Integrated actuation and harvesting system for a bio-inspired underwater robot
Can piezoelectrics be used to both charge and actuate a soft underwater robot?
I.M. van Noesel (TU Delft - Mechanical Engineering)
Gabriel D. Weymouth – Mentor (TU Delft - Ship Hydromechanics)
J. Jovanova – Mentor (TU Delft - Transport Engineering and Logistics)
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Abstract
This report describes a design research project for a bio-inspired soft underwater robot that can both propel itself and harvest energy. The design is inspired by the remora suckerfish, which attaches itself to other species and hitchhikes to conserve energy. The underwater robot design is able to propel itself and harvest current energy when stationary and attached to an object.
The design process aims to address operational efficiency for both energy harvesting and propulsion. To reduce operational maintenance and approach fish like swimming, a simple dual system is designed using piezoelectric materials.
A literature review is performed to determine the most important efficiency parameters for both modes (propulsion and harvesting) and the most suitable simple system.
The design process follows the double diamond, which is a design process from the Delft method. The design process includes literature, goal-oriented prototyping, testing and evaluating. The design process was iterative, based on an existing design. The existing design originates from a propulsion optimised model, which can fully be reproduced. This design has been altered in terms of stiffness in the flexible part of the underwater robot and the actuation and harvesting system. The original electromotor has been replaced by a piezoelectric system for propulsion and harvesting.
The harvesting capabilities have been tested and quantitatively measured. Multiple tests have been performed to determine the underwater robots’ characteristics. The harvesting capabilities have been tested and quantitatively measured. The actuation performance has been determined based on predictive calculations.
The harvesting results are similar to a previous design which uses piezoelectric materials to actuate and harvest energy from the same system. However, the current output of piezoelectric materials in general is very low, making it challenging to use the harvested energy to be stored in a battery. Additionally, piezoelectric materials require high voltage sources, making the system complex and unsuitable for series connections.
The results of this design research show the challenges of using piezoelectrics for both actuation and energy harvesting. Many improvements need to be made, both mechanically and electronically, for such a design to be feasible. ii