Technology and Task Parameters Relating to the Effectiveness of the Bracing Strategy

To appear in Proceedings of the NASA Conference on Space Telerobotics, Jan. 31 - Feb. 2, 1989, Pasadena, CA.The bracing strategy has been proposed in various forms as a way to improve robot performance. One version of the strategy employs independent stages of motion. The first stage, refered to here as the large or bracing arm, carries the second stage of motion. After the first stage has completed its motion it is braced to provide a more rigid base of motion with a more accurate relationship to the parts to be manipulated. The hypothesis of this research is that more rapid completion of certain tasks is possible with lighter arms using the bracing strategy. While it is easy to make conceptual arguments why this should be so, it is less easy to specify even approximately when this will be true for some reasonably generic situation. There is no relevant experience base with bracing arms to be compared to non-bracing arms. Furthermore, if one were interested in obtaining such practical, or at least relevant, experience, there would be no methodical guidance on the selection of an interesting case. An "interesting case" is one in which the unproven approach, bracing in this paper, can show its superiority. If one such case exists, only the extent of applicability of the new approach is in question. One set of "interesting cases" is likely to be applications in which a large workspace must be covered, but where a series of small accurate moves will remain within a smaller region of the total workspace. A prototype application with these characteristics will be set up and a skeleton design of arms using the competing strategies will be compared