Institute for Systems Research
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Item Design of a Paper Regulating Gearbox for Parallel Hybrid Electric Vehicles(1996) Tsai, L.W.; ISRA parallel-hybrid electric vehicle usually employs two power sources, an engine and an electric motor/generator, to drive a vehicle. Typically, the electric motor receives power stored in batteries to drive the vehicle at low vehicle speeds. Both the electric motor and the engine provide power to the vehicle for maximal acceleration and/or hill climbing. The engine alone drives the vehicle and, at the same time, charges the batteries via the electric motor/generator during highway cruising. And during braking periods, the kinetic energy of the vehicle is used to recharge the batteries. For such a parallel hybrid electric vehicle to function properly, an electro-mechanical system that manages the power flow among the two power sources and the vehicle i necessary. This paper describes the design of an innovative power regulating gearbox. The proposed mechanism can provide a vehicle with six different operating modes including a continuous variable transmission capability to optimize the performance, improve the fuel economy, and reduce the hazardous emissions. To illustrate the capability of the gearbox, kinematics, statics, and power flow analysis are performed for each of the six operation modes.Item A Methodology for Enumeration of Clutching Sequences Associated with Epicyclic-Type Automatic Transmission Mechanisms(1996) Hsieh, Hsin-I; Tsai, L.W.; ISRThis paper presents a systematic methodology for the enumeration of clutching sequences associated with epiclyclic-gear-type automatic transmission mechanisms. The methodology is based on the concept that an epicyclic gear mechanism can be decomposed into several fundamental geared entities and that the overall speed ratio of an epicyclic gear mechanism can be symbolically expressed in terms of its fundamental geared entities. First, a procedure for estimating the overall speed ratio of an epicyclic gear mechanism, without specifying the exact gear dimensions, is outlined. Then, an algorithm for comparing various possible speed ratios of an epicyclic gear mechanism is described. Finally, a methodology for systematically enumerating all possible clutching sequences of an epicyclic gear mechanism is established.Item An Application of Graph Theory to the Detection of Fundamental Circuits in Epicyclic Gear Trains(1995) Tsai, L.W.; ISRIn this paper, a systematic procedure is developed for the identification of fundamental circuits and transfer vertices in epicyclic gear trains. The method utilizes the well-established concepts of graph theory and related matrices. The procedure leads to automated formulation of the kinematic equations in a systematic manner.Item Design of Tendon-Driven Manipulators(1995) Tsai, L.W.; ISRThis paper presents an overview of the current state-of-the-art in the design of tendon-driven manipulators. A special characteristic associated with tendon-driven manipulators is that tendons can exert only tension, not compression. Based on this unique characteristic, the fundamental mechanics associated with the design of tendon-driven manipulators are reviewed. The review includes structure classification, kinematics, statics, dynamics and control.Item Isotropic Design of Tendon-Driven Manipulators(1995) Ou, Y.J.; Tsai, L.W.; ISRThis paper deals with the synthesis of mechanical transmission structures for tendon-driven manipulators. Based on static force analysis, necessary conditions are developed for the synthesis of tendon-driven manipulators with isotropic transmission characteristics. It is shown that an n degree-of-freedom (dof) manipulator will possess the isotropic transmission characteristics, if it satisfies two isotropic conditions. Furthermore, a design equation is derived for the construction of isotropic transmission structure matrices and a three-dof spatial manipulator is synthesized to demonstrate the methodology. It is shown that the isotropic design leads to a more uniform tendon force distribution.Item The Development of Flex-Gears for the Conduction of Electricity Across a Continuously Rotating Joint(1995) Peritt, J.; Tsai, L.W.; Vranish, J.; ISRThe transfer of electricity across a continuously rotating joint is especially important in robot joints and brush-type motors. In this paper, the shortfalls of present technologies, such as electric brushes, are discussed. Flex-gears are presented as an alternative method of transferring electricity across a continuously rotating joint. A new type gear, called a pitch- folling-gear, is developed from involute gear technology for use as a flex-gear. Finally, the design of planetary flex-gear devices using pitch-rolling-gears is studied.Item On the Stiffness of a Novel Six-DOF Parallel Minimanipulator(1995) Tahmasebi, F.; Tsai, L.W.; ISRThe dimensionally-uniform Jacobian matrix of a novel three- limbed, six degree-of-freedom (DOF) minimanipulator is used to derive its dimensionally-uniform stiffness matrix.The minimanipulator limbs are inextensible and its actuators are base-mounted. The lower ends of the limbs are connected to bi- directional linear stepper motors which are constrained to move on a base plane. The minimanipulator is capable of providing high positional resolution and high stiffness.
It is shown that, at a central configuration, the stiffness matrix of the minimanipulator can be decoupled (diagonalized), if proper design parameters are chosen. It is also shown that the stiffness of the minimanipulator is higher than that of the Stewart platform. Guidelines for obtaining large minimanipulator stiffness values are established.
Item An Efficient Algorithm for the Automatic Enumeration of the Topological Structures of Mechanisms(1993) Hsieh, Hsin-I; Tsai, L.W.; ISRIn this paper, a new algorithm for the automatic enumeration of the topological structures of mechanisms is developed. The algorithm permits the deviation of conventional graphs from contracted graphs by the partition of binary vertices. A row vector is formed to present the binary-vertex chains. The partition of binary vertices is transformed into the solution of one linear equation in several unknown integers. No permutation of binary-vertex chains is necessary. This leads to the development of a highly efficient computer algorithm for the enumeration of conventional graphs.Two tables of conventional graphs with seven and eight vertices, and with up to five loops have been developed. We believe that the results of these conventional graphs are new. Mechanisms of higher pair joints up to five loops and with eight links can now be synthesized from these tables.
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.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.