A new method of creating expandable structure for spatial objects

This paper presents a new method of creating expandable structure for spatial objects which are constructed by connecting a serial of parallelogram mechanisms whose edges are all equal in length with revolute joints. Any spatial object can be constructed with a certain number of basic cube units, and each basic cube unit is designed into an expandable one by being constructed with parallelogram mechanisms. By designing the basic cube unit in certain ways, not only can it be expanded and contracted synchronously, but also it can be expanded in some parts and contracted in others. During expansion, the basic cube unit is mobile with one degree of freedom. As a result, any spatial object assembled with these basic cube units is created into expandable structure, and that the entire structure can be expanded and contracted without being affected, even if there are some broken parts in it. To verify the feasibility of the method, two examples are provided.