The optimum dimensioning of an underwater manipulator for weld inspection

Abstract

The optimum dimensioning of an underwater inspection manipulator is discussed in this paper. The inspection of a weld seam using an alternating current field measurement (ACFM) probe was identified as a five-dimensional Cartesian task. Due to the forward positioning of the required workspace, this manipulator requires two additional axes to locate its base with respect to the weld seam. This leads to a seven-axis manipulator, comprising a two-axis launching stage and a five-axis dexterous inspection stage. The optimization of the architecture of the latter five-axis inspection manipulator is the subject of this paper. In optimizing the architecture, various postures of the manipulator during the inspection process were considered, which thus allows identification of the limiting values of the joint angles for maximum dexterity. The optimum link lengths to ensure the highest dexterity were then determined from the results of the analysis. It is shown that the weld seam diameter and the manipulator condition number can be used as the deciding parameters for determining the relative link lengths of the five-axis inspection stage of the manipulator.

Keywords

underwater manipulator dimensioning dexterity condition number

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