Retractable Structure Based On Closed-Loop Linkages

In this dissertation we construct some retractable structures using existing spatial overconstrained linkages with only revolute joints directly. Bricard linkages consist of six basic cases, which are all single closed-loop overconstrained linkages with only revolute joints. To build deployable structures and retractable structures, we research the threefold-symmetric six-bar linkage, threefold-symmetric six-bar linkage is a special case of the Bricard linkage, which is overconstrained and with a single degree of mobility.Starting with the derivation of the compatibility condition and the study of deployment behaviour, it has been found that for some particular twists, the threefold-symmetric six-bar linkage can be folded completely in to a bundle and deployed to a flat triangular profile. Based on this linkage, we explore the possibility of constructing structural networks.Based on the theories of Kaleidocycles, a new retractable structure is developed, which consist of some tetrahedra. The design principles of this structure are described in detail. The configurations and dimensions of the tetrahedra were determined by basic geometric parameters, and the relationship between the rings of tetrahedra and the corresponding threefold-symmetric Bricard linkages was derived. Then the input-output equation about the sloped angles of revolution joints is found out. Additionally, the monodrome relationship between the opening degree of the structure and the displacement of the supports is analyzed, under given geometric parameters.Then the load analysis of the retractable is studied, with the help of our own program MstCAD and finite element program ANSYS. Considering the stress and displacement of the structure under certain basic geometric parameters, the shortage of the structure is analyzed. According to these characteristics, some structural forms of optimization are presented and the geometric and load analysis of the models are studied.