Institute for Systems Research

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Author: search.filters.author.Tsai, L.W.

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    Design of a Paper Regulating Gearbox for Parallel Hybrid Electric Vehicles
    (1996) Tsai, L.W.; ISR
    A 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.
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    A Methodology for Enumeration of Clutching Sequences Associated with Epicyclic-Type Automatic Transmission Mechanisms
    (1996) Hsieh, Hsin-I; Tsai, L.W.; ISR
    This 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.
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    An Application of Graph Theory to the Detection of Fundamental Circuits in Epicyclic Gear Trains
    (1995) Tsai, L.W.; ISR
    In 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.
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    Design of Tendon-Driven Manipulators
    (1995) Tsai, L.W.; ISR
    This 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.
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    Isotropic Design of Tendon-Driven Manipulators
    (1995) Ou, Y.J.; Tsai, L.W.; ISR
    This 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.
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    The Development of Flex-Gears for the Conduction of Electricity Across a Continuously Rotating Joint
    (1995) Peritt, J.; Tsai, L.W.; Vranish, J.; ISR
    The 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.
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    On the Stiffness of a Novel Six-DOF Parallel Minimanipulator
    (1995) Tahmasebi, F.; Tsai, L.W.; ISR
    The 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.

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    An Efficient Algorithm for the Automatic Enumeration of the Topological Structures of Mechanisms
    (1993) Hsieh, Hsin-I; Tsai, L.W.; ISR
    In 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.

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    An Improved Model for the Dynamics of Spur Gear Systems with Backlash Consideration
    (1993) Shing, T.K.; Tsai, L.W.; Krishnaprasad, Perinkulam S.; ISR
    An improved model which accounts for backlash effects is proposed for the dynamics of spur gear systems. This dynamic model is mainly developed for the purpose of real time control. The complicated variation of the meshing stiffness as a function of contact point along the line of action is studied. Then the mean value is used as the stiffness constant in the improved model. Two simulations, free vibration and constant load operation, are performed to illustrate the effects of backlash on gear dynamics. Also given are comparisons of the simulation results with that of the Yang and Sun's model. This model is judged to be more realistic which can be used in real time control to achieve high precision.
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    Dynamic Simulation of Tendon-Driven Manipulators
    (1991) Lee, Jyh-Jone; Tsai, L.W.; ISR
    This paper investigates some dynamic characteristics of tendon- driven manipulators. The dynamic equations including the effect of rotor inertia for a class of n x (n +1) tendon-driven manipulators are formulated. A control algorithm based on the computed torqued method is developed. Then, the implementation of such control algorithm is demonstrated in the simulation of a three-DOF tendon-driven manipulator. Through the simulation, several dynamic characteristics of the system are identified. In particular, it is shown that rotor inertia can have significant effect on the system dynamics and that pretension can play an important role on the stability of the system. It is also shown that among the five non-isomorphic kinematic structures of three- DOF manipulators, the one which satisfies the isotropic transmission and least maximum tendon force conditions also requires smallest tendon force in the dynamic simulations.