We use the adaptive probabilities of crossover and mutation, elitist strategy, and extinction and immigration strategy to improve the simple genetic algorithm in this study. We expect that the search technique can avoid falling into the local maximum due to the premature convergence, and the chance of finding the near-optimal parameter in the larger searching space could be obviously increased. The accelerometer is then taken as the sensor for output measurement, and the designed actuator and digital PID controller is implemented to actively suppress the vibration of the plain that is due to the excitation effect of the high-speed and precision positioning of the linear motor. From the computer simulations and the experimented results, it is obvious that the near-optimal digital PID controller designed by modified genetic approach can improve the effect of vibration suppression; the settling time is also decrease. For the vibration suppressions of high-speed precision positioning problems, the vibrating plain system can fastly be stabilized.

Biodynamic feedthrough occurs in many types of operator controlled machines where the operator is a passenger and the motion of the controlled machine excites motion of the human operator, creating unwanted feedback. It is a significant cause for control performance degradation in backhoes. In this research, the problem of biodynamic feedthrough is investigated in a backhoe control system. For simplification, the system is limited to a single degree of freedom. Several controller based approaches are investigated to reduce cab vibration, while maintaining cylinder tracking performance. These controllers are tested in hardware, with and without the human operator and associated biodynamic feedthrough. The effect of this cab vibration reduction on biodynamic feedthrough is tested in a small set of human subject tests. The results indicate that some vibration reduction and improvement in the operator's control performance can be achieved by adding cab vibration compensation.

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Models, modelling and control design play important parts in automatic control. The contributions in this thesis concern topics in all three of these concepts. The poles are of fundamental importance when analyzing the behaviour of a system, and pole placement is an intuitive and natural approach for control design. A novel parameterization for state feedback gains for pole placement in the linear multiple input case is presented and analyzed. It is shown that when the open and closed loop poles are disjunct, every state feedback gain can be parameterized. Other properties are also investigated. Hammerstein models have a static non-linearity on the input. A method for exact compensation of such non-linearities, combined with introduction of integral action, is presented. Instead of inversion of the non-linearity the method utilizes differentiation, which in many cases is simpler. A partial differential equation (PDE) can be regarded as an infinite order model. Many model based control design techniques, like linear quadratic Gaussian control (LQG), require finite order models. Active damping of vibrations in a viscoelastic beam, modelled as a PDE, is considered. The beam is actuated by piezoelectric elements and its movements are measured by strain gauges. LQG design is used, for which different finite order models, approximating the PDE model, are constructed. The so obtained controllers are evaluated on the original PDE model. Minimization of the measured strain yields a satisfactory performance, but minimization of transversal deflection does not. The effect of the model accuracy of the finite order model approximations is also investigated. It turns out that a model with higher accuracy in a specified frequency interval gives controllers with better performance. The wave equation is another PDE. A PDE model, with one spatial dimension, is established. It describes wave propagation in a tube perforated with helical slots. The model describes waves of both extensional and torsional type, as well as the coupling between the two wave types. Experimental data are used for estimation of model parameters, and for assessment of the proposed model in two different cases. The model is found adequate when certain geometrical assumptions are valid.

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Thesis (doctoral)--Helsinki University of Technology, 2007. / Includes bibliographical references (p. 142-151). Also available on the World Wide Web.

Este trabalho consiste no desenvolvimento de uma metodologia de projeto ótimo de estruturas ativamente controladas (inteligentes), com o objetivo de suprimir as vibrações induzidas por perturbações externas. O projeto é realizado simultaneamente para a topologia estrutural e a localização de atuadores. O problema de otimização topológica é formulado para três fases materiais (dois materiais sólidos e vazio),com dois grupos de variáveis de projeto. Um material não piezelétrico elástico isotrópico forma a parte puramente estrutural, enquanto um material piezelétrico compõe a parte ativa. Uma vez que não há método eficiente para tratar as variáveis de projeto estruturais e de controle em um mesmo ambiente de otimização, este trabalho propõe uma abordagem de solução aninhada. Nesta solução, o posicionamento dos atuadores e a síntese do sistema controlador são considerados em um laco de projeto paralelo ao processo de otimização que lida com a topologia estrutural. O laço de otimização principal está relacionado `as variáveis de projeto estruturais, ou seja, ´e calculado onde deve haver material sólido e onde deve haver espaços vazios, através de um problema de minimização de flexibilidade. A localização de atuadores ´e determinada por uma otimização baseada em uma lei de controle que define onde o material deve ter propriedades piezelétricas, através da maximização de uma medida de controlabilidade. Os exemplos numéricos mostram que a abordagem utilizada neste trabalho pode produzir uma topologia estrutural bem definida com uma boa colocação para os atuadores. Além disso, as topologias ótimas encontradas são capazes de melhorar o amortecimento ativo da estrutura. / This work develops an optimal design methodology for actively controlled structures, aiming to suppress vibrations induced by external disturbances. Design is conducted simultaneously for the structural topology and actuator placement. A topology optimization problem is formulated for three material phases (two solid materials and void) with two design variables groups. A non-piezoelectric elastic isotropic material forms the structural only part of the design, while a piezoelectric material composes the active part. Since there is no efficient method to treat structural and control design variables in the same optimization framework, this work proposes a nested solution approach, where the actuator locations and controller syntheses are regarded as a parallel design to the main optimization process dealing with the structural topology. The main optimization loop designs the structural variables, i.e., it is decided where there should be solid material and where there should be voids, through a minimum compliance design problem. The actuators are placed by considering a control law optimization that defines where the material should have piezoelectric properties, through the maximization of a measure of controllability. Numerical examples show that the approach used in this paper can produce a clear structural topology with a good actuator placement. Besides, the optimal topologies can improve the active damping.