A Study On Error Analysis And Synthesis Of Parallel Manipulators

Based on the typical structure—Stewart platform, this dissertation deals systematically with the error analysis and synthesis of parallel manipulators.The forward kinematics error model for the pose error analysis of the end effector has been formulated in terms of the differential relationship of robot and close-loop vectors of a parallel manipulator. For 6-SPS Stewart platform and its relevant configurations, the pose errors of the end effector can be directly obtained when the structural parameters and errors are given. The modeling method can also be used to the accuracy analysis of other parallel manipulators and spatial mechanisms.The effects of structure and pose parameters on the pose errors of the end effector is analyzed. The positions where uncertain configurations and the maxim deviations of the pose occur have been determined. Under the control of the maxim deviations, reasonable structure parameters, which are not sensitive to the pose errors, can be obtained.A new method—influence factor analysis is put forward according to the characteristics of the pose errors of parallel manipulators. Applying the method, the position of geometrical singularity and the changing trend can be uncovered. The influence factors of 6-3 and 3-3 Stewart platform are found to be approximate and both are far from one of the 6-6 Stewart platform. This results will provide a guideline in the design, manufacturing and assembly of the parallel manipulators.The accuracy synthesis model has been formulated by means of the error theory. Based on the principle that primary errors exert the same effects on the driven member and the concept--influence factors of the pose errors, two methods for pose error synthesis of parallel manipulators have been presented. The numerical examples indicate the necessity and effectiveness of the methods.