Optical grid analyzer system for automatically determining strain in deformed sheet metal
First Claim
1. A system for automatically determining strain in sheet metal by a forming operation, the sheet metal having a grid of open circles thereon, the open circles having a predetermined circle size parameter prior to the forming operation and wherein the open circles are stretched into patterns of generally elliptical shape as a result of the forming operation, the system comprising:
- means for producing signals representative of light intensity of pixels of an image of a portion of the sheet metal in which including one of the patterns;
means for converting each of the signals to a binary value representative of whether the light intensity exceeds a threshold to produce a binary image;
means for producing transition point data representing coordinates of pixels of the binary image which are located on an image edge;
means for deriving an outer edge of the pattern from the transition point data;
means for deriving an inner edge of the pattern from the transition point data;
means for deriving first ellipse parameters of the outer edge;
means for deriving second ellipse parameters of the inner edge;
means for deriving average ellipse parameters of the pattern based upon the first and second ellipse parameter; and
means for calculating strain values based upon the ellipse parameters and the predetermined circle size parameter of the undeformed circle.
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Accused Products
Abstract
An optical grid analyzer automatically determines strain in sheet metal during or following a forming operation by measuring the change in radius of open circles which are stretched into ellipse patterns as a result of the forming operation. The system includes a hand-held video camera unit which produces an analog video image of one of the ellipse patterns. An interface device converts the analog image to a binary image, and then converts the binary image to a transition point image which represents the coordinates of those pixels located at an edge of the pattern. A digital computer sorts the transition point data into inner and outer edges of the pattern. The digital computer then derives major and minor radii for the outer edge and for the inner edge, and averages the inner and outer edge radii to produce average major and minor radii representing the center of the pattern. The computer then calculates strain values based upon the average major and minor radii and the radius of the undeformed circle.
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Citations
22 Claims
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1. A system for automatically determining strain in sheet metal by a forming operation, the sheet metal having a grid of open circles thereon, the open circles having a predetermined circle size parameter prior to the forming operation and wherein the open circles are stretched into patterns of generally elliptical shape as a result of the forming operation, the system comprising:
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means for producing signals representative of light intensity of pixels of an image of a portion of the sheet metal in which including one of the patterns; means for converting each of the signals to a binary value representative of whether the light intensity exceeds a threshold to produce a binary image; means for producing transition point data representing coordinates of pixels of the binary image which are located on an image edge; means for deriving an outer edge of the pattern from the transition point data; means for deriving an inner edge of the pattern from the transition point data; means for deriving first ellipse parameters of the outer edge; means for deriving second ellipse parameters of the inner edge; means for deriving average ellipse parameters of the pattern based upon the first and second ellipse parameter; and means for calculating strain values based upon the ellipse parameters and the predetermined circle size parameter of the undeformed circle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system for automatically determining strain in a sheet metal resulting from a forming operation, the sheet metal having a grid of open circles thereon, each of the circles having a predetermined circle size parameter prior to the forming operation, which opens circles are stretched into patterns of generally elliptical shape as a result of the forming operation, the system comprising:
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video camera means for producing a gray scale video image of a portion of the sheet metal which includes one of the patterns; threshold means for converting the gray scale video image to a binary image by comparing each pixel of the gray scale video image to a threshold; edge location means for converting the binary image to a transition point image which represents coordinates of pixels of the binary image which are located on an image edge; and digital computer means for separating the transition point image into data representative of an outer edge of the pattern and data representative of an inner edge of the pattern;
for fitting the outer edge to a first ellipse and the inner edge to a second ellipse;
for deriving first and second ellipse parameters from the first and second ellipses;
for deriving average ellipse parameters of the pattern from the first and second ellipse parameters; and
for calculating strain values based upon the average ellipse parameters and the predetermined circle size parameter. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of automatically determining strain in sheet metal resulting from a forming operation, the sheet metal having a grid of open circles thereon, each of the circles having a predetermined circle size parameter prior to the forming operation, which open circles are stretched in patterns of generally elliptical shape as a result of the forming operation, the method comprising:
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producing a gray scale video image of a portion of the sheet metal which includes one of the patterns; converting the gray scale video image to a binary image; converting the binary image to a transition point image which represents coordinates of pixels of the binary image which are located on an image edge; separating the transition point image into data representative of an outer edge of the pattern and data representative of an inner edge of the pattern; fitting the outer edge to a first ellipse; fitting the inner edge to a second ellipse; deriving first ellipse parameters from the first ellipse; deriving second ellipse parameters from the second ellipse; deriving average ellipse parameters of the pattern from the first and second ellipse parameters; calculating strain values based upon the average ellipse parameters and the predetermined circle size parameter.
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Specification