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

Lead Research Organisation: Imperial College London
Department Name: Dept of Aeronautics

Abstract

Natural fliers achieve exceptional aerodynamics by continuous adjustments on their geometry through a mix of dynamic wing compliance and distributed sensing and actuation. This enables them to routinely perform a wide range of manoeuvres including rapid turns, rolls, dives, and climbs with seeming ease. Despite a good knowledge of the physiology of bats and birds, engineering applications with active dynamic wing compliance capability are so far few and far-between. Recent advances in development of electroactive materials together with high-fidelity numerical/experimental methods provide a foundation to develop biologically-inspired dynamically-active wings that can achieve "on-demand" aerodynamic performance. However, this requires first to develop a thorough understanding of the dynamic coupling between the electro-mechanical structure of the membrane wing and its unsteady aerodynamics. In this collaborative initiative between the University of Southampton and Imperial College London, we will develop an integrated research programme that carries out high-fidelity experiments and computations to achieve a fundamental understanding of the dynamics of aero-electro-mechanical coupling in dynamically-actuated compliant wings. The goal is to utilise our understanding and devise control strategies that use integral actuation schemes to improve aerodynamic performance of membrane wings. The long-term goal of this project is to enable the use of soft robotics technology to build integrally-actuated wings for Micro Air Vehicles (MAV) that mimic the dynamic shape control capabilities of natural flyers.

Publications

10 25 50

publication icon
Buoso S (2014) A Comparative Study on Nonlinear Material Models for Electroactive Polymers in 11th World Congress on Computational Mechanics

publication icon
Buoso S (2015) Electro-aeromechanical modelling of actuated membrane wings in Journal of Fluids and Structures

 
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 have integrated our high-fidelity fluid-structure interaction with the open-source SU2 CFD software. This has allowed us directly distribute the results of our research to the very large user base for this software, which includes practicing engineers, undergraduate students and researchers from across the world. They all now have access to our methods to support wing design. It is still early for tangible outcomes from this exercise, but we are aware of major aircraft companies testing our implementation to evaluate their potential to support their airframe design process.
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 of Great Britain & Northern Ireland (UK)
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 of Great Britain & Northern Ireland (UK)
Start 07/2013 
End 07/2013
 
Description Collaboration in Multidisciplinary Optimization Methods with TU Kaiserslautern 
Organisation Technical University Kaiserslautern
Country Germany, Federal Republic of 
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 of America 
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 SU2FSI 
Description Fluid-structure interaction capabilities, including adjoints for design, on the CFD solver SU2. Our contributions started to appear in the official distribution from version 4 of the software. 
Type Of Technology Software 
Year Produced 2016 
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 http://su2.stanford.edu/teams/IC_Team.html
 
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