Research On The Optical Measuring System For The Coaxiality Of Compound Gear Shaft With Bevel Gear And Spline

With the development of modern testing technology,many experts and scholars at home and abroad have begun to apply new measurement techniques and methods for the detection of coaxiality errors of parts,and the optical measurement technology is one of them.In this paper,the compound gear shaft composed of bevel gear and spline is used as the part to be tested,and its current coaxiality measurement method is improved.Aiming at the shortcomings of traditional contact measurement methods such as low efficiency,high cost and low accuracy,we put forward a non-contact optical measurement method based on the laser displacement sensor to obtain the spatial geometric profile information of the parts,and adopts targeted data processing methods for each link of coaxiality evaluation.Finally,the coaxiality error of the bevel gear relative to the spline for one compound gear shaft is evaluated,which realizes the fast and accurate measurement of coaxiality.According to the relevant provisions of the coaxiality error evaluation standard,combined with the structural characteristics of the compound gear shaft,a targeted optical measurement scheme of coaxiality is developed.According to the multiple cross-section data obtained by sensors,the outlier filtering method based on "distance difference threshold" and "scale threshold" is used to remove the outlier data existing in the cross-section data.On this basis,the extraction method of gradually approaching the periphery from the interior of the remaining data is used to separate the data of the top of the gear.Four fitting methods of the center point of the cross-section are compared,and the least square method is selected to calculate the center point coordinates of the top data of the gear.The particle swarm optimization(PSO)is used to fit the axis of the minimum containment cylinder of the centers of the spline part,which is taken as the reference axis.According to the criterion of minimum contained area,the coaxiality error of bevel gear relative to spline is evaluated.According to the measurement scheme of coaxiality,the hardware test platform is designed and constructed,and the corresponding software is developed.The laser displacement sensors of spline and bevel gear are calibrated by using the stepped shaft with standard diameters.For three different parts to be measured,the data of several cross-sections is obtained respectively.Furthermore,the measurement tests of single section center and circle run-out error and multi sections coaxiality are carried out.The test results of single section measurement show that the data processing methods of cross-section data can effectively separate the top data of the spline and gear;Meanwhile,the outliers can be removed successfully,and the fitting method of section center can correctly calculate the coordinates of the section center point.The test results of multi section measurement show that the measurement methods in this paper can realize the fast and accurate measurement and evaluation of coaxiality error.The measurable radius of the spline part of the compound gear shaft is 2.666～44.664 mm,the measurable radius of the bevel gear part is 0.902～44.672 mm,the maximum measurement length in the axial direction is 200 mm,the coaxiality measurement result can be accurate to the second decimal place,and the uncertainty of the system is 0.020 mm.