Infrared imaging helps transfer technology from tanks to autos

The Applied Research Group (ARG) of the Keweenaw Research Center at Michigan Technological University (Houghton, MI) specializes in vehicle thermal modeling and measurement. Until recently, it primarily received funding from the US Army Tank-Automotive Command as a field station for its ground vehicles such as the M-1 tank. Now, a concerted effort at securing private-industry contracts is paying off as the group parlays its thermal expertise into solving automotive heat-related problems and investigating new materials and manufacturing techniques for designers at the Ford Motor Company (Dearborn, MI).

The ARG developed a first-principles thermal predictive code for targets and backgrounds as part of its military- vehicle-signature research. This program has been adapted as a modeling tool for Ford designers. In use at more than 75 US and foreign government laboratories and research centers, PRISM (physically reasonable infrared signature model) can predict thermal performance of a part directly from a designer`s CAD/CAM drawings, saving time and the cost of building a model.

"In the past, by the time the model had been built and tested, the part had often been redesigned, and the test results were irrelevant," says Keith Johnson, ARG senior research engineer. "With the automotive version of PRISM, we can provide same-day results." Dual Thermovision 900 infrared imaging systems from Agema Infrared Systems (Secaucus, NJ) are used to validate the predictions of PRISM, which is constantly being updated and refined.

Both a short-wavelength (3-5 µm) and long-wavelength (8-12 µm) camera are used to gain a complete infrared signature; the data they produce are integrated through a single controller. Two areas of interest comprise automotive heat management: exhaust behavior and under-the-hood performance.

Cars are different than tanks

"When we look at a tank with the long- and short-wavelength imagers, we are, of course, interested in radiance, what kind of target against a given background the tank presents," says Johnson. "With automotive modeling verification, temperature is our main concern, and the dual Thermovision 900s can tell us how much heat a given part is generating and where it is concentrated." Johnson reports that in the exhaust area, the work has concentrated on helping to develop a better shield to protect the gas tank, car interior, and underbody components from the intense heat (1200°F) generated by the catalytic converter.

Shields vary in shape and composition, and the ARG engineers often test proposed new materials or samples from different vendors in "A-B" comparisions. Typically, two samples are placed between a floor pan and a heater set at 1100°F. The two IR cameras record the temperature of the top surface of the floor pan as it increases, stabilizes, and cools down; this process may take about two hours.

Infrared imaging not only identifies hot spots on the floor-pan surface, it shows the heating pattern across it. Johnson says, "In future tests, we will test different shield geometries and, as at least one shield manufacturer is doing, install fans to simulate the air flow that would occur across it if the car were in motion." Testing without airflow actually simulates worst-case conditions, because the car is most vulnerable when it is running but not moving.

The management of heat generated under the hood of a car is also an area in which the ARG combines infrared imaging with automotive design. In modern cars, an increasing number of electrical and electronic components and systems are all forced to operate in a more-compact and more-airtight space and to satisfy aerodynamic concerns. The infrared cameras will be used to validate computer-model-generated predictions of thermal behavior of proposed component configurations. Johnson says, "Once a prototype is built, one of our other groups might then test the solution in the field," finding another commercial, rather than military, use for thermal imaging cameras.