Screw System Variation Enabled Reconfiguration of the Bennett Plano Spherical Hybrid Linkage and Its Evolved Parallel Mechanism

Abstract

This paper presents the Bennett planospherical hybrid linkage and proposes a novel metamorphic parallel mechanism consisting of this planospherical linkage as part of limbs. In light of geometrical modeling of the Bennett planospherical linkage, and with the investigation of the motionscrew system, the paper reveals for the first time the reconfigurability property of this planospherical linkage and identifies the design parameters that lead to change of constraint equations, and subsequently to variation of the order of the motionscrew system. Arranging this linkage as part of limbs, the paper further investigates the reconfiguration property of the planospherical linkage evolved parallel mechanism. The analysis reveals that the platform constraintscrew system varies following both bifurcation and trifurcation with motion branch variation in the 6R linkage integrated limb structure. Consequently, this variation of the platform constraintscrew system leads to reconfiguration of the proposed metamorphic parallel mechanism. The paper presents a way of analyzing reconfigurability of kinematic structures based on the screwsystem approach.