Motion structures: deployable structural assemblies of mechanisms

This book focuses on the second category. The term Motion Structures is adopted to represent this branch of the deployable structure family owing to the existence of internal mechanisms. A mechanism in machine theory, which is referred to as a conventional mechanism hereafter, is commonly identified as a set of moving or working parts used essentially as a means of transmitting motions or controlling movement of one part relative to another. It is often assembled from gears, cams and linkages, though it may also contain other specialised components, e.g. springs, ratchets, brakes, and clutches, etc. There are close similarities as well as distinct differences between a motion structure and a conventional mechanism. First, the primary function of a motion structure is to have shape alteration essential to practical requirements, rather than transmitting or controlling motions. Second, as a structure, a motion structure is usually composed of far more parts than a conventional mechanism.