Nonlinear Reconstruction Methods for Process Tomography Systems

Electrical Capacitance Tomography (ECT) is a method used to obtain the spatial permittivity distribution inside closed pipes. The principle is based on the measurement of the capacitances between distinct electrodes located on the exterior of the pipe. Since the capacitance depends on the permittivity value of the material located between the electrodes, substances of differing dielectric properties can be distinguished by means of this method. To obtain a spatially resolved image of the permittivity distribution inside the pipe, multiple electrodes are arranged on the tube and all inter-electrode capacitances are measured. The application of suitable algorithms yields the permittivity distribution inside the pipe. Common ECT systems are based on a linear relationship between capacitance and permittivity values. Such systems (LBP and SIRT systems) are fast but the reconstruction quality is not satisfying since the true relationship between capacitance and permittivity is strongly nonlinear and cannot be approximated by a linear mapping for high-quality reconstruction purposes. Research at the Institute is focused on the implementation of nonlinear deterministic as well as stochastic reconstruction principles in order to increase the quality of permittivity images. The main goal of the research is the development of a method yielding high-quality images that is usable for real-time process tomography systems.