Title

Comparative Analysis of Flight Control Designs for Hypersonic Vehicles at Subsonic Speeds

Date of Award

1-1-2018

Degree Name

Ph.D. in Engineering,

Department

Department of Electrical and Computer Engineering

Advisor/Chair

Advisor: Raúl Ordóñez

Abstract

Hypersonic vehicles are complex nonlinear systems with uncertain dynamics. Multiple designs of control systems for hypersonic vehicles based on nonlinear dynamic models have been applied with simulation results under high aircraft speed and altitude conditions. In contrast, the main contribution of this work is the design of three control systems: proportional-integral-derivative (PID), feedback linearization (FL, also known as dynamic inversion), and adaptive control (AC) for the flight operations of these vehicles at subsonic speeds and low altitude conditions. The complexity of the aerodynamic system is considered in the design of each control approach, in order to address robustness issues. The hypersonic vehicle model considered in this work has a v-tail and elevons, which makes the development of its flight control system more challenging to design. The longitudinal and lateral aerodynamics are decoupled as a means to control vehicle under specific flight conditions. Therefore, this work is focused on both longitudinal and lateral aerodynamics. The longitudinal aerodynamics (three degrees of freedom, or 3 DOF), which are divided into two subsystems: forward speed and flight-path angle. Two cases are considered for the lateral aerodynamics: fixed roll angle (5 DOF), and full stability analysis (6 DOF). The 5 DOF lateral aerodynamics are divided into three subsystems, for forward speed, flight path angle, and yaw angle, and the 6 DOF case includes a fourth subsystem for roll angle. Longitudinal and lateral aerodynamics contain uncertain parameters of three forces (drag, lift, and lateral) and three moments (pitch, roll, and yaw); further, the design of different control systems is necessary in order to achieve robust control and reduce the uncertainties. Different control design methodologies are implemented to provide asymptotic tracking of a desired forward speed (Vdes), desired flight-path angle (?des), desired roll angle (?des), and desired yaw angle (?des). The control approaches are compared in terms of longitudinal and lateral climbing flights and several performance measures, such as robustness. Based on the stability analysis, the FL and AC techniques are performed utilizing a Lyapunov function candidate of feedback closed-loop system. The simulation results of longitudinal and lateral aerodynamics determine the range of flight stability that is possible for this hypersonic vehicle model. Additionally, the simulation results for each control technique demonstrate the effectiveness of flight control inputs.

Keywords

Aerospace Engineering, Electrical Engineering, Hypersonic Vehicle, Adaptive Control, Flight Control, Subsonic Speed, Control Design

Rights Statement

Copyright 2018, author

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