In testing, there were often only a few
points defined on a given component and measurement at a given
point in only a few directions. These conditions led to confusing
displays. These findings led to the development of methods where
the measured DOFs could be used to estimate missing DOFs.
One method was to estimate rigid-body properties for a rigid
component or for a section of the component that behaved in a
rigid fashion. The rigid body properties were estimated from the
measured data, and the resulting rigid body characteristics could
be used to interpolate and predict the response for missing DOFs.
A second method used a slave DOF (a point whose motion is the
same as a measured point to estimate missing DOFs. Completion
algorithms were particularly important for impact testing, since it
is difficult or impossible to make measurements at certain points
and in certain directions.