Thesis (M.S.)--Ohio University, March, 1993. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, March, 1994. / Title from PDF t.p.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains viii, 104 p. : ill. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--Lehigh University, 1997. / Includes vita. Bibliography: leaves 317-330.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: Parametric optimization; nonlinear dynamics; functional equations; chemical reaction system dynamics; time scale multiplicity; robust control; nonlinear observers; invariant manifold; process monitoring; Lyapunov stability. Includes bibliographical references (leaves 92-98).

An airship with a moving gondola is investigated with the goal of achieving a large pitch angle and of minimizing the total energy consumption required to goal position. The airship in this study is equipped with different actuation tools such as a moving gondola and a vectoring thrust, which can be used for various flight modes. The efficiency of the actuation methods employed is studied and compared in various flight scenarios, based on the airship’s ability to reach the desired position while consuming the least amount of energy. The nonlinear dynamic model is derived using Newton-Euler equations. Backstepping and incremental nonlinear dynamic inversion (INDI) controllers are designed to track a desired trajectory by controlling the position of the gondola and the thrust. The dynamic models are then implemented and simulated in the Matlab/Simulink to evaluate the effectiveness of the controllers in different environmental conditions. The simulation results show the effectiveness of the controllers used, and a larger pitch angle of -89o, can be reached thanks to the movement of the gondola to the front of the airship on the curved keel. The airship prototype was used for the experimental test to evaluate the pitch tracking performance of each of the controllers. The experimental results show that the prototype used can generate a -90o pitch angle, thereby improving manoeuvrability and allowing for rapid changes in altitude. The energy model is developed to evaluate and compare the energy required by the airship for ascent, cruise, and descent flights, using different actuation methods. The effectiveness of the composite control strategy is demonstrated by completing the flight mission with the least amount of energy consumed. An optimization method is then developed to find the optimum design configuration to reduce the cost function, based on energy consumption, of the different flight scenarios while always respecting the design constraints. The Heuristic technique is used to obtain the optimal flight trajectory based on the platform’s ability to complete the desired mission while minimising energy consumption. The results show that for pitch tracking, the vectored thrust has a rapid response, and the required thrust is high. Therefore, this configuration requires more energy than the moving gondola control configuration, in all cases studied. The composite configuration is found to be the most efficient method for completing the flight trajectory with the least amount of energy. The total energy consumption of the entire flight is reduced by about 17% by using the optimization algorithm to select the best actuation method for each flight mode.

The recent addition of autonomous formation flying spacecraft to the world's satellite fleet provides new motivation to study feedback control techniques. In this thesis, we develop nonlinear orbit control laws for use in spacecraft orbital maneuvers, and spacecraft formation flying. We apply these new control laws to a number of sample maneuvers, including formation stablishment and formation keeping maneuvers for NASA-Goddard's Leonardo-BRDF formation, and coupled orbit, and attitude maneuvers for HokieSat, a spacecraft designed, and built by students at Virginia Tech to fly in the Ionospheric Observation Nanosatellite Formation (ION-F). To provide target orbit states for feedback control, we develop and apply an algorithm to calculate a formation master orbit representing the geometric center of the formation. We also define a new technique for choosing orbital element feedback gains which appropriately scales the gains for orbit maintenance, and provides an excellent starting point for gain optimization. The orbital element feedback control law, augmented by mean motion control, and applied with appropriate gains, forces asymptotic convergence to a spacecraft target orbit, for a large variety of spacecraft maneuvers. / Master of Science

Master of Science / Department of Mechanical Engineering / Warren N. White / The subject of linear control is a mature subject that has many proven powerful techniques. Recent research generally falls into the area of non-linear control. A subsection of non-linear control that has garnered a lot of research recently has been in underactuated dynamic systems. Many applications of the subject exist in robotics, aerospace, marine, constrained systems, walking systems, and non-holonomic systems. This thesis proposes a sliding mode control law for the tracking control of an underactuated dynamic system. A candidate Lyapunov function is used to build the desired tracking control. The proposed control method does not require the integration of feedback as does its predecessor. The proposed control can work on a variety of underactuated systems. Its predecessor only worked on those dynamic systems that are simply underactuated (torques acting on some joints, no torques acting on others). For dynamic systems that contain a roll without slip constraint, often a desired trajectory to follow is related to dynamic coordinates through a non-holonomic constraint. A navigational control is shown to work in conjunction with the sliding mode control to allow tracking of these desired trajectories. The methodology is applied through simulations to a holonomic case of the Segbot, an inverted cart-pole, a non-holonomic case of Segbot, and a rolling wheel. The methodology is implemented on an actual Segbot and shown to provide more favorable tracking results than linear feedback gains.

The objective of this thesis is to develop a theoretical understanding of computation in networked dynamical systems and demonstrate practical applications supported by the theory. We are interested in understanding how networks of locally interacting agents can be controlled to compute arbitrary functions of the initial node states. In other words, can a dynamical networked system be made to behave like a computer? In this thesis, we take steps towards answering this question with a particular model class for distributed, networked systems which can be made to compute linear transformations.