Design, Fabrication and Assembly of a Flapping-Wing with Integrated Compliant Hinge

Design, Fabrication and Assembly of a Flapping-Wing with Integrated Compliant Hinge: Application in a Bio-Inspired, Resonant Micro Air Vehicle

Ras, Meindert (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Precision and Microsystems Engineering)

Goosen, Hans (mentor)
Tolou, Nima (graduation committee)
Zhang, Lidan (graduation committee)

Delft University of Technology

Mechanical Engineering

2020-07-10

The Atalanta is a palm-sized, insect-inspired, flapping-wing micro air vehicle developed by the University of Technology Delft. In its current form, the Atalanta has a lift-to-mass ratio of 0.12 which inhibits it from taking off. Getting the Atalanta to fly would greatly benefit the research into areas such as aerodynamic modelling, on-board electronics, control and navigation and more. Designing and realizing a new, energy-efficient wing-system capable of producing 1.5 gram lift is found to be the most effective solution, with an expected lift-to-mass ratio of 0.85. Developing this new wing-system requires the design, manufacturing and integration of two parts: a wing and a compliant hinge. The wing is a wing-shaped, rigid plate that pushes air around to generate lift. The hinge is the interface between the Atalanta body and the wing, and allows the wing to passively rotate, i.e.: pitch, around its spanwise axis. For the fabrication of the wing, a hybrid structure is created by stacking sheets of different materials on top of each other, each with its own purpose. The sheets are laser cut before assembly to distributed material only where needed. The result is a wing consisting of a carbon frame for stiffness, a Mylar sheet for enclosing the wing surface area and a double-sided adhesive layer to bond the two together. For the compliant pitching hinge, a cross axis configuration of three leaf-flexures is selected. The combined pure bending motion of all three flexures allows the wing to rotate around its pitching axis. The flexures are fabricated and subsequently integrated into the wing structure, forming the new wing-system. The two main tests qualitatively asses the performance of the new wing-system. The first test measures the average stiffness of four hinges, and finds it to be a factor 27.8 higher than was expected. Measurement errors, incorrect input parameters, hinge flexure misalignment and corrugation at the edges of the flexures all can reduce the factor to 13.9, but the dominant reason is estimated to be curving of the flexures along their width. The second test determines the kinematic profile of the new wing-system; i.e. the sweeping and pitching angles during a single stroke. The results show that the wing-system operates at its resonance frequency of 8.5 Hz. This indicates that the energy efficiency of the new wing-system should be improved compared to the current wing-system. The 8.5 Hz sweeping frequency does mean a lower lift generation than expected, but this can be improved by reducing the mass of the wing and optimizing its topology. With some weight saving improvements the new wing-system should be more energy efficient while producing more lift compared to the current wing-system. The design and manufacturing processes are more flexible and consistent which makes experimental optimization of the mechanical properties of the wing-system easier. The novel cross axis hinge concept proves to be a valuable addition to the wing, although its fabrication can be improved upon.

Flapping-Wing
compliant mechanism
Fabrication
Lift generation
Energy Efficiency
Atalanta

http://resolver.tudelft.nl/uuid:2a355529-790a-426a-85bd-deb9e3732691

Student theses

master thesis

© 2020 Meindert Ras