Abstract

Manipulators, usually resembling a human arm, are widely used in industry. The most popular manipulators are serial chain manipulators. But low transportable load and poor accuracy increasingly become problems of the usage with such kinds of robots. Consequently, closed loop chain mechanisms are introduced to resolve these problems. In comparison to serial robots, parallel robots have many advantages. But the complexity of singularity analysis and relatively small workspace are the major drawbacks for parallel robots.

This thesis is focused on singularity analysis and kinematic design of parallel robots. The thesis makes three major contributions to the research of parallel robot kinematics. Firstly, the determination of unmanipulable singularities are presented. Through the decomposition of the composite manipulability Jacobian, they are identified as single-arm singularities or coincident with unstable singularities. Secondly, singularities are classified due to their relationship with the design purpose. A sequential design procedure is introduced for singularity free workspace design. For an n-arm parallel robot, n-1 arms are designed first to satisfy workspace requirements, then the last arm is designed to provide a singularity-free workspace. Planar and spatial parallel mechanism singularity-free workspace design examples are presented to verify the efficacy of this design method. Modeling of this design method is discussed, and optimization tools are suggested to solve the design problem. Thirdly, a novel 6-Degree Of Freedom composite parallel mechanism is introduced. It consists of two parallel mechanism–the planar 3-RPR and the spatial 3-UPS-1-PU. Inverse kinematics and singularity of this mechanism are analyzed. Different combinations are demonstrated for different applications.