Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006. / White, Donald, Committee Member ; Will, Kenneth, Committee Member ; Zureick, Abdul Hamid, Committee Member ; Hodges, Dewey, Committee Member ; Muhanna, Rafi, Committee Chair ; Haj-Ali, Rami, Committee Member.

The use of active control actuators integral to a structure's construction has been suggested in large space structure technology. A 3-D active truss is presented and analyzed and control of the actuators to reduce the vibration of a flexible rod attached to the structure is discussed. A state feedback control law is used. Experiments are performed using digital control implementation. Some experimental results are acceptable compared to expected theoretical analysis. Conclusions and recommendations are made for future research. / M.S.

M. Tech. Electrical Engineering. / Aims to develop these railways applications for a better use of the electrical power to reduce pollution and consumption. The specification of this project is to improve the conversion of the electrical energy. This also involves improving the connection between the train and the electrical networks using the pantograph. In this research, I will propose a new architecture for the converters and a structure to provide to the grid the electricity generated through braking. Another point regards the command of the converters, which is directly involved in the system behaviour. In order to obtain the best behaviour possible, a different control as usual will be described and modelled to reduce the total harmonics distortion rate and reach a better efficiency.

Thèse : Mécanique : Faculté des sciences de Paris : 1854. Thèse : Astronomie : Faculté des sciences de Paris : 1854. / Titre provenant de l'écran-titre. Notes bibliogr.

Bibliography: leaves 184-192. / xii, 198 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis reports on problems associated with design and structural modification of vibratory systems. Several common problems encountered in practical engineering applications are described and novel strategies for solving this problems are proposed. Mathematical formulations of these problems are generated, and solution methods are developed. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1997

Recent demands in large space structure technology have suggested the use of active control actuators integral to a structures' construction. The concept of a 3-D (triangular cross-sectioned) active truss is presented. The linear equations of motion for one plane of the truss are derived. A model for a generic flexible beam is then appended to the planar truss model. A linear time-invariant optimal control law is found, followed by a presentation of an experimental planar truss built to test the concept. Physical parameters are then substituted into the dynamic model and several sets of control gains are found. The "Kalman'' gains are applied to the experimental structure. Experimental results are compared to expected theoretical results with good (30%) correlation. Conclusions are drawn and suggestions are made for further research. / Master of Science

Soft robotics are robots, manipulators, and technologies using soft/compliant materials as the key elements of the robotic bodies instead of traditional rigid materials like metals. However, they face problems in the following areas: 1. Low energy density. In many cases of soft robots, the large blocks of elastomer are barely stiff enough for self-supporting and working as end-effectors, let alone high-speed motion or high-force manipulation. 2. Inconvenient actuation methods. The most widely used actuation method of soft robots is fluidic pumping to the elastomeric bodies, which is called pneumatic networks (Pneu-Nets). However, the tube and pipe system dissipate too much energy via viscous friction, leading to a low energy efficiency, especially when the actuation frequency is high. 3. Difficulty in estimating robotic morphology or motion trajectory. The elastic body of a soft robot is usually made of an infinite number of tiny elastic cubes that deform continuously. Each of the cubes has six degrees of freedom (DOF), and they all together form an integrated constitutive equation that has a number of six times DOF coefficients, even if we only consider statics or pseudo-statics. During dynamic analysis, the comparable magnitudes of elastic energy, kinetic energy, and gravitational energy make the calculations even harder. With the inspiration from the prestressing assembly and the snapping of a steel hair clip, this work proposes that we use a prestressed bistable self-interacting kinked ribbon, which we term hair clip mechanism (HCM), made from paper, plastic, metal, carbon-fiber-reinforced plastic (CFRP) plates, etc., as the force amplifier to increase the functionalities of soft/compliant robots and manipulators. The efforts and contributions in this research include all three aspects of theory, simulation, and applications: 1. New mathematical model and solutions (theory). The assembly and actuation of HCMs include the processes of lateral-torsional buckling, post-buckling morphing, and snap-through bucking, which are highly non-linear. To calculate and estimate the deformation of such mechanisms, a mathematical model based on elastic instability and Euler-Bernoulli beam theory is derived and used for analyses and applications. Corresponding design algorithms for HCM robots are derived based on the theory. 2. Finite-element (FE) simulation and verification. To ensure the accuracy of the theoretical solutions and the correctness of the experiments, FE software is used to replicate the processes of lateral-torsional buckling, post-buckling morphing, snap-through buckling, specific robotic applications, etc. 3. Robotic applications of HCMs. The energy-storing-and-releasing properties of HCMs make them very suitable for increasing the controllability and controllability of soft robots/manipulators. Different from both rigid materials and elastomeric soft materials, HCMs and their major materials were termed “compliant mechanisms/materials.” These materials have moduli comparable to rigid materials but are compliant and deformable thanks to their small out-of-plane bending stiffness. Because of the small deformation assumption used, the mathematical model and solutions built and derived in this work are only a first approximation with qualitative-level correctness. However, they offer an estimation error within 5% compared to the experiments and FE simulation data in the specific problem of the assembly of HCMs involving lateral-torsional buckling and post-buckling responses. To calculate the snap-through buckling, they give an error of ~10% because of the additional assumption of the snapping trajectory used. As for applications, the bistable HCMs are mounted on a soft gripper, a terrestrial galloping runner, and three different soft robotic fish. The motor-driven snapping soft gripper exploits the elastic instability of HCMs to achieve rapid closing within 46ms and reversible operation over a span of 86mm, 2.7 times and 10.9 times better than the reference gripper, respectively. The single-actuated untethered terrestrial soft crawler is capable of jumping off and can gallop at a speed of 313 mm/s or 1.56 body length per second (BL/s), faster than most previous soft crawlers in mm/s and BL/s. The pneumatic HCM fish swim at 26.54 cm/s or 1.40BL/s in a lab-condition aquarium tank, about twice as fast as its reference group. The motor-driven HCM fish has a speed of 2.03 BL/s or 42.6 cm/s, 2-3 times faster than previous untethered soft robotic fish. The newest HCM fish robot uses CFRP as its material, herein referred to as “CarbonFish.” Preliminary evaluations of CarbonFish have evidenced an undulation frequency approaching 10~13 Hz and an operating time of about 40 min, suggesting its potential to outperform other biologically inspired aquatic entities and real fish.

This thesis presents a nontraditional treatment for uncertainties in the material, geometry, and load parameters in linear static finite element analysis (FEA) for mechanics problems. Uncertainties are introduced as bounded possible values (intervals). FEA with interval parameters (interval FEA, IFEA) calculates the bounds on the system response based on the ranges of the system parameters. The obtained results should be accurate and efficiently computed. Toward this end, a rigorous interval FEA is developed and implemented. In this study, interval arithmetic is used in the formulation to guarantee an enclosure for the response range. The main difficulty associated with interval computation is the dependence problem, which results in severe overestimation of the system response ranges. Particular attention in the development of the present method is given to control the dependence problem for sharp results. The developed method is based on an Element-By-Element (EBE) technique. By using the EBE technique, the interval parameters can be handled more efficiently to control the dependence problem. The penalty method and Lagrange multiplier method are used to impose the necessary constraints for compatibility and equilibrium. The resulting structure equations are a system of parametric linear interval equations. The standard fixed point iteration is modified, enhanced, and used to solve the interval equations accurately and efficiently. The newly developed dependence control algorithm ensures the convergence of the fixed point iteration even for problems with relatively large uncertainties. Further, special algorithms have been developed to calculate sharp results for stress and element nodal force. The present method is generally applicable to linear static interval FEA, regardless of element type. Numerical examples are presented to demonstrate the capabilities of the developed method. It is illustrated that the present method yields rigorous and accurate results which are guaranteed to enclose the true response ranges in all the problems considered, including those with a large number of interval variables (e.g., more than 250). The scalability of the present method is also illustrated. In addition to its accuracy, rigorousness and scalability, the efficiency of the present method is also significantly superior to conventional methods such as the combinatorial, the sensitivity analysis, and the Monte Carlo sampling method.