Research Of Virtual Assembly Combining Geometric Constraint With Physical Simulation Techniques

During conventional design and production process, producing physical prototypes to evaluate assembly design is very costly and time consuming. With the advance of science and technology during the last two decades, VR technology has brought the way of product assembly design with a new possibility: Virtual Assembly. By means of advantages of VR technology, virtual assembly simulations allow designers to perform assembly evaluations during the early design stages, thus reducing the need for physical assembly prototyping resulting in the possibility to reduce cost and shorten product’s time to market. Therefore, researching techniques of virtual assembly is of significant. This dissertation is focused on research of virtual assembly combining geometric constraint with physical simulation techniques.Firstly, in order to solve the problem of sudden change of components’ position and orientation during conventional assembly allocation navigation, an algorithm based on interpolation is proposed, meanwhile, parameters optimization of trigger conditions for parts’ allocation transformation to realize assembly constraint is studied so as to avoid the collision situation during transforming. A method based on force feedback device taking initiative lead during parts’ allocation transformation is presented to solve the problem of control signal separation after assembly allocation navigation. In order to realize degrees-of-freedom constraints of parts’ in assembly motion navigation, a method that takes advantages of force feedback device to create force constraint models is proposed. Considering three basic mechanical fit, namely interference fit, transit fit and clearance fit, simulation of assembly force during assembly motion navigation is realized.Secondly, a basic procedure integrating Bullet physics engine into virtual assembly system is given so as to realize physically-based assembly simulation. Then, optimum selection of collision detection algorithms provided by Bullet physics engine is studied considering characteristics of virtual assembly. A haptic model for manipulating parts in physically-based assembly system is presented, which is based on virtual coupling and impact impulse. The proposed haptic model can improve the reality of physically-based assembly system.Finally, this dissertation discussed how to combine geometric constraint with physical simulation techniques in a virtual assembly system, and accordingly developed an integrated virtual assembly prototype system. Theories and methods presented by this dissertation are applied and validated in the prototype system by a assembly case.This dissertation preliminarily realized a virtual assembly system combining geometric constraint with physical simulation techniques, fully took advantages of both techniques and made up both techniques’ disadvantages. The research contributed to the development of virtual assembly.