Development And Experiment Of Contact On-machine Measurement System For Complex Surface

In recent years,with the rapid development of the global economy and modern manufacturing technology,people have higher and higher requirements on the appearance and function of products,and products with complex surfaces are increasing.Complex surfaces have been widely used in aviation,aerospace,automobile,household appliances,biomedicine,optics,mold and other fields.The design and manufacture of complex surfaces are inseparable from the measurement of complex surfaces.At present,the measurement method of complex surfaces is mainly off-line measurement.Although off-line measurement is relatively mature and has high measurement accuracy,off-line measurement needs multiple clamping and positioning in the processing of complex surfaces with multiple iterations and approximations,which will introduce clamping error,which is not conducive to the correction and accuracy of the surface shape of the determined area of the workpiece.It will reduce the efficiency of machining and measurement,so it is difficult to meet the requirements of highefficiency and high-precision machining of complex surfaces.On-Machine measurement is currently a better solution.In this paper,based on the principle of contact on-machine measurement,the hardware system of contact on-machine measurement for complex surface is developed by using the self-developed precision polishing system.Utilize VB6.0 to develop the contact on-machine measurement system motion control and data acquisition software under Windows platform.The measurement system software consists of XYZ threeaxis motion platform control module,probe control and data acquisition module,origin positioning module,curve measurement module,rectangular area measurement module,circular area measurement module and automatic measurement module.The seven modules cooperate with each other to realize the three-axis linkage control of the XYZ motion platform,the measurement and data acquisition control of the probe,and the fusion and integration of the position information of the measurement system's motion axis and the probe data,thereby achieving the automatic measurement of complex surfaces.In this paper,the influencing factors of the origin positioning error and the probe tilt error of the on-machine measurement system are studied.The mathematical models of the origin positioning error and the probe tilt error are established.The origin positioning error and the probe tilt error are simulated and analyzed by MATLAB.The correctness of the mathematical model of the origin positioning error is verified by the standard spherical measurement experiment.In this paper,the method of measuring trajectory planning for complex surface is studied.The software of measuring trajectory planning by curvature difference method and the software of measuring trajectory planning by line angle method are developed by MATLAB.The data processing method of curve and surface measurement is studied,and the curve and surface data processing software based on the least square fitting method is developed with MATLAB.The surface profile curves of cylindrical convex surface and cylindrical concave surface are measured.The curve fitting and radius compensation are carried out for the measured data by using the developed curve data processing software.The measurement results are compared with those of Taylor Hobson PGI 1240,and the measurement accuracy of the measurement system is verified.The off-axis paraboloid is measured,and the surface fitting and radius compensation are carried out for the measured data by using the developed surface data processing software.The off-axis paraboloid's surface data is obtained,which verifies the effectiveness of the measurement system.The results of theoretical analysis and experimental research show that the contact on-machine measurement system of complex surface developed in this paper can achieve the accuracy of micrometer level,realize the automatic measurement of complex surface,and meet the requirements of on-machine measurement.