Development Of Thin-plate Flat Butt Weld Tracking System Based On PSD

In view of the shortcomings of the current thin-plate welding automatic tracking system,such as welding plate reflection,high requirements on optical focusing system and large calculation amount,combined with the characteristics of PSD sensor sensitive to light spot and strong robustness,PSD-based thin-plate planar butt weld tracking system is designed.The PSD distortion correction,weld corner identification and weld trajectory fitting algorithms were studied.The research content has the following aspects:(1)The PSD-based laser scanning scheme is used in this dissertation.And the optical path model is established.The key components are selected.The utilization of the photosensitive surface is improved by adjusting the placement angle of the PSD.The actual acquisition data is analyzed and optimized.The dark field optical path model is used.And make reasonable arrangement of the position layout of each device.(2)According to the nonlinear distortion existing in the PSD sensor,an improved bicubic interpolation model is established.And the effect is obvious.According to the characteristics of the output displacement and time curve of the PSD,an algorithm for extracting the weld corner information is proposed to find the starting point and end point in the increase to achieve real-time access to diagonal points.(3)A real-time segmentation fitting algorithm for weld trajectory is proposed.Firstly,the position of the segmentation point is judged.Then the least squares polynomial is used to fit the trajectory.At the same time,the method of judging the best polynomial fitting order is proposed.Combined with the fitting effect and the goodness of fit to choose the best polynomial order.(4)Based on the weld tracking experimental platform,the two integrated welds were collected and fitted by using the algorithms proposed in this paper.The results show that,The distance between the fitted value of the intersection of the trajectory and the measured value is less than 0.5mm;and compared with the linear trajectory,the angular point set of the oblique line and the curved trajectory is larger than the trajectory equation obtained by manual measurement,indicating the angle of the system to the straight line.The point collection effect is better.The system can achieve the real-time accurate fitting of the butt weld trajectory of the thin plate.