Measurement Method Of Four-DOF Error Motions Based On Non-diffracting Beam And Moire Fringe

In the parts of processing and measuring, the movement precision of the stage decides the quality of processing and production of the parts. So the precision of measuring the movement of stage is especially important. In this paper, the characteristic of non-diffracting beams can keep the same form in a long rang is combined with the characteristic of Moire fringe can scale the singa to propose a measurement method of multi-DOF motion error in high precision. The main contents are as follows:Firstly, on the basis of the characteristics of non-diffracting beam central spot and non-diffracting Moire fringes, a measurement system of multi-DOF motion error is designed. Beam splitter combined with right-angle prism into a sensing unit of multi-DOF motion error. Two CCD cameras is used to accept non-diffracting beams with motion error informations. By analyzing the location of the central spots of non-diffracting beams, the error measuring of vertical straightness error, yaw error, pitch error and roll error. Is achieved.Secondly, vectorial formulations is used to build the mathematical model of multi-DOF motion error system. on the basis of light reflection and light refraction, the non-diffracting beams that are accepted by two CCD cameras are vector analysed separately. Then, the calculation formulas to calculate the variation of position of non-diffracting beams center points and error are deduced in different motion errors.Thirdly, the calculation method to calculate the coordinates of the central spots of non-diffracting beams accepted by two CCD cameras is studied. The non-diffracting beam accepted by camera CCD1 has a character of concentric annulus, so least-square circle fitting is used to get the coordinates of the central spot. For the Moire fringes formed by two non-diffracting beams in the camera CCD2, the relationship between Moire fringes numbers and the increasing space of two non-diffracting beams center spots is analyzed.A method of using Moire fringes numbers to calculate the central point coordinates is came up.Finally, theoretical simulation and measuring experiment have been carried out. MATLAB is used to imulate variation of coordinates in different errors. And measuring experiments in 300 mm guideway have been carried out. Then according to the variation of central spots position of non-diffracting in two CCD cameras, the four kinds of errors in different position of the stage is calculated, and the errors variable rules in the range of 300 mm is studied out.