Research On Accuracy Improvement Technology Of Laser Triangulation Measurement Of Complex Surface

The laser measurement has the advantages of high precision,high speed and simple operation.The laser measurement system manufactured by the working principle of laser triangulation is widely used to measure the surface contour of objects,various geometric dimensions and free-form surface features.This paper studies the influence of the geometrical characteristics of the complex surface on the:measurement accuracy of the laser beam in any installed position,and an error correction model is established to improve the accuracy,which provides a basis for high-precision measurement and reverse engineering of complex curved surfaces.This paper reviews the measurement principle of laser triangulation at first,then summarizes the factors affecting the accuracy and error correction methods.All lays a solid theoretical foundation for the development of the subj ect.The measurement error of inclination angle and rotation angle are proposed and defined for the geometric characteristics of the measured surface which affects the accuracy of laser measurement.Aiming at the laser probe installation error,a calibration method which converts it into inclination error and rotation error is proposed.An experimental platform was built to complete the measurement error calibration experiment of the laser displacement sensor under the influence of the above factors.After processing the data,the influence factor of inclination angle and rotation angle on the measurement accuracy is analyzed and summarized.Based on the above experimental data,a laser measurement error correction model is established.From the laws of data,it can be seen that there is a linear relationship between the measurement depth and the measurement error in the case where the inclination angle and the rotation angle are determined,simplifying the error compensation model.The research on the influence of inclination angle,rotation angle and measuring depth to the measurement error is converted into the research on the influence of inclination angle and rotation angle to the error-depth ratio.On the one hand,the random forest model is used to predicted the error.It takes the object inclination angle,the object rotation angle and the measuring depth as the model features,and the measurement error is used as the prediction value,and the sample data is divided into the training set and the test set.After training on the training set data,in the same test set,two models were used to predict the measurement error respectively.On the other hand,A mathematical model was established using the response surface methodology.From the analysis of variance,it is concluded that the four-time response surface model has the best fitting effect on the experimental data.Based on the standard error and the decision coefficient,the performance of the two models was evaluated.It was found that the four-time response surface model has a better predicted effect.This paper takes cycloid gear as the measuring object to verify the correction effect of error correction model in the measurement of complex curved surface.After obtaining the tooth profile data,the geometric model of the measured surface is established,and the angle between the normal direction of the tooth profile point and the direction of the laser beam,namely the inclination angle,is obtained.The inclination angle,rotation angle and the measured depth of the object surface are substituted into the error correction model to obtain the error correction.Taking the normal error of tooth profile as the evaluation basis and comparing the corrected profile and tooth profile with the actual tooth profile,it is found that the corrected tooth profile accuracy is greatly improved,which proves that the error correction model proposed has a good effect on improving the measurement accuracy.