Zhu W.-D.,Zhejiang University |
Cao L.-H.,Zhejiang University |
Mei B.,Zhejiang University |
Li J.-X.,Zhejiang University |
Feng P.-J.,Shanxi Aircraft Industry Group Corporation LTD.
Guangxue Jingmi Gongcheng/Optics and Precision Engineering | Year: 2014
The calibration of industrial cameras usually uses circular points as control points. However, there is asymmetric projection in the calibration, so that the calibration results have errors. In order to avoid the introduction of asymmetric projection error and to correct the error in an iteration form, this paper proposes a new camera calibration method by utilizing the asymmetric projection of circular centers. Firstly, the theoretical coordinate of the projection ellipse center from a circular point on the planar pattern was deduced, then the center coordinate of actual ellipse for the image of a calibration board was extracted and the projective transformation matrix was obtained by using nonlinear least square method. Finally, the camera intrinsic parameters were obtained by using all projective transformation matrixes. Experimental result reveals that the re-projection error of the calibration result of Baumer TXG12 industrial camera is just about 1/50 pixels by using proposed method. The method can complete the calibration at a time and is able to meet the precision requirement of industrial measurement in simpler calculation and higher accuracy. Source
Bi Y.-B.,Zhejinag University |
Li Y.-C.,Zhejinag University |
Gu J.-W.,Zhejinag University |
Guo Y.-J.,Zhejinag University |
And 3 more authors.
Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science) | Year: 2014
A robotic automatic drilling system which integrates the technology of laser measurement, computer control, off-line programming and robotics is established in order to realize automatic flexible drilling with high efficiency and good quality in the field of aircraft assembly. In drilling process, the normal vector of the aircraft surface can be obtained through the 3D model, but there is deviation between the 3D model and the real surface of part. To improve the holes' quality, a surface-normal adjustment system based on four laser displacement sensors is developed. The sensor' origin point position and laser direction are obtained by calibration. Then with the measured values of laser displacement sensors, the surface-normal vector is calculated. The attitude of the robot is changed to make sure the drilling direction is close to the surface-normal direction. The drilling test results show that the system can increase the drilling efficiency and assembly quality of the aircraft components immensely. The efficiency of drilling can achieve 6 holes per minute, and the surface-normal accuracy is better than 0.5°. Source