Research On Key Technologies Of Augmented Reality For CNC Machining Simulation

It is an effective way to perform the NC machining simulation and evaluate the machinability of product by using Virtual NC system (VNC) which based on Virtual Reality (VR). However the result of that separates users from the real machining environments. Users are immersed in the virtual world. Using the technology of NC machining simulation that based on Augmented Reality (AR) can solve the problem effectively. Starting with the theories of augmented reality and NC machining simulation, this paper discusses the 3D real-time registration and rapid generating of virtual machining scenes, and on the other hand, the display and interactive operations of synthetic scenes and system computational strategies are also studied.Firstly, the technology scheme and architecture of augmented reality system for NC machining simulation are presented on the basis of analyzing the virtual NC and augmented reality. When the NC machining simulation scenes are merged into the real machining environment by augmented reality, the system puts forward a more strict condition for the 3D registration and virtual machining scene generating. Against the characteristics of real machining environment, a new method for real-time 3D registration based on markerless image is proposed. To obtain the correspondence point pairs between the target in real scene and its 3D model, a new method is put forward that rapidly calculate the projection matrix of virtual machining scene by replacing the correspondence point pairs with the help of training image.Secondly, on the basis of the method of uniform triangulation, another two methods of NC machining simulation are proposed. If the machining target is known and its finished surface is simple, the method of down-top non-uniform triangulation is more efficient. If the machining target is unknown or the mathematic representation of the finished surface is complex, the method of top-down adaptive triangulation is attractive. Both the methods are quite similar in principle as ensuring the machining precision by increasing the local density of triangulation. In the premise of improving the quality of simulation display, the algorithms have a good performance in reducing the computation burden, and guarantee the implementation of geometrical transformation of virtual machining scenes in principle.Furthermore, the implementation of illumination consistency between the real environment and the virtual scenes is researched. The system implements the output of the realistic scenes in OpenGL by interactively installing virtual light source to simulate the illumination effect in the real workshop, such as ambient illumination, lamp and spotlight on the machine. In interactive system, the paper puts much emphasis on the interaction between the user and the virtual scene. It provides some functions such as the selection of virtual object or command button to implement the initial settings and the operational control of the virtual machining system in the synthetic scenes.Because the heavy computational burden of each subsystem brings severe obstacle to the real-time dynamic display and the constant output of synthetic scene, some computing strategies are proposed to optimize those subsystem and balance global computation, such as the analysis of image motion, pre-calculate, LOD rendering control. Through those ways, the implementation of the real-time dynamic display and the constant frame rate output of synthetic scene is accessible.Finally, a prototype of augmented reality system for NC machining simulation is investigated and developed by use of the above theories and technologies. Taking a clamp in the real environment as the reference target, the instance implements 3D registration and machining simulation of the virtual NC 3-axis milling system that composed of workpiece and cutter in real environment.