Interactive task planning in virtual assembly

Abstract

We propose a task planner that incorporates with a virtual reality interface for 3D immersive interaction of CAD models and high-level task planning of mating processes. The planner is constructed with the following objectives: 3D immersive VR interface, assembly analysis, feature/constraint update, and assembly path planning.A virtual-assembly system has been developed based on the modeling features and mating constraints proposed in our approach. Our system supports a VR interface for performing task-oriented virtual assembly, constraint analysis, feature/constraint update during assembling, and collision-free assembly planning. An assembly task is described by the relationship of parts or subassemblies, translation of constraints and operation restrictions. Our task planner provides a virtual reality interface which allows users to freely navigate in the assembly environment, select one of the parts, and move it around in all directions. To accomplish the goal of a two-part assembly, the free motion of a 3D input device (e.g. 3D mouse) is restricted by both a collision-free path and allowable motion derived from mating constraints between the parts. The allowable motion with reduced degrees of freedom guides the user assembling the parts in a constrained direction or around a specified rotating axis. Any illegal motion that will possibly cause a collision or disabled movement is not allowed, which prompts a warning sound or error messages to alert the user.When two components are assembled, the two graphs are updated in such a way by joining the common attributes, removing those overlapped or duplicated ones after mating, and creating the new attributes or features that are produced. So a new attribute graph is generated for the new object.