KEYSIGHT: Computer Vision Inspection of Valve Spring Assemblies on Engine Heads

PROGRAM

The movie describes a computer vision program used to inspect valve spring assemblies on engine heads for the presence of valve spring cap keys. A mis­ sing key can cause considerable engine damage as the assembly will ultimately come apart, dropping the valve onto the piston. At the automatic in­ spection station, the engine head is moved past a linear-array camera which takes a 64 by 64 pixel picture of the area near each valve spring assem­ bly center. The program first finds the center of each assembly and then checks for the presence of both keys. The center is found by: (1) obtaining a thinned edge array (which has considerable cir­ cular symmetry) from the picture intensity array, and (2) finding the vertical and horizontal axes of symmetry. The inspection involves examination of the intensity profile along the circumference of a circle which passes through the center of the expected key location. The keys vary significant­ ly in brightness, but they are always brighter than the hole formed by the absence of a key. KEYSIGHT, which inspects 400 heads per hour at assembly line speeds, has demonstrated cost effectiveness and high reliability.

W. A. Perkins

Computer Science Department General Motors Research Laboratories Warren, Michigan 48090