A Spatial Eight Bar Linkage and Its Association With the Deployable Platonic Mechanisms

Abstract

This paper presents for the first time a novel two degrees of freedom (2DOF) singlelooped dualplanesymmetric spatial eightbar linkage with exact straightline motion. Geometry and kinematics of the eightbar linkage are investigated and closedform equations are presented revealing the exact straightline motion feature of the linkage on the condition that two symmetric inputs are given. In order to secure two symmetric inputs, a geared eightbar linkage is then proposed converting the linkage into a 1DOF linkage of exact straightline motion. The direction of the straightline motion produced by the proposed eightbar linkage is changeable and is only dependent on the structure parameters of the two pairs of Vshaped RR dyads of the linkage. Further, the proposed eightbar linkage is applied to the synthesis and construction of a group of deployable Platonic mechanisms with radially reciprocating motion. The virtualcenterbased (VCB) method is presented for the synthesis and prototypes of the deployable Platonic mechanisms are fabricated verifying the mobility and motion of the proposed mechanisms.