Semester

Summer

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Xi Yu

Committee Co-Chair

Mike Zugger

Committee Member

Jason Gross

Committee Member

Guilherme Pereira

Abstract

Buoyancy-driven, underactuated vehicles offer a compelling solution for long-duration autonomous operations in constrained environments. By leveraging buoyancy to generate lift, these vehicles can remain aloft for extended periods with minimal power requirements, making them well-suited for applications in atmospheric monitoring, planetary exploration, and communications. However, their limited actuation authority, strong coupling with environmental forces, and operating domains introduce significant control challenges, including nonlinearity, sensitivity to external disturbances, and limited observability.

This work investigates the design and implementation of lightweight, reactive model-free control strategies that enable robust autonomy in such constrained settings. A digital Extremum Seeking Controller (ESC) is first implemented as a reference behavior, offering an adaptive, model-free framework that guides the system toward a visual target using only local measurements. Building on this foundation, a fully analog control system is developed that leverages the ESC framework and classical PID control strategies using phototransistor-based optical tracking, bandpass filtering, and hardware-integrated motor drive circuits. By eliminating computation and software, the analog controller enables real-time reactive behavior in environments where localization and digital processing are difficult. Both strategies are benchmarked against a nonlinear Model Predictive Controller (MPC) using a validated 6DOF dynamic model of a custom-designed airship platform.

Simulation and experimental results show that while MPC achieves superior tracking accuracy when full-state feedback and modeling are available, the analog and ESC controllers offer viable alternatives for low-power, real-time control in resource-limited environments. This work contributes to the advancement of deployable autonomous systems by demonstrating that simple, reactive controllers can effectively operate in nonlinear, uncertain, and underactuated domains without reliance on global state estimation or high-performance computation.

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