tailieunhanh - Mechanism Design - Enumeration of Kinematic Structures According to Function P4

Structural Analysis of Mechanisms Structural analysis is the study of the nature of connection among the members of a mechanism and its mobility. It is concerned primarily with the fundamental relationships among the degrees of freedom, the number of links, the number of joints, and the type of joints used in a mechanism. It should be noted that structural analysis only deals with the general functional characteristics of a mechanism and not with the physical dimensions of the links. A thorough understanding of the structural characteristics is very helpful for enumeration of mechanisms. In this text, graph theory will be used. | Chapter 4 Structural Analysis of Mechanisms Introduction Structural analysis is the study of the nature of connection among the members of a mechanism and its mobility. It is concerned primarily with the fundamental relationships among the degrees of freedom the number of links the number of joints and the type of joints used in a mechanism. It should be noted that structural analysis only deals with the general functional characteristics of a mechanism and not with the physical dimensions of the links. A thorough understanding of the structural characteristics is very helpful for enumeration of mechanisms. In this text graph theory will be used as an aid in the study of the kinematic structure of mechanisms. Except for a few special cases we limit ourselves to those mechanisms whose corresponding graphs are planar. Although there are a few mechanisms whose corresponding graphs are not planar these mechanisms usually contain a large number of links. In addition we also limit ourselves to graphs that contain no articulation points or bridges. A graph with an articulation point or a bridge represents a mechanism that is made up of two mechanisms connected in series with a common link but no common joint or with a common joint but no common link. These types of mechanisms can be treated as two separate mechanisms and therefore are excluded from the study. A thorough understanding of the structural topology can be helpful in several ways. First of all mechanisms can be classified into families of similar structural characteristics. Various families of mechanisms can be quickly evaluated during the conceptual design phase. Secondly a systematic methodology can be developed for enumeration of mechanisms according to certain prescribed structural characteristics. Correspondence Between Mechanisms and Graphs Since the topological structure of a kinematic chain can be represented by a graph many useful characteristics of graphs can be translated into the .