Informationally-Complete Product Models of Complex Arrangements for Simulation-Based Engineering: Modelling Design Constraints using Virtual Solids (original) (raw)
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This paper presents a constraint-based methodology for product design with advanced virtual reality technologies. A hierarchically structured and constraintbased data model is developed to support product design from features to parts and further to assemblies in a VR environment. Product design in the VR environment is performed in an intuitive manner through precise constraint-based manipulations. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction to establish constraints between objects, and are further realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix and derived from constraints between objects by constraint solving. A procedure-based degrees-of-freedom combination approach is presented for 3D constraint solving. A rule-based constraint recognition engine is developed for both constraint-based manipulations and implicitly incorporating constraints into the VR environment. An intuitive method is presented for recognizing pairs of mating features between assembly components. Examples are presented to demonstrate the efficacy of the proposed methodology.
Assembly modelling by geometric constraint satisfaction
Computer-Aided Design, 1996
A new approach for representing and reasoning about assemblies of mechanical parts has been developed. The approach combines a formalism for representing relationships among features with a new method for geometric constraint satisfaction. The method employs symbolic reasoning about the geometric structure of parts to solve spatial constraints between the parts, in contrast to other approaches that reduce the geometric relationships to a set of non-linear equations to be solved. The system characterizes over-, under-, and fullyconstrained assemblies. For under-constrained assemblies, the remaining degrees of freedom are automatically coalesced into a set of kinematic joints that capture some of the functionality of the assembly. For over-constrained situations, redundant constraints are identified and checked for consistency, and degenerate cases are handled; this allows multiple feature relationships between two parts to be handled. A computer implementation in a limited feature domain is described and used to illustrate the approach with an example. Copyright 0 1996 Elsevier Science Ltd