Feedback Control of a Single-Tail Bioinspired 59-mg Swimmer

TL;DR

This paper introduces a biologically inspired, subgram-scale robotic swimmer with feedback control, demonstrating precise trajectory tracking and significantly increased swimming speed using a novel SMA-based bimorph actuator.

Contribution

The development of a controllable, feedback-driven, single-tail aquatic robot at the subgram scale with enhanced speed and maneuverability, enabled by a physics-informed design and new actuation method.

Findings

Achieved up to 13.6 mm/s swimming speed

Demonstrated accurate 2D trajectory tracking with 2.6 mm RMS error

Enabled precise turning with small radii and high turning rates

Abstract

We present an evolved steerable version of the single-tail Fish-&-Ribbon-Inspired Small Swimming Harmonic roBot (FRISSHBot), a 59-mg biologically inspired swimmer, which is driven by a new shape-memory alloy (SMA)-based bimorph actuator. The new FRISSHBot is controllable in the two-dimensional (2D) space, which enabled the first demonstration of feedback-controlled trajectory tracking of a single-tail aquatic robot with onboard actuation at the subgram scale. These new capabilities are the result of a physics-informed design with an enlarged head and shortened tail relative to those of the original platform. Enhanced by its design, this new platform achieves forward swimming speeds of up to 13.6 mm/s (0.38 Bl/s), which is over four times that of the original platform. Furthermore, when following 2D references in closed loop, the tested FRISSHBot prototype attains forward swimming speeds of up to 9.1 mm/s, root-mean-square (RMS) tracking errors as low as 2.6 mm, turning rates of up to 13.1 {\deg}/s, and turning radii as small as 10 mm.