A Qualitative Approach to Mechanical Constraint

The goal of Qualitative Mechanics (QNI) is to produce a common sense theory of mechanical analysis sufficient to describe the behavior of rigid body mechanisms . In order for machines to reason about manipulation of objects in the physical world we need to develop theories of mechanics sufficiently flexible to describe not only common mechanisms such as the gear trains, pistons, and ratchets, but also unusual devices such as .mutilated gears, Wankel engines, and clock escapements . These descriptions may be used to predict the behavior of an unknown mechanism, determine the suitability of a given device for a task, diagnose mechanical failures, and critically analyze new mechanisms . There is a great deal of interest in .developing Al tools to assist in mechanics, both by mechanical engineers and Al researchers . Our approach is to build qualitative theories which are applicable to a wide range of real problems and construct programs to test these theories . This paper begins with a short definition of terms, then describes the computations of mechanical constraints on motion, and concludes with examples which have been implemented using these ideas .