Thèse (Ph.D.)--Université de Sherbrooke (Canada), 2008. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thèse (M.Sc.A.)--Université de Sherbrooke (Canada), 2007. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thèse (M.Sc.A.)--Université de Sherbrooke (Canada), 2008. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6543. Adviser: Victoria Coverstone. Includes bibliographical references (leaves 135-138) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6545. Adviser: John E. Prussing. Includes bibliographical references (leaves 79-80) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1133. Adviser: Bruce Conway. Includes bibliographical references (leaves 143-148) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1133. Adviser: Michael Bragg. Includes bibliographical references (leaves 196-203) Available on microfilm from Pro Quest Information and Learning.

In this thesis a preliminary formulation of large space structures and their stabilization is considered. The system consists of a (rigid) massive body and flexible configurations which consist of several beams, forming the space structure. The rigid body is located at the center of the space structure and may play the role of experimental modules. A complete dynamics of the system has been developed using Hamilton's principle. Euler-Bernoulli, Rayleigh and Timoshenko beam theories are utilized to derive the dynamic equations governing the vibration of the beams. The equations that govern the motion of the complete system consist of six ordinary differential equations and several partial differential equations together with appropriate boundary conditions. The partial differential equations govern the vibration of flexible components. The ordinary differential equations describe the rotational and translational motion of the central body. The dynamics indicate very strong interaction among rigid body translation, rigid body rotation and vibrations of flexible members through nonlinear couplings. Hence any rotation of the rigid body induces vibration in the beams and vice-versa. Also any disturbance in the orbit induces vibration in the beams and wobbles in the body rotation and vice-versa. This makes the system performance unsatisfactory for many practical applications. In this thesis stabilization of the above mentioned system subject to external disturbances is considered. The asymptotic stability of the perturbed system by applying several types of stabilizing controls such as proportional controls, deadzone controls or saturation controls is proved using Lyapunov's method. Numerical simulations are carried out in order to illustrate the impact of dynamic coupling or interaction among several members of the system and the effectiveness of the suggested feedback controls for stabilization. Stability of a spacecraft and a space station under the influence of slew maneuvering is numerically investigated.

Autonomous control of robot vehicles has been studied recently by AI researchers with simulations and implementations emerging using both Neural Networks and Fuzzy Systems. The application is important primarily for autonomous control of planetary surface rovers and deep space vehicles where telepresence control (remote human operator) is precluded because of the long signal transit time. The problem of vehicle docking is specifically addressed in this thesis and the results of experiments on a small model truck and trailer using a mechanical based position sensing systems is reported. Fuzzy logic controls both forward and backward motion of the vehicle to successfully dock the trailer. Additionally, it is shown how the position sensing system can be improved using a small laser-based bar code engine. Future research including use of the system on other mobile robot platforms is discussed and we describe other research planned for the platform. In this thesis the author shows that the use of fuzzy logic for vehicle control simplifies the analysis of motion required to produce proper docking. In particular, the discontinuity of control produced by switching from forward to reverse is readily handled by fuzzy logic.

Nearly homogeneous, uniformly sheared, turbulent flow was generated in a high speed wind tunnel at shear rates ranging from 436 to 705 s$\sp{-1}$ and Mach numbers below 0.2. The shear rates are substantially higher than those generated in the past, and comparable to those in the inner region of turbulent boundary layers. Measurements were obtained using a three-beam, two-component, laser-Doppler velocimetry (LDV) system in back-scatter mode. The system employs a 100mW Argon-Ion laser, which is connected to the measuring probe via fibre optics. Although the signal was filtered by the data acquisition system, additional computer programs were required to remove extraneous noise, which was defined as data samples beyond 2.5 standard deviations from the mean. LDV measurements show that the turbulence structure attains a self-similar state with approximately constant dimensionless stresses and exponential kinetic energy growth. The main difference from realizations at lower shear rates (comparable to those in outer boundary layers) is a marked decrease in the dimensionless Reynolds shear stress, $-K\sb $, which attained an average value of 0.11 over all present experiments, compared to the value 0.15 obtained previously in uniform shear flow and outer boundary layers. The Reynolds shear stress correlation coefficient averaged over all the present shear flows was 0.35, and was consistently lower than the value of 0.45 which has been found in outer boundary layers and uniform shear flows at lower shear rates. It was concluded that although the partition of turbulent kinetic energy among its components most likely depends on the proximity of a wall, the rate of production of turbulence in shear flow depends mainly on the rate of mean shear, irrespectively of the shear generation mechanism. (Abstract shortened by UMI.)