The GEC Tetrabot-a new serial-parallel assembly robot

An assembly robot, the GEC Tetrabot (tetrahedral robot) is presented. It includes a parallel structure consisting of 3 threaded actuator rods which form the edges of a tetrahedron. The equilateral triangle base is part of the support structure for the manipulator. Each threaded rod is free to pivot at its attachment point about 2 axes which are perpendicular to the rod axis. The rods are driven in axial translation via a recirculating ball screw assembly, which minimises friction. a 3 axis wrist, attached to the lower end of the radial arm, provides the remaining 3 degrees of freedom. The wrist mechanism is conventional, comprising three further links arranged serially. The design thus combines the advantages of serial and parallel mechanisms, leading to a stiffer, faster, more accurate robot