tim@LINC.CIS.UPENN.EDU.UUCP (04/25/87)
Qualitative reasoning of mechanical devices and repair automation Pearl Pu COmputer and Information Science University of Pennsylvania 216 Moore School 1pm April 28, 1987 A knowledge representation scheme, QUORUM (QUalitative reasoning of Repair and Understanding of Mechanisms), has been constructed to apply qualitative techniques to the mechanical domain, which is an area that has been neglected in qualitative reasoning field. In addition, QUORUM aims at providing foundations for the construction of a repair expert system. The problem in constructing a representation is the difficulty of recognizing a feasible ontology with which we can express the behavior of mechanical devices and, more importantly, faulty behaviors of a device and its cause. Unlike most other approaches, our ontology employs the notion of force and energy transfer, and motion propagation. We discuss how the overall behavior of a device can be derived from the knowledge about the structure and topology of the device, and how faulty behaviors can be predicted based on information about the perturbation of some of the original conditions of the device. Necessary predicates and functions are constructed to express the physical properties of a wide variety of basic and complex mechanisms, and the interconnection relationships among the parts of a mechanism. Several examples analyzed with QUORUM include a pair of gears, a spring-driven cam mechanism, and a pendulum clock. An algorithm for the propagation of force, motion, and causality is proposed and examined.