This work presents the model of a shear frame type structure composed of six flexible beams and three rigid masses. Fixed on the ground, outside the structure, two voltage controlled electromagnetic actuators are used for vibration control. To model the flexible beams, unidimensional finite elements were used. Non-linear equations for the actuators electromagnetic force, noise in the position sensor, time delays for the control signal update and voltage saturation were also considered in the model. For controlling purposes a discrete linear quadratic regulator combined with a predictive full-order discrete linear observer was employed. Results of numerical simulations, where the structure is submitted to an impulsive disturbance force and to a harmonic force, show that the oscillations can be significantly reduced with the use of the electromagnetic actuators.
This paper presents a model of a target tracking system assembled in a moving body. The system is modeled in time domain as a nonlinear system, which includes dry friction, backlash in gear transmission, control input tensions saturation, and armature current saturation. Time delays usually present in digital controllers are also included, and independent control channels are used for each motor. Their inputs are the targets angular errors with respect to the system axial axis and the outputs are control tensions for the motors. Since backlash in gear transmission may reduce the systems accuracy, its effects should be compensated. For that, backlash compensation blocks are added in the controllers. Each section of this paper contains a literature survey of recent works dealing with the issues discussed in this article.
Resumo-Essa pesquisa teve por objetivo verificar por meio da Análise Ergonômica do Trabalho, os aspectos comportamentais (gestos e posturas) e as condições ambientais vivenciadas por três costureiras de uma fábrica de roupa jeans situada no Estado do Espírito Santo. A pesquisa apresenta uma abordagem descritiva e qualitativa sendo utilizado o estudo de caso. Para coleta de dados foram utilizadas a observação direta e entrevistas. Utilizou-se a Análise Ergonômica do Trabalho como metodologia, que é guiada através da análise da demanda, da tarefa e das atividades, possibilitando um diagnóstico com possíveis recomendações ergonômicas. Essa análise possibilitou a identificação de problemas relacionados ao mobiliário e ao ambiente de trabalho. Observou-se também a presença de dores advindas da má postura relacionada à atividade de costura. Como recomendações sugere-se alguns deslocamentos e a revisão do sistema de prêmio por assiduidade e produção que elevam o ritmo de trabalho e a permanência por longas horas na postura sentada.
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