Research On Straightness Measurement Device Of Three-dimensional System

Straightness measurement is a very important test content in shape error measurement,which has a direct impact on the accuracy of the instrument,and is the key in mechanical manufacturing,instrument calibration and error compensation.In the current straightness measurement research,most of the measurement methods are based on laser as carrier.Starting from practical application,this paper designs a straightness measurement method for three-dimensional system based on laser beam spot center offset using three axes of coordinate measuring machine(CMM)as the research object.The specific research contents are as follows:Firstly,the existing measurement methods of straightness error of guideway are analyzed,and a design scheme of straightness measuring device based on calculation of laser beam spot center offset is proposed,and the three-dimensional measurement device is built and debugged.A laser beam is emitted by a laser interferometer and arrives at a planar reflector installed on the slide table of the guiderway through the optical path,then the light beam is reflected back to the CCD camera,and the laser spot image is acquired by the camera.By moving the slide on the guideway several times with equal steps,multiple spot images are obtained.Secondly,combined with image processing technology,processing of the acquired spot image is carried out.The sub-pixel edge of the spot image is extracted by Gauss curve fitting method,and the edge profile of the spot is fitted by Hough circle detection method,then obtaining the coordinates of the center of the circle the centroid method.The distance between the center coordinates of each measuring position and the center coordinates of the initial measuring position is calculated,and the actual value is calculated by using the method of pixel size calibration.The straightness error of the measured guideway can be obtained by using the least square data processing method.Finally,the experiment of sampling interval of measuring points is designed to determine the appropriate number of measuring points and sampling interval of measuring points when measuring straightness error of guideway;the design and comparison experiment of CMM are carried out,and after processing the experimental data obtained by this scheme,the comparison is made with the measurement data of CMM to verify the correctness of the experimental measurement scheme;measuring straightness errors of Three axis in three-dimensional System with experimental design Scheme,and the experimental error is also analyzed.The experimental results show that the measurement error is less than 25 ?m.In this paper,a straightness measurement device is proposed,which combines optical measurement technology and digital image processing technology.The straightness error measurement of three axes in three-dimensional system is realized,which obtains accurate results.And the measuring device is simple in structure and easy to operate,which provides a good reference for straightness error measurement of large and long guideways and axes in large three-dimensional system.