Research On Assembly Modeling Oriented Constraint Management System

Concurrent Engineering is now becoming a hot issue in the manufacturing industry by virtue of cutting the time and cost of product developing process considerably. Assembly modeling is a new modeling method turns up in recent years also attracts the world eyesight since it supports product cycle-life development and concurrent design. How to deal with the complicated and intertwined constraint relationships during the product developing process is the core issue in the Concurrent Engineering, while developing an assembly modeling oriented constraint management system seems to be a good way to tackle it as introduced in this thesis . This paper divides the constraints into two kinds, namely engineering constraint and assembly constraint after analyzing the character of all constraints during the process of product development, and then it proposes to manage these constraints with different methods. In order to support assembly modeling, the assembly sequence problem is also discussed in this paper. It puts forward a method based on directed graph and database tables to manage the engineering constraints since they are easily expressed by equation or inequation. An Engineering design example is also given to describe the method concretely. According to the character of assembly constraint, a DOF based algorithm is put forward to solve it by computing the part's DOF in terms of the different combination of constraints obtained from an assembly model built in advance, and then giving corresponding response to the user in the light of different results. For the sake of supporting assembly modeling, a new method with high efficiency to solve the assembly sequence problem is described. It produces a liaison matrix with the constraint information obtained from the assembly model, and then outputs the assembly sequence according to the different constraint value, whilst the user input is also considered to adjust the assembly order. At last, a constraint management system—ConMan is developed using the theories mentioned in this paper. The fact that the system applied to several engineering examples has shown the correctness and efficiency of it.