Institute for Systems Research
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Item AI Planning Versus Manufacturing-Operation Planning: A Case Study(1995) Nau, D.S.; Gupta, Sandeep K.; Regli, W.C.; ISRAlthough AI planning techniques can potentially be useful in several manufacturing domains, this potential remains largely unrealized. In order to adapt AI planning techniques to manufacturing, it is important to develop more realistic and robust ways to address issues important to manufacturing engineers. Furthermore, by investigating such issues, AI researchers may be able to discover principles that are relevant for AI planning in general. As an example, in this paper we describe the techniques for manufacturing-operation planning used in IMACS (Interactive Manufacturability Analysis and Critiquing System), and compare and contrast them with the techniques used in classical AI planning systems. We describe how one of IMACS's planning techniques may be useful for AI planning in general -- and as an example, we describe how it helps to explain a puzzling complexity result in AI planning.Item Manufacturing Feature Instances: Which Ones to Recognize?(1994) Gupta, Satyandra K.; Regli, W.C.; Nau, D.S.; ISRManufacturing features and feature-based representations have become an integral part of research on manufacturing systems, largely due to their ability to model correspondences between design information and manufacturing operations. However, several research challenges still must be addressed in order to place feature technologies into a solid scientific and mathematical framework: One challenge is the issue of alternatives in feature- based planning.Even after one has decided upon al abstract set of features to use for representing manufacturing operations, the set of feature instances used to represent a complex part is by no means unique. For a complex part, many (sometimes infinitely many) different manufacturing operations can potentially be used to manufacture various portions of the part - - and thus many different feature instances can be used to represent these portions of the part. Some of these feature instances will appear in useful manufacturing plans, and others will not. If the latter feature instances can be discarded at the outset, this will reduce the number of alternative manufacturing plans to be examined in order to find a useful one. Thus, what is required is a systematic means of specifying which feature instances are of interest.
This paper addresses the issue of alternatives by introducing the notion of primary feature instances, which we contend are sufficient to generate all manufacturing plans of interest. To substantiate our argument, we describe how various instances in the primary feature set can be used to produce the desired plans. Furthermore, we discuss how this formulation overcomes computational difficulties faced by previous work, and present some complexity results for this approach in the domain of machined parts.
Item Recognition of Volumetric Features from CAD Models: Problem Formalization and Algorithms(1993) Regli, W.C.; Nau, D.S.; ISRAutomated recognition of features from CAD models has been attempted for a wide range of application domains in mechanical engineering. However, the absence of a clear mathematical formalism for the problem has made it difficult to develop a general approach - and thus most of these methods are limited in scope.In this paper, we develop a formalization of the problem of recognizing a class of machinable features expressed as MRSEVs ( a PDES/STEP library of machining features) [19], and an algorithm for solving this problem. Some of the characteristics of this approach are: the algorithm handles a large variety of hole and pocket features along with elementary accessibility constraints and blends for those features; it is provably complete, even if the features interest with each other in complex ways; it has O(n4) worst-case time complexity,
Item Evaluating Product Machinability for Concurrent Engineering(1992) Nau, D.S.; Zhang, G.M.; Gupta, Satyandra K.; Karinthi, Raghu R.; ISRDecisions made during the design of a machined part can significantly affect the product's cost, quality, and lead time. Thus, in order to address the goals of concurrent engineering, it is important to evaluate the machinability of the proposed design, so that the designer can change the design to improve its machinability, To determine the machinability of the part, all of the possible alternative ways to machine the part should be generated, and their machinability evaluated. This chapter describes the techniques we have developed to do this automatically.The information provided by these techniques will prove useful in two ways: (1) to provide information to the manufacturing engineer about alternative ways in which the part might be machined, and (2) to provide feedback to the designer identifying problems that may arise with the machining.
Item A Simple Approach to Performing Set Operations on Polyhedra(1991) Vanecek, G., Jr.; Nau, D.S.; Karinthi, Raghu R.; ISRIn performing regularized set operations on two solids, the most difficult step is boundary classification, in which the boundaries of each solid are split into portions that are inside, outside, or on the surface of the other solid. In this paper, we present a method for doing boundary classification on polyhedra solid. The approach is based on recursively decomposing space based on the boundaries of the solids being classified.This approach has several appealing properties: it is simple to describe, efficient (tests indicate O (n log n) complexity in a variety of cases), and can handle both manifold and non-manifold 3-D solids. This approach serves as the basis for set operations in the Protosolid solid modeler.