Reconfigurability and unified kinematics modeling of a 3rTPS metamorphic parallel mechanism with perpendicular constraint screws

摘要

This paper investigates reconfigurability and unified analytical kinematics analysis of a new 3rTPS metamorphic parallel mechanism consisting of three reconfigurable rTPS limbs in perpendicular base planes. Constraint screw systems show that in one phase the rTPS limb has no constraint to the platform and in the other phase obtained by altering the reconfigurable Hooke joint, it provides a constraint force. The two phases of the limb qualify the 3rTPS metamorphic parallel mechanism to have four topologies with ability of mobility change among 3R (three rotations), 3R1T (three rotations one translation), 3R2T and mobility 6. By considering the difference of the two phases of the limb, a unified kinematics modeling is proposed based on the actuation scheme analysis by taking one phase as a special case of the other. Following this, a unified kinematics modeling of the 3rTPS metamorphic parallel mechanism is obtained by covering all its four topologies. Both inverse and forward kinematics analysis are solved analytically and numerical examples confirm these theoretical results.