Method for measuring vibration inherent frequency of looped blade structure based on computer vision
A technology of computer vision and blade structure, applied in measurement devices, measurement of ultrasonic/sonic/infrasonic waves, instruments, etc., can solve the problems of complicated installation of rotating structure vibration measurement devices, easy to be affected by power frequency, etc., to achieve high signal-to-noise ratio, The effect of measuring high efficiency
Active Publication Date: 2019-12-10
XI AN JIAOTONG UNIV
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[0005] In order to overcome the shortcomings of the above-mentioned prior art and solve the current problems such as complicated installation of the vibration measurement device for rotating structures and being easily affected by power frequency, the present invention provides a non-contact, computer vision-based measurement of the natural frequency of the vibration of the looped blade structure. Measurement method, the measurement method is simple, the signal-to-noise ratio is high, and it can be applied to various rotating structures
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[0024] The present invention will be further described below in conjunction with the accompanying drawings.
[0025] Such as figure 1 As shown, a computer vision-based method for measuring the natural frequency of vibration of a looped blade structure includes the following steps:
[0026] 1) Use a circular patch with high contrast to the surface color of the original structure to mark the rotating shaft and blades of the looped blade structure, such as figure 2 As shown, a patch is used to make a mark on the rotating shaft of the looped blade structure, and a certain number of patches are marked on the tested blade according to the needs, and a high-speed camera is used to record the motion of the looped blade structure at a constant speed;
[0027] 2) Construct the gradient operator H in the x direction by graying the frame-by-frame images x and the gradient operator H in the y direction y as follows:
[0028]
[0029] Calculate the image pixel gradient frame by fram...
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The invention discloses a method for measuring the vibration inherent frequency of a looped blade structure based on computer vision, and the method comprises the steps: marking a rotating shaft and ablade of the looped blade structure through a circular patch, and recording the movement of the looped blade structure in a rotating state through a high-speed camera; analyzing the video frame by frame, constructing a gradient operator to calculate an image pixel gradient amplitude, obtaining patch edge pixel coordinates, performing circle fitting on the edge pixel coordinates of the same patch,and calculating pixel coordinates of a central point of the patch; calculating the rotating center and the rotating speed of the rotating shaft by utilizing the patch center point on each frame of rotating shaft, and calculating the absolute motion of the blade by utilizing the patch center point on each frame of blade; acquiring vibration time domain information of the blade through the absolutemotion of the blade and the rotating speed of the rotating shaft; carrying out the fourier transform on the vibration time domain information, and finally obtaining the inherent frequency of the structure. Compared with an existing contact type measurement method, the method is simple in measurement mode, high in signal-to-noise ratio and suitable for various rotating structures, and has the advantages of being high in adaptability, convenient to popularize and the like.
Description
technical field [0001] The invention belongs to the related technical field of vibration measurement of mechanical structures, and in particular relates to a method for measuring the natural frequency of vibration of a looped blade structure in a rotating state. Background technique [0002] Large rotating machinery is the key equipment widely used in industrial systems such as aviation, ships, and electric power, mainly including aeroengines, gas turbines, steam turbines, blowers, etc. As the core component of various large rotating machines, the looped blade structure is prone to fatigue failure when working in harsh environments such as high temperature, high pressure, and high speed. Fatigue failure is the result of damage accumulation under long-term alternating stress, and alternating stress is mainly caused by blade vibration in the final analysis. Therefore, measuring the structural vibration of the looped blade can effectively grasp the natural vibration characteri...
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IPC IPC(8): G01H9/00
CPCG01H9/00
Inventor 徐自力辛存王存俊
Owner XI AN JIAOTONG UNIV