Amplitude Modulation of Nonlinear Piezoelectric Transducers for Ultrasonic Levitation

Ultrasonic levitation bearings are a new kind of bearing system that offers the advantages of air-bearings combined with dynamically adjustable supporting force without the need for pressurized air. Such systems are typically driven close or in their resonance frequency, due to energetic reasons. In this contribution the two possible driving methods, namely forced- and self-excitation, are compared in sense of their transient amplitude behavior in the presence of nonlinearities. It is known that during amplitude changes at high vibration amplitudes the system’s resonance frequency varies with Duffing-characteristic due to the nonlinear stiffness of piezoelectric material. It will be shown that self-excitation is the preferable driving method in sense of obtaining a high bandwidth of amplitude.