An Electromagnetic Time-Reversal Imaging Algorithm for Moisture Detection in Polymer Foam in an Industrial Microwave Drying System

Abstract

Microwave tomography (MWT) based control is a novel idea in industrial heating systems for drying polymer foam. In this work, an X-band MWT module is designed and developed using a fixed antenna array configuration and integrated with the HEPHAISTOS industrial heating system. A decomposition of the time-reversal operator (DORT) algorithm with a proper Green’s function of multilayered media is utilized to localize the moisture location. The derived Green’s function can be applied to the media with low or high contrast layers. It is shown that the time-reversal imaging (TRI) with the proposed Green’s function can be applied to the multilayered media with a moderately rough surface. Moreover, a single frequency TRI is proposed to decrease the measurement time. Numerical results for different moisture scenarios are presented to demonstrate the efficacy of the proposed method. The developed method is then tested on the experimental data for different moisture scenarios from our developed MWT experimental prototype. Image reconstruction results show promising capabilities of the TRI algorithm in estimating the moisture location in the polymer foam.

A Review on Fast Tomographic Imaging Techniques and Their Potential Application in Industrial Process Control

“…Over the years, the MWT has been applied in various fields, including medical imaging [ 67 , 68 ], non-destructive testing [ 69 ], geophysical prospecting [ 70 ], and security [ 71 ]. In industry, MWT has been widely utilized [ 72 , 73 ]; for example, in multiphase flow imaging [ 74 ] and detecting moisture distribution in microwave drying of porous materials [ 75 , 76 , 77 ].…”

Multistatic Uniform Diffraction Tomography Derived Structural-Prior in Bayesian Inversion Framework for Microwave Tomography

“…The process efficiency can be improved by use of the spatial moisture distribution as measured and controlled variable in the intelligent controller design [8]. Therefore, integration of MWT operating in Xband (from 8 GHz to 12 GHz) was proposed [9], [10]. Based on the estimated spatial moisture information from MWT, the control unit can tune the power of the distributed microwave sources, pulse duration and achieve desired uniform moisture level.…”