Research On The Problem Of Repeated Positioning Measured By Ultra-precision Large-scale Straightness Inversion Method

Straightness measurement has the fundamental position in manufacturing technology.Ultra-precision large-scale straightness measurement has been the key influence on precision and ultra-precision manufacturing technology.At present,sub-micron ultra-precision manufacturing technology has proposed an accuracy requirement of 0.1 ?m/m in the scale of 700-1000mm.Straightness measurement precision is the limiting factor.Error Separation Technology(EST)of straightness measurement can separate the inherent straightness error of the benchmark line.Thus,the straightness of benchmark line and the measured line can be measured simultaneously.EST can realize the absolute measurement and is a necessary technology in ultra-precision straightness measurement.Reversal method of straightness measurement which is an important method of EST has advantages such as simple mathematical model,no sampling interval limitation,no zero error,accurate reconstruction,etc.The accuracy of reversal method depends on the measurement repeatability accuracy.The repetitive positioning accuracy of the reversal line affects the error separation result directly and is a significant content of the repeatability accuracy.To improve the accuracy of reversal method of straightness measurement,it is necessary to study the repetitive positioning problem of reversal method of ultra-precision large-scale straightness measurement.The influence of the repetitive positioning accuracy on the error separation accuracy of reversal method of straightness measurement is studied by theory and simulation.This paper analyzes the influence of the six positioning errors of the reversal straight line on the error separation accuracy of the reversal method.This paper also simulates the influence of the repetitive positioning error on the measurement accuracy of the reversal method.The results show that the accuracy of reversal method of straightness measurement is directly related to the repetitive positioning error of the reversal straight line.This paper presents a measuring positioning method to improve the repetitive positioning accuracy of the reversal straight line.The six-dimensional high-precision positioning of the reversal straight line is realized by the measurement and positioning of the three-dimensional positioning of the two endpoints of the reversal straight line and the roll angle of the surface.The three-dimensional positioning of the two endpoints of the reversal straight line is achieved by a capacitive micro-displacement sensor and a mental sphere.The method of the measuring positioning method has been simulated and experimented.The results show that the method can achieve the positioning accuracy better than 0.1 ?m in y direction,better than 2?m in x or z direction and better than 11? of the roll angle.A six-dimensional adjustment platform has been designed for the measuring positioning method of the reversal straight line.The platform can adjust the 3-dimensional position of the two endpoints of the reversal straight line and the roll angle,which can realize the six-dimensional adjustment of the reversal straight line in space.Combined with the measuring positioning method of the reversal straight line,the accuracy of six-dimensional adjustment platform has been analyzed.The results show that the repetitive positioning accuracy is better than 0.2?m in y direction,better than 2?m in x or z direction,better than 11? of the roll angle,better than 7? of the pitch angle and better than 2? of the yaw angle.Comparison results of reversal straightness measurement indicate that the positioning accuracy of the reversal straight line has a direct influence on the accuracy of the straightness measurement of the reversal method.A straight line with a length of 500mm has been measured by reversal method.When the confidence is 95%,the straightness uncertainty of the measured straight line is 0.038?m and the straightness uncertainty of the benchmark guide rail is 0.050?m.By high precision repetitive positioning of the reversal straight line,the accuracy of straightness measurement by reversal method can be improved efficiently.It is also expected to achieve ultra-precision large-scale straightness error separation and measurement with an accuracy of 0.1?m/m.