The Study Of Flatness Error Evaluation System Based On Plane Air Bearing Guide

Recently,the air bearing guide has been applied to the measurement of form tolerance owing to the error averaging of gas film.It can improve the measurement accuracy as the measuring datum.In order to improve the measuring accuracy of flatness error,the error averaging effect of air bearing guide was studied in this paper.The nature of the error averaging effect of air bearing guide is the ratio of the motion error when air bearing guide moving along the surface of the static guide rail under two states of aeration(gas lubrication)and airless(dry friction).For the sake of researching the error averaging effect of air bearing guide in a complete two-dimensional plane model,the fractal interpolation surface method was used to simulate the upper surface of the static guide,and the related information of the surface topography height was stored.Based on the three point support balance principle,the author firstly obtained the trajectory of the air bearing guide under dry friction condition,and then used the minimum area method to get the straightness error or flatness error.In order to theoretically calculate the motion trajectory of the air bearing guide in the state of gas lubrication,firstly,the author derived its gas lubrication control equation according to the basic equation of gas bearing(Navier-Stokes equation).Based on the finite difference method,the control equations were discretized.And the bearing capacity of air bearing guide under the theoretical gas film thickness was obtainedon the basis of numerical calculation.Secondly,with the bearing capacity and the mechanical balance equation of the air bearing guide as the initial condition,the trajectory in the equilibrium position was calculated when it moved along the surface of the static guide,and its motion trajectory error was also obtained at the same time.The calculation results show that: the gas has obvious effect on realizing the error averaging of the air bearing guide.Finally,in order to verify the correctness of the theoretical calculation results,the author designed the motion error exploration experiment plan,and tested the trajectory of air bearing guide under different conditions.The error averaging effect in the actual state was calculated.The experimental results verified the correctness of the theoretical calculation and the reliability of the calculation method.On account of the theoretical results,A new two-dimensional X-Y flatness tester based on air bearing guide was designed.The 3D parts drawing of the related parts were drawn,and the related components were selected and analyzed.The air bearing guide was used as the base plane of the flatness measuring instrument.The linear motor and stepper motor were the driving sources,and the flexure hinge was the micro adjustment mechanism in it.The structure is simple,economical,easy to realize.In order to improve the whole flatness error evaluation system,the author used MATLAB to compile flatness and straightness error evaluation procedures based on various methods.Besides,the graphical interface of error evaluation system was designed based on the GUIDE of MATLAB.A more complete software evaluation system was formed.