Date of Award
Doctor of Philosophy (PhD)
Mechanical & Aerospace Engineering
In the ground-based validation testing, the adverse effect of terrestrial conditions such as a gravitational force interferes with the dynamic behavior of space structures. A suspension system is developed to assess the structural characteristics in a simulated zero-gravity environment. Using a mechanisms approach, the synthesis of a noncircular disk with a torsional spring at its rotational axis is designed to counteract the gravitational force of test structures during the testing.
The multibody dynamics of a flexible steel beam carried on a rigid trolley has been investigated. The system is constructed in such a way that the rapid and large-angle slewing maneuver is performed by means of hybrid rotational/translational motions.
A flexible one-beam structure and a flexible two-beam structure with such noncircular gears will be investigated. The varying gear ratio of noncircular gears is specified to produce varying output speeds so as to tune the rapid slewing maneuver while suppressing structural vibration. One optimization technique based on the Generalized Reduced Gradient Method is employed to determine the optimal design of the controllers as well as the noncircular gears for vibrational suppression during the rapid slewing maneuvers. The numerical simulations are implemented to evaluate the effectiveness of the integrated design of control and mechanism for the slewing maneuvers of flexible space structures.
Based on Lyapunov's stability criterion, the stability analysis of space structures leads to the design of a Lyapunov-based controller that yields a stable closed-loop system. Such a controller is developed by combining a linear part and a nonlinear part for the rotational/translational maneuver. The simulations of three kinds of nonlinear dynamic systems are performed to verify the usefulness of Lyapunov-based nonlinear feedback control. Two types of beam-like flexible space structures, i.e., the flexible one-beam structure on a trolley and the flexible articulated two-beam structure on a trolley, are simulated to implement maneuvering tasks of position control while suppressing the structural vibration simultaneously. An inverted pendulum is stabilized through its Lyapunov-based nonlinear controller to confirm the feasibility of such a nonlinear controller for unstable systems.
"Control and Mechanism Interaction for Ground-Based Testing of Space Structures"
(1990). Doctor of Philosophy (PhD), Dissertation, Mechanical & Aerospace Engineering, Old Dominion University, DOI: 10.25777/yt29-e026