Multi-degrees-of-freedom swimmer using an ultrasonic longitudinal transducer

Abstract

Acoustic underwater propulsion systems based on an ultrasonic transducer have been studied. In previous research, the self-propelled acoustic swimmer using thickness-vibration-mode transducer is evaluated widely. The thickness-vibration-mode transducer is excited in the thickness and radial direction. Because the acoustic propulsion system is based on the acoustic driving force, the vibration in the radial direction is hard to provide the propulsion thrust. In this study, a cylindrical transducer, the pure longitudinal vibrator, is evaluated for the acoustic underwater propulsion system. A prototype swimmer with multiple transducers is designed and fabricated. The admittance characteristics of the cylindrical transducer are investigated in air and in water. The zero speed propulsion and no load speed are measured in water. Multi-degrees-of-freedom swimmer with the multiple cylindrical transducers is evaluated. Because of the small size, high power density, simple structure and multi-degrees-of-freedom, self-propelled acoustic swimmer is suitable for applications such as inspection and repairment robots in a liquid environment.