The inverse kinematics of the SPRP screw-based manipulator

The paper reports the inverse kinematic analysis of a 6-degree-of-freedom robot manipulator possessing a very particular mechanical architecture capable of performing pick-and-place operations. The mentioned manipulator possesses the SPRP arrangement and it resembles the well-known screw-based mechanism which is a serially linked chain based on the Rodrigues" formula for the general screw displacement. The latter mentioned mechanism provides a non-flexible motion: the work piece goes from an initial pose to a final one., through a spiral-shaped path. The corresponding, screw parameters of the mechanism are calculated in terms of the positions of three non-collinear points belonging to the piece for the two ends of the fixed path. In case of changing the task conditions, it is necessary to find new screw parameters. ne paper proposes a manipulator with the ability of changing them as a function of the current conditions. In order to find the adequate screw configuration, it is necessary to develop the corresponding inverse kinematics in terms of the operational coordinates.