The influence of actuator dynamics on the position of acoustically levitated particles

Acoustic Levitation (AL) employs high-intensity ultrasonic fields to manipulate small objects without physical contact. This paper examines the effects of actuator dynamics on the formation and movement of levitation sites by considering the mechanical impedance of the transducers and their phase-dependent interactions with the acoustic field. A propagating wave formulation is used to derive analytical expressions for the induced pressure field and its potential wells based on Gor'kov’s theory. The study demonstrates that the equilibrium positions of levitated objects are significantly influenced by actuator dynamics, which affect both the field structure and the stiffness of the potential wells. Experimental validation using a single-axis levitation device featuring controlled boundary actuators shows that accounting for the mechanical impedance of actuators is crucial for accurately predicting the locations of levitation sites while adjusting the relative phase between transducers. It is observed that the actuator phase impacts the ratio of the magnitudes of traveling and standing waves, which influences the particle holding stiffness of the potential wells. Furthermore, the temporal change in the relative phase creates dynamic excitation for the levitated particles, which is valuable for investigating their dynamical behavior. These findings highlight the essential role of actuator-field interaction in determining levitation stability and dynamic response, offering insights for precise modeling of acoustic levitation systems for manipulation tasks.