| With the development of social economy,China's scientific and technological strength has also been continuously enhanced,and the construction of large-scale equipment has been increasing.The subsequent measurement and installation of large-scale equipment has become more and more relevant,and the coverage has become wider and wider,and the accuracy of various installations and inspections has become higher and higher.In these large-scale equipment installations,traditional measurement methods require multiple stations,and the submillimeter accuracy required is a challenge to existing instruments and measurement methods.Traditional measurement instruments and methods are difficult to meet the accuracy requirements.With the advent of laser trackers,this problem has been solved.As the most accurate measuring instrument at present,the laser tracker has a full-scale coordinate measurement accuracy of 15?m+6?m/m and a measuring radius of 80 m.It is the most accurate large-scale measuring instrument in industrial measurement,which can realize real-time tracking of observation targets and measurement of three-dimensional coordinates,with high precision,high efficiency,real-time tracking measurement,quick installation,easy operation,etc.,suitable for large-scale workpiece fitting measurement.The refore,this paper has carried out a series of analysis on the measurement accuracy of the laser tracker.Based on this,a spatial three-dimensional edge measurement network is established by using the high-precision distance observation value of the laser tracker.The specific research contents and conclusions are summarized as follows:(1)Elaborating the measurement principle of the laser tracker and analyzing the single station measurement accuracy of the laser tracker through experiments.According to the basic principle of laser tracker measurement,the threed-imensional coordinate calculation formula of the target point measured by the laser tracker and the error calculation formula in the point are derived.Detailed angle error analysis is carried out from three aspects: dial error,shafting machining error and atmospheric refractive error and detailed ranging error is also carried out from three aspects: laser frequency stability error,reference distance measurement error and meteorological element error.The repeated observation experiments verify that the angular accuracy and ranging accuracy are within the nominal accuracy range.Then this paper summarize the effects of the incident angle of the target sphere and the environmental factors on the angle measurement and ranging of the laser tracker.(2)Establishing the laser tracker transfer station accuracy distribution model according to the principle of laser tracker transfer and the coordinate transformation model with its parameters,which can be used to calculate the transfer precision of the test point at any position in the space.Using MATLAB soft ware to model and simulate,which inferred that the points with the same accuracy of the transfer station are distributed on the same ellipsoid in three-dimensional space.The points with different precision are distributed on different ellipsoids,and all ellipsoids are distributed in a cluster of concentric ellipsoids.The accuracy of the transfer station and the RMS transfer error solved by the SA spatial analysis software are compared and analyzed.The result verifiedthe feasibility and reliability of the transfer station accuracy distribution model.According to the model,under the premise of consistent measurement accuracy,the factors affecting the accuracy of the transfer station are mainly determined by the number of common points and the spatial distribution.Based on the transfer station model,a series of contrast experiments were designed to solve the accuracy of the test point.The influence of these factors was verified and summarize the method of improving the accuracy of the transfer station.(3)Based on the characteristics of high precision ranging of laser tracker,the distance observations are used to derive the 3D edge measurement network adjustment model to eliminate the influence of angle measurement accuracy.The solution method of rank-deficient free network adjustment is expounded and the corresponding MATLAB program is written and then establish several sets of spatial three-dimensional edge-measuring nets in the laboratory by AT960 laser tracker.At the same time,the laser tracker unified spatial metrology network(USMN)is used for analog measurement,and the coordinates of the control points based on the three-dimensional control network adjustment based on laser interference ranging are compared and analyzed,which proves the reliability of the spatial three-dimensional edge measurement network adjustment results.According to the quantitative constraint relationship between the test station and the control point,the law of the control network accuracy and the number of control points to be tested is analyzed in detail.Finally,change the selection method of the initial valueby removing the observation data with poor quality and adjust the weight matrix by using the weight matrix with unequal precision observation value to perform the data processing,which achieve the optimization of the control network. |
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