3-D Measurement of Large Scale Steel Structure

提出了一种新的大尺寸三维测量方法，该方法利用细准直激光束和五棱镜构成测量坐标。用激光光斑指出了要测量的位置。它们由一台CCD摄像机探测，并由一台个人计算机计算出坐标。将该方法应用于某大型悬索桥主塔钢箱构件的加工精度检测，验证了该方法的可行性。悬索桥主塔高度为100m以上，是由多个钢箱构件堆叠而成。最终构型的垂直直线度取决于每个箱体构件的端面的平坦度和平行度。因此，在端面的最终加工过程中需要高精度的加工，这可以通过在机测量成功地实现。传统的测量仪器，如经纬仪和水准仪，很难满足这一要求。原型装置安装在专门为加工大型零件而设计的平面机上，并对塔架钢箱构件的端面进行加工和测量。工件的尺寸约为6m×6m×5m。实验结果表明，用该方法进行“在机测量”可显著提高加工精度。例如，获得的端面平坦度和脱平行度分别为0.2 mm和3x10^-5 rad。

A new measuring method is presented for large scale three dimensional measurement, in which the measurement coordinates are constructed by finely collimated laser beam and pentaprism. The positions to be measured are pointed out with laser spots. They are detected by a CCD-camera and the coordinates are calculated by a personal computer. The feasibility of the presented method is investigated applying a prototype device to the measurement of machining accuracy of steel box members of a main tower of a large suspension bridge.The main tower of a suspension bridge, the height is 100m or more, is built by heaping up many steel box members one over another. The vertical straightness of the final configuration depends of the flatness and parallelism of end surfaces of each box member. Therefore, highly accurate machining is required in the final machining process of the end surfaces, which can be successfully achieved by "on the machine measurement". The conventional surveying instruments, such as theodolite and level, are hardly available for this purpose.The prototype device is installed in a facing machine which is specially designed for machining a large workpiece, and end surfaces of a steel box member of a tower are machined and measured. The size of the workpiece is of around 6m x 6m x 5m. Experimental results verified that the "on the machine measurement" with the presented method can considerably improve the machining accuracy. For instance, the achieved flatness and out-of-parallelism of end surfaces are 0.2mm and 3x10^<-5>rad., respectively.