Design and experimental characterization of a multifrequency flexural ultrasonic actuator

In this work, a multifrequency flexural ultrasonic actuator is proposed, designed, and experimentally characterized. The actuator is composed of a Langevin transducer and of a displacement amplifier. The displacement amplifier is able to transform the almost flat axial displacement provided by the Langevin transducer at its back end into a flexural deformation that produces the maximum axial displacement at the center of its front end. Design and analysis of the actuator have been performed by using finite element method software. In analogy to classical power actuators that use sectional concentrators, the design criterion that has been followed was to design the Langevin transducer and the flexural amplifier separately at the same working frequency. As opposed to sectional concentrators, the flexural amplifier has several design parameters that allow a wide flexibility in the design. The flexural amplifier has been designed to produce a very high displacement amplification. It has also been designed in such a way that the whole actuator has 2 close working frequencies (17.4 kHz and 19.2 kHz), with similar flexural deformations of the front surface. A first prototype of the actuator has been manufactured and experimentally characterized to validate the numerical analysis.