Research on interference wave elimination technology for ultrasonic guided wave liquid level sensors

Abstract The liquid level sensor based on ultrasonic guided waves has been applied in the aircraft fuel level measurement system due to its advantages such as high accuracy, strong anti-electromagnetic interference ability, and immunity to water accumulation. It compensates for the shortcomings of capacitive liquid level sensors. However, high order mode waves, interference noise and aircraft vibrations have affected the accuracy and reliability of the ultrasonic liquid level sensor. A conical orthogonal matrix ring structure is designed to eliminate interference waves through mechanisms of acoustic scattering and absorption, leading to a notable improvement in signal-to-noise ratio and operational reliability. Furthermore, an envelope superposition algorithm grounded in multi-wave superposition theory is proposed for processing ultrasonic signals under dynamic liquid level conditions. This algorithm not only counteracts vibration-induced signal degradation but also further enhances signal-to-noise ratio. Experiments show that the proposed structure and algorithm have effectively reduced the interference from clutter and overcome the influence caused by aircraft vibration. The signal-to-noise ratio at low liquid level has increased from 3.3 dB to 13.9 dB. The signal-to-noise ratio during low-frequency vibration has increased from 6.4 dB to 11.5 dB. At the same time, it has enhanced the reliability of the sensors and their ability to adapt to the onboard environment, which holds significant engineering application value.