A miniature self-moving ultrasonic actuator with dual-axis translational movements and high moving/carrying capability inspired by turtle’s crawling/earthworm’s wriggling motions

This article presents a miniature self-moving ultrasonic actuator (MSMUA) with dual-axis translational movements and high moving/carrying capability. When the longitudinal-torsional (L-T) hybrid vibration is excited with the spiral-groove-shaped transducer, the MSMUA can move in the x and y axes by combining the y-axis bending (By)/L-T vibrations and the z-axis bending (Bz)/L-T vibrations, respectively, which interestingly imitate turtles’ crawling/earthworms’ wriggling motions. First, by building the Krimhertz-transmission-theory-based dynamic model, the modal degeneration was performed among the L-T, Bx, and By vibrations. Then, a prototype with the sizes of 67.5 × 42 × 10 mm3 and the weight of 27.23 g was fabricated to assess the moving/carrying/ positioning performance. When the MSMUA in a tethered manner moved in the x and y axes, it yielded the maximal speeds of respectively 483 and 233 mm/s (7.15 and 5.55 times of the body length per second) and the maximal payloads of respectively 1218.5 and 711.5 g (44.7 and 26.1 times of the self-weight). In an untethered manner, the minimal step displacements reached 112 and 128 nm in the x and y axes, respectively. These results demonstrate the MSMUA’s high moving/carrying capability and provide technical reference for designing multi-DOF piezoelectric actuators.