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Browsing by Author "Williams, Robert L."

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    Planar robotic mechanisms: analysis and configuration comparison
    Williams, Robert L. (Virginia Polytechnic Institute and State University, 1988)
    Robotic mechanisms are defined in this dissertation to be closed-loop, in-parallel actuated mechanical devices possessing several degrees-of-freedom. Parallel robotic mechanisms have recently received attention in the robotics literature as a potential alternative to the existing serial industrial robot. Serial robots are in a cantilever configuration which makes them relatively compliant and Ieads to poor accuracy. Many serial manipulators have motors that are carried on moving links which limits dynamic performance. Robotic mechanisms are in a parallel configuration which provides excellent stiffness, load-bearing, and accuracy. Robotic mechanisms combine the advantages of serial robots and closed-loop single-degree-of-freedom mechanisms to form a versatile new robotic tool. This dissertation presents theoretical kinematic analysis and design of planar robotic mechanisms. The topics covered are type and number synthesis, kinematic position solution, velocity and acceleration analysis, kinetostatic analysis, workspace optimization, and link interference avoidance. Throughout this work, comparisons are made among three general manipulator configurations: serial, parallel-serial, and fully parallel. Strengths and limitations are discussed for each configuration type. This investigation provides the analytical foundation for implementation of planar robotic mechanisms. Closed-form solutions to the kinematic position, velocity, and acceleration problems are presented. Manipulator reachable hand areas are maximized. An underlying theme of this work is tradeoffs between competing factors relating to various configurations of parallel robotic mechanisms; these tradeoffs are important design considerations. The recommendation of this dissertation is to pursue practical development of robotic mechanisms for general industrial manipulation tasks.
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    Synthesis and design of the RSSR spatial mechanism for function generation
    Williams, Robert L. (Virginia Tech, 1985-08-05)
    The purpose of this thesis is to provide a complete package for the synthesis and design of the RSSR spatial function generating mechanism. In addition to the introductory material this thesis is divided into three sections. The section on background kinematic theory includes synthesis, analysis, link rotatability, transmission quality, and branching analysis. The second division details the computer application of the kinematic theory. The program RSSRSD has been developed to incorporate the RSSR synthesis and design theory. An example is included to demonstrate the computer-implemented theory. The third part of this thesis includes miscellaneous mechanism considerations and recommendations for further research. The theoretical work in this project is a combination of original derivations and applications of the theory in the mechanism literature.