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

The paper presents an improved version of a small, fish-inspired swimming robot (FRISSHBot) that weighs 59 mg. The robot is driven by a new shape-memory alloy (SMA)-based bimorph actuator. The authors report that the updated design allows control in a 2D plane, enabling feedback-controlled trajectory tracking. They describe this as the first demonstration of feedback-controlled trajectory tracking for a single-tail aquatic robot with onboard actuation at the subgram scale. They attribute the improved performance to a physics-informed design change, including an enlarged head and a shortened tail. The prototype achieves forward swimming speeds up to 13.6 mm/s, and in closed-loop 2D reference tracking it reports speeds up to 9.1 mm/s with low RMS tracking errors, fast turning rates, and small turning radii.