Feedback sine wave driver design for ultrasonic transducers

LIEN, University Henri Poincaré – Nancy 1, BP 239, 54506 Vandœuvre-Lès-Nancy, France

Corresponding author: Patrick.Schweitzer@lien.uhp-nancy.fr

Received: 28 May 2008
Revised: 25 September 2008
Accepted: 25 September 2008
Published online: 17 February 2009

Abstract

The optimal sinusoidal excitation of an ultrasonic transducer requests a knowledge of the frequency and the impedance of the used ceramic. These parameters, that vary during the application, depend on the characteristics of the transducer but also on the acoustic load of the propagation medium. In the search for an adaptive excitation, we propose the design of a digital generator assuring the functions of automatic tuning and impedance matching. The design uses the Butterworth-Van Dycke model of pizoelectric ceramics. The method of determination and identification of the model parameters is presented and applied on three different transducers. The negative feedback of the generator is carried out by the signal measured on the transducers. The dynamic voltage being very variable, the output resistor of the driver is controlled by transducer impedance. This feedback control allows the stability of the output voltage to a constant value whatever the frequency and the medium is. A Simulink^® model of the regulation loop shows that the frequency tuning could be realized by exploiting the command signal of the driver resistance. The precision and the stability of the feedback system are tested for frequencies between 1 to 3 MHz.