| Optical complex surface has attracted widespread attention due to an increaseing demand in the military and civil fields,and optical complex surface is developing towards a direction of high precision,structure function integration,lightweight and complexity.Although the wavefront-interferometry method has a high measurement accuracy,the method lacks versatility and flexibility.For some complex surfaces,it is necessary to develop special measuring means,including the design of optical path,the production of compensator and the corresponding correction algorithm.Emerging high-precision profile coordinate measurement technology has a high measurement accuracy and versatility;the main large-diameter high-precision profile coordinate measurement system is almost monopolized by foreign countries;these coordinate measurement systems all realize high-precision large-diameter measurement by reducing the Abbe offset or dual frame design for structural and measurement.The systems are also some shortcomings,such as complex structure,high price and so on.In order to realize a high-precision universal measurement of complex surface,a different approach is exploited by employing glass as the guideway material in this paper.A highly acurate wavefron-interferometer stage is used for the measurements.The measurement results will provide a good guide for the processing.Therefore,the glass aerostatic guideway can achieve high precsion and reduce the Abbe angle.Moreover,based on the Cartesian coordinate measuring machine tool,a high precision three-dimensional profilometer is developed by the glass guideway.This paper foucus on the issue of the high accuracy and versatility measurement by self-deveolped a high precision profilometer.This paper puts forward a calculation method of effect ratio of 21 geometric errors,reveals the influence of single geometric error on the measurements,forms the manufacturing process and assembly process,proposes the measurement method and design method,investigaes the error identification and compensation theory,standarlizes the measurement result evaluation and traceability.Based on the research cited above,the profilormeter achieves a high accuracy.The main work of this paper includes:(1)The geometric error model of Cartesian coordinate measurement system is studied.The influence of each single error in 21 geometric errors on the measurement results is analyzed.The effect ratio of geometric error of fixed bridge measuring machine is obtained,and the design value of geometric error in profilometer measurement system is allocated according to the ratio.Among 21 geometric errors,the straightness of X / Y axis in Z direction and the angle error of X axis account for a large proportion,which need to be strictly controlled.(2)The combined process of CCOS(computer-controlled optical surfacing)and MRF(magnetorheological finishing)are studied for manufacturing the guideway.Based on wavefront-interferometer,turntable and standard square brick,the measurement method of form and position error of long glass guideway is proposed.Through the processing and the measurement,the surface accuracy of each working surface of glass guideway is better than 100 nm,and the form and position error is better than 1 μm.Based on the aerostatic theory,the air bearing for the glass guideway are designed and optimized.The glass guideway is driven by belt,the position data is recorded in real time by glass grating ruler,and the straightness of the guideway is measured by standard flat method.The straightness is only 30 nm in the range of 200 mm.(3)The high accuracy measurement methods of geometric error based on optical standard parts are studied.Due to the low accuracy of traditional geometric error measurement methods,it is not competent for the geometric error measurement of high accuracy glass guideway profile measurement system.Based on the optical flat,the straightness measurement and compensation method is studied.After the straightness compensation,the two-dimensional plane measurement accuracy of the system is improved.The sqaureness measurement based on the optical square brick is studied.The optical square brick belongs to cuboid workpiece,and the high accuracy squareness measurement of orthogonal guideway is realized by using the principle that the sum of internal angles of datum plane is 2π.The measurement method of guideway angle error based on optical flat and autocollimator is studied to achieve a high accuracy.(4)The effects of stress deformation,temperature,vibration noise and sensor error on the measurement results are studied.In order to improve the measurement accuracy,a high accuracy stress deformation measurement method based on wavefront interferometer is proposed.The experimental results show that the horizontal guideway has a good repetitive motion accuracy.In order to explore the influence of environmental temperature and local temperature on the measurement of the system,the surface figure changes of the guideway under different temperatures are studied;the influence of local temperature such as z-axis motor on the measurement surface figure is analyzed;and a certain measurement path strategy is proposed.The vibration amplitude and frequency characteristics of the profilometer in three directions are measured by displacement sensor and accelerometer respectively,and the measurement error caused by vibration is analyzed.Based on the standard concave surface,the measurement accuracy of the confocal sensor is calibrated.(5)The measurement result evaluation method of glass guideway profilometer is studied,the accuracy traceability chain of the profilometer is established.The uncertainty of the measurement results of the profilometer is obtained according to the international and national standards.The uncertainty of one-dimensional and two-dimensional measurement of glass guide profilometer can reach 25nm(2σ).The measurement uncertainty of 160 mm diameter complex curved surface is 69.02nm(2σ). |
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