Metronics Quadra-Chek 200 - Best Fit Algorithms

Chapter 8 Reference
8-4
Best Fit Algorithms
There are four basic algorithms used by the QC200 to determine the best
geometrical form fit of measured features. When the QC200 measures a line it
uses the first two points probed to estimate the form fit of the line. The first three
points are used to estimate the form of a circle. Keep in mind that the form
estimate simply defines the starting point for the best fit algorithm. The esti-
mated form geometry is shifted among the data points by the selected algorithm
to find the actual form.
NOTENOTE
NOTENOTE
NOTE
LSBF and ISO algorithms apply to lines and circles. Inner andLSBF and ISO algorithms apply to lines and circles. Inner and
LSBF and ISO algorithms apply to lines and circles. Inner andLSBF and ISO algorithms apply to lines and circles. Inner and
LSBF and ISO algorithms apply to lines and circles. Inner and
outer algorithms apply only to circles.outer algorithms apply only to circles.
outer algorithms apply only to circles.outer algorithms apply only to circles.
outer algorithms apply only to circles.
Here's how the various QC200 algorithms determine form fit.
LSBF (lines and circles)
The deviation of each point from the estimated form is measured, then squared,
and then added together. Adjustments are made to the line seeking the smallest
possible sum of the squared deviations. All points count equally when using
LSBF.
ISO (lines and circles)
The ISO best fit algorithm simply shifts the angle and location of the line until
it has achieved the smallest possible deviation of the outlying points. This
algorithm yields the geometry with the closest outlying data points. The ISO
algorithm considers only the furthest data points.
Inner (circles only)
This algorithm produces the largest inscribed circle possible. This means that the
circle form is defined by the inner most points of the data cloud. In simpler
terms, the inner algorithm produces the smallest circle geometry possible from
the data points.
Outer (circles only)
This algorithm produces the smallest circumscribed circle possible. This means
that the circle form is defined by the outer most points of the data cloud. In
simpler terms, the outer algorithm produces the largest circle geometry possible
from the points.