Piezoelectric Soft Robot Inchworm Motion by Tuning Ground Friction Through Robot Shape: Quasi-Static Modeling and Experimental Validation

Electrically-driven soft robots based on piezoelectric actuators may enable compact form factors and maneuverability in complex environments. In most prior work, piezoelectric actuators are used to control a single degree of freedom. In this work, the coordinated activation of five independent piezoelectric actuators, attached to a common metal foil, is used to implement inchworm-inspired crawling motion in a robot that is less than 0.5 mm thick. The motion is based on the control of its friction to the ground through the robot's shape, in which one end of the robot (depending on its shape) is anchored to the ground by static friction, while the rest of its body expands or contracts. A complete analytical model of the robot shape, which includes gravity, and contact is developed to quantify the robot shape, friction, and displacement. After validation of the model by experiments, the robot's five actuators are collectively sequenced for inchworm-like forward and backward motion.

I. Introduction

While most soft robots are driven by pneumatic power [1], soft robots driven by piezoelectric actuators may be easier to integrate [2], [3], less bulky, faster to respond (with driving frequencies up to thousands of Hertz [4], [5]), lighter, and potentially microsized [6].