Position And Orientation Calibration Of Chromatic Confocal Probe And Motion Error Analysis For On-Machine Measurement

On-Machine Measurement is widely used in the processing of precision parts,to achieve the coordination of automatic measurement and digital processing.Spectral confocal displacement sensor has received extensive attention in the research of non-contact on-line measurement because of its high accuracy and easy integration.Ensuring the reliability of on-machine measurement results is an effective way to achieve high-quality feedback processing of parts.However,due to the small range and short working distance of the spectral confocal sensor,the beam direction and spot spatial position are difficult to obtain accurately,resulting in the inability to accurately coordinate the position of the measuring point.On the other hand,the geometric errors of the machine tool exist at the same time in the processing and measurement process,and the actual contour deviation of the part is difficult to obtain accurately,which limits the improvement of the measurement accuracy.To this end,this paper focuses on the on-machine measurement technology of spectral confocal in multi-axis machining of complex curved surfaces,and proposes an automatic calibration method for the sensor beam direction and spatial position,and accurately obtains the spatial measurement pose of the sensor;The influence law of the process and the identification of sensitive errors have laid the foundation for realizing precise on-machine measurement of spectral confocal.The main research contents are as follows:First,to solve the problem of measuring the space vector direction of the measuring beam and the installation offset of the sensor,a sensor space and pose calibration method based on a standard sphere and a standard plane is proposed.By calibrating the standard spherical section line and the standard plane,a sensor calibration model based on spherical constraints and plane constraints is established,and the least-squares method is used to solve the overdetermined equations,the sensor pose parameters are obtained,and the beam space vector is measured.Accurate calibration of direction and rotation axis installation offset.Then,based on the multi-body system(MBS)theory,a four-axis linkage machine tool geometric error model is established,and the relationship between the machine tool geometric error and the measurement error is studied.In order to quantify the degree of influence of each geometric error term on the measurement accuracy,a number of error terms with greater influence are identified,and the sensitivity coefficient is used to characterize the relationship between the trajectory error and the geometric error,and the sensitive error term in the measurement process is accurately identified.Finally,for the sensor position and orientation calibration method and the machine tool geometric error analysis method,an in-machine measurement verification experiment was carried out.After the calibration using the proposed spatial pose calibration method,the experimental results under different measurement paths are compared.The results show that the analysis of the experimental results obtained under different measurement paths based on the error model is in line with the engineering reality,and a reasonable measurement path is adopted After that,the measurement error is significantly reduced,which effectively improves the non-contact on-machine measurement accuracy.The measurement system can realize the on-machine measurement of the curved surface,and the measurement accuracy reaches micron level to meet the requirements of on-machine measurement.