Research On 6-DOF Measurement In Large-Scale Precision Engineering

Large engineering projects are basic guarantee of modern society development,and precision measurement for large engineering projects is one of the basic supporting techniques in modern engineering construction.The measurement for large-scale precision engineering is focused on three-dimensional(3D)coordinate measurement nowadays compared with single dimension measurement in early stage,but 3D coordinate measurement cannot entirely meet the needs in the field,and it is an inevitable trend to develop six-degrees-of-freedom(6DOF)measurement for large-scale precision engineering.However,modern large-scale precision engineering has the characteristics of large-scale field space,various objects and harsh work environment,and these characteristics bring many difficulties to 6DOF measurement.Hence,it is imperative to develop 6DOF measurement techniques,which has long measurement distance,high measurement accuracy,high measurement efficiency,good real-time performance and strong robustness,to meet the demands of large-scale precision engineering.On the background of the demands for 6DOF measurement in large-scale precision engineering,this dissertation analyzes the limitations of the existing 6DOF measurement techniques,and studies a 6DOF measurement system that using total station as base station,and integrating optics,vision,inclinometer and inertial measurement unit as single cooperative target.By exploiting the characteristics of each measurement unit,this technique performs well on measurement accuracy,measurement distance,measurement efficiency,portability and reliability.Focused on the realization of 6DOF measurement and improvement of performance,this dissertation researches on the measuring principle,measurement model,dynamic performance improvement and system calibration successively,and verifies the system through simulations,experiments and specific engineering applications.The main contents of this dissertation are as follows:1.Based on the characteristics of total station,the measuring principle that using total station as base station and integrating optics,vision,inclinometer and inertial measurement unit as single cooperative target is studied.A cooperative target is designed,light path of the system is studied,and an effective method of image processing and spot extraction is proposed.2.The imaging model of measurement system is studied and two attitude solving models are presented: non-redundant attitude solving model and attitude solving model based on the weighted vectors.Error analysis and comparison of two measurement models is conducted through Monte Carlo simulations.3.Based on the fact that the measurement of inclinometer is instable under dynamic conditions,a dynamic measurement method assisted with inertial navigation system is presented.In order to realize system fusion,the Karman filter algorithm is introduced and the selection of Karman filter model is studied.Filter equations are established and filter parameters are determined.A troubleshooting method is also presented.Finally,the measurement method is verified through simulation.4.For the unknown parameters in measurement model,two calibration methods are presented,they are the step-by-step calibration method of calibration parameters and the integrated calibration method based on precise three-axis turntable.The two methods are also verified through experiment.Moreover,the 6DOF measurement system is verified through experiments in laboratory and in specific cases.