Independent tube position verification system

A tube position verification method for use in the inspection and service of the tube sheet (12) of steam generators (10) of the type having a plurality of tube ends (14) in a tube sheet (12) arranged pursuant to a predetermined coordinate system and a robotic arm (20) for moving an end effector (EE) adjacent to the surface of the tube sheet (12) to successive specified tube end positions, characterized by:

• illuminating the tube sheet (12) so as to create shadow effects thereon;
• taking successive image frames of the tube sheet (12) from the robotic arm (20);
• processing the successive images from the imaging device (16) to discern relative displacement of image artifacts from frame to successive frame;
• and
• updating position coordinate registers for registering displacement changes from the relative displacement of image artifacts from frame to successive frame,
• wherein the processing step is further characterized by a control function to maintain the imaging device (16) at a selected optimum spacing distance z(n) from the surface of the tube sheet (12) under observation, and further characterized by observing an apparent angle of convergence between objects in an image frame, comparing the observed angle to an optimum value, and moving the end effector (EE) toward the optimum spacing distance z(n).

An end effector (EE) positioning system for use in the inspection and service of the tube sheets of steam generators (10) of the type having a plurality of tube ends (14) in a tube sheet (12) arranged pursuant to a predetermined coordinate system and a robotic arm (20) for moving an end effector (EE) adjacent to the surface of the tube sheet (12) to successive specified tube end positions, characterized by:

• a imaging device (16) connected to the robotic arm (20) for imaging successive image frames as the robotic arm (20) moves an end effector (EE) across the surface of the tube sheet (12), the imaging device (16) positioned to provide image frames with a perspective view of objects within the image frame, the perspective view such that objects appear to converge toward a distant vanishing point;
• a light source (18) for illuminating the tube sheet (12) so as to create shadow effects within the field of view of the imaging device (16);
• an image processor (104,106) for processing successive images from the imaging device (16) to discern an apparent angle of convergence of image artifacts from frame to successive frame;
• and
• an actuator for effecting movement of the end effector (EE) toward or away from the tube sheet (12) to maintain an optimal spacing distance z(n) as a function of the apparent angle of convergence.

An end effector (EE) positioning method for use in the inspection and service of the tube sheet (12) of steam generators (10) of the type having a plurality of tube ends (14) in a tube sheet (12) arranged pursuant to a predetermined coordinate system and a robotic arm (20) for moving an end effector (EE) adjacent to the surface of the tube sheet (12) at an optimum spacing distance z(n) to successive specified tube end positions, characterized by:

• illuminating the tube sheet (12) so as to create shadow effects thereon;
• taking successive image frames of the tube sheet (12) from the robotic arm (20), the successive image frames taken at an angle relative to the surface of the tube sheet (12) to provide a perspective view thereof in which objects in the image frame appear to converge toward a distant vanishing point;
• processing the successive images from the imaging device (16) to discern an apparent angle of convergence of objects within the image frame;
• and
• maintaining the imaging device (16) a selected optimum spacing distance z(n) from the surface of the tube sheet (12) under observation as a function of the apparent angle of convergence of objects within the image frame.