Measurement Model Of Circular Profile With Double Parameters And Separation Of Position Error Using Characteristic Features

With the rapid development of precision equipment manufacturing industries,the machining and assembly requirements for cylindrical precision parts are becoming increasingly stringent,so are the measuring accuracy requirements for cylindricity measurements.However,a model needed for the measurement of circular profile can not be easily available,and it is also very difficult to accurately separate position error between datum lines,and they limit the further improvement of cylindricity measuring accuracy,because the probe offset error is not taken into consideration in existing measurement model of circular profile,and there is a larger error for the estimation of offset error using a linear model.In addition,the original status of the cylindricity measuring instrument is seriously destroyed,and self-calibration for separation accuracy can not easily be achieved after separation of position error between datum lines.This dissertation intends to address:The establishment of a model for the measurement of circular profile,which is a complete and accurate reflection of eccentricity and probe offset errors.Moreover,a solution method of offset errors is proposed,which is based on least-squares fitting and simplex optimization algorithm,and the accurate estimation for eccentricity error,probe offset error and other parameters of measurement model can be realized using this method.A separation method for position error between datum lines is proposed,which is based on characteristic features of cylindrical standard itself.The basic idea of this method is keeping the original measuring status of cylindricity measuring instrument unchanged,and making full use of geometrical features invariability of cylindrical standard during position error separation,by measuring the corresponding cross-sections of cylindrical standard when the cylindrical standard is placed respectively upright or upside down,then the geometrical relationship of the corresponding positions between geometrical features of measured cross-sections and linear motion datum line can be established,and the real spatial location of rotary datum line can be established accurately.Thus the position error between datum lines can be separated through analysis.The effectiveness of key technologies are verified through experiments.Firstly,the measurement model with double offset parameters and separation method of offset errors based on parameter optimization are verified,and experimental results indicate that the proposed circular profile measurement model is perfect in principle,and the separation method based on nonlinear least-squares fitting and simplex optimization algorithm is valid.Secondly,the proposed separation method for the position error between datum lines is verified through experiments.On the one hand,the same position error between datum lines is separated using three cylindrical standards with different geometric characteristics,and experimental results indicate that the separation results have good consistency.On the other hand,after the position error between datum lines of cylindricity measuring instruments is compensated,and the three cylindrical standards are measured when they are respectively placed upright or upsidedown,and experimental results indicate that the influence of integrated measurement error that including the temperature and mechanical drift on separation accuracy is less than 25nm/100 mm,and the cylindrical form gained while the cylindrical standard is placed upright or upsidedown is consistent,and the separation accuracy of position error between datum lines could be improved by one order of magnitude using this method.