基于OpenCasCade的虚拟三坐标测量机碰撞检测方法

Collision Detection Method of Virtual Coordinate Measuring Machine Based on OpenCasCade

为了解决三坐标测量机测量过程中可能出现的碰撞问题,提出将虚拟空间与实际空间相结合的防碰撞方法,同时提出一种基于OpenCasCade(OCC)的快速、准确的虚拟空间碰撞检测方法.防碰撞方法在虚拟空间中建立与实际空间具有一一对应关系的虚拟模型,从而在计算机向三坐标测量机发送运动指令时先在虚拟空间中检测该指令是否会造成碰撞,将有碰撞的指令修改为无碰撞的安全指令输出,以达到防碰撞的目的.根据OCC建模的特点,可以将虚拟空间碰撞检测方法分为2步,第1步利用包围盒法快速剔除不可能碰撞的部分,第2步利用三角面片相交检测法进行较为精确的碰撞检测.为了提高速度,利用OpenMP将碰撞检测程序的计算并行化.相关的碰撞检测实验验证了该碰撞检测方法的可行性,并根据记录的数据对碰撞检测时间和精度进行了分析,证明该碰撞检测方法具有一定的实用价值.

To solve the collision problems which may occur during the measurement process of the coordinate measuring machine （CMM）, an anti-collision method combining the real and virtual spaces was pro- posed, so was a rapid and accurate collision detection method based on OpenCasCade （OCC）. The models of the CMM and the parts in the virtual space, built by using OCC, are exactly correspondent with their counterparts in the real space. So, every time when the instructions were sent to the CMM by the computer, the virtual space collision detection would be done first to determine whether there was colli- sion along the paths the instructions gave. If collision was detected in the virtual space, the instructions would be modified to ensure no collision occurred in the virtual space, and then the modified instructions would he sent to the actuator of the CMM. The collision detection method involves two steps according to the features of OCC modelling. The first step utilizes bounding box method to cull the parts that would not collide, the second step triangulates the parts left after the culling, and then the triangle facet intersection testing method is adopted to get a pretty accurate collision detection result. To improve the speed, OpenMP is employed to parallelize the calculation of the collision detection. Meanwhile, some collision detection experiments were conducted, the feasibility of the collision detection method was verified through these experiments, and the time and accuracy of the collision detection were analyzed by using the data recorded, which proved the practical value of the method proposed.