Research On Multilateral Laser Tracking 3D Coordinate Measurement System

Multilateral method is a method that uses multiple measurement base stations to solve the three-dimensional coordinates of points only using the distance information.It can effectively reduce the error caused by angle measurement in single station measurement and has an important application in the large-scale measurement environment requiring high precision.In the process of application and research of multilateral method,it is found that the system of multilateral method can be improved from two aspects: one is the heavy workload of transfer station measurement;the other is the instability of system parameter solution caused by the optimization of system without additional constraints.In view of these two aspects,a multilateral laser tracking 3D coordinate measurement system based on plane constraints is proposed in this dissertation first.By adding standard plane constraints to the measurement field,the constraint equations are provided without increasing the number of unknowns in the system.Further improve the system accuracy,if the system layout parameters are adjusted,the number of stations required by the multilateral system can be reduced to three.In addition,an interface program is written for the four-station algorithm of plane constraint,which is written in QT environment with C++.In addition,based on the self-calibration model of no target point,a kind of fixture has been designed,which can mount the tracker target ball on the tracker,and then puts forward a multilateral system self-calibration method based on spherical center fitting,which uses indirect measurement to complete the self-calibration.The error of the scheme is analyzed and the influence of the error on the measurement result is also studied.The experimental results show that both two self-calibration schemes proposed have higher measurement accuracy compared to the single-station laser tracker.After the reduction of the number of station,the performance of the three-station multilateral system is no better than that of the four-station multilateral system,however,it is still better than the single-station measurement and the traditional multilateral method.