This research resolves an inconsistency problem that arises from assessing
circularity of workpiece measured by coordinate measuring machines (CMMs).
Although the notion of circularity is employed to constrain two-dimensional
circular features, in practice the measured points are obtained in a three
-dimensional spare and are in general nor in the same plane, let alone bein
g in a "perpendicular" cross-section. All of the algorithms currently used
for assessing circularity deal with data in a single plane that is perpendi
cular to the axis of a cylindrical feature from which the circular feature
is extracted. This discrepancy causes the assessed circularity significantl
y departing from the actual circularity and resulting in rejection of in-to
lerance parts. This research designs a compensation procedure for deriving
two-dimensional data from three-dimensional biased measured points. The cir
cularity is assessed based on the compensated two-dimensional data points.
The assessment results with the compensation are compared with those withou
t compensation. A program containing a variety of implementations of form f
itting algorithms is developed and used to illustrate the improvement on th
e accuracy of assessment.