Institute for Systems Research

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Author: search.filters.author.Tsai, L.W.Subject: search.filters.subject.Intelligent Servomechanisms

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Now showing 1 - 7 of 7
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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.
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    Torque Resolver Design for Tendon-Driven Manipulators
    (1991) Lee, Jyh-Jone; Tsai, L.W.; ISR
    Given desired joint torques in an n-DOF tendon-driven manipulator with n +1 control tendons, the determination of tendon forces is an indeterminate problem. Usually, the pseudo-inverse technique can be used to solve for such a problem. In this paper, rather than using the pseudo-inverse technique, an efficient methodology for transforming joint torques (n elements) to motor torques (n + 1 elements) has developed. This technique, called "torque resolver", utilizes two circuit-like operators to transform torques between two different vector spaces. It can be easily programmed on a digital computer or implemented into an analog- circuit system. It is hoped that this technique will make real- time control using computed torque method feasible. The technique has been demonstrated through the dynamic simulation of a three- DOF manipulator.
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    The Workspace of Three-Degree-of-Freedom, Four-Jointed Spherical Wrist Mechanisms
    (1990) Lin, Chen-Chou; Tsai, L.W.; ISR
    In 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.
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    The Trajectory Analysis of Spherical Planetary Gear Trains
    (1990) Lin, Chen-Chou; Tsai, L.W.; ISR
    In 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.
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    Topological Analysis of Tendon-Driven Manipulators
    (1990) Lee, Jyh-Jone; Tsai, L.W.; ISR
    This paper investigates the effect of tendon routing on kinematic and static force transmission associated with tendon-driven manipulators. The transmission characteristics can be described by the velocity and/or force ellipsoid. We have shown that the effect of tendon routing can be characterized by a condition number and the direction of a homogeneous solution. The condition number is defined as the ratio of the maximum to the minimum singular value of the structure matrix and the homogeneous solution is the set of tendon forces that results in no net joint torques. A methodology for calculating maximum tensions in a tendon-driven manipulator has been developed. We have also shown that among the various tendon routings in three- DOF manipulators, the one with an isotropic transmission ellipsoid possesses minimal maximum tendon force.