High Precision Pre-Alignment Method Based on Laser Tracker

  Objectives  Higher accuracy is needed for the alignment and installation of key components in new generation particle accelerators. However, the existing measuring instruments are limited by the technological development, it is difficult to significantly improve the measurement accuracy in a short time.

  Methods  In this paper, we proposed a novel pre-alignment method based on 3D trilateration network adjustment of laser trackers. Firstly, we established multiple survey stations surrounding the component which needs to be pre-aligned. Then, we utilized only distance observations between station points and location points to establish 3D trilateration network. Finally, we regarded all coordinates of both station points and location points as unknown parameters, and adopted a 3D free trilateration network adjustment.

  Results  Experimental results show that the root mean squared error (RMSE) of location points calculated by 3D triangulateration are three times higher than that calculated by 3D trilateration. In addition, the average RMSE of location points can reach the highest precision as 8.9 μm by establishing 22 survey stations. Because the precision is no-more-than 10 μm by establishing 12 survey stations, we consider 12 as the quantity of locally optimal survey stations.

  Conclusions  This method can provide crucial engineering values for the practical work during the high-precision alignment and installation of devices.