  This article presents a new variable actuation mechanism based on the 3-RPR
parallel robot. This mechanismis an evolution of the NaVARo robot, a 3-RRR
parallel robot, for which the second revolute joint of the threelegs is
replaced by a scissor to obtain a larger working space and avoid the use of
parallelograms to operate thesecond revolute joint. To obtain better spatial
rigidity, the leg mechanism is constructed by placing the scissorsin an
orthogonal plane to the plane of the manipulator displacement (3-RRR or even
the 3-RPR). This geometricproperty brings the significant consequence of
allowing the scissors to directly substitute the prismatic chains in the3-RPR
and enjoy the same kinematics advantages for the overall robots as only one
solution to the inverse kinematicmodel. From the Jacobian expression, surfaces
of singularity can be calculated and presented in a compact form.The
singularity equations are presented for a robot with a similar base and mobile
platform. The properties of thescissors are then determined to have a
prescribed regular workspace.
