Wavelets for ultrasonic echo identification in aircraft fuel tanks

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Wavelets for ultrasonic echo identification in aircraft fuel tanks

Sadok, M.

Goodrich Corp., Fuels and Utility systems Division, has launched a research effort to investigate various sensing and computing techniques to gauge fuel in commercial and military aircraft. Ultrasonics are among other techniques that were tested for such purposes. Generally, in ultrasonic fuel measurement systems, a transducer is excited to create sonic bursts into the fuel and measure the reflected echo off the fuel surface. A fixed target or pin is usually disposed at a fixed and predetermined distance from the ultrasonic transducer within the tank so as to compute the speed of sound through the fuel in the tank. Knowing the speed of sound in the fuel and being able to measure the round trip time from when an ultrasonic burst is generated until it is reflected off the fuel surface, the fuel height may be calculated. With a priori knowledge of the tank geometry, the fuel quantity can be estimated. This measurement process seems straightforward. A problem however is being able to discriminate between echoes reflected off various objects within the tank. In particular, it is crucial to discriminate among echoes reflected off the fuel surface and echoes reflected off other object within the tank, like the fixed target or tank sides. This paper presents a discrimination method based on wavelets to assign various ultrasonic echoes to their appropriate reflective surfaces.