Automatic traveling wave excitation of structures with imperfect cyclic symmetry

Abstract

A method to generate traveling waves with maximal amplitudes in elastic structures with imperfect cyclic symmetric topology is presented. Traveling waves are useful in testing turbine-bladed disks and for the propulsion of ultrasonic motors. However, open-loop excitation of traveling waves may yield a partially standing wave due to imperfections and mode-mistuning. The present work puts forward a method that automatically locks onto the optimal excitation of the system, producing the largest possible pure propagating wave. The excitation uses autoresonance with modal filtering, and force projection control, utilizing optimum-seeking methodology. To validate the presented method, an experimental system consisting of a ring of coupled acoustic Helmholtz resonators was built. The ring was excited by the proposed method, and the ability to overcome the imperfections and automatically lock onto the optimal excitation was observed. In addition, the method was realized on a simulated, ultrasonic, acoustic levitation motor that utilizes traveling waves to control levitated objects.