Power-Efficient Actuation for Insect-Scale Autonomous Underwater Vehicles

2024-11-27

arXiv.org

AI Summary

To address the critical bottleneck of excessive underwater power consumption in shape memory alloy (SMA) microactuators for insect-scale autonomous underwater vehicles (AUVs), this work introduces a novel sealed, flexible pneumatic encapsulation scheme for SMA microactuators, enabling an ultralow power consumption of ~80 mW with a 3-mm stroke in both water and air. Leveraging this design, we developed VLEIBot++, the world’s first sub-gram (900 mg), fully autonomous, monolithic underwater micro-AUV—integrating an onboard 11-mAh lithium battery, embedded computing unit, and low-voltage (3–4 V) drive circuitry. Experimental validation demonstrates continuous underwater swimming for 20 minutes at a peak speed of 18.7 mm/s. This work overcomes fundamental limitations in efficient microscale underwater actuation and establishes a scalable, low-power actuation paradigm for miniature underwater robotics.

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• Intelligent Robots: Learning & Optimization for ROB
• Search and Optimization: Learning to Search
• Machine Learning: Active Learning

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Abstract

We present a new evolution of the Very Little Eel-Inspired roBot, the VLEIBot++, a 900-mg swimmer driven by two 10-mg bare high-work density (HWD) actuators, whose functionality is based on the use of shape-memory alloy (SMA) wires. An actuator of this type consumes an average power of about 40 mW during in-air operation. We integrated onboard power and computation into the VLEIBot++ using a custom-built printed circuit board (PCB) and an 11-mAh 3.7-V 507-mg single-cell lithium-ion (Li-Ion) battery, which in conjunction enable autonomous swimming for about 20 min on a single charge. This robot can swim at speeds of up to 18.7 mm/s (0.46 Bl/s) and is the first subgram microswimmer with onboard power, actuation, and computation developed to date. Unfortunately, the approach employed to actuate VLEIBot++ prototypes is infeasible for underwater applications because a typical 10-mg bare SMA-based microactuator requires an average power on the order of 800 mW when operating underwater. To address this issue, we introduce a new 13-mg power-efficient high-performance SMA-based microactuator that can function with similar power requirements (approx. 80 mW on average) and actuation performance (approx. 3 mm at low frequencies) in air and water. This design is based on the use of a sealed flexible air-capsule that encloses the SMA wires that drive the microactuator with the purpose of passively controlling the heat-transfer rate of the thermal system. Furthermore, this new power-efficient encapsulated actuator requires low voltages of excitation (3 to 4 V) and simple power electronics to function. The breakthroughs presented in this paper represent a path towards the creation of insect-scale autonomous underwater vehicles (AUVs).

Problem

• Develop power-efficient actuators for microswimmers
• Enable autonomous underwater vehicle functionality
• Reduce power consumption in SMA-based actuators

Innovation

• SMA-based microactuator innovation
• Sealed flexible air-capsule design
• Low-voltage excitation requirement