Modeling Pulsed High-Power Spikes in Tunable HV Capacitive Drivers of Piezoelectric Wideband Transducers to Improve Dynamic Range and SNR for Ultrasonic Imaging and NDE

Antonio Ramos, Abelardo Ruiz and Enrique Riera
Sensors 2021, 21(21), 7178

The signal-to-noise ratios (SNR) of ultrasonic imaging and non-destructive evaluation (NDE) applications can be greatly improved by driving each piezoelectric transducer (single or in array) with tuned HV capacitive-discharge drivers. These can deliver spikes with kW pulsed power at PRF ≈ 5000 spikes/s, achieving levels higher even than in CW high-power ultrasound: up to 5 kWpp. These conclusions are reached here by applying a new strategy proposed for the accurate modeling of own-design re-configurable HV capacitive drivers. To obtain such rigorous spike modeling, the real effects of very high levels of pulsed intensities (3–10 A) and voltages (300–700 V) were computed. Unexpected phenomena were found: intense brief pulses of driving power and probe emitted force, as well as nonlinearities in semiconductors, though their catalog data include only linear ranges. Fortunately, our piezoelectric and circuital devices working in such an intense regime have not shown serious heating problems, since the finally consumed “average” power is rather small. Intensity, power, and voltage, driving wideband transducers from our capacitive drivers, are researched here in order to drastically improve (∆ >> 40 dB) their ultrasonic “net dynamic range available” (NDRA), achieving emitted forces > 240 Newtonspp and receiving ultrasonic signals of up to 76–205 Vpp. These measurements of ultrasonic pulsed voltages, received in NDE and Imaging, are approximately 10,000 larger than those usual today. Thus, NDRA ranges were optimized for three laboratory capacitive drivers (with six commercial transducers), which were successfully applied in the aircraft industry for imaging landing flaps in Boeing wings, despite suffering acoustic losses > 120 dB.

An example of industrial NDE imaging of controlled small flaws artificially induced inside a landing flap of Boeing 777, using CSIC technologies

Acknowledgments

The authors gratefully acknowledge the paper support of the R&D Projects: Spanish National Plan RETOS DPI 2017-90147-R (Low-intensity ultrasounds for early detection and modulation of tumor and stroma); Ibero-American Network CYTED-DITECROD-218RT0545 (New non-invasive ways for early diagnosis of chronic and degenerative diseases); CDTI (Spain) COI-20201153 (Ultracov: Ecógrafo para COVID-19). Special thanks to: J. G-Vegas, P.T. Sanz, J.L. San Emeterio, L. Diez and C. Fritsch, for their useful collaboration in industrial applications; to CSIC, CICYT, CC.EE., CINVESTAV, URU, and two CYTED international cooperation networks; and finally, to L. Leija for their precise and objective opinions about this paper.