A Family of Overconstrained 6R Linkages With the Rotational Symmetry of Order 2

This paper presents a family of overconstrained 6R linkages with the rotational symmetry of order 2 which refers to rotation by an angle of 360°/n (n = 2) with respect to a particular axis leaves the linkage unchanged. The overconstrained 6R linkages are evolved from a reconfigurable 8R linkage which is extracted from deployable origami-fold. The structure evolution of the 8R linkage takes the concept of metamorphosis in the sense of structural evolution. This leads to a generic way for investigating new mechanisms inspired from origami fold. The geometry and two-fold rotational symmetry reveal that the overconstrained 6R linkages are special line-symmetric Bricard 6R loops and the parametric constraints of the 6R linkages are identified. The kinematics of the overconstrained 6R linkage is analyzed and motion parameters of the joint space are derived. The unique mobility of the overconstrained 6R linkages is further verified in terms of screw theory.Copyright © 2012 by ASME