Research Projects (2004)

When a dust laden gas is sucked through a filter, the dust remains on its surface and forms a compact dust layer called filter cake. Periodically the filter cake is at least partially removed by inverse high pressure air pulses to allow continuous operation of the filter. Knowledge of the distribution of the filter cake on the filter surface at different stages of operation is decisive for filter operation. It is shown that the principle of calibrated shape from stereo with pattern projection for generating texture on the surface gives a robust 3D reconstruction of the filter surface when accessing through a glass window. Rigid registration of surface patches using landmark points, combined with an Iterative Closest Point Algorithm as a refinement procedure gives a continuous 3D model of the entire visible filter surface. Cake thickness is calculated by taking the height difference of two surface models, acquired before and after dust deposition. The challenging problem is to account for the non-rigid deformation of the filter cloth. A global deformation model is estimated using Thin Plate Spline Interpolation based on landmark points on the filter surface.