Browsing by Author "Lin, Chen-Chou"
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Item The Creation of True Two-Degree-of-Freedom Epicyclic Gear Trains.(1988) Tsai, L.W.; Lin, Chen-Chou; ISRTo date, most of the multi-DOF (degree-of-freedom) epicyclic gear trains have been used as a series of one-DOF devices. Comparatively little is known with regard to the existence and synthesis of true multi-DOF epicyclic gear trains. This paper presents a systematic methodology for the identification and enumeration of the kinematic structure of true multiDOF epicyclic gear trains. It has been shown that there exist no true two-DOF epicyclic gear trains with five or less links and, that there exist two nonisomorphic rotation graphs of six vertices and twenty nonisomorphic rotation graphs of seven vertices. An atlas of nonisomorphic displacement graphs which can be used to construct true two-DOF epicyclic gear trains with six and seven links has been developed. It is hoped that this atlas will lead to more optimum and efficient designs of machines with multiple actuating requirements such as robotic wrists, grippers and walking machines.Item Kinematic Synthesis of Bevel-Gear-Type Robotic Wrist Mechanisms(1990) Lin, Chen-Chou; Tsai, L.W.; ISRBevel-gear-type robotic wrist mechanisms are commonly used in industry. The reasons for their popularity are that they are compact, light-weight, and relatively inexpensive. However, there are singularities in their workspace, which substantially degrade their manipulative performance. The objective of this research is to develop an atlas of three-degree-of-freedom bevel- gear-type wrist mechanisms, and through dimensional synthesis to improve their kinematic performance. The dissertation contains two major parts: the first is structural analysis and synthesis, the other is kinematic analysis and dimensional synthesis.To synthesize the kinematic structures of bevel-gear-type wrist mechanisms, the kinematic structures are separated from their functional considerations. All kinematic structures which satisfy the mobility condition are enumerated in an unbiased, systematic manner. Then the bevel-gear-type wrist mechanisms are identified by applying the functional requirements. Structural analysis shows that a three-degree-of-freedom wrist mechanism usually consists of a non-fractionated, two-degree-of-freedom epicyclic gear train jointed with the base link. Therefore, the structural synthesis can be simplified into a problem of examining the atlas of non-fractionated, two-degree-of-freedom epicyclic gear train jointed with the base link. Therefore, the structural synthesis can be simplified into a problem of examining the atlas of non- fractionated, two-degree-of-freedom epicyclic gear trains. The resulting bevel-gear-type wrist mechanisms has been categorized and evaluated. It is shown that three-degree-of-freedom, four- jointed wrist mechanisms are promising for further improving the kinematic performance.
It is found that a spherical planetary gear train is necessarily embedded in a three-degree-of-freedom, four-jointed wrist mechanism. Therefore, to study the workspace and singularity problems of three-degree-of-freedom, four-jointed spherical wrist mechanisms, we have to study the trajectories of spherical planetary gear trains. The parametric equations of the trajectories and some useful geometric properties for the analysis and synthesis of workspace are derived. The workspace boundary equations can be derived via both geometric consideration and Jacobian analysis. The workspace is divided by inner and outer boundaries into regions of accessibility of zero, two and four. The design criteria of full workspace and a maximum four-root region are established. Finally, a design is suggested based on its kinematic performance.
Item The Trajectory Analysis of Spherical Planetary Gear Trains(1990) Lin, Chen-Chou; Tsai, L.W.; ISRIn this paper, the trajectory of spherical planetary gear trains has been studied. The parametric equations of trajectory are derived. We have shown that the trajectory generated by a tracer point on the planet of a spherical planetary gear train is analogous to that of the planar case. Two cases, gear ratio equal to one and two, are presented in a detail including the geometric description, planes of symmetry, extent of trajectories, number of nodes (cusps) and their locations. The criteria for the existence of cusps are verified algebraically, and interpreted from geometrical point of view.Item The Workspace of Three-Degree-of-Freedom, Four-Jointed Spherical Wrist Mechanisms(1990) Lin, Chen-Chou; Tsai, L.W.; ISRIn this paper, orientational workspace of three-degree-of- freedom, four-jointed spherical wrist mechanisms have been investigated. We have derived the workspace boundary equations via both geometric consideration and Jacobian analysis. It is shown that for the first type wrist mechanisms with links 2 and 3 coupled, the workspace boundary consists of circles centered at fixed axis of rotation; while for the second type mechanisms with links 1 and 2 coupled, the boundary consists of two branches of curves. The workspace is divided by inner and outer boundaries into regions of accessibility zero, two and four. The criteria for full workspace design as well as for maximum four-root region have been established.