Multi-DOF Error Measurement Method For Workbench Based On Non-diffracted Light And Dove Prism

In modern manufacturing engineering,how to accurately and effectively obtain the multi-degree-of-freedom error of the worktable is a hotspot in the field of precision manufacturing.Among them,laser measurement has the advantages of fast,accurate,non-contact,etc.It has been widely used in multi-degree-of-freedom error measurement,but the performance of the laser beam is affected by many factors that limit the system accuracy and stability to further improve.In order to address this shortcoming,this paper takes advantage of the stability of the non-diffracted light transmission process and the characteristics of moiré fringe magnification,combined with the sensitivity of Dove prisms to angular changes(roll angle,pitch angle),through theoretical analysis,attitude error model derivation and image processing,it provides a practical measurement method for the four-degree-of-freedom error of the precision worktable.The main contents are as follows:First,combining the mathematical model of non-diffracted light,the spot size and intensity do not change with the propagation distance and the self-healing characteristics.Several different methods of generating non-diffracted light are compared,from which the axicon is preferred to generate the non-diffracted light required for measurement and its light intensity distribution is simulated;The relationship between the number of moiré fringes and the center distance between two non-diffractive spots is theoretically analyzed,and the measurement method of the center distance between two spots is given,which is verified by combining with specific experiments;The imaging characteristics of the Dove prism are analyzed.The conversion matrix of the Dove prism to the incident light is established by vector analysis and matrix conversion.The change of the direction of the outgoing light under three angle errors is obtained.Secondly,combined with the theoretical basis,a measurement scheme using Dove prisms and transflective mirrors as error-sensitive components is given,and the measurement principles and procedures,as well as hardware selection are explained;According to the change of the direction of the two measurement light rays under each error,a specific mathematical model of the offset of the two measurement points and four kinds of errors is established,and a multi-degree of freedom mixed error decomposition method is given;According to the light intensity distribution characteristics of the two measuring points,an appropriate centering method was selected,and the source of error in calculating the position of the measuring point 2using the Moiré fringe number was analyzed.Thirdly,the four degrees of freedom errors of roll angle,yaw angle,pitch angle and plumb direction displacement and the positions of the measuring points 1 and 2under different displacements of the workbench are simulated by Matlab,and the specific changes of the coordinates of the two measuring points corresponding todifferent error values are obtained.Finally,a verification experiment light path was built.Use the rotating table and the lifting table to simulate the change of the three directions of angle and the displacement deviation of the plumb direction,The step angle is 0.1 °and the stepping displacement is 0.1mm.The coordinate change of the measuring point is collected,and the calculation results of angle and displacement are obtained.On this basis,three repeatability tests were carried out.Compared with the given value,the angle error is less than 6%,the displacement error is less than 3%,the angle repeat error is 0.01 °,and the displacement repeat error is 0.005 mm,which proves the measurement method.Feasibility and stability.