Date of Award

1-1-2019

Document Type

Dissertation

Degree Name

Ph.D.

Department

Engineering

First Advisor

Matthew J. Rutherford

Second Advisor

Kimon P. Valavanis

Keywords

Ceiling Effect, Ground Effect, Helicopter, Mechatornics, Unmanned Aerial Vehicle, Wall effect

Abstract

Ground effect refers to the apparent increase in lift that an aircraft experiences when it flies close to the ground. For helicopters, this effect has been modeled since the 1950's based on the work of Cheeseman and Bennett, perhaps the most common method for predicting hover performance due to ground effect. This model, however, is based on assumptions that are often not realistic for small-scale rotorcraft because it was developed specifically for conventional helicopters. It is clear that the Cheeseman-Bennett model cannot be applied to today's multirotor UAVs. Experimental findings suggest that some of the conventional thinking surrounding helicopters cannot be applied directly to rotorcraft using fixed propellers at variable speeds (e.g. multirotors). A parametric multirotor-specific ground effect model is developed and presented to overcome some of the limitations in classical helicopter theory.

Likewise, ceiling effect refers to the apparent increase in lift that a rotorcraft experiences when flying close to a ceiling or any similar surface that is present above the rotor(s). Ceiling effect is similar in principle to ground effect, and can be explained using a similar equation. Ceiling effect, however, was never explored in detail for conventional helicopters because large manned aircraft do not operate in enclosed spaces. For multirotors, the work presented in this dissertation suggests that the classical helicopter theory adequately describes ceiling effect performance.

Wall effect is the phenomena that occurs when a rotorcraft flies near a vertical wall, and has the tendency to pitch towards the wall and be drawn into it. Wall effect is the least-understood of these three areas of interest. Wall effect has not been explored in great detail for any aircraft, and is addressed in detail in this dissertation.

The recent widespread use of small-scale UAVs and the demand for increased autonomy when flying in enclosed environments has created a need for detailed studies of ground effect, ceiling effect and wall effect. Ultimately, this work provides foundations for the development of an improved UAV flight controller that can accurately account for various aerodynamic disturbances that occur near surfaces and structures to improve flight stability.

Provenance

Recieved from ProQuest

Rights holder

Stephen Austin Conyers

File size

126 p.

File format

application/pdf

Language

en

Discipline

Electrical engineering, Mechanical engineering

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