UA researchers patent a system to measure vibrations in civil constructions with compact pocket cameras
Alicante, 18 November 2014
Researchers at the University of Alicante have developed and patented an ingenious system to detect movement and measure the frequency of vibration in civil structures with compact pocket cameras capable of video recording at high speed.
The system, developed by the Optics and Vision Sciences research group, in collaboration with the Department of Civil Engineering, both UA centres, has many advantages as it can be used from a long distance. It does not need any contact with the object being measured, and no particularly sophisticated or expensive video equipment is required. Very high accuracy of measurement can be obtained even with low quality images.
Different techniques exist to detect the vibration of objects and structures at present but access to the measuring point is required which is not always easy and it can even be dangerous. This new method allows the measurement to be done without installing devices on the structure. As explained by Director of the research group in Optics and Vision Sciences, David Mas, they can obtain basic frequencies of vibration by simply placing the camera on a tripod at a certain distance.
The patented method relies on the detection and quantification of subtle changes in the light reflected or scattered from an object due to its motion. The detection and quantification of these changes is performed by analysing and manipulating the frames. When these movements are small or the object is far away, these changes are detected by a few pixels scattered and will not be noticeable, so that the image need to be analysed by especially designed methods to take them into account and set the movement frequency, David Mas states.
The system has been tested in labs and on footbridges. Also, it was successfully tested in the city council of Lorca, for measuring the frequency of some tensioning rods, which made possible the calculation of the stress they bear and whether they were affected by the earthquake. The measurement of the accelerometers required the use of technical staff, forklifts and the isolation of the intended area of measurement from foot traffic. In contrast, our approach did not need any special installation or performance, as David Mas said.
Apart from civil works, other other fields have studied, such as in ophthalmology where its application for the measurement of eye movements, of great significance in neuroscience, is being examined. At present, there are no non-invasively method to measure gaze fixation small movements, so the success of this proposal would be very well welcome. In collaboration with the University of Valencia and the University of Bar Ilan University, in Israel, they have also studied its use for the measurement of motility of certain cells and distinguishing different stages of a malaria infection.
David Mas concludes that they are planning, in future projects, the possibility of measuring large structures with very difficult access. For this purpose, they propose the use of telescopic systems combined with high-speed cameras. Also, they plan the possibility of using drones for particularly complicated access points. This would allow us to measure far points such as suspension bridges, large antennas or buildings without costly installations and with safe conditions for both the staff responsible for the measurement and the users of the structure, as well as the material used.
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