An novel algorithm of vibration resonance control for power ultrasonic device via extremum seeking control based maximum conductance searching

• A maximum conductance series RFT method based on ESC is proposed. • The series RFT accuracy does not influenced by the static capacitor C 0 of the transducer. • The ultrasonic transducer identification process using impedance analyzer can be reduced. • A controller board with DSP controller is designed to evaluate the theory. The vibration control based on the resonance frequency tracking (RFT) to the piezoelectric transducer is critical for an ultrasonic device. The speed and accuracy of the RFT is significant to ensure the resonant vibration and transmit enough ultrasonic power in real time and high electrical-acoustic energy transform efficiency. Conventionally, the RFT methods is based on the Phase Locked Loop (PLL) and or the maximal current feedback. More, it need to measure the parallel static capacitor, which is difficult to achieve in the circuit or hardware component. In this investigation, we propose a novel algorithm to fast control the resonant vibration based on the RFT method by using the admittance circle model. In the proposed method, the model of the admittance circle of the transducer is established, following the the maximum conductance value in the admittance circle is accurately searched. In order to fast and accurately lock the optimal resonance frequency, we adopt the extremum seeking control (ESC) to find the maximum conductance value. The admittance circle model and the RFT based on ESC is validated by the simulation. We setup an experimental platform based on DSP-FPGA controller to verify the above algorithm, and the results proves that our proposed method can lock the mechanical frequency and control the resonance vibration of the power ultrasonic device in 15 ms. Moreover, in our RFT algorithm, it is no need to measure the parallel static capacitor of the transducer, which can ensure the high energy output.