This paper presents the singularity analysis of a family of 14 composite se
rial in-parallel six degree-of-freedom robots, having a common parallel sub
mechanism. The singular configurations of this class of robots are obtained
by applying line geometry methods to a single, augmented Jacobian matrix w
hose rows are Plucker coordinates of the lines governing the submechanism m
otion. It is shown that this family of robots possesses three general paral
lel singularities that are attributed to the general complex singularity. T
he results were verified experimentally on a prototype of a composite seria
l in-parallel robot that was synthesized and constructed for use in medical
applications.