| NC lathe controls the action of the lathe through program control system, and it has the features of high-precision and high efficiency. While programming mistakes may lead to collisions between NC lathe cutters and work pieces or fixtures thus do harm to lathe and work pieces. Real-time collision detection should be executed to ensure the correctness of NC program, which is a key problem in virtual manufacturing. By means of reading the parameter information of shape and pose of objects in processing environment, through a collision detection algorithm, it can be judged whether there are collisions between target and other objects ahead of time, so that mistaken action could be prevented from happening, thus the economy loss brought by equipment injury could be avoided.Based on the characteristics of NC lathe, a collision detection algorithm based on AABB and octree space division is discussed, whose main work includes contents below:1. Basic primitives constituting NC lathe equipment model are defined and AABBs are built, then the correctness of AABBs are tested and verified through VC++6.0 graph display. AABB has the advantage of intersection testing briefness; it can reject the objects that don't intersect quickly, and hierarchical bounding boxes are easily built.2. The surface of basic primitives forming objects are divided into basic elements represented by triangles and round plane, and an algorithm of fast intersection detection between elements is implemented using geometry method.3. Environment space is divided into nodes using octree, and objects are inserted into leaf nodes or non- leaf nodes, intersection detection are only executed between two objects when they occupy the same node or when one object occupies a non- leaf node and the other occupies its child node, that is to say, it is not necessary to execute all the pair wise test in the space, so that the number of objects pairs are reduced, and detection speed are raised. |
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