The On-orbit Vibration Measurement Research Of Large-scale Flexible Structures Based On Binocular Stereo Vision

With the development of science and technology, large-scale flexible structures are widely used in daily life and many fields. Especially in aerospace field, large flexible structures, such as solar arrays and space-borne antennas, are playing more and more important roles. A space-borne antenna is used to transmit electromagnetic signals between the satellite and the earth station as a necessary part of the satellite communication system, which is usually loaded on the man-made earth satellite. The vibration and deformation inevitably happen when the large flexible on-orbit structure works in aerospace. Nevertheless, these badly influence the precision and stability of the antenna, even makes the antenna invalid. So it has important significance both on theory and practical application to measure the geometric and mechanical characteristics of the structure in real-time which can help to know about the deformation and vibration of it and to take action to repair deformation and control vibration.A technology of binocular stereo vision is used to measure the three-dimensional vibration displacement of the large flexible on-orbit structure in the paper. The calibration methods of the camera’s interior and exterior parameters are investigated in the paper. And a new approach, which is suitable for the validating experiment on the earth of the large flexible structure, is put forward based on the combination of the available methods and the requirements of the precision and the complexity. A feature extraction method of higher precision and less time, which is improved on the traditional detection algorithm, is introduced to research the pictures.The methods of feature extraction are researched, after which the advantages of the Harris corner detection algorithm than the gray extract algorithm is certified. Besides, the precision is increased and the time is saved by improving the simple Harris corner detection algorithm.The time-domain curves of the displacement in every direction are obtained by measuring the vibration of the cantilever beam, the flexible sheet and the antenna model. The frequency of the vibration is picked up by the modal identification of the curve, which verifies the feasibility of the3-D vibration measurement using the binocular stereo vision technology. Using digital photogrammetry get free cantilever vibration signal accurately identify the first-order natural frequencies and mode shapes, and laser vibration meter results were compared to verify the feasibility of this method. A three-dimensional model of the antenna vibration measurements was obtained. which identifies the vibration frequency, and shows that the method can be effectively used in three-dimensional vibration displacement measurement for the antenna; Based on the validating experiment on the earth of the practical structure, a series of parameters are determined such as the resolution of imaging system, the frame frequency of the camera, the camera’s position, and the viewing angles and so on.