Automated weld torch guidance control system

• US 4,567,348 A
• Filed: 12/27/1984
• Issued: 01/28/1986
• Est. Priority Date: 01/25/1983
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Wall, William A., Smith, Hubert E., Burns, Morrison R. Jr.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US06/685,607
• Time in Patent Office: 397 Days
• Field of Search: 901/42, 901/47, 219/124.34, 219/124.22, 318/577, 358/101
• US Class Current: 219/124.34
• CPC Class Codes: B23K 9/1274 Using non-contact, optical means, e.g. laser means
• CPC Class Codes: B23Q 35/127 using non-mechanical sensing

Abstract

A device for automatically controlling the movement of a welding torch (10) while welding an elongated joint (18). A charge injection television camera (30) is carried on a movable support (20) and includes a matrix of individual light sensing video elements (pixels, 32) which generate voltages responsive to light reflected off of the joint (18) and surrounding areas of the workpiece (12). The voltages produced by the pixels (32) are converted to digital words which are fed to a microprocessor (54) for generating an error signal. This error signal is fed to a digital motor (26) which is used to drive a movable support (20) upon which the television camera (30) is carried.

Claims

1. Apparatus for positioning a member relative to a surface location which reflects less light than adjacent surface areas comprising:

a movable member;

an actuating means for moving said member in a desired direction relative to said surface location;

a camera means adapted to view a selected area including said surface location and portions of said adjacent surface areas;

said camera means having light sensing video elements arranged in a two-dimensional matrix of rows and columns which are adapted to generate individual voltages according to the intensity of light incident on said light sensing video elements so that said surface location is represented as a dark location appearing darker in said viewed surface location than said portions of adjacent surface areas;

a predetermined reference including a single prescribed row of said video elements and a single one of said video elements arranged in said single row and selected as a reference point for determining the position of said dark location;

converting means for changing the individual voltages of said light sensing video elements into digital information;

a light means adapted to direct constant light toward said selected surface area viewed by said camera means for illuminating said selected area with an uninterrupted and continuous solid light pattern;

said video elements in said two-dimensional matrix generating voltage signals responsive to the light intensity received by said video elements;

said processor means receiving digital information of said two-dimensional matrix and calculating an average value representing a dark area, an average value representing a lighted area, and then producing a threshold level so that signals therebelow are considered dark signals and all signals thereabove are considered light signals;

processor means for receiving the digital information from said converting means and further calculating from digital information only from said single reference row and single reference point the location of said dark location within said selected surface area viewed by said camera means and comparing said location to said reference point, and generating therefrom a signal causing said actuating means to shift said movable member to a predetermined position relative to said surface location.

2. An apparatus as set forth in claim 1 further comprising:

a controller means for said camera means for controlling the sequencing of said light sensing video elements of said camera means;

a first memory means adapted to receive said digital information from said converting means and adapted to supply said digital information at a controlled rate to said processor means;

a control circuit means for said first memory means, said control circuit means including a counter circuit; and

said controller means for said camera means and said control circuit means for said first memory means selecting digital information from only said one prescribed row of said light sensing video elements to provide to said processor means.

3. An apparatus as set forth in claim 2 further comprising:

said processor means after completing its action on digital data from one row of said light sensing video elements provides a signal to said control circuit means to repeat the sequence upon a select control pulse of said controller means.

4. An apparatus as set forth in claim 2 further comprising:

said controller means providing a vertical sync pulse at a first field scan of said matrix of light sensing video elements, and a horizontal sync pulse on each horizontal scan of said matrix of light sensing video elements, said vertical sync pulse entering said control circuit means and setting said counter circuit and each said horizontal sync pulse entering the control circuit to be counted by said counter circuit,

said control circuit means at a predetermined number of horizontal sync pulses which is approximately at the center of said matrix of light sensing video elements causes the first memory means to receive digital data from said converting means, afterwhich the next horizontal sync pulse stops the input of digital data from said converting means.

5. Apparatus for positioning an implement along a seam which reflects less light than adjacent areas comprising:

a movable support means adapted to be positioned adjacent said seam;

an implement carried by said support means;

a camera means carried by said support means, said camera means having light sensing video elements arranged in a two-dimensional tracking matrix of rows and columns which provide tracking data and are adapted to generate individual voltages according to the intensity of light incident on said light sensing video elements so that said seam is represented darker than said adjacent areas and voltage output signals are generated accordingly;

light source means adapted to direct a constant light beam toward said seam and adjacent areas for illuminating said seam and adjacent areas with an uninterrupted and continuous solid light pattern;

said camera means adapted to be positioned to receive said light reflected from said adjacent areas and said seam;

converting means for changing the individual voltages of said light sensing video elements of said camera means into digital tracking information;

processor means for receiving said digital tracking information representing the light intensity levels incident upon said light sensing video elements in said two-dimensional matrix of said camera means and generating therefrom an average threshold value which determines light and dark voltage signals; and

said processor means also determining from digital tracking information from only a single prescribed row of said two-dimensional matrix the location of said seam, and for producing an error signal representative of the distance of said implement from its desired location relative to said seam,

actuating means for causing said support to move relative to said seam,

said actuating means being activated by said error signal of said processor means to move said movable support means so as to place said implement at its desired location relative to said seam.

6. An apparatus as set forth in claim 5 further comprising:

said light means carried by said support means and adapted to direct light on the area viewed by said camera means;

said camera means having a lens means for focusing the reflected light.

7. An apparatus as set forth in claim 6 further comprising:

a first memory means adapted to receive said digital information from said converting means and adapted to supply said digital information at a controlled rate to said processor means; and

a control circuit means for said first memory means, said control circuit means including a counter circuit.

8. An apparatus as set forth in claim 7 further comprising:

a controller means for said camera means for controlling the sequencing of said byte-sensing video elements of said camera means;

said controller means for said camera means and said control circuit means for said first memory means selecting only said one prescribed row of said light sensing video elements to provide digital information to said processor means.

9. An apparatus as set forth in claim 8 further comprising:

said processor means in determining the location of said seam calculates from the received digital information from said two-dimensional matrix an average value representing a dark area, an average value representing a lighted area, and then produces a threshold level so that signals therebelow are considered dark signals and all signals thereabove are considered light signals, and then calculates therefrom the location of both edges of the seam which is dark, and then calculates the center of the dark seam and produces said tracking error signal for said actuating means.

10. An apparatus as set forth in claim 9 further comprising:

said actuating means having a digital drive motor and said tracking error signal to said drive motor is digital and represents the number of pulses necessary to align said implement with said seam.

11. An apparatus as set forth in claim 10 further comprising:

said processor having values stored in its memory of previous error signals and threshold levels, and said processor compares these stored values with current values so as to provide a shut down operation signal when predetermined change values are exceeded.

12. An apparatus as set forth in claim 9 further comprising:

said processor means being a microprocessor;

said camera means being a charge injection device television camera;

said implement being a welding tool; and

said camera means and said implement adapted to be approximately aligned with said seam.

13. An apparatus for controlling the movement of a welding implement so that said welding implement is properly positioned relative to a joint of a work piece to be welded, comprising:

a movable support member adapted to be placed in a cross position of the joint to be welded;

a welding implement carried by said support member;

a camera means carried by said support member and adapter to track the joint to be welded;

said camera means having light sensing video elements arranged in a two-dimensional matrix of rows and columns which have a predetermined spaced position relative to one another to provide known tracking positions including a reference position, said reference position consisting of a single prescribed reference video element in a single prescribed row of said two-dimensional matrix, said video elements adapted to generate individual voltages according to the intensity of light incident on each of said light sensing video elements;

converting means for changing the individual voltages of said sensing video elements of said camera means into digital tracking information representing said tracking positions in said single prescribed row;

a light means carried by said support member, and adapted to direct a constant solid light onto an area about and including the joint of a work piece to be welded;

said joint is characterized by reflecting less light toward said camera means as compared with the surrounding area;

processor means for receiving said digital information representing the light intensity levels incident upon said light sensing video elements of said camera means and determining the positions of said light sensing video elements upon which said reflected light from said joint is incident upon and determining from said tracking information only from said prescribed row a deviation of said welding implement from said prescribed reference video element and the location of the joint to be welded, and for producing an error signal representative of the distance of said welding implement from its desired location relative to the joint to be welded;

actuating means for causing said support member to move in a cross direction to the joint to be welded;

said actuating means being activated by said error signal of said processor means so as to position said welding implement at a desired location relative to the joint to be welded.

14. An apparatus as defined by claim 13 further comprising:

said light sensing video elements being in a matrix of rows and columns;

a controller means for said camera means for controlling the sequencing of light sensing video elements of said camera means;

a first memory means adapted to receive said digital information from said converting means and supply at a later time said digital information to said processor means;

a control circuit means for said first memory means, said control circuit means including a counter circuit;

said controller means for said camera means and said control circuit means selecting only said one prescribed row of said light sensing video elements to provide digital information to said processor means.

15. An apparatus as defined by claim 13 further comprising:

said processor means adapted to calculate from the received digital information from said two-dimensional matrix an average value representing a low light reflected area, an average value representing a brighter lighted area, and produce a threshold level so that signals therebelow are considered dark signals, and all signals thereabove are considered light signals, and thereby calculates the location of both edges of the joint to be welded, and determines the error signal to be applied to said actuating means to place said welding implement at its desired location relative to the joint to be welded.

16. An apparatus as defined by claim 15 further comprising:

said camera means and said welding implement adapted be approximately aligned with the joint to be welded.