General QR decomposition of the observation matrix is used to solve identification functions to evaluate identification results of every parameter in parallel mechanism calibrations. A relationship between measured information and identification results is obtained by analyzing numerous matrix transforms and QR decompositions. When distributions of measurement error are determined, random distributions of iden- tification result disturbances (IRDs) can be obtained from this relationship as a function of measurement er- rors. Then the ranges of the IRDs can be effectively estimated, even if true parameter values are unknown. An optimization index based on IRD estimate is presented to select measurement configurations to achieve smaller IRDs. Two simulation examples were carried out with different modes and calibration methods. The results show that the method is effective and that the optimization index is useful. Some regular parameter identification problems can be explained by the IRD estimates.
Closed-form solutions were developed to optimize kinematics design of a 2-degree-of-freedom (2-DOF) planar parallel manipulator. The optimum design based on the workspace was presented. Meanwhile, a global, comprehensive conditioning index was introduced to evaluate the kinematic designs. The optimal parallel manipulator is incorporated into a 5-DOF hybrid machine tool which includes a 2-DOF rotational mill-ing head and a long movement worktable. The results show that the planar parallel manipulator-based ma-chine tool can be successfully used to machine blades and guide vanes for a hydraulic turbine.
Parallel manipulators have many advantages over serial manipulators in terms of high load/weight ratio, velocity, stiffness and precision.A dimensional design theory and methodology of six degrees of freedom scissor parallel manipulator (SPM) is investigated.The SPM kinematics inverse equation is given.Based on the formulation of the local dexterity and the definition about the indexes of workspace incircle radius, the effects of the design parameters on the dexterity and workspace are discussed.Moreover the incircle radius change ratio about workspace are defined and used as the evaluated indicator to analyze the effects of the design parameters on the performances.A dimensional design theory that could satisfy the requirement of dexterity and workspace is proposed.The dimensional design theory and methodology can be of help in the design, trajectory planning and control of parallel manipulator.
