Keywords

Autorotation, flight control, equilibrium characteristics, autogyro, renewable energy, energy-efficient surveillance system

Abstract

Long-duration deployment of UAVs for surveillance and communication purposes can be very energy-consuming and expensive. Tethered autogyro-based UAVs can provide an energy-efficient solution to this problem and produce energy in the presence of a strong and persistent wind field at higher altitudes. Instead of using an engine, the unpowered autogyro rotors produce lift by creating an upward thrust force while relative airflow passes up through the rotor blades. The tether provides mooring action and can be used bidirectionally for transmitting or receiving power from the autogyro. Thus, tethered autogyros can address recent environmental concerns by reducing carbon footprint via efficient use of renewable energy resources. This thesis presents a simple model-based altitude and pitch control method of a tethered multi-rotor autogyro as a starting step to make a contribution towards green technology in the low-altitude surveillance field.

This study adopts a quad-copter-based autogyro, connected to the ground by a tether, for modeling in the 2D plane assuming that the roll and yaw motions of the system are already being controlled by the rotors in the lateral direction which simplifies the highly nonlinear system by decreasing the number of states. Blade-Element-Momentum (BEM) theory combined with static catenary mechanics is employed to model the aerodynamic forces and tether tension which results in producing the equations of motion of the system. The equations of motion are solved to study transient behavior and characterize the equilibrium space of the tethered system, thereby identifying optimal operating ranges associated with the rotors' tip-speed ratio and the system's pitch angle.

A proportional-feedback controller is designed and a stability analysis is conducted for pitch actuation and altitude tracking of the system. Results suggest that the proportional controller efficiently tracks the higher reference altitude in both uniform and variable wind fields. However, it cannot track the reference altitude set at less than 85% of the tether length. This prompts the design of a PD-feedback controller. Stability analysis and simulation results show that the PD controller is more effective in modulating pitch and controlling the autogyro's altitude using the restoring effect from the tether tension within the entire operating region.

Completion Date

2024

Semester

Spring

Committee Chair

Das, Tuhin

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Guidance, Control, and Dynamics Track

Format

application/pdf

Language

English

Rights

In copyright

Release Date

November 2024

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Campus Location

Orlando (Main) Campus

Accessibility Status

Meets minimum standards for ETDs/HUTs

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