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This paper prcscnts a compact rcprcscntation of all possible asscmbly plitns of ;I givcn prodiict using AND/OR gr;iphs. Such a rcprcscntation forms thc basis Tor cfficicnt planning iilgoritllt1IS which cnablc iin iiicrcasc in asscmbly systcm Hcxibility by allowing an intclligcnt robot to pick a coursc of action according to instantaneous conditions. 'lwo applications arc discussed: thc sclcction of the bcst asscinbly plan (off-linc planning), and opportunistic schcduling (on-linc planning). An cxamplc of an asscmbly with four parts illustrittcs the use of thc AND/OR graph rcprcscntation to find thc bcst asscmbly plan based on weighing of operations according to complcxity of manipulation and stability of subasscmblics. In practicc, a gcncric search algorithm, such its thc AO* may bc uscd to find this plan. l'hc schcduling cfiiciency using this rcprcscntation is comparcd to fixcd scqucncc and prcccdcnce graph reprcscntauons. 'I'hc AND/OR graph consistcntly rcduccs tlie avcragc nurnbcr of opcrations.

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It occurs frequently in robotic applications that a robot manipulates a workpiece which is free to slide on a work surface. Because the pressure distribution supporting the workpiece on the work surface cannot in general be known, the motion of the workpiece cannot be calculated uniquely. Yet despite this indeterminacy, several researchers have shown that sliding motions can be employed to accurately align workpieces without visual or other feedback. Here we find the locus of centers of rotation of a workpiece for all possible pressure distributions. The results allow a quantitative understanding of open-loop robot motions which guarantee the alignment of a workpiece. Several sample problems are solved using the results, including the distance that a flat "fence" or robot finger must push a polygonal workpiece to assure that a facet of the workpiece comes into alignment with the fence.