The Summarization On Measuring Of Large Diameter Based On Chord Length And Bow Altitude

Machines and equipments with large diameter more than 500mm have been widely applicated.However,it still has so many obstacles on the way to high accuracy and precision measurements.It is difficult to measure diameter of the large-scale work piece with direct method of measurement,especially for the incomplete circle work piece.At presents,indirect measurements become the development direction of measuring large diameter.So this paper just includes developing tendency of the measuring methods of large diameter workpieces and gives what we want to resolve in this research.To the measurement of large diameter,it is based on the measurement principle of bow altitude and chord length and analysis of its standard deviation.Then computational analysis each error transfer coefficient in different simulation diameter.It is concluded that it is easy for us to improve the accuracy of measurement of bow altitude and chord length method by control the way of bow altitude.By analyzing and comparing the measurement errors,it is disclosed that the reasons of measurement errors and how measurement errors affect measurement precisions.The relationship between the ratio of measurable a bow altitude and chord length method and its sensitivity coefficient has been derived in-depth exploration in this paper.Based on the error theory,we deduce where is the optimum measuring point for measuring a circle's diameter and when the standard error of bow altitude and chord length method are both defined in the paper,as well as the derivation that bow altitude and chord length method has a superiority over the diameter direct measuring method.By the evaluation of uncertainty in measurement of bow altitude and chord length method with the Monte-Carlo numerical simulation method.Through the analysis and comparison the Monte-Carlo simulation curve and the computing values curve,deducing the relationship between arc-height and chord-length and diameter.Through the evaluation of uncertainty in measurement, the size of sensitivity coefficient can judge the scope of measured diameter by use of measuring bow altitude and chord length rapidly and the optimum allocation of check tool basic structure dimension is put forward.Based on the analysis of diameter standardization circle and value of the bow altitude and chord length using in measurements,so the selecting methods of appropriate dimension of the standardization circle and value of the bow altitude and chord length are gained.In conclusion that the best dimension subsection of large diameter in 300～1200mm.The lowest measuring uncertainty is divided diameter into five sections when measuring large diameter by using the bow altitude and chord length method.We can have the minimum value and stability uncertainty of measurement in every section.The research findings can not only improve measurement precisions of large diameter,but also provide theoretical supports for the developments of portable measurement instruments of large diameter.