Towards Biologically-inspired active-compliant-wing micro-air-vehicles

Lead Research Organisation: Imperial College London
Department Name: Aeronautics

Abstract

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Description We developed the first high-fidelity electro-aero-mechanical model for integrally-strained membrane wings. This is a critical step to explore complex designs of shape-changing wings for small flyers (typically less than 50cm in length). We have identified the key elements in the analysis and their relative importance. For example, our numerical simulations have shown that damping by viscoelastic stress get magnified by the presence of the aerodynamics and modify quite substantially the dynamic response of membranes wings built with dielectric elastomers.

We have also demonstrated a closed-loop mechanism to obtain on-demand aerodynamics on shape-controlled membrane wings. It is based on a feedback strategy to define the wing electromechanic actuation based on instantaneous wing lift and/or wind preview measurements. This has been seen to stabilize small wings in gusty outdoor flight under realistic atmospheric turbulence levels.

Finally, to investigate optimal actuation strategies we have also developed a general method to obtain design sensitivities on coupled high-fidelity fluid-structure problems. It is based on state-of-the-art algorithmic differentiation strategies on an discretization on complex domains of the Navier-Stokes equations for the fluid and the nonlinear solid mechanics equations for the structure. This will facilitate future wing and wind turbine blade designs that consider simultaneously both the structural (internal layout) and aerodynamic (external geometry) characteristics as optimization parameters.
Exploitation Route We have demonstrated a new concept for wing design for small air vehicles that would allow both long range and high manoeuvrability. Our investigations have shown the expected dynamic characteristics, strategies for closed-loop actuation for outdoor flight, and limits of performance. This paves the way for innovative designs for fixed and flapping wing small vehicles, using our proposed actuation mechanism or an equivalent one.

The software that he needed to develop for our investigations have been made open source, within the highly popular SU2 CFD suite. This has provided SU2 with fluid-structure interaction capabilities, which may be further explored by other researchers and designers to develop new wing concepts. Furthermore, we have very recently implemented on that code our new method to obtain fully-coupled design sensitivities, therefore releasing to the wider research and engineering community a solution for the simultaneous design of the structure and aerodynamic characteristics of wings and wind turbine blades.
Sectors Aerospace, Defence and Marine
URL http://www.imperial.ac.uk/aeroelastics/projects/membranes/
 
Description We implemented and distributed our high-fidelity fluid-structure interaction as part of the leading open-source SU2 CFD software. Imperial's originated FSI module has been available since version 4 of the software in 2017. This has allowed us directly make available the results of our research to the very large user base for this software (in the tens of thousands), which includes practicing engineers, hobbyists, as well as undergraduate students and researchers from across the world.
First Year Of Impact 2017
Sector Aerospace, Defence and Marine
Impact Types Economic
 
Description Integrally-Actuated Membrane Wings
Amount £55,815 (GBP)
Organisation European Office of Aerospace Research & Development (EOARD) 
Sector Public
Country United Kingdom
Start 03/2013 
End 03/2016
 
Description Window on Science Travel Grant 2013
Amount £2,369 (GBP)
Organisation European Office of Aerospace Research & Development (EOARD) 
Sector Public
Country United Kingdom
Start 07/2013 
End 07/2013
 
Description Collaboration in Multidisciplinary Optimization Methods with TU Kaiserslautern 
Organisation Technical University Kaiserslautern
Country Germany 
Sector Academic/University 
PI Contribution We have jointly developed a method to obtain design sensitivities in large-scale fully-nonlinear fluid-structure interactions problems, for instance, for the optimization of a wing internal construction to achieve an optimal shape while in flight. Imperial's team was in charge of the development and implementation of the coupled theory.
Collaborator Contribution The team at TU KL developed an implemented the algorithmic differentiation strategy and have supported the parallelization of the software for large-scale computations.
Impact We have one journal paper under review (not reported yet) and we are preparing a release of our solution under the open-source SU2 CFD software.
Start Year 2016
 
Description Development of an open-source fluid-structure interaction solver 
Organisation Stanford University
Country United States 
Sector Academic/University 
PI Contribution Our research is developing the FSI module within the open-source SU2 CFD software.
Collaborator Contribution The SU2 team menbers at Stanford and TU Kaiserlautern and is providing support and feedback to the developers at Imperial.
Impact The main outcome is an open-source multiphysics solver developed. The solver has been downloaded over 100,000 times as of early 2017, making it one of the most successful in its field. The first developers meeting took place in September 2016 in TU Delft, with Imperial representatives. It was attended by industrial representatives from Boeing (USA) and Rafael (Israel), among others. The work is multidisciplinary within computational mechanics, as it includes fluid dynamicists at Stanford, TU Delft and Politecnico Milano, Computational Science and Engineering experts at TU Kaiserlautern, and Computational Mechanics expertise at Imperial College.
Start Year 2014
 
Title SU2: The open-source CFD software 
Description SU2 is one of the leading open-source fluid dynamic solvers for aerospace applications. Most of the fluid-structure interaction capabilities have been developed at Imperial, including adjoints for design, and the architecture for simultaneus aerodynamic shape and structural topology optimization. Our contributions started to appear in the official distribution from version 4 of the software and have grown to include also new parallelization strategies, preconditioners for unsteady low-Mach solutions and sparse linear algebra libraries. 
Type Of Technology Software 
Year Produced 2016 
Open Source License? Yes  
Impact SU2 has a very large user base, with over 100k downloads as of January 2017. Users include aircraft companies, start-up, and students from all over the world. Our contribution expands the range of available simulation and it is currently being tested at Boeing to support wind design. 
URL https://su2code.github.io/
 
Description Feature article at The Guardian 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Article in The Guardian after an EPSRC press release
Year(s) Of Engagement Activity 2016
URL https://www.theguardian.com/science/2016/feb/18/is-it-a-bird-is-it-a-bat-no-its-the-future-of-drone-...
 
Description Interview at BBC World Service 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interview to Dr Palacios at BBC Click
Year(s) Of Engagement Activity 2016
URL http://www.bbc.co.uk/programmes/p03jpn3t