Roundness Measurement Technology And Surface Fitting Analysis Of Profile Measuring Instrument

The high-precision surface elements,represented by spherical and aspheric surfaces,are widely used and play a very important role in national defense,aerospace and other fields.Their measurement methods are various,which is a hot topic of current research.In this paper,a set of high-precision profile measuring instrument is proposed,which adopts the point scanning measurement method.It has the characteristics of strong universality,high precision and easy to realize the traceability of measurement value.The structure of the profile measuring instrument is mainly composed of measuring frame,structure frame,X-axis and Z-axis guide rail,rotary table and spindle system,scanning probe,etc.Among them,the spindle rotation accuracy of the rotary table is one of the key factors that affect the accuracy of the surface measurement.In order to ensure the spindle rotation accuracy,it is necessary to conduct in-depth research on its measurement method.In addition,the measurement data obtained by single point scanning is scattered data,which must be processed by data optimization,fitting,etc.in order to achieve a complete measurement finally.Based on the above,the main research contents of this paper include:1.Proposed a method to calculate the period of roundness measurement signal without angle position information.This method is based on the principle of correlation analysis.It can analyze roundness signal without angle encoder or circular grating.2.The real-time measurement and analysis interface of roundness signal is designed to realize the dynamic real-time detection and analysis calculation of roundness signal collected by the probe and transmitted to the upper computer through the serial port,so as to obtain the image and period information of roundness signal measured more intuitively and quickly.An experimental system composed of a turntable,a motor,a standard ball and a probe is built.The standard ball with a diameter of 75 mm is used as the tested device of the spindle rotation information.The turntable speed is adjusted to measure the roundness signal period under different speeds.The period calculation error is better than 0.26 s,and the repeatability is good.3.Aiming at the super quadratic aspheric equation,a method of fitting fractional terms and higher terms separately is proposed,which effectively solves the problem of many parameters and inaccurate fitting of super quadratic equation.The₂ term is added to the high-order term to make the high-order term more linear and more accurate.Finally,the₂ term is eliminated.The aspherical elements with known design parameters are measured in meridian direction with Taylor Hobson profilometer,and the original data obtained are used to fit in the above way,and the results are compared with the calculation results of the software provided by Taylor Hobson profilometer.The results are in good agreement.4.The X-axis and Z-axis guide rails of the profile measuring instrument are tested by the Renishaw xm-60 multi beam laser interferometer.The results show that the axial runout errors of X-axis and Z-axis guide rails are less than 5.30?m and 3.10?m respectively,and the radial runout errors are less than 3.57?m and 1.81?m respectively.It can be seen that the guide rail has high positioning accuracy,good motion repeatability and is not affected by the direction of motion.