Thesis (M.S.)--Virginia Polytechnic Institute, 1966. / Vita. Abstract. Includes bibliographical references (leaves leaf 61). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 76-80). Also available via the Internet.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 226-230). Also available via the Internet.

The principal objective of th1s thesis has been accomplished. The technique for the analysis of a space frame has been developed and described. A computer program has been wr1tten and presented. A test frame was constructed, analyzed and tested and the results for deflections and rotations compared. / Master of Science

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

Thesis (M.S.)--Ohio University, November, 1987. / Title from PDF t.p.

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 108-113).

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017. / The aim of this thesis is to investigate the applications of multifunctional compos- ite (MFC) technology to nano-satellite structures and to produce a working concept design, which can be implemented on future Cube-Satellites (CubeSats). MFC tech- nologies can be used to optimise the performance of the satellite structure in terms of mass, volume and the protection it provides. The optimisation of the structure will allow further room for other sub-systems to be expanded and greater payload allowance. An extensive literature view of existing applications of MFC materials has been conducted, along with the analysis of a MFC CubeSat structural design account- ing for the environmental conditions in space and well-known design practices used in the space industry. Numerical analysis data has been supported by empirical analysis that was done where possible on the concept material and structure. The ndings indicate that the MFC technology shows an improvement over the conventional alu- minium structures that are currently being used. Improvements in rigidity, mass and internal volume were observed. Additional functions that the MFC structure o ers include electrical circuitry and connections through the material itself, as well as an increase electromagnetic shielding capability through the use of carbon- bre composite materials. Empirical data collected on the MFC samples also show good support for the numerical analysis results. The main conclusion to be drawn from this work is that multifunctional composite materials can indeed be used for nano-satellite structures and in the same light, can be tailor-made to the speci c mission requirements of the satellite. The technology is in its infancy still and has vast room for improvement and technological development beyond this work and well into the future. Further improvements and additional functions can be added through the inclusion of various other materials.

The control problem of a large-order flexible system in the form of a beam-lattice is presented using the Independent Modal-Space Control (IMSC) method. The method is based on a transformation of the system equations of motion to modal space, yielding internally independent modal equations of motion. The control laws are designed in the modal space, permitting independent control of each mode, providing complete decoupling of the equations of motion. Linear optimal control with quadratic performance index is designed to control the response of the elastic as well as the rigid body modes, using the IMSC method. Actuators placement is of fundamental importance in the control of two-dimensional domains if IMSC is used. A method is presented as to the selection of actuators configuration in order to avoid singularity in the mode participation matrix, guaranteeing system controllability. The minimum-fuel problem is a very important one in the design of various space structures. Solution of the minimum-fuel problem is feasible in a coupled form for a fourth order system at most, but will be of insurmountable computational difficulty in the control of a flexible structure, since the model of such system will require a large number of degrees of freedom. A reformulation of the problem in the framework of "Modal Minimum-Fuel Problem" is presented, using the IMSC method. By this method, the complexity inherent in a high-order system is reduced, thus treatment of the coupled high-order system is avoided. Numerical examples for linear optimal control, with quadratic performance index, as well as for the minimum-fuel problem, are presented. / Ph. D.

The partial differential equations of motion for an uncontrolled distributed structure can be transformed into a set of independent modal equations by means of the system eigenfunctions. In vibration analysis, the modal coordinates are referred to as natural coordinates. Active control forces generally recouple the modal equations so that the natural coordinates for the open-loop (uncontrolled) system cease to be natural coordinates for the closedloop (controlled) system. Control of this form is known as coupled control. In contrast, it is shown that a method known as the independent modal-space control method is a natural control method; i.e., the natural coordinates of the open-loop system and of the closed-loop system are identical. Furthermore, it is shown that natural control provides a unique and globally optimal closed-form solution to the linear optimal control problem for the distributed structure. The optimal control forces are ideally distributed. If implementation of distributed control is not feasible, then the distributed control forces can be approximated by finite-dimensional control forces. The class of self-adjoint systems are first considered following a treatment of non-self-adjoint systems. Numerical examples of a beam, a membrane and a whirling shaft are presented. In general, the eigenquantities for a distributed structure cannot be computed in closed-form, so that spatial discretization of the differential eigenvalue problem is necessary. A common discretization method is the finite element method leading to a discrete eigenvalue problem. Two bracketing theorems characterizing convergence of the discrete eigenvalue problem derived by the finite element method to the differential eigenvalue problem are formulated. The independent modal-space control method requires as many actuators as controlled modes. In contrast, coupled control is capable of controlling any number of modes using a single actuator, provided controllability is ensured. However, coupled control is sensitive to errors in the system parameters. As a compromise between coupled control and independent mbdal-space control, a block-independent control method is developed in which blocks of modes are controlled independently. The performances of independent modal-space control, coupled control and block-independent control are compared. / Ph. D.