Screw Analysis Of Bennett And Some Minor-Mobility Mechanisms

The spatial minor-mobility mechanism enjoys a broad perspective in industry production and other fields for such advantages as simple mechanism, easy control and low cost and draws extensive attention of the scholars at home and abroad, thus becomes a focus of interest in mechanism research. This dissertation, by applying the screw theory, probes the characteristics of instantaneous kinematics of the four typical minor-mobility mechanisms in the one or two degrees of freedom. Firstly, this dissertation, based on the analysis of the geometric condition of the Space Bennett Mechanism and of the degree of freedom, sets up an appropriate coordinate system and reveals all the linear natures of the displacement screw, then, with the newly built coordinate system proves the side-angle relationship it bears. And then we consider the manner in which the Bennett linkage is related to the hyperboloid defined by its joint axes and the one defined by its links. We go on to algebraically inter-relate these and an equivalent screw of the overall instantaneous motion, which help us understand its kinetic property. Secondly, this thesis analyzes the Plane closed-loop five-bar mechanism, the planar differential gear trains, the spatial gear trains which bears two degrees of freedom, their instantaneous motion of initial position and possible position and the general position of instantaneous motion after initial position and possible position, then presents the constraint conditions of every motion and the function chart between the input angle and the input rate that instant. Moreover, by using the screw theory, the thesis gives an analysis of the changes of the degree of freedom of the Plane closed-loop five-bar mechanism at certain position. Finally, by using algebraic approach of the two-system screws, we determine both the ranges of the twist pitches and the spatial distributions of all the twist axes.The application of screw theory puts this paper at a high theoretical level. This paper is also an important supplement to and application of the minor-mobility mechanism theory. At the same time, it is of great leading significance for the innovation of new minor-mobility mechanisms...