Graduation Semester and Year

2016

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Aerospace Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Atilla Dogan

Abstract

The control of space, aerial and underwater vehicles requires moment generation mechanisms to change their orientation. In addition to or in place of conventional moment generation actuators, internally moving-mass actuation has been proposed and/or used for such vehicles. The primary principle for mass-actuation is to reposition gravitational force to change the associated moment while the secondary effect may come from the inertial force due to the motion of the masses. Recent development/miniaturization in flight control sensor, computing and actuation, and electric motors and expansion of applications for small UAV (Unmanned Aerial Vehicle) offer a potential for implementation of internal mass-actuation in small UAV. The mass-actuation offers various advantages over the conventional mechanisms in airplane flight such as reduced drag and lift loss due to aerodynamic control surface deflections, simplified wing and tail design, improved lift-generation performance of wing, smaller radar signature for stealth aircraft. This dissertation research investigates the feasibility and benefit of mass-actuation of a small UAV in various flight phases and full missions consisting of all these flight phases and transitions between them. Three different configurations of the same airplane are considered: (1) aero-actuated, conventional airplane with three standard aerodynamic control surfaces, aileron, elevator and rudder, (2) mass-actuated, a mass moving along the fuselage to mainly generate pitching moment, and another mass moving along the wing to generate rolling moment, and (3) mass-rudder actuated, mass-actuation as in case-2 augmented with a rudder. The airplane is an electric powered and has a single propeller at the nose. A full 6-DOF (Degrees of Freedom) nonlinear equations of motion are derived, including the terms modeling inertia forces induced by the motion of the internal masses, and the effect of this internal mass motion on the variation of the center of mass and inertia matrix. The dynamics of the electric motor of the propeller and the servos of the actuators are also modeled. The effect of the propeller on the dynamics of the aircraft is also included. Modeling also includes electric power consumption by the electric motor driving the propeller, and servos of the aerodynamic and mass actuators. An integrated simulation environment is developed that includes all these factors and can be switched between the different configurations defined above. Trim analyses of all three configurations of the airplane are carried out in all four flight conditions (steady climb, cruise, steady turn, steady descent). Trim analyses consider all the constraints of the control and state variables such as limits on the deflections of the aerodynamic surfaces, position of the mass actuators, battery provided voltage, and angle of attack. These analyses demonstrate the feasibility of flying the airplane with mass-actuation only within varying speed ranges depending on the actuation mechanism. The results also show the benefit of mass-actuation over the conventional aero-actuation in terms of range and endurance especially in cruise flight, as compared to the other two configurations. In the second phase of the research, controllability of the airplane with each actuation mechanisms is determined and compared over the feasible speed range of each trim condition. A new relative controllability metrics is defined and calculated for this purpose. This analysis, based on the linearized model of the aircraft in each trim flight condition, show that the mass-actuation provides full controllability with various degree over the speed ranges. Once the controllability is verified, an LQR-based gain scheduling controller is designed for each aircraft configuration to track commanded climb/descent rate, altitude, airspeed, and turn rate. These controllers are implemented in the integrated simulation environment to simulate various flight profiles including full missions that start with a hand-launch of the airplane, climb to a specified altitude, and cruise at that altitude with various commanded speed, and loiter with commanded left and right turn rates, and descend to land with varying approach speed. These simulations also demonstrate the feasibility potential benefits, and/or limitations of mass actuation.

Keywords

Applied sciences, Internal mass-actuation, Small UAV control, Mass-actuated airplane, Trim analysis, Flight control, Controllability of mass-actuation, Flight dynamic simulation, Propeller effect

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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