The subject of flapping wing Micro Air Vehicles '(MAVs) has been an area of increasing interest in the fields of aerodynamics and vehicle dynamics and control. The low Reynolds number region in which they operate, coupled with the periodic nature of the inputs to the control surface and the flexibility of the primary force-generating surfaces, has led to body models that are far from conventional, well established models used in the aerospace industry. It is therefore difficult to evaluate stability and sensitivity to design and operational parameters. The objective of the work in this thesis is to investigate the inherent nonlinear behaviour in flapping wing longitudinal flight to gain a deeper understanding of the stability attributes of the flight regime. To this end, a rigid flapping wing model was developed from first principles and analysed using continuation methods to determine the stability deviation with varied design and operating parameters. Additional continuation runs provided solutions trimmed to hover and forward flight, on which further stability and performance studies were carried out. The research revealed the existence of multiple steady-state solution branches within flapping wing flight and provided insight into the variations in behaviour of the nonlinear periodic system as input parameters vary. In particular, the III flapping frequency, the wing lead-lag motion, wing position and vehicle mass were shown to have the largest influence on stability. Further study revealed branches of stable and unstable limit cycles trimmed to hover and forward flight; analysis of which demonstrated that the areas of poor stability characteristics I correspond to low power requirements. Additionally, it was shown that previously stable areas in hover flight underwent per.io d doubling bifurcations with increased forward speed, leading to unstable and undesirable solutions. IV
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:654468 |
| Date | January 2014 |
| Creators | Mwongera, Victor Mwenda |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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