Optimized Design of High-sensitivity Ultrasonic Sensor Based on Piezoelectric Bending Vibration

Early-stage failure signals of rotating machinery are weak, and only high-sensitivity sensors can detect the mechanical damage status. This paper proposes a design method for a highly sensitive ultrasonic sensor based on piezoelectric bending vibration. First, based on the full-element rectangular thin plate theory, the resonant frequency equation of the rectangular piezoelectric bimorph is derived. Then, the attenuation and propagation characteristics of sound waves in the medium are considered, and the sound transmission coefficient model for the attenuation and propagation of sound waves in the double-matching layer is established. Based on the acoustic-piezoelectric coupling effect, the electroacoustic characteristics of the ultrasonic sensor are numerically simulated. The influence of the structure of each part of the sensor on the receiving sensitivity and the working frequency is simulated and analyzed. The structure of the ultrasonic sensor has been optimized. Finally, an ultrasonic sensor with a resonant frequency of 40 kHz and a peak receiving sensitivity of 65.18 dB was developed. An early fault detection experiment was conducted on a gearbox fault simulation experimental platform. By comparing it with a vibration sensor, the sensitivity of the ultrasonic sensor developed in this study to the early fault state of rotating machinery was demonstrated.