Browsing by Author "Tsai, L.W."
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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 An Application of the Linkage Characteristic Polynomial to the Topological Synthesis of Epicyclic Gear Trains.(1987) Tsai, L.W.; ISRIn this paper, a random number technique for computing the value of a linkage characteristic polynomial is shown to be an effective method for identifying isomorphic graphs. The technique has been applied to the topological synthesis of one- degree-of- freedom, epicyclic gear trains with up to six links. All the permissible graphs of epicyclic gear trains were generated by a systematic procedure, and the isomorphic graphs were identified by comparing the values of their corresponding linkage characteristic polynomials. It is shown that there are 26 nonisomorphic rotation graphs and 80 displacement nonisomorphic graphs from which all the six-link, one-degree-of- freedom, epicyclic gear trains can be derived.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 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 The Design of a Three-Degrees-of-Freedom Walking Machine.(1989) Tsai, L.W.; Chen, Jie; Azarm, Shapour; ISRThe walking machine presented in this paper consists of six walking legs arranged in a triangular configuration. Each leg may have two modes of operation: an elliptical mode for walking on a flat plane and a circular mode for stair climbing. The six legs are mechanically coupled to a single drive motor through the use of chains and sprockets. the coupling is arranged in such a way that three of the six legs, one from each corner of the triangle, are always in phase while the other three are 180 degrees out of phase. When walking, three of the six legs are always on the ground propelling the machine forward, while the other three are in the air in an opposing position rotating forward. Turning is achieved through the use of a two degres-of-freedom mechanism. Through the use of a prismatic joint, the body of the machine can be lifted up-anddown, and through the use of a revolute pint, it can be rotated to any desirable orientation. The result is a simple, three degrees of freedom, walking machine that is capable of walking on a flat plane and performing some limited stair climbing. Because of the simple construction, the control system is also extremely simple and fast locomotion may be achieved for a small sacrifice of flexibility.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 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 Dynamic Simulation of Tendon-Driven Manipulators(1991) Lee, Jyh-Jone; Tsai, L.W.; ISRThis 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.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 Evaluation of the Oldham-Coupling-Type Balancer on a90ﮠV6 Engine.(1987) Tsai, L.W.; Maki, E.R.; Jacques, R.L.; ISRThis paper describes the effectiveness of an Oldham- coupling- type balancer in reducing the first- and second-harmonic rotating unbalance couples of a90ﮠV6 even-firing engine. It is shown that the prototype balancer can be configured to eliminate the residual, first-harmonic rocking couple usually remaining in a conventionally balances 90ﮠV6 engine. Further, the Oldham- coupling- type balancer can be used to reduce the elliptical second-harmonic rotating couple to a horizontal rocking couple. The power consumption of the balancer was measured to be approximately 0.35 kW at 2000 r/min and 1.5 kW at 4500 r/min.Item An Improved Model for the Dynamics of Spur Gear Systems with Backlash Consideration(1993) Shing, T.K.; Tsai, L.W.; Krishnaprasad, Perinkulam S.; ISRAn 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.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 Kinematic Analysis of Tendon-Driven Robotic Mechanisms Using Graph Theory.(1988) Tsai, L.W.; Lee, Jyh-Jone; ISRThe kinematic structure of tendon-driven robotic mechanisms has been investigated with the aid of graph theory. The correspondence between the graph representation of the kinematic structure and the mechanism has been established We have shown that the kinematic structure of tendon-driven kinematic chains is similar to that of epicyclic gear trains. We have also shown that, using the concept of fundamental circuit, displacement equations of tendon driven robotic mechanism can be systematically derived from the kinematic structure. The theory has been demonstrated by the kinematic analysis of three articulated robotic devices.Item The Kinematics of Robotic Bevel-Gear Trains.(1987) Tsai, L.W.; ISRA systematic approach has been developed for the kinematic analysis of multi-degree-of-freedom robotic bevel-gear trains. The approach is based on the idea that the motion of the end- effector can be described by an equivalent open-loop chain and that the relative rotations between every two adjacent links in the equivalent open-loop chain can be derived from a set of fundamental circuit equations. The theory is demonstrated by the kinematic analysis of a robotic wrist.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 On The Conceptual Design of A Novel Class of Robot Configurations.(1988) Tsai, L.W.; Freudenstein, Ferdinand; ISRThe conceptual design has been investigated of the kinematic structure of relatively small robots with positive, rigid-body drive elements of minimum complexity in order to maximize rigidity, minimize vibrations and response time and optimize payload. Several novel robot configurations have been conceived and their displacement analysis and static torque analysis derived directly from their kinematic structure. It is believed that these configurations can be advantageous in the design of high-performance robots relative to current designs involving cables and push/pull elements.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 On the Structural Synthesis of Tendon-Drive Manipulators Having Pseudo-Triangular Structure Matrix.(1988) Lee, Jyh-Jone; Tsai, L.W.; ISRTendons have been widely used for power transmission in the field of anthropomorphic manipulating systems. This paper deals with the identification and enumeration of the kinematic structure of tendon-driven robotic mechanisms. The structural isomorphism of tendon-driven manipulators is defined and the structural characteristics of such mechanical systems are described. Applying these structural characteristics, a methodology for the enumeration of tendon-driven robotic mechanisms has been developed. Mechanism structures with up to six degrees of freedom have been enumerated.Item Topological Analysis of Tendon-Driven Manipulators(1990) Lee, Jyh-Jone; Tsai, L.W.; ISRThis 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.Item Torque Resolver Design for Tendon-Driven Manipulators(1991) Lee, Jyh-Jone; Tsai, L.W.; ISRGiven 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.