Research On Engineering-Object Observation And Recognition Based On Image Technology

In this paper, engineering-object observation is to estimate the attidude, the position and other features of the object in engineering. Traditional measurement methods, such as theodolite, GPS or gyro, may consume much time in engineering, and may be affected by many unexpected factors. Especially, many measurement problems of engineering-object are unresolved in ocean due to its special environment. In these cases, to measure the attitude of engineering-object with image technolgy has the advantages of non-contact, high efficiency and high degree of automation. Therefore, to make research on image measurement is very important in engineering.Generally, the attitude of engineering-object can be computed directly with image reconstruction. The first part in this paper has introduced two object reconstructions:laser scanner reconstruction and multi-view reconstruction. The first one is to reconstruct engineering-object with two laser scanners and a digital camera. The second method is multi-view reconstruction. An image homography estimation which combining both line and point correspondences is introduced in the reconstruction, and the method is used to make image rectification. Experimental results have shown that the method can make an effective reconstruction to a rigid object in a long distance.Based on the improvement of the two image reconstruction method, this paper mainly studies the following problem:(1) Make research on vision based measurement and has proposed a single view estimation method for rigid object attitude measurement. The measurement error is mainly analyzed, and a normalization method is proposed to improve the measurement accuracy. Simulation experiments and image experiments have shown that the method is robust, and the measurement errors of rigid object rotation angle is less than 1.4°and the displacement measurement error is approximately 16m (relative measurement error is less than 1%). This single-view based measurement method has been applied to estimate the launching parameters of an offshore Jacket.(2) Make research on the image metric rectification and has proposed a general metric rectification for ocean surface image. The method utailze a circle float on the ocean surface to compute the metric rectification matrix of ocean surface image. The variation of the normal vanishing point position of the circle support plane is analyized with simulation, and a method to select the proper attitude of the circle is proposed to decrease the compute errors. Experimental data have shown that the rectification is robust, and the angle rectified error is less than 2°.(3) Make research on the image recognition and has proposed a chain code based image recognition method. Firstly, the image of engineering-object is consider as a kind of texture image and the edges of texture unit is extracted and transformed into chain code; secondly, the feature codes of each kind of image texture are obtained with string matching method. At last, Gaussian mixture model is introduced to distinguish the texture with the feature codes and its repeat frequency rate in each image. Experimental results have shown that the method is suit to recognize the circular texture image.