Investigation to resonant frequency control of high power ultrasonic transducer based on the beating model

The response time of the resonant frequency tracking is a critical parameter to evaluate the performance of a high power ultrasonic system. In this investigation, we present a novel approach of frequency tracking based on the beating vibration model, which demonstrates improvement result compared with the conventional PLL method. We explore and enclose quantitatively the static and dynamic characteristics of the transducer at conditions of different temperatures, driving voltages and frequencies. It is found that the beating vibration occurs if the driving frequency is deviated from the optimal natural frequency. To reveal the mechanism of the beating vibration, an equivalent model is established. We propose a novel calculation algorithm of trust domain method to search accurately the resonant frequency in the response time, ensuring the resonant vibration of the ultrasonic transducer. The verification experiment is conducted in a PFGA and DSP controller, which verifies that the resonant frequency is determined within 30 ms. Our proposed approach can quickly decrease the beating time and fast achieving the resonant vibration, compared with the other frequency tracking methods.