A Novel High-Efficiency Energy Transmission Method for Piezoelectric Ultrasonic Transducers in Rail Structural Health Monitoring

To achieve the high-efficiency energy transmission of piezoelectric ultrasonic transducers (PUTs) at the transmitting end and high signal-to-noise ratio of PUTs at the receiving end, this paper proposes a novel and efficient energy conversion method, which combines source-load conjugate matching with a passive voltage gain mechanism. Firstly, L type, T type, second-order L type, and IV type matching network topologies are designed based on the maximum power transfer condition for PUTs located at the transmitting end. By comparing transducer power gain (TPG), active power, and reflection coefficients S11, the second-order L type network presents the optimal performance. Secondly, for PUTs at the receiving end, a voltage maximizing strategy is involved. To increase the input impedance of PUTs at the receiving end, LC tuning networks are used. It is shown that the second-order L type significantly increases the input impedance of PUTs, thereby highly enhancing the output voltage of PUTs across the entire frequency band. Then the parameters of Butterworth–Van Dyke (BVD) model of PUTs are optimized by nonlinear fitting. Moreover, to verify the effectiveness of the proposed electrical impedance matching (EIM) method, a simulated circuit by utilizing the BVD model of PUTs and an experimental platform based on the pitch-catch mechanism are built. Finally, the effect of the second-order L-type network on the receiving and transmitting ends is compared using the above experimental platform and simulated circuit. The input impedance is increased by more than four times, and the voltage gain ratio exceeds 300%.