TLCD Video Analysis using Matlab
To measure the liquid heights in a Tuned Liquid Column Damper, either very expensive wave bob metres are needed, or the researcher can go through video image frame by frame estimating the height of the liquid columns from a scale attached to the TLCD. To avoid this laborious task, and to increase the number of experiments we can do, I developed a video analysis toolkit that processes the image automatically for the liquid heights. Here’s a video of the analysis:
The output can be converted to time and length (in mm say) using the rulers to get a scale (mm per pixel say) and the frame rate of the video. The ‘redness’ of the liquid is the key here: the video is split into RGB and the red channel isolated and converted to black and white once a filter is applied. This image is then scrubbed to get rid of any objects smaller than a threshold size, leaving only the liquid of the column. The image is then split in two at the centre of the bounding box to analyze each column separately. Since a black and white image is represented by a matrix of 1 and 0s, summing the columns of the matrix (ie the vertical direction) gives the column height in pixels. A few other adjustments are needed, but that’s the basic idea.
