A Bio-Inspired Hybrid Flapping Wing Rotor for High-Efficiency Micro Rotorcraft

A Bio-Inspired Hybrid Flapping Wing Rotor for High-Efficiency Micro Rotorcraft | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Bio-Inspired Hybrid Flapping Wing Rotor for High-Efficiency Micro Rotorcraft Xun Huang, Linghai Lu, James Whidborne, Marilena Pavel This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8445101/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Enhancing propulsive efficiency at micro aerial vehicle (MAV) scale remains challenging because low Reyn-olds number aerodynamics, structural flexibility, and severe power constraints limit the effectiveness of conventional rotor design strategies. This paper investigates a new hybrid flapping-rotary propulsion concept, termed the Hybrid Flapping Wing Rotor (Hybrid FWR), which superposes controlled flapping on a rotating blade to exploit stroke-wise asymmetry while retaining a compact rotorcraft architecture. A unified analytical framework is developed, comprising (i) a kinematic model that captures mechanically constrained flapping and inertia-driven passive pitching with experimentally informed transition coefficients, (ii) a blade-element-based aerodynamic model to estimate stroke-resolved forces, and (iii) an experimentally fitted motor–power model to enforce constant input power while varying the hybridisation ratio. The resulting lift-coefficient evaluation accounts explicitly for unequal upstroke and downstroke durations. Model predictions indicate a consistent optimum hybridisation ratio near 0.7-0.8, where aerodynamic loading in the upstroke is minimised, and lift production is concentrated in the downstroke, maximising the cycle-averaged lift coefficient for a given power. More than 200 bench-top trials using a two-motor prototype corroborate the existence of an optimum near a hybrid ratio of 0.7, demonstrating up to a 2.148-fold improvement in power efficiency relative to pure rotation under comparable lift conditions. The findings clarify the physical mechanism governing the optimum and provide a practical basis for efficiency-oriented design and further high-fidelity refinement. Hybrid flapping–rotary propulsion Micro air vehicles (MAVs) Low Reynolds number aerodynamics Bioinspired rotorcraft Power-efficient lift generation Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8445101","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":575985445,"identity":"28133177-3265-45b4-b08d-d7e4027834e2","order_by":0,"name":"Xun Huang","email":"","orcid":"","institution":"Cranfield University","correspondingAuthor":false,"prefix":"","firstName":"Xun","middleName":"","lastName":"Huang","suffix":""},{"id":575985446,"identity":"7502be85-30a5-491b-b1a3-4795a418fd15","order_by":1,"name":"Linghai 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This paper investigates a new hybrid flapping-rotary propulsion concept, termed the Hybrid Flapping Wing Rotor (Hybrid FWR), which superposes controlled flapping on a rotating blade to exploit stroke-wise asymmetry while retaining a compact rotorcraft architecture. A unified analytical framework is developed, comprising (i) a kinematic model that captures mechanically constrained flapping and inertia-driven passive pitching with experimentally informed transition coefficients, (ii) a blade-element-based aerodynamic model to estimate stroke-resolved forces, and (iii) an experimentally fitted motor–power model to enforce constant input power while varying the hybridisation ratio. The resulting lift-coefficient evaluation accounts explicitly for unequal upstroke and downstroke durations. Model predictions indicate a consistent optimum hybridisation ratio near 0.7-0.8, where aerodynamic loading in the upstroke is minimised, and lift production is concentrated in the downstroke, maximising the cycle-averaged lift coefficient for a given power. More than 200 bench-top trials using a two-motor prototype corroborate the existence of an optimum near a hybrid ratio of 0.7, demonstrating up to a 2.148-fold improvement in power efficiency relative to pure rotation under comparable lift conditions. 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