Omnidirectional Vibration Measurement Method For Thin-walled Parts Of Aero-engine Based On Binocular Vision And Object Tracking

The thin-walled parts of the aero-engine have the characteristics of low stiffness and weak strength,and they are easily affected by external excitation to generate vibration.Long-term vibration may cause the thin-walled parts to crack or even break,resulting in major safety accidents.Therefore,in order to ensure the safe operation of the aero-engine,it is very necessary to monitor the vibration of the thin-walled parts of the aero-engine.At the same time,due to the complex structure of the aero-engine,the casings in different parts have different structural forms and installation characteristics,and the exterior of the casing is connected with a very complicated pipeline structure,which causes the vibration mode of the thin-walled parts of the aero-engine to be very complicated.In working conditions,it often shows complex omnidirectional vibration.However,the existing non-contact vibration measurement method has been unable to meet its omnidirectional vibration measurement needs.To solve this problem,based on binocular stereo vision and target tracking method,an omnidirectional vibration measurement method for thin-walled parts based on binocular vision and optical flow tracking with an omnidirectional vibration measurement method for thin-walled part based on virtual binocular vision are proposed,and the effectiveness of the two omnidirectional vibration measurement methods are verified from theoretical analysis and experimental research.The main research contents are as follows:First,the pinhole imaging model of the camera and the principle of coordinate conversion are analyzed,the binocular vision measurement model is established,and the process of calculating the three-dimensional world coordinates of the target object is studied.The calibration method of the left and right camera internal and external parameter matrix is studied.The principles and deficiencies of various existing calibration methods are analyzed.The causes of image distortion are analyzed,and the method of image distortion correction is studied.The basis of some image processing methods required in the process of visual measurement is also studied.Secondly,the feature stereo matching method based on the principle of epipolar constraints and the feature tracking method on sequence images are studied,an omnidirectional vibration measurement method for thin-walled parts based on binocular vision and optical flow tracking is proposed.The experiment plan of the vibration measurement of the thin-walled parts is designed.The effectiveness of this method is verified by the vibration measurement experiment of thin cantilever beam.On the premise of knowing the theoretical vibration information of a feature point in three directions,the vibration image sequence of the feature point is constructed by combining the internal and external parameters of the camera.The vibration information of the feature point is calculated by this method,and it is compared with the theoretical vibration information to verify the accuracy of the method.A comparative analysis was conducted to verify the accuracy of the method.The analysis of experimental results shows that this method can accurately measure the omnidirectional vibration displacement information of thin-walled parts.Finally,the measurement principle of virtual binocular vision is studied,and an omnidirectional vibration measurement method of thin-walled parts based on virtual binocular vision is proposed.An experimental scheme of virtual binocular visual vibration measurement is designed.Using the corresponding thin cantilever beam vibration measurement experimental platform,a virtual binocular vision measurement system calibration experiment is performed to obtain the internal and external parameters of the camera,and the effectiveness of the method was verified by the thin cantilever beam omnidirectional vibration measurement experiment.At last,the two omnidirectional vibration measurement methods are compared and analyzed.In this paper,the relevant theories of omnidirectional vibration measurement technology for binocular vision are studied,and an omnidirectional vibration measurement method for thin-walled parts based on binocular vision and optical flow tracking with an omnidirectional vibration measurement method for thin-walled part based on virtual binocular vision are proposed.With the thin cantilever beam as the experimental object,an omnidirectional vibration measurement experiment was carried out.The experimental results show that the two omnidirectional vibration measurement methods can effectively obtain the full-field vibration information of the thin-walled parts,which provides an effective technical basis for further health monitoring and working modal analysis of thin-walled parts of the aero-engine.