This Small Business Innovation Research (SBIR) Phase I project will develop a biologically inspired undulatory swimming device in which all motion is achieved by the cyclical elastic deformation of a pre-stressed form-finding structural system actuated by Electroactive Polymer (EAP) transducers. The design presents and integrates multiple mechanical, electrical and system control innovations to:
? separate the challenges of form-finding from actuation to enable a relatively simple system to reproduce undulatory motion (simplifying manufacture and control, improving reliability) ? maximize energy efficiency by recycling priming energy, both electrical and mechanical, required by EAP transducers. ? overcome limitations of EAP transducers as pull-actuators ? develop low duty cycle power electronics and control algorithms for flexible support of phased EAP actuation/generation cycles
Using numerical modeling and transfer functions, analytical models will be developed for (i) the electromechanical response of selected EAP transducers (ii) the microcontroller-driven architecture for operating arrays of high-voltage, low duty cycle transducers (iii) the fluid-structure interactions produced by resilient bi-stable finlike elements. The company will integrate these models with its existing Abaqus FEA model of fin-like elements to achieve system virtualization and parameter extraction for proof of concept and further optimization. A drive system subassembly will be built for testing and model validation.
The broader impact/commercial potential of this project will be development of a propulsor emulating the high efficiency and maneuverability of animal models with potential applications in propulsion and as well as other fluid-structure-interaction devices. Implementation in Unmanned Underwater Vehicles (UUVs), particularly if a potential self-recharging variant is developed, would enable enhanced performance and endurance. The market for new UUV?s 2010-2019 has been estimated at 1,144 units, value $2.3 billion, indicating the economic incentive to enhance UUV energy efficiency and reliability to minimize downtime and operational risk associated with re-charging or repair in the field. Improved economics for UUV technology may facilitate socially important work in engineering and research, including development of offshore power generation and oceanographic surveying and sensing to monitor climate change and its impacts. The work explores the opportunities presented by bi-stable form-finding behavior in actuated systems to achieve useful mechanical work. Rigorous physical modeling is required both to develop such systems and test the limits of EAP actuators.
The goal of the Phase I project was to develop the design, and to model the feasibility of the Core Frond Propulsor (CFP), a biologically-inspired undulatory swimming mechanism that uses novel mechanical principles to create a propulsive thrust similar to that observed in the efficient swimming action of the Ghost Knifefish and Oar Fish. The CFP utilized elastic longitudinal fins along which traveling waves of material deformation travel in a periodic manner. Potential advantages of the proposed CFP mechanism compared with conventional bladed propulsion include greater efficiency, reduced noise and reduced impact on aquatic organisms and ecosystems. During Phase I, six major iterations of the CFP were developed using Abaqus, a multi-physics modelling software package well suited to nonlinear mechanical simulations. Custom add-on software for Abaqus was developed to predict the hydrodynamic forces exerted by the mechanism under operation. Proof-of-concept for a CFP utilizing Electroactive Polymer (EAP) artificial muscle transducers was achieved in MATLAB/Simulink. In addition of proof-of-concept, this modeling work resulted in a suite of engineering design tools for future iterative development of an EAP-powered CFP. An alternative to the EAP-actuated mechanism was modelled and built with electric motors replacing the EAP transducers. Motor control algorithms were developed and lab testing demonstrated predicted and desired fin actuation and behavior via the motors.
