Institute for Systems Research

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Author: search.filters.author.Tsai, L-W.Subject: search.filters.subject.Intelligent Control Systems

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    Kinematics and Workspace of a Novel Three DOF Translational Platform
    (1996) Tsai, L-W.; Walsh, G.C.; Stamper, R.E.; ISR
    A novel 2 DOF parallel manipulator is presented that employs only resolute joints and constrains the manipulator output to translational motion. Closed-form solutions are developed for both the inverse kinematics produces four solutions for each leg of the manipulator. In general, the four solutions are realized in only two unique leg configurations. The forward kinematic solution is reduced to a quadratic equation. So that in general, there are two poses the manipulator can assume for a given set of input joint angles. The manipulator workspace is also determined for a manipulator with fixed and moving platforms of the same size.
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    Multiobjective Optimization of a Leg Mechanism with Various Spring Configurations for Force Reduction
    (1996) Shieh, W-B.; Azarm, Shapour; Tsai, L-W.; Tits, A.L.; ISR
    In this paper, the design of a two degree-of-freedom leg mechanism is accomplished by a two-stage optimization process. In the first stage, leg dimensions are optimized with respect to three design objectives: minimize (i) leg size, (ii) vertical actuating force, and (iii) peak crank torque for an entire walking cycle. Following the optimization of leg dimensions, in the second stage, spring elements with various placement configurations are considered for further reduction of the actuating force and crank torque. Several tradeoff solutions are obtained and a comparison between variously spring configurations is made. It is shown that the inclusion of spring elements can significantly reduce the actuating force and crank torque.
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    A New Class of Six-Bar Mechanisms with Symmetrical Coupler Curves
    (1996) Shieh, W-B.; Azarm, Shapour; Tsai, L-W.; Tits, A.L.; ISR
    A new class of six-bar mechanisms with symmetrical coupler-point curves is presented. This class of mechanisms is made up of a four-bar linkage with an additional dyad to form an embedded regular or skew pantograph. Because the coupler curve generated at an output point is amplified from that of a four-bar, a compact mechanism with a relatively large coupler curve can be obtained. In addition, due to their structure arrangement, the analysis and synthesis of such mechanisms can be easily achieved. It is shown that the admissible range of transmission angle for such mechanisms is smaller than that of a four-bar mechanism. It is also shown that mechanisms with an embedded skew pantograph exhibit better design flexibility than those with an embedded regular pantograph. Finally, an example mechanism from this class is illustrated and compared with a four-bar linkage with the same coupler curve.
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    Systematic Enumeration of 1:-1 Constant-Velocity Shaft Couplings
    (1996) Madhavan, Bharath; Tsai, L-W.; ISR
    A systematic methodology is employed for the enumeration of 1:-1 constant-velocity shaft couplings. As a result, four potential 1:-1 constant-velocity shaft couplings that are free from singular conditions are enumerated. A promising mechanism is selected for the dynamic analysis. The analysis shows that the mechanism does have the potential for use as a 1:-1 constant- velocity shaft coupling and as a gearless differential.