Welding control using fuzzy logic analysis of video imaged puddle dimensions
First Claim
1. A welder comprising a welding torch on a controlled robotic arm, imaging means in the torch, a wire feeder on the torch and a weld controller for controlling the position of the torch and electric current supplied by the torch, characterized in that:
- the weld controller comprises signal processing means for producing a first signal indicating a weld dimension in response to an output signal from the imaging means produced by the weld puddle;
for providing from a plurality of stored logic sets and in response to the first signal a second signal indicating a degree of membership in a first set calling for a first current change and a third signal indicating a degree of membership in a second set calling for a lesser change in current;
for providing a fourth signal that represents the product of the second signal and a first stored area value associated with said fist set;
for providing a fifth signal that represents the product of the third signal and a second stored area value associated with the second set;
for providing a sixth signal that represents the product of the second signal and a moment value for the first set;
for providing a seventh signal that represents the product of the third signal and a moment value for the second set; and
for providing an eighth signal that represents the value of the sixth signal divided by the seventh signal to initiate a change in the electric current.
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Accused Products
Abstract
A welding system includes an imaging system that takes frame by frame pictures of a weld puddle. The imaging system is located in the weld torch. From the images puddle length and width are determined. The length and width are applied against stored membership functions that cover a range of different weld current characteristics and the degree of membership of each dimension in those functions is determined, producing an alpha factor for each membership function. This provides a fuzzy current requirement. Stored values for moment and area for each membership function are multiplied by the alpha for the respective function. The total of the moments is divided by the total of the areas to produce a desired weld current. The weld head includes a weld wire feeder that is driven by a servo by which the wire can be feed along either side of the weld joint. The wire feeder is gear driven in such a way that it does not interfere with the optics in the weld torch. The optics include a strobe to illuminate the puddle. Signal processing includes a process for interpolating the puddle centerline from the range in puddle widths over successive strobed images of the puddle. The head is positioned automatically over the centerline.
14 Citations
18 Claims
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1. A welder comprising a welding torch on a controlled robotic arm, imaging means in the torch, a wire feeder on the torch and a weld controller for controlling the position of the torch and electric current supplied by the torch, characterized in that:
the weld controller comprises signal processing means for producing a first signal indicating a weld dimension in response to an output signal from the imaging means produced by the weld puddle;
for providing from a plurality of stored logic sets and in response to the first signal a second signal indicating a degree of membership in a first set calling for a first current change and a third signal indicating a degree of membership in a second set calling for a lesser change in current;
for providing a fourth signal that represents the product of the second signal and a first stored area value associated with said fist set;
for providing a fifth signal that represents the product of the third signal and a second stored area value associated with the second set;
for providing a sixth signal that represents the product of the second signal and a moment value for the first set;
for providing a seventh signal that represents the product of the third signal and a moment value for the second set; and
for providing an eighth signal that represents the value of the sixth signal divided by the seventh signal to initiate a change in the electric current.- View Dependent Claims (2, 3, 4, 5)
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6. A welder comprising a welding torch on a controlled robotic arm, imaging means in the torch, a wire feeder on the torch and a weld controller for controlling the position of the torch and electric current supplied by the torch, characterized in that:
the weld controller comprises signal processing means for producing a first signal indicating a weld puddle length and width in response to an output signal from the imaging means from the weld puddle, for providing from a plurality of stored logic sets and in response to the first signal a second signal indicating a degree of membership in a first set calling for a first current change and a third signal indicating a degree of membership in second set calling for a lesser change in current;
for providing a fourth signal that represents the product of the second signal and a first stored area value associated with the first set, and for providing a fifth signal that represents the product of the third signal and a second stored area value associated with the second set;
for providing a sixth signal that represents the product of the second signal and a stored moment value for the first set;
for providing a seventh signal that represents the product of the third signal and a stored moment value for the second set;
for providing an eighth signal that represents the value of the sixth signal divided by the seventh signal to indicate a change in the electric current;
for storing said logic sets for different wire feed rates for different changes in current level, and for controlling the electric current in response to said eighth signal and the wire feed according to said logic sets.- View Dependent Claims (7, 8)
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9. A welder comprising a torch contains a camera that provides sequential snapshots of a weld puddle and a controller for increasing and decreasing weld current as a function of puddle dimensions, characterized in that the controller comprises:
means, responsive to an a puddle dimension signal from the camera indicating a puddle dimension, for summing two values for desired current change from two adjacent fuzzy logic sets defined by respective puddle dimensions and current change levels, and for changing the weld current as a function of said sum, said two fuzzy logic sets being selected from a plurality of fuzzy logic sets for possible puddle dimensions ranging from a minimum to a maximum and said two values being determined as proportional function of the degree of membership in each of said two adjacent fuzzy logic sets for the puddle dimension signal. - View Dependent Claims (10, 11, 12)
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13. An inert electric gas welder comprising an electric current torch containing means for providing an image of a weld puddle, characterized by:
signal processing means operating in successive computing cycles for determining from the image a dimension of the weld puddle, for determining from stored functions the degree of membership of said dimension in a plurality of fuzzy logic functions indicating discrete changes in weld current, said degree of membership being an alpha value, for storing a moment and area for each fuzzy logic function, for providing for each alpha value greater than a set minimum a current temp moment value that is the product of the alpha for the function and the moment for the membership function, for providing a current temp moment value that is the product of the alpha for the membership function and the area for the membership function, for providing, in a discrete signal processing cycle, a first value that is the sum of each of said current temp moments and a second value that is the sum of each of said areas, for providing, during a computing cycle, a third signal that is the value of the first value divided by the second value, and for providing a signal to the electric current torch to modify the current through the electric current torch as a function of the magnitude of said third signal. - View Dependent Claims (14, 15)
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16. A welder comprising imaging means for producing image signals indicating the length and width of a weld puddle beneath the torch, characterized by:
signal processing means for providing length and width values from the image signals, for storing moment and area values for different discrete ranges of puddle length and puddle width that identify fuzzy membership functions associated with weld current levels, for selecting the membership functions associated with said length and width values, for providing a membership signal indicating the degree of membership of the length and width values in each of said selected associated membership functions, for selecting among a pair of said length and width values the one with the lowest degree of membership, for providing a moment value that is the product of said lowest degree of membership and one of the stored moment values;
for providing an area signal that is the product of said lowest degree of membership and one of the stored area values, and providing a current signal that represents the sum of all moment signals divided by the sum of all area signals, said current signal controlling weld current.
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17. A welding method characterized by:
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illuminating a weld puddle with a strobe light during welding; providing signals indicating a weld puddle dimension based on individual video frames of the weld puddle produced from the strobe light on a video camera in a weld torch above the puddle; storing N membership functions, each identifying a discrete change in weld current for a range of said dimensions and storing a moment value and an area value for each membership function; providing an alpha signal for each membership function in which said puddle dimension falls, the alpha signal indicating the degree of membership of said dimension in the membership function, based on a stored value for the function and the dimension; providing for each membership function for which an alpha value is produced, a pair of signals indicating the product of said alpha value and a moment and area stored for said membership function; changing weld current as a function of the sum of all said pair of signals for which alpha signals are produced. - View Dependent Claims (18)
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Specification