US 5,572,102 A · Method and apparatus for vision control of welding robots

Abstract

A vision system for controlling welding robots and a method of controlling a welding robot using a vision system are disclosed. The vision system includes an ordinary unoriented light source, such as a fluorescent light source, to illuminate a part to be welded so that a light intensity gradient is created along a seam to be welded. An image of the light intensity gradient is captured by one or more fixed solid-state video cameras. The image is compared with a stored image of a reference part so that a deviation of the seam to be welded with respect to the seam of the reference part can be computed for each of a plurality of predefined reference points. The deviation at each reference point is translated by a microprocessor into a coordinate adjustment which is downloaded to a controller for the robot. The controller converts the learned coordinates of the reference part into the actual coordinates of the seam to be welded using the coordinate adjustments provided by the microprocessor, permitting the robot to weld the seam without vision sensing or weld path adjustments during the welding process. The advantage is a cost effective vision system which can be shared among robots, simpler equipment, simpler control software, and increased efficiency because real time weld path correction maneuvers are eliminated.

Claims20

Dependent claims

Apparatus for controlling the operation of a robot welder to effect the sequential welding of a plurality of parts having seams to be welded, each of the parts being similar to a known reference part, comprising:

means for supporting a one of the parts to be welded in a predetermined welding position so that the seam to be welded is supported in a predetermined plane;
an unoriented light source that is independent of the robot and positioned to illuminate the seam to be welded so that a light intensity gradient is detectable along the seam;
vision sensor means for acquiring a digital image of the seam to be welded, the vision sensor means being independent of the robot and positioned to acquire images that capture the light intensity gradient along the seam;
image processor means for accepting the images from the vision sensor means and for processing the images to determine from a digitized representation of the light intensity gradient a deviation of the seam with respect to a reference weld path on the reference part at each of a plurality of reference points spaced along the reference weld path;
data processor means for accepting each deviation from the image processor means and for converting each deviation to a coordinate adjustment for a respective one of each of the plurality of reference points, each coordinate adjustment being expressed in a format readable by a controller of the robot;
and
means for communicating the coordinate adjustments to the controller of the robot, whereby the robot is enabled to weld along the seam using predetermined adjusted coordinates for the seam to be welded in uninterrupted real time without further weld path scanning, computation or adjustment.

4 more elements

A method for controlling the operation of a robot welder to effect the automatic welding of a seam on a part to be welded that is similar to a reference part having a weld path that has been taught to the robot, comprising:

a) illuminating the part to be welded with an unoriented light source that is independent of the robot to create a light intensity gradient that is detectable along the seam to be welded;
b) operating an electronic vision system sensor that is independent of the robot to acquire at least one digital image of the seam to be welded;
c) operating a vision system controller to analyze the at least one digital image to isolate an image of the seam to be welded;
to compare the image of the seam to be welded with a stored image of the weld path on the reference part;
and, to compute deviations in at least one plane of the image of the seam on the part to be welded from the weld path on the reference part;
d) operating the vision system controller to communicate the deviations to a data processor;
e) operating the data processor to translate the deviations to respective coordinate adjustments expressed in a format readable by a controller of the robot welder and to communicate the respective coordinate adjustments to the controller of the robot welder;
f) operating the controller of the robot welder to adjust the learned coordinates of the weld path of the reference part using the coordinate adjustments to provide an adjusted set of coordinate points that correspond to a weld path for the seam to be welded;
and
g) operating the robot to effect the welding of the seam using the set of adjusted coordinate points so that the seam can be accurately welded without visual detection or weld path corrections during the welding process.

7 more elements

An apparatus for controlling the operation of a robot welder to effect the sequential welding of a plurality of parts having seams to be welded, each of the parts being similar to a known reference part, comprising:

means for supporting a one of the parts to be welded in a predetermined welding position so that the seam to be welded is supported in a predetermined plane;
a fluorescent light source that is independent of the robot and positioned to illuminate the seam to be welded so that a light intensity gradient is detectable along the seam;
at least one solid state camera for acquiring a digital image of the seam to be welded, the at least one solid state camera being independent of the robot and positioned to acquire images that capture the light intensity gradient along the seam;
an image processor for accepting images from the solid state camera and for processing the images to determine from a digitized representation of the light intensity gradient a deviation of the seam with respect to a reference weld path at each of a plurality of reference points spaced along the reference weld path;
a microcomputer for accepting each deviation from the image processor and for converting each deviation to a coordinate adjustment for a respective one of each of the plurality of reference points, each coordinate adjustment being expressed in a format readable by a controller of the robot;
and
a robot controller for accepting coordinate adjustments from the microcomputer and interpolating each coordinate adjustment into an adjustment of six axis coordinates learned by the robot at each of the plurality of reference points spaced along the reference weld path.

4 more elements

a) illuminating the part to be welded using a fluorescent light source that is independent of the robot to create a light intensity gradient that is detectable along the seam to be welded;
b) operating a solid state video camera that is independent of the robot to acquire at least one digital image of the seam to be welded;
c) operating a vision system controller to analyze the at least one digital image to isolate an image of the seam to be welded;
to compare the image of the seam to be welded with a stored image of the weld path on the reference part;
and, to compute deviations in at least one plane of the image of the seam on the part to be welded from the weld path on the reference part;
d) operating the vision system controller to communicate the deviations to a microcomputer;
e) operating the microcomputer to examine each deviation for range and to substitute values for deviations out of range;
f) operating the microcomputer to translate the deviations to respective coordinate adjustments expressed in a format readable by a controller of the robot welder and to communicate the respective coordinate adjustments to the controller of the robot welder;
g) operating the controller of the robot welder to adjust the learned coordinates of the weld path of the reference part using the coordinate adjustments to provide an adjusted set of coordinate points that correspond to the weld path for the seam to be welded;
and
h) operating the robot to effect the welding of the seam using the set of adjusted coordinate points so that the seam can be accurately welded without visual detection or weld path correction during the welding process.

8 more elements

Dependencies are inferred from the claim text.

Method and apparatus for vision control of welding robots

Life of this patent

Method and apparatus for vision control of welding robots

Life of this patent

Abstract

Claims20