Error Analysis And Compensation Of On-line Inspection System For Complex Surface

With the continuous progress of human society,there is an increasing dependence and demand on high-end manufacturing.In the field of high-end mechanical manufacturing,such as aerospace,mold,ship,etc.,there is a higher standard for the surface quality,dimensional accuracy and processing efficiency of complex surface parts,which requires the necessary surface dimension detection and processing measures in the production process of parts.The high-precision coordinate measuring machine(CMM)is usually used to detect the complex curved parts that have been machined by CNC machine tools in the traditional off-line inspection.However,this method will bring the positioning error of the second clamping of the workpiece and slow down the overall production efficiency of the parts.A new life for the production process of complex curved parts is caused by the emergence of on-machine measurement(OMM)based on CNC machining center.The closed-loop production process of "processing-detection-error compensation" can be completed by the same CNC machining center based on the online detection technology,which is the first choice for machining precision complex surface parts.This has also become a research hotspot in the field of CNC system processing.Aiming at the problem of insufficient measurement accuracy in the process of online measurement of free/distorted curved surface parts,an in-depth research is conducted on key technologies such as compensation of CNC machining error and pre-travel errors of inspection probe,and random error separation of inspection data.The main research contents of this dissertation are as follows:(1)An in-depth research on present situation and application research status of OMM technology of domestic and foreign development in the field of complex curved surface highprecision detection are studied.The existing methods of analyzing and compensating the machine tool error and the detection probe system error in the OMM system are summarized and analyzed.At the same time,it is pointed out that there are still some difficult problems worthy of further study in this field.(2)Factors influencing the detection errors of the OMM system based on the three-axis CNC machining center are analyzed.The error items that have a greater impact on the detection accuracy,such as the geometric error of the machine tool,the pre-travel error of the detection probe and the radius error of the probe are studied in detail.Aiming at the geometric error of three-axis CNC machining center,a geometric error modeling and compensation method of machine tool in small space is proposed.Aiming at the problem of pre-travel error of touch probe,a pre-travel error prediction model based on least square collocation method is proposed,which can accurately predict the pre-travel error of touch probe in each normal direction to realize real-time detection of the OMM process pre-travel error compensation.(3)The problem of random error in on-line inspection data of complex surface parts is considered.A method of random error separation based on Ensemble Empirical Mode Decomposition(EEMD)is proposed.By decomposing the test data into a series of intrinsic mode functions,the random error components are found out and eliminated,so that the detection accuracy of on-line detection system is further improved.(4)On the basis of the above research,the programming tools are used to develop "detection random error separation" module and "pre-travel error compensation" module of the OMM system.Furthermore,the experimental comparison of the CMM measurement results and the on-line detection results of the experiment which is based on the two complex surface parts processing is carried out.Then,the effectiveness of the detection error compensation method for OMM system is verified by the experimental data.Finally,the research contents and innovations of the dissertation are summarized,and the technical problems that need to be further studied and solved are pointed out.