The design, analysis and display of three-dimensional mechanisms using a CAD executive

Abstract

Computer tools for the solution of three-dimensional mechanical systems have been available for some time. Still, one finds practicing engineers reluctant to use them. They are discouraged by the tedious and error-prone process of entering the required three-dimensional description of the system. They are ill-prepared to supply the masses, centers of mass, and moments of inertia that are often needed. They also find that displaying the analysis results in a meaningful way is difficult at best.This paper describes the use of a computer-aided design executive called Leo and its application to the CAD problem of three-dimensional mechanical dynamics. For this application, Leo is used both as a modeling and user information management system. Leo is capable of using stick geometry for kinematic applications. When solid volumetric geometry is required, it is created as Boolean combinations of constructive solid geometry primitives. A solid modeler processes the database to product mass properties and adds those to the database. A mechanical dynamics package processes that database and returns predicted motions. An imaging program processes that new database to produce computer graphics images of the predicted results on both vector and color raster displays. This entire process occurs with minimal user intervention.