A bioinspired multimotion modality underwater microrobot

Given the ongoing human exploration of underwater environments, such as underwater archaeology and coral reef expeditions, numerous researchers are engaged in the development of micro– underwater robots suited for confined aquatic settings . One critical challenge inherent to these miniaturized submersibles is ex- ecuting agile maneuvers within these narrow confines. Compared to traditional underwater robots with characteristic dimensions ex- ceeding 10 cm (often reaching meter scales), underwater microro- bot with dimensions below 10 cm is inherently suited for navigating and exploring confined aquatic environments. Replicating the multimodal locomotion of aquatic fauna for adaptive explora- tion in these narrow underwater spaces is nontrivial and requires a microrobotic design satisfying several criteria. These consist of su- perior locomotive performance, diminutive turning radius, and a capacity for flexible transitions between motion modalities.
Nonetheless, meeting these criteria simultaneously with existing technology remains challenging for micro–underwater robots, de- spite a range of biomimetic propulsion methods inspired by aquatic life. Notable examples include fish-like robots, snake-like robots, and jellyfish-like robots. Most of these ro- botic designs exhibit considerable locomotive capabilities while ex- ploring a variety of domains, from basic research in biomimetic dynamics to practical real-world applications. Constraining factors, such as their size, the propulsion mechanism, and control signals, limit most of these robots to movement along one or two axes. These inherently limit the potential of miniature submersibles in execut- ing exploration missions within confined underwater environments. The pteropod, a small aquatic creature, offers the design paradigm. Propelled by the flapping of its flexible wings on either side of the body, the pteropod exhibits freedom of motion within aquatic environments. Notably, this creature demonstrates a unique modality shift in locomotion, actively altering its wing attack angle and generating forces in multiple directions. This pro- vides a perspective on the challenge of multimodal locomotion in underwater settings. Taking inspiration from the pteropod, we de- signed an integrated biomimetic system termed RoboPteropod, characterized by a flapping appendage as a biomimetic propulsor and capable of actively adjusting its angle of attack, reflecting a mul- timodal locomotive scheme. The system measures 7.5 cm in length, 4 cm in width, and 4.5 cm in height, with a weight of 34 g.
The platform incorporates a bioinspired, piezoelectric-driven flap- ping wing as a primary propulsion module, capitalizing on the com- pactness and light weight properties of piezoelectric actuators to accomplish multifunctional and high-performance biomimetic flapping propulsion. By synergizing biomimetic propulsion modules on both sides of the robotic body, the platform achieves fast and low- disturbance motion. It is capable of an antigravitational ascent speed reaching up to 8.5 cm/s [roughly 1.88 body height (BH)/s], with a power consumption of merely 580 mW. In addition, because ofa de- sign that allows active alteration of its bioinspired propulsion mod- ule’s attack angles, the robot can swiftly switch between different movement modalities, accomplishing underwater three-dimensional (3D) movement without the necessity of intricate mechanical struc- tures. Building upon a singular RoboPteropod, we demonstrate its capacity to manipulate a range of underwater movement states, in- cluding underwater hovering, helical motion, pitch control, and sta- tionary rotation among others. Last, we unveiled a motion demo comprising a sequence of maneuvers such as vertical climbing, lateral crossing, bypassing, and obliquely ascending, showcasing its agile multi–degree of freedom mobility. This miniaturized underwater ro- botic platform demonstrates great potential in tasks related to the ex- ploration of narrow underwater spaces.