Tomographic Sensing for 3D Temperature, Flow, and Chemical Cloud Mapping
Our goal is to develop a system that is capable of mapping the full 3D distributions of quantities such as temperatures, air flows and certain gas chemical compositions using line-of-sight measurements between cooperating transceivers. This system uses ultrasonic signals for temperature and air flow velocity field sensing and Fourier Transform Infrared (FTIR) spectroscopy for sensing chemical composition.
The ultrasonic system is based on the fact that the speed of sound in air is altered by both temperature and air flow velocity. A pair of cooperating ultrasonic transceivers can obtain a line-integral measurement of the average temperature and air flow vector components along the line joining them. With a sufficient number of such cooperating fixed or mobile transceiver pairs, it is possible to reconstruct the full 3D temperature and air flow velocity fields by solving the inverse problem of tomography. Similar techniques can be used with FTIR sensing to determine 3D distributions of chemicals in a gas cloud from line-of-sight measurements using sensors outside the cloud.
Mathematical simulation of Acoustic Tomography of 3D temperature distributions. Left: 10 Ultrasonic transceivers (red dots) make 45 line integral measurements (blue lines) of a 3D temperature distribution (iso-surfaces shown). Right: Tomographic reconstruction of temperature distribution clearly shows that the bimodal nature of the distribution.
This process is similar to Computerized Tomography (CT) with X-Rays that is commonly used in medical diagnosis. However, unlike in CT, our reconstruction relies on far fewer measurements, and thus the linear inverse problem is severely underdetermined. We compensate for this lack of data by incorporating physics-based models into our reconstruction techniques.
Our current work aims to use physical models of the dynamics of temperature and air flow fields and to incorporate measurements into a dynamical estimator to obtain much more accurate 3D estimates from continuous measurements over time.
Poster from the 2011 ICB Army-Industry Collaboration Conference