| Electrical Capacitance Tomography (ECT) is a sensing modality commonly used to find the dielectric permittivity distribution inside a region of interest (RoI) from the boundary electrode capacitance measurements. ECT finds applications in various industrial processes due to its low-cost and noninvasive/nonintrusive nature. The ECT reconstruction problem is inherently nonlinear, and the imaging resolution is limited by the soft-field nature and limited number of measurements (due to minimum electrode size constraints to provide a given SNR) enabled by the capacitance measurement system. In order to increase the number of measurement without degrading SNR, adaptive electrical capacitance tomography (AECT) and its 3-D variant adaptive electrical capacitance volume tomography (AECVT) are introduced. The proposed adaptive strategy is based on the manipulation of synthetic electrodes comprised of a set of smaller physical electrodes (segments) enabled by AECT/AECVT hardware. AECT increases the number of measurements; however, the increased amount of correlation between different measurements makes the inverse problem (image reconstruction) more ill-conditioned. Spatially adaptive reconstruction techniques (SART) are introduced that take advantage of the Laplacian nature of the interrogating field in AECT/ECT by utilizing synthetic electrodes based on different segment partition sizes while reconstructing in different portions of the RoI. The reconstruction can be sequentially performed starting from the peripheral region of the RoI, where the achievable resolution is higher, towards the center region of the RoI. SART also makes it possible to use different AECT sensing modes together to achieve higher spatial and radiometric resolution as well as to ameliorate some the nonlinear artifacts.;The simultaneous activation of multiple electrodes can be advantageous to manipulate the sensing field distribution and capture more spatial information for imaging purposes. However, conventional methods for sensitivity map computation in ECT are inadequate in the presence of multielectrode activation because the mutual coupling between electrodes is not properly accounted for. This coupling becomes especially critical in adaptive electrical capacitance volume tomography (AECVT) sensors, where signals from many small electrode segments are combined into synthetic electrodes. To address this issue, a more general approach is presented for sensitivity map computation in AECVT. |
