160 resultados para controlo por montante


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Dissertação de mest., Finanças Empresariais, Faculdade de Economia, Univ. do Algarve, 2003

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Dissertação de mest., Engenharia do Ambiente, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2010

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Tese de dout., Engenharia Electrónica e Computação, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2003

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Tese de dout., Ciências e Tecnologias do Ambiente (Modelação Ambiental), Univ. do Algarve, 1999

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Dissertação de mest., Ciências Económicas e Empresariais, Faculdade de Economia, Univ. do Algarve, 2002

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Dissertação de mest., Biologia Marinha, Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2010

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Dissertação de mest., Finanças Empresariais, Faculdade de Economia, Universidade do Algarve, 2005

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The implementation of an accurate and reliable data acquisition system is the first step to develope a good control system. This data acquisition should provide valuable data readings, not only for control purposes but also for applications in different research areas.

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One of the aspects of modern agriculture is characterised by a culture without soil (hydroponic cultures). These culture techniques are identified by possessing automatic control systems to control the nutrient solution. In first hydroponic cultures this control was accomplished by “on- off” analog controllers that applied a single control law implemented in hardware. Therefore, the changes of the control law resulted in the change of all interface electronics. In digital control implemented by micro-controllers the alteration of such control law is easily performed by changing only a computer program, leaving untouched all the interface hardware. In this way, the use and substitution of the control strategy is improved, as well, the use of advanced control strategies.

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The problem with the adequacy of radial basis function neural networks to model the inside air temperature as a function of the outside air temperature and solar radiation, and the inside relative humidity in an hydroponic greenhouse is addressed.

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A real-time data acquisition and identification system implemented in a soil-less greenhouse located in the south of Portugal is described. The system performs real-time data acquisition from a set of sensors connected to a data logger.

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In this paper a recent approach for PID autotuning, involving neural networks, is ferther developed. To make this approach adaptive, optimal PID values must be known on-line. In this paper neural network models of tuning criteria, together with the use of genetic algorithms, are proposed to solve this problem.

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In this paper climate discrete-time dynamic models for the inside air temperature of a soilless greenhouse are identified, using data acquired during two different periods of the year. These models employ data from air temperature and relative humidity.

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Multilayer perceptrons (MLPs) (1) are the most common artificial neural networks employed in a large field of applications. In control and signal processing applications, MLPs are mainly used as nonlinear mapping approximators. The most common training algorithm used with MLPs is the error back-propagation (BP) alg. (1).

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The PID controllers are widely used in industry. Whether because the plant is time-varying, or because of components ageing, these controllers need to be regularly retuned. During the last years, several methods have been proposed for PID autotuning.