An ultrasonic transducer and generator assembly and method for controlling the assembly are disclosed. The method includes sensing a current signal and a voltage signal at the transducer, differentiating the voltage signal, multiplying the differentiated voltage signal by a bulk capacitance value to determine a bulk capacitance current signal, determining the difference between the current signal and the bulk capacitance current signal to determine a motional current signal corresponding to mechanical motion of the transducer, determining an updated bulk capacitance value based on the determined motional current signal and the bulk capacitance current signal, generating a transducer signal based on the motional current signal, and driving the transducer with the transducer signal. The method may further include filtering the difference between the current signal and the bulk capacitance current signal using a band-pass filter. The updated bulk capacitance may be determined using a least mean squares adaptive filter.
