Research Of Vibration Detection Based On The Visual Microphone Technology

Vibration generally occurs in human daily life.The vibration of the device may cause some abnormal changes,resulting in a decrease in its reliability,what's more,it may cause the device to stop working.Recently,researchers have developed various vibration monitoring systems according to different measured objects.Among these methods,electrical measurement is mostly used.This method is contact measurement method,which will have a certain influence on the vibration of the measured object,and make the monitoring result biased.The Visual Microphone technology is a new non-contact vibration monitoring technology,and has significant advantages.Firstly,it will not affect the vibration of the measured object.At the same time,the technology has high sensitivity and long working life.However,subject to the high price of high-speed cameras,its application is still not mature.Further research on low cost and detection range is needed.This article is based on the Visual Microphone technology,and combines non-imaging technology to achieve real-time monitoring of object vibrations.It should realize that the characteristics of low cost and high monitoring range of the vibration frequency when ensure the high sensitivity detection.The main work is as followings:(1)Design the optical vibration detection system based on Visual Microphone technology.The system uses the sound source to make the object vibrate,and records the vibration by an ordinary home-use SLR camera.For the obtained video image,gradient method is firstly used to get the point where the object vibrates more obviously,and optical flow method is adopted to track the position of the point in the image to get the locus of it.Finally,fast Fourier transform is directly performed on the trajectory of the point,and the monitoring of vibration frequencies of objects is completed.(2)Design the high-speed visual system.It is must reasonable when design system hardware and light path functions based on the principles of low cost,high rate and high precision.To reduce the cost of the system,the principle of non-imaging optics and light intensity is combined.The white LED light is used for active illumination of objects,and the reflected light is coupled to the multimode fiber by Fresnel lens.The ray tracing method is used for theoretical analysis of illumination distribution.By calculating the coupling efficiency of the optical fiber and the influence of the radial shift of the reflected light on the coupling efficiency of the optical fiber,and perform signal processing such as noise reduction on the collected data.The amplitude of the vibration of the object is theoretically calculated.Finally,the above design is simulated and analyzed.(3)Do the experiment of the vibration monitoring system based on visual microphone.The real-time monitoring of the thin steel plate vibration caused by the sound source proves the feasibility and accuracy of the system.The vibration of the aviation hydraulic pipeline is monitored to achieve the signals under normal conditions,and the monitoring result by the fiber grating system is compared to verify the universal of the system.The real time multi-point monitoring in case of loose pipe clamps is implemented to realize the fault warning of the pipeline.