Physically based modeling in virtual assembly

Recently, virtual reality (VR) has been used by engineers to bridge the gap between the vision and the finished product. A major benefit of VR is the reduction of time and costs required by physical prototyping. One important use of VR in design and manufacturing is ""virtual assembly"". This research addresses the key problems and issues concerning virtual assembly, including enhanced constrained motion simulation, physically base modeling, swept volume generation and trajectory editing, and integration of the virtual reality with CAD systems. Results of this research have been implemented in the software system Virtual Assembly Design Environment (VADE).; VADE can simulate axial and planar constrained motion for multiple parts with any combination and application order. The assembly operation sequences can be recorded and stored for later usage. A guidance mechanism has been included to assist users performing assembly operations. Dynamic simulation methods are included to simulate object behavior in the virtual assembly environment using physical laws and collision detection algorithms. Methods for extracting physical properties of the assembly models from CAD systems (including mass properties) have been created. This information is transferred to the virtual environment and utilized for dynamics simulation. The parts behave realistically in the user's hand, constrained on the base part, or moving freely in space.; A novel method to generate swept volume directly in the CAD system is proposed. This swept volume generated this way is more accurate and compact than those created using numerical methods and can be easily processed by CAD systems. A swept volume trajectory editing mechanism has been implemented. Real time bidirectional data transfer between the VR environment and the CAD system has been achieved. The user can perform parametric design modifications in the virtual environment through a CAD system (ProEngineer(TM)).; The main thrust of the research is the direct realistic interaction between the human and the virtual objects and full integration of the VR environment with CAD systems.