Understanding the relationship between pitch agility and propulsive aerodynamic forces in bio-inspired flapping wing vehicles

Zohaib Hasnain, James E. Hubbard, Joseph Calogero, Mary I. Frecker, Aimy A. Wissa

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

Ornithopters, or flapping wing mechanical birds, represent a unique category of aerial vehicles that fill a need for small-scale, agile, long range, and payload-capable flight vehicles. This study focuses on understanding the relationship between the propulsive aerodynamic forces and pitch agility in these flapping wing vehicles. Using analytical methods, the aerodynamic moment acting upon a wing undergoing elastic flapping was calculated. A method to determine the pitch stiffness of the vehicle was then derived using a preexisting stability analysis. This method was used to demonstrate that pitch agility in flapping wing birds is intricately tied to the flapping cycle with different parts of the cycle creating stabilizing and destabilizing effects. The results indicated that pitch agility, and propulsive force generation, have a dependency on the shape of the wing, and that deformations such as bend and sweep are capable of making the vehicle more agile. Contactaided compliant mechanisms with nonlinear stiffness were designed and inserted into the wing of an ornithopter to induce controlled morphing. These elements have varying stiffness during the upstroke and downstroke parts of the cycle which introduces an asymmetry between the two halves of the flapping cycle. The resulting flapping motion exhibited a two fold increase in horizontal propulsive force over the baseline case. A motion tracking system was used to capture the free flight response of the ornithopter in steady level flight. This information was then used to calculate the pitch stiffness of the ornithopter with a rigid spar, and, one with a nonlinear compliant element inserted into the spar to induce a desired shape change. The results revealed that an upstroke in which the aerodynamic forces are similar in magnitude to that of the downstroke, may be necessary to make the vehicle more agile, and, that there is a compromise between vehicle agility and flight propulsive forces.

Original languageEnglish (US)
Title of host publicationIntegrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting
PublisherAmerican Society of Mechanical Engineers
ISBN (Electronic)9780791857304
DOIs
StatePublished - Jan 1 2015
EventASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2015 - Colorado Springs, United States
Duration: Sep 21 2015Sep 23 2015

Publication series

NameASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2015
Volume2

Other

OtherASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2015
CountryUnited States
CityColorado Springs
Period9/21/159/23/15

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Control and Systems Engineering
  • Mechanics of Materials
  • Building and Construction

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  • Cite this

    Hasnain, Z., Hubbard, J. E., Calogero, J., Frecker, M. I., & Wissa, A. A. (2015). Understanding the relationship between pitch agility and propulsive aerodynamic forces in bio-inspired flapping wing vehicles. In Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting (ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2015; Vol. 2). American Society of Mechanical Engineers. https://doi.org/10.1115/SMASIS2015-8835