Please use this identifier to cite or link to this item: https://hdl.handle.net/10321/5499
Title: An investigation of a scalable flight control system for a variable pitch, fuel powered, quad-rotor craft
Authors: Nielsen, Byron Vaughn Roy 
Keywords: Quadrotor platforms;Blade Element Momentum Theory (BEMT);Rotor model
Issue Date: May-2024
Abstract: 
Quadrotor platforms continue to face scalability issues that can be linked to factors such as
energy density of polymer battery power sources and the limited efficiency of their fixed pitch
propulsion systems.
This study employs a dual-method analysis, integrating both experimental and theoretical
approaches, to explore the trade-offs between endurance and payload capacity in a quadrotor
equipped with a scalable variable pitch rotor system. By applying this development framework,
the key objective of this work is to broaden the scope of feasible mission profiles by clarifying
the inherent constraints and compromises between endurance and payload capacity and
illuminating factors contributing to efficiency.
In this pursuit, the first main aspect focused on empirically validating various rotor geometries
using test bench system. Data collected is analysed using the computational tool MATLAB,
whereas XFOIL simulates airfoil lift and drag characteristics. Rotor performance is then
characterised through comparative analysis between experimental data and theoretical
predictions made by the Blade Element Momentum Theory (BEMT) rotor model. From
comparisons it was found that the BEMT model performance and behaviour remained
consistent at varying rotor geometry scales and correlated well with empirical thrust results. It
was also found that approximations for power output levels were marginally overestimated at
high blade pitch angles – the possible causes of which are further explored in an article
published in parallel to this work. [1]
The 6-DOF (degrees of freedom) nature of quadrotors in a dynamic environment is then
explored using Simulink wherein a flight control system (FCS) architecture is formulated by
integrating control laws with a BEMT rotor model. Comparative performance evaluations
focusing on dynamic behaviour, thrust generation, and power efficiency are then realised by
subjecting a standardised quadrotor airframe with varying rotor geometry and payload
capacities to an idealized climb-to-hover (C2H) trajectory.
From comparisons of simulation tests, it was significant to find that varying rotor geometry and
payloads yielded highly contrasting dynamic behaviours and efficiency performance in terms
of thrust generation and power demands. Simulation data also indicated that the B04 rotor
configuration was the most energy efficient and enabled superior climb rates and accelerations.
By employing figures for simulated hovering power demands, abstracted endurance times are shown to be greatly affected by the energy density and payload constraints between chemical
battery systems and carbon fuels. Comparative analysis of rotor performance also revealed that
the choice of hardware configuration may necessitate prioritising durability and responsiveness
over efficiency. Moreover, mission profiles optimised for high dynamic responsiveness must
ensure that FCS sensitivity does not exceed the strength constraints of mechanical subsystems
or airframe structure.
Collectively, this work successfully established a robust framework for future research and
early-stage development of scalable quadrotor platforms can be achieved by integrating
variable pitch rotor systems with modularized quadrotor control system architectures. This
framework provided key insights into improving quadrotor performance and efficiency,
particularly through scalable rotor geometry and payload capacity.
Description: 
Submitted in the fulfillment of requirements of the degree of Master of Mechanical Engineering, Durban University of Technology, Durban, South Africa, 2023.
URI: https://hdl.handle.net/10321/5499
DOI: https://doi.org/10.51415/10321/5499
Appears in Collections:Theses and dissertations (Engineering and Built Environment)

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