Implement positioning apparatus and process

• US 4,412,121 A
• Filed: 08/28/1981
• Issued: 10/25/1983
• Est. Priority Date: 08/28/1981
• Status: Expired due to Fees

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International
• Inventors: Kremers, Jan H., Bolles, Robert C.
• Primary Examiner(s): Shaw, C. C.
• Application Number:
  US06/297,514
• Time in Patent Office: 788 Days
• Field of Search: 219/124.34, 219/124.22, 219/130.01, 219/124.02, 219/130.21, 358/107, 358/139, 356/376, 318/569, 318/575, 318/577
• US Class Current: 219/124.34
• CPC Class Codes: B23K 37/04 for holding or positioning work
• CPC Class Codes: B23Q 35/127 using non-mechanical sensing
• CPC Class Codes: G01B 11/022 by means of tv-camera scanning
• CPC Class Codes: G01B 11/2522 the position of the object changing and being recorded

Abstract

An apparatus for controlling positioning of an implement relative to a workpiece, such as a welding head with respect to members to be welded, projects light patterns including an array of light elements each having a known shape and spacing relative to one another on the workpiece. The light elements as reflected from the workpiece are detected and output signals produced in response to the detected light elements. The output signals are classified into groups based on at least one common characteristic resulting from workpiece geometry. The workpiece geometry is defined from at least one relationship between different ones of the groups of the first output signals. Second output signals are produced indicative of the so-determined workpiece geometry. The second output signals are used to control positioning of the implement relative to the workpiece. This apparatus and process allows workpiece geometry to be defined and the implement to be positioned relative to the workpiece on a real-time basis.

Claims

1. A process for controlling positioning of an implement relative to a workpiece, which comprises:

projecting a light pattern including an array of light elements, each having a known shape and spacing relative to one another, on the workpiece,

sensing the array of light elements as reflected from the workpiece,

clustering the sensed light elements into groups based on at least one common characteristic resulting from workpiece geometry of the light elements as reflected,

defining a plurality of surfaces of the workpiece geometry by fitting a mathematical surface to at least some of the clustered groups of sensed light elements,

defining the workpiece geometry from at least some of the defined surfaces, and

controlling the positioning of the implement and the workpiece relative to one another based on the so-defined workpiece geometry.

2. The process of claim 1 in which the implement is a welding head.

3. The process of claim 2 in which at least two of the surfaces form a joint to be welded.

4. The process of claim 1 in which the sensed light elements are clustered into at least two groups, with each group containing light elements having a similar slope.

5. The process of claim 4 in which the light elements having a similar slope of each group are further clustered into sub-groups each having a similar distance from a predetermined point.

6. The process of claim 1 in which an edge of at least one of the mathematical surfaces is located by finding a step height discontinuity in the sensed light elements.

7. The process of claim 6 in which the implement is a welding head and the edge of the at least one of the mathematical surfaces is used to define a welding joint path for the welding head to follow with respect to the workpiece.

8. The process of claim 7 in which the welding joint is defined by fitting a curve to the edge of the at least one of the mathematical surfaces.

9. The process of claim 8 in which the curve is used as a baseline to measure welding joint width and the so-determined welding joint width is used to modify the welding joint path.

10. Apparatus for controlling positioning of an implement relative to a workpiece, which comprises:

means for projecting a light pattern including an array of light elements each having a known shape and spacing relative to one another on the workpiece,

means, spaced from said projecting means, for detecting the array of light elements as reflected from the workpiece and for producing first output signals in response to the detected light elements,

means for classifying the first output signals into groups based on at least one common characteristic resulting from workpiece geometry for the first output signals of each group,

means for defining workpiece geometry from at least one relationship between different ones of the groups of first output signals by defining a surface of the workpiece for each group of the first output signals, and for producing second output signals indicative of the so-determined workpiece geometry, and

means, responsive to the second output signals, for positioning the implement relative to the workpiece.

11. The apparatus of claim 10 in which the implement is a welding head.

12. The apparatus of claim 11 in which the at least one relationship between the first output signals of different ones of the groups of the first output signals are utilized to define an intersection between at least two surfaces of the workpiece.

13. The apparatus of claim 10 in which the light pattern projected by said means for projecting includes a plurality of lines including at least one line having a different spacing from an adjacent line than the spacing between any other lines in the array.

14. The apparatus of claim 13 in which any two adjacent lines of the array have a unique spacing between them.