Design, fabrication and analysis of novel dragonfly-bioinspired, flapping wing system for a micro air vehicle / Erfan Salami

Erfan , Salami (2021) Design, fabrication and analysis of novel dragonfly-bioinspired, flapping wing system for a micro air vehicle / Erfan Salami. PhD thesis, Universiti Malaya.

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Abstract

In the recent decades, the design and development of biomimetic micro air vehicles (BMAV) have gained increased interest from the global scientific and engineering communities. This has given greater motivation to study and understand the aerodynamics involved with winged insects. Dragonflies demonstrate unique and superior flight performance than most of the other insect species and birds. They are capable of sustained gliding flight as well as hovering and are able to change direction very rapidly. Pairs of independently controlled forewings and hindwings give them an agile flying ability. There are still many technological challenges involved with designing the BMAV. One of these is designing the ultra-lightweight materials and structures for the wings that have enough mechanical strength to withstand continuous flapping at high frequencies. In this study, biomimicry of a dragonfly wing (frame structure and membrane) is done by fabricating them with different materials: acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), high impact polystyrene (HIPS) and Ultrat. Since it is extremely difficult to fabricate the complex microstructures of an actual dragonfly wing, the fabricated wings (forewing and hindwing) are simplified replications of the actual wing set. This simplification was performed using the spatial network analysis method. The BMAV wings were fabricated using a 3D printer, based on these simplified models. Nanoindentation tests of the actual dragonfly wings and the BMAV wings were conducted to measure their hardness and Young’s modulus. Analysis of these measurements forms a structural engineering basis that is important for future BMAV wing design. The test result demonstrates the feasible solution in the development of strong, practical, and low-cost BMAV wings, this work is a stepping-stone on the path to flying robotic dragonfly. These wings were then attached to an electromagnetic actuator and passively flapped at frequencies of 10–250 Hz. A three-dimensional high frame rate imaging system was utilized to capture the flapping motions of these wings at a resolution of 320 pixels x 40 pixels and 35000 frames per second. The maximum wing tip deflection, maximum bending angle, maximum wing tip twist angle, and wing tip twist speed of each wing were measured and compared to each other and the real dragonfly wing. The outcomes display that the ABS wing has considerable flexibility in the chordwise direction, whereas the PLA and Ultrat wings show better conformity to a real dragonfly wing in the spanwise direction. Earlier investigations have indicated that the aerodynamic performance of a BMAV flapping wing is improved if its chordwise flexibility is increased and its spanwise flexibility is reduced. Therefore, the ABS wing (fabricated using a 3D printer) shows the most promising results for future applications. This article presents a novel inexpensive 3D printed tandem flapping wing system that was used to experimentally investigate the aerodynamic forces. Such a system was yet to be investigated and could be used in a future biomimetic micro air vehicle (BMAV) design. The mechanism uses an electromagnetic actuator to flap the wings in a linear up-down stroke motion with a variable beat frequency (30 to 210 Hz) at various angles-of-attack (-10° to 20°). The results show that the tandem wings generate approximately 50% higher lift, compared with the forewing or hindwing pairs acting alone. The tandem wings also improve stability, which could potentially allow hovering.

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