A Multi-mode Parallel Mechanism with Kinematically Bifurcated Closed-chains

Abstract

Stretchable mechanism based on the variable degree of freedom, multi-axis linkage machine tool and gait flexible emerging reconfigurable equipment such as mobile devices of actuator design problem, this paper designs the movement bifurcation closed chain pattern parallel mechanism, and based on screw theory of bifurcation closed chain, including bifurcation of closed cone of mixed branched chain and many kinds of DOF(degree of freedom) parallel mechanism are analyzed.In this paper, we present a bifurcation closed chain of URRC(U-universal joint, R-rotating pair, C-cylinder pair) configuration, which has two degrees of freedom instantaneous motion when it is in singular configuration, and one degree of freedom continuous rotation of the whole space or one degree of freedom plane continuous motion when it is in general configuration. Furthermore, URRC bifurcation closed chain was connected with 4 DOF PRRR (P-prismatic pair) open chain to obtain a hybrid branched chain with one constraint couple and one constraint line vector. Finally, three symmetrically arranged URRC-PRRR and mixed branch chains assembled into a motion bifurcation parallel mechanism, which have four variable motion modes of 2R3T, 2R2T, 2R1T and 3R1T (T-translation, R-rotation).