Kinematic Optimization of 3-PUU Parallel Manipulator with Large Spatial Workspace

This paper deals with the kinematic optimization of a 3-PUU parallel mechanism for friction stir welding of large parts. The main requirement in the friction stir welding which should be fulfilled by the 3-PUU parallel mechanism is the reachable workspace in the horizontal plane should be large enough. The 3-PUU parallel mechanism consists of an equilateral triangle platform and the base which are connected by a limb. The aim of the optimization is to synthesize a set of optimum dimensions of the moving platform, the base, and the limb length for a given value of the Local Condition Index (LCI). The LCI used in this paper is based on the inverse of condition number and its value is bounded within zero and one, which can ease the optimization process. A genetic algorithm is employed for the optimization method and a single optimum design can be obtained. The workspace of the selected design of the 3-PUU parallel mechanism is presented.