Research On The Measurement Method Of Geometric Error For Heavy-duty Machine Tools Based On The Sequential Multilateration Method

As large-scale parts processing equipments,heavy-duty machine tools mainly serve national key areas such as national defense,aerospace and energy,and their precision determines the processing precision of large parts.Due to the large number of measurement points in the geometric error detection of heavy machine tools,the measurement error caused is large.Therefore,it is important to find a high-precision and high-efficiency geometric error detection method to improve the machining accuracy of heavy-duty machine tools.The sequentially multilateration method of laser tracker is widely used in the detection and identification of geometric error of heavy machine tools as a measurement method capable of quickly and accurately detecting large-scale spatial error.However,the current sequential multilateration method does not consider the structural characteristics of heavy-duty machine tools,and the measurement error is large in practical applications.In order to solve the above problems,this thesis studies the detection algorithm and station configuration of the sequential multilateration method,and improves the detection accuracy of the geometric error of heavy machine tools by improving the detection algorithm and optimizing the station configuration.According to the structural characteristics of the linear axis and the rotary axis of the heavy machine tool,the geometric error identification algorithm is established by the homogeneous transformation matrix,and the relationship between the spatial error and the geometric error of machine tools is obtained.Then the spatial error detection algorithm is established based on the sequential multilateration method.Considering the large-size working space of heavy-duty machine tools,the machine repeatability error and the laser tracker length error are large,resulting in large errors in the process of solving spatial errors.Regarding the issue above,an improved algorithm for spatial error detection of heavy machine tools is established based on the least squares method with Tikhonov regularization.The Monte Carlo method is used to simulate the average deviation and uncertainty before and after the improvement of the algorithm,and the rationality of the improved algorithm is verified.Considering that the measurement accuracy of the sequential multilateration method is affected by the station configuration of the laser tracker,a station configuration optimization model of the linear axis and rotary axis that meets the actual measurement conditions of the heavy machine tool is established based on the error amplification factor.Taking the heavy-duty floor-milling and boring machine and the vertical turning and milling machine center as examples,the Monte Carlo method is used to analyze the configuration of the regular tetrahedron under unconstrained conditions,the optimized station configuration and the unoptimized general station configuration under the constraint conditions.The measurement uncertainty of the station configuration evaluates the accuracy of the station configuration optimization.Considering the position error of the actual set-up of the laser tracker,the Monte Carlo method is used to evaluate the system measurement uncertainty of the theoretical optimization of the station configuration and the actual station configuration of the added position error,and verify the robustness of the station optimization configuration.For the results of the above research work,the precision verification experiment of the sequential multilateration method,the algorithm improvement of linear axis and rotary axis and the verification experiment of station optimization accuracy are designed.Taking the measurement result of the coordinate measuring machine as a reference,comparing the measurement error of the single station method and the sequential multilateration method,the results show that the measurement accuracy of the sequential multilateration method can meet the measurement requirements of heavy-duty machine tools.Under the general station configuration and optimized station configuration,the geometric error of the heavy-duty floor-milling and boring machine and the vertical turning and milling machine center is detected by the sequential multilateration method based on the general algorithm and improved algorithm,and the SP geometric error measuring instrument and laser interferometer.The single geometric error comparison of direct measurement method is used to verify the accuracy of linear axis and rotary axis algorithm and the accuracy of station optimization.The results show that both algorithm improvement and station optimization can improve the measurement accuracy of geometric error of heavy machine tools.