No description available.

No description available.

A feedback design procedure known as extended linearization consists in replacing a mathematical model of a nonlinear dynamical system with its family of linearizations, parametrized by the operating point, and then combining feedback gains designed for representatives of the family into a single nonlinear feedback law. The principles of the procedure, applicable both to lumped-parameter and distributed-parameter systems, are discussed at the outset. The development shows limits on feedback laws that can be designed, as well as nonuniqueness of solutions, inherent in the method. / Ph. D.

The design of controllers for structural systems, particularly those associated with large space structures, has received a considerable amount of attention in the past few years. The usual approach to designing these controllers is to apply modern control theory to a reduced linear system obtained from finite element analysis or from a truncated modal analysis. In most of these designs, the sensor signal must be processed to separate out the contributions from each mode so that it may be sent to the appropriate actuators. The analysis presented here, on the other hand, obtains exact solutions for a selected set of sensor and actuator positions for simple structural elements. Sensor signals are fed back directly to the actuators with appropriate gains. The method of analysis is that of classical control theory using Laplace transforms and the associated open and closed-loop transfer functions. Single-input-single-output feedback control is applied to various flexible cable and beam configurations. Root-loci for various values of gain are constructed and the system characteristics and the global system stability are determined. Although the procedure outlined above can be carried out for basic structural elements, more complex structures and control configurations are synthesized using the dynamic stiffness matrix method. With this method, the exact relationships of the basic elements can be combined to allow analysis of multi-input-multi-output control of more complex structures. Using this approach, examples for flexible cable and beam configurations are presented. It was found that exact solutions can be obtained using a finite number of sensors and actuators. It was also determined that a single co-located sensor-actuator at the boundary of a fixed-free cable or beam can control all the vibrational modes of the cable or beam. Also, pure signals from a perfect sensor can be used without any additional signal processing. The multi-input-multi-output investigation demonstrates that, even without cross-gain feedback, there is interaction between the sets of co-located sensor-actuator pairs. It appears that this interactive effect needs to be included in any multi-input-multi-output control design. By starting with fundamental elements of beams and cables, it was shown that reasonably sophisticated systems can be modeled. Finally, considerable insight is offered by analyzing the control of flexible structures using exact transfer function relationships. / Ph. D.

Thèse doctorat : Informatique : Villeurbanne, INSA : 2005. / Thèse rédigée en anglais. Résumé étendu en anglais. Titre provenant de l'écran-titre. Bibliogr. p. 214-226.

Viscoelastic materials can today be found in a wide range of practical applications. In order to make efficient use of these materials in construction, it is of importance to know how they behave when subjected to dynamic load. Characterization of viscoelastic materials is therefore an important topic, that has received a lot of attention over the years. This thesis treats different methods for identifying the complex modulus of an viscoelastic material. The complex modulus is a frequency dependent material function, that describes the deformation of the material when subjected to stress. With knowledge of this and other material functions, it is possible to simulate and predict how the material behaves under different kinds of dynamic load. The complex modulus is often identified through wave propagation testing, where the viscoelastic material is subjected to some kind of load and the response then measured. Models describing the wave propagation in the setups are then needed. In order for the identification to be accurate, it is important that these models can describe the wave propagation in an adequate way. A statistical test quantity is therefore derived and used to evaluate the wave propagation models in this thesis. Both nonparametric and parametric identification of the complex modulus is considered in this thesis.  An important aspect of the identification is the accuracy of the estimates.  Theoretical expressions for the variance of the estimates are therefore derived, both for the nonparametric and the parametric identification. In order for the identification to be as accurate as possible, it is also important that the experimental data contains as much valuable information as possible. Different experimental conditions, such as sensor locations and choice of excitation, can influence the amount of information in the data. The procedure of determining optimal values for such design parameters is known as optimal experiment design. In this thesis, both optimal sensor locations and optimal excitation are considered.

No description available.

Alexander H. Levis [et al.]. / Prepared for Air Force [Office] of Scientific Research, Bolling Air Force Base, Washington, D.C. Contract AFOSR - 80-0229. / Description based on: July 1981/June 1982.

Orientador: Fernando de Azevedo Silva / Banca: Erick Siqueira Guidi / Banca: Rosinei Batista Ribeiro / Resumo: Esta dissertação tem como objetivo desenvolver uma ferramenta paramétrica em linguagem de programação de software ANSYS (linguagem APDL) para se calcular a estrutura de um pórtico rolante de vigas centrais e reduzir o tempo gasto em horas de cálculo. Neste trabalho primeiro são apresentados os principais tipos de equipamentos bem como os próprios pórticos rolantes e para estes últimos descreve quais são seus tipos e quais os componentes compõem sua estrutura Descreve sobre a parametrização em linguagem APDL, sobre as principais solicitações atuantes que devem ser levadas em consideração durante o dimensionamento da estrutura, de acordo com as especificações da norma NBR8400. Apresenta como foi desenvolvida a ferramenta, quais são suas interfaces com o operador e qual o esquema de operação da mesma. Ao final relata sobre o ganho na economia de tempo ao se utilizar o programa e analisa os resultados, de tensão e deslocamento, obtidos com a simulação de um modelo gerado / Abstract: This dissertation aims to develop a parametric tool in ANSYS software programming language (APDL language) to calculate the structure of a gantry crane of central beams and reduce the time spent in hours of calculation. This paper first presents the main types of equipment as well as the own gantry cranes, and for this latter describes what are their types and what components make up its structure. Describes about the parameterization in APDL language, about the main solicitations that should be taken into consideration during the dimensioning of the structure, according to the specifications of the standard NBR8400. Present show it was developed the tool, what are their interfaces with the operator and how it works. At the end relates about gaining in saving time when using the program and analyzes the results, of tension and displacement, obtained with the simulation of a generated model / Mestre

Made available in DSpace on 2015-07-13T12:10:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-13. Added 1 bitstream(s) on 2015-07-13T12:25:43Z : No. of bitstreams: 1 000832525.pdf: 2129764 bytes, checksum: d2af9e6ba5e35d31cc21884b21d7aa31 (MD5) / Esta dissertação tem como objetivo desenvolver uma ferramenta paramétrica em linguagem de programação de software ANSYS (linguagem APDL) para se calcular a estrutura de um pórtico rolante de vigas centrais e reduzir o tempo gasto em horas de cálculo. Neste trabalho primeiro são apresentados os principais tipos de equipamentos bem como os próprios pórticos rolantes e para estes últimos descreve quais são seus tipos e quais os componentes compõem sua estrutura Descreve sobre a parametrização em linguagem APDL, sobre as principais solicitações atuantes que devem ser levadas em consideração durante o dimensionamento da estrutura, de acordo com as especificações da norma NBR8400. Apresenta como foi desenvolvida a ferramenta, quais são suas interfaces com o operador e qual o esquema de operação da mesma. Ao final relata sobre o ganho na economia de tempo ao se utilizar o programa e analisa os resultados, de tensão e deslocamento, obtidos com a simulação de um modelo gerado / This dissertation aims to develop a parametric tool in ANSYS software programming language (APDL language) to calculate the structure of a gantry crane of central beams and reduce the time spent in hours of calculation. This paper first presents the main types of equipment as well as the own gantry cranes, and for this latter describes what are their types and what components make up its structure. Describes about the parameterization in APDL language, about the main solicitations that should be taken into consideration during the dimensioning of the structure, according to the specifications of the standard NBR8400. Present show it was developed the tool, what are their interfaces with the operator and how it works. At the end relates about gaining in saving time when using the program and analyzes the results, of tension and displacement, obtained with the simulation of a generated model