Planar robotic mechanisms: analysis and configuration comparison

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Virginia Polytechnic Institute and State University

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.