An Untethered Ring-Shaped Miniature Robot with Axisymmetric Vibrations and Non-axisymmetrically Arranged Feet.

Miniature robots inspired by nature are appealing, and the achievement of their rapidity has become uncomplicated after years of development. However, one of the critical challenges of miniature robots is achieving rapidity and agile motions under high load capacity. To address this challenge, this work proposes a unique tripodal piezoelectric robot, featuring axisymmetric vibration modes and non-axisymmetrically arranged feet. On the one hand, by selecting appropriate vibration modes and arranging the 3 feet at unequal spacing, multidimensional and unequal amplitude actuation trajectories at different feet are achieved, enabling the robot to achieve agile motions. On the other hand, strong load capacity is realized through a high-stiffness ring base. The selected vibration modes and different actuation trajectories at foot ends are validated through simulation analysis. A prototype of the robot is developed, and a miniature specialized power supply is designed and integrated into the robot. The wireless linear and rotational speeds reach 93 mm/s and 438°/s, respectively, and the load capacity reaches 200 g, while the resolution is 0.63 μm. Owing to its small size, high load capacity, high resolution, and agility, the robot demonstrates potential for micro-manipulation applications and motion capabilities in confined spaces.