Synthesis Of Structure-Based Mechanism Based On Basic Elements

In this dissertation, the topological structure, geometric structure, type synthesis, dimensional synthesis and design method of a family of mechanisms, Structure-based Mechanisms (SBM), were researched systematically and deeply. The research aimed to promote the development of innovative design of mechanical products. The dissertation contains researches on two types of mechanisms with characters of SBM: Scaling mechanisms and Remote-center-of-motion (RCM) mechanisms. Firstly, the topological structure, geometric structure, configurations of elements and their optimization, association of close-loop constrained mechanisms, optimization of mechanical design of the scaling mechanisms were researched. Then, based on the characteristics of RCM mechanism, dual-RCM mechanism and multi-RCM mechanisms were proposed. Type synthesis, dimensional synthesis, optimization design method of dual-RCM mechanisms were researched, also an application development of minimally invasive surgery (MIS) application is given. To multi-RCM mechanism, the research dedicated to angular analysis, position analysis, dimensional synthesis and application in multi-RCM scaling mechanisms.In the first part, the topological structure of a type of close-loop constraint mechanism——scaling mechanism was analyzed based on the description method of topological structure in graph theory. According to the topological graphs of scaling mechanisms, there exist two different types of graphs. The first type is a planar graph, which can be embedded into surface of prism, named Prism Graph. The other type is a non-planar graph, which satisfies the Kuratowski theorem and can be embedded into the surface of Mobius strip, named Mobius Graph. Then, by using triangulation method to prove that the Euler characteristic of this non-planar topology is equal to Mobius topology. Finally, mechanisms with the same topological characteristics were deserved.In the second part, adjacency graph and its associated joints adjacency matrix were presented to describe the evolution of mechanisms, which is a mathematical method. Comparing with the description method used for topology graph of metamorphic mechanisms, this method is much more intuitive, comprehensive in describing structural information and has a much wider application. Using this method, scaling mechanisms, metamorphic mechanisms and origami mechanisms were verified and some mechanisms were obtained.In the third part, an application for planar and spatial scaling mechanisms based on characteristics of SBM was proposed. Researches started from planar to the spatial graphs. Firstly, basic elements used to associate planar graphs were researched and a method using tetragon as the element was proposed. This method simplifies the design of planar scaling mechanisms by looking up the tables concluded. Then, scissor-like element was optimized for constructing planar and spatial scaling mechanisms. A type of hybrid-scissor-like element was designed to amplify the scale ratio of mechanisms. This research result was used to design scaling fullerence polyhedrons. Finally, application software was coded for the parametric model design and interface design.In the fourth part, remote-center-of-motion (RCM) mechanism used in minimally invasive surgery was researched. By analyzing the structure and kinematic characteristics of this type of mechanisms, dual-RCM mechanism was obtained by adding SLAEs. And its configuration and dimensional synthesis method were reached. Based on the methodology analysis, dual-RCM bracket with adjustable RCM positions was designed. Further, we developed a conceptual device with dual-RCM mechanism for eye surgery to overcome involuntary movement of eyes during the surgery.In the fifth part, we analysised the geometric and kinematic characteristics of dual-RCM mechanisms, and proposed a dimensional synthesis method by using multi-loop kinematic chain. This method is also available for the design of open-loop or closed-loop multi-RCM mechanisms. Two applications, multi-RCM scaling mechanisms and foldable stages, were proposed by further analysis of multi-RCM mechanism, closed-loop mechanisms and scaling mechanisms.Structure-based mechanism (SBM) was defined as that which was associated with movable elements and has structural characteristics of expanding and folding. This dissertation focuses on the methodology for topology and structure of mechanisms. After then, the relationship between scaling mechanisms and RCM mechanisms was obtained. The integrated researches between mechanism and structure obtain theoretical and practical basis. The integrated researches between mechanism and aesthetics open up a new development path. The research objective dedicates that innovative design of mechanisms is not only for the realization of some functions, but also for the changing of people’s life style, values and continuing modern civilization.