjusted using a graphical user interface, and the servo operates in accordance with a servo command waveform and execution of the servo command waveform in accordance with the first closed-loop control parameter during the first scan period and in accordance with the second closed-loop control parameter during the second scan period.

27. The method of claim 26, wherein each bandwidth closed-loop control parameter is associated with at least a portion of a forward scan.

28. The method of claim 26, wherein switching from the first bandwidth set of closed-loop control parameters to the second bandwidth set of closed-loop control parameters is carried out in real-time in response to at least one of internal states and external commands.

29. The method of claim 26, wherein the second bandwidth closed-loop control parameter has a bandwidth less than the first bandwidth closed-loop control parameter, thereby providing fine scan control relative to the first bandwidth closed-loop control parameter.

30. The method of claim 26, wherein the first bandwidth closed-loop control parameter is used for marking and the second bandwidth closed-loop control parameter is used for jumping between marks.

31. The method of claim 26, wherein the first bandwidth closed-loop control parameter is used for marking outlines and the second bandwidth closed-loop control parameter is used for filling outlines.

32. The method of claim 26, further comprising:

commanding a third bandwidth closed-loop control parameter during a third scan period of the making application;

wherein the first bandwidth closed-loop control parameter is used for marking outlines, the second bandwidth closed-loop control parameter is used for jumps between outlines, and the third bandwidth closed-loop control parameter is used for filling outlines.

33. The method of claim 26, further comprising simulating analog control inputs in real-time for one or more servo closed-loop control parameters using a graphical user interface.

34. The method of claim 26, further comprising real-time tuning the scanning system using a graphical user interface.

35. The method of claim 26, further comprising displaying at least one of servo closed-loop control parameter values and states using a graphical user interface.

36. The method of claim 26, further comprising programming servo operation using a graphical user interface as a set-up tool.

37. The method of claim 26, further comprising visually designing a servo notch filter in the frequency domain using a graphical user interface.

38. The method of claim 26, further comprising programming executable sets of closed-loop control parameters based on user input.

39. The method of claim 26, further comprising automatically sequencing available sets of closed-loop control parameters during subsequent operations.

40. A laser marking system comprising:

a galvanometer optical scanning subsystem including a digital controlled servo adapted for controlling a galvanometer scanner; and

a means for defining a first bandwidth closed-loop control parameter for use during a first scan period of a marking application and for defining a second bandwidth closed-loop control parameter for use during a second scan period of the marking application;

wherein each of said first and second bandwidth closed-loop control parameters can be adjusted using a graphical user interface, and the servo operates in accordance with a servo command waveform and the first bandwidth closed-loop control parameter during the first scan period and operates in accordance with the servo command waveform and the second bandwidth closed-loop control parameter during the second scan period.

41. The system of claim 40, wherein the means for defining the first bandwidth closed-loop control parameter and the second bandwidth closed-loop control parameter are implemented with a digital processor and computer code.

42. The system of claim 41, wherein the graphical user interface is operatively coupled with the digital processor, and is adapted to allow a user to provide input for the closed-loop control parameters.

43. The system of claim 40, further comprising a means for automatically switching from the first bandwidth closed-loop control parameter to the second bandwidth closed-loop control parameter in real-time in response to at least one of internal states and external commands.

44. The system of claim 40, wherein the first bandwidth closed-loop control parameter is used for marking and the second bandwidth closed-loop control parameter is used for jumping between marks.

45. The system of claim 40 wherein the first bandwidth closed-loop control parameter is used for marking outlines and the second bandwidth closed-loop control parameter is used for filling outlines.

46. The system of claim 40, wherein the means for defining the first bandwidth closed-loop control parameter and the second bandwidth closed-loop control parameter are configured to allow real-time tuning of the laser marking system.

47. The system of claim 40, wherein the servo command waveform causes the galvanometer optical scanning subsystem to direct a laser beam to mark an article in accordance with the marking application.

48. The system of claim 40, further comprising a means for carrying out the marking application.

49. The system of claim 48, wherein the means for carrying out the marking application includes a processor and computer code defining the marking application as applied to an article, the marking application including at least one of marking outlines, filling outlines, and jumping between marks.