A novel manipulator architecture for the production of SCARA motions

SCARA denotes a class of 4-DOF manipulators that exhibit a finite stiffness in four directions of their motion space, while being infinitely stiff in the remaining two directions. These four directions comprise translation along three axes and rotation about one single axis. Therefore, a SCARA is noncompliant in two directions of rotation. SCARA systems were originally developed for assembly tasks. We term here any motion with the foregoing features a SCARA motion. Current manipulators producing this class of motions are invariably designed with a common architecture, namely, three revolutes and one prismatic joint, the latter being indistinctly collocated either at the proximal to the base or at the distal joint. We introduce here a novel architecture producing SCARA motions that is based on what is known as a II-joint, as introduced elsewhere. The kinematics of this manipulator is fully discussed