Browsing by Author "Perez, R"

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    Experimental evaluation of combined model reference adaptive controller in a pH regulation process
    (WILEY, 2002) Duarte Mermoud, MA; Rojo, FA; Perez, R
    An experimental evaluation of the combined model reference adaptive control (CMRAC) is presented in this paper. This adaptive control scheme was used to control a relatively complex process like the pH of a solution in a tank reactor at laboratory level. For comparison purposes, some very well-known control strategies were also implemented, which include PID control and standard model reference adaptive control (M RAC). Tracking and regulation capabilities of the control strategies studied were analysed and compared. Experimental results indicate that CMRAC behaves as well as the standard MRAC and a very well-tuned PID for a specific and known operating point. Advantages of the adaptive controllers are shown when the operating point changes. Copyright (C) 2002 John Wiley Sons, Ltd.
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    Forecasting ozone daily maximum levels at Santiago, Chile
    (PERGAMON-ELSEVIER SCIENCE LTD, 1998) Jorquera, H; Perez, R; Cipriano, A; Espejo, A; Letelier, MV; Acuna, G
    In major urban areas, air pollution impact on health is serious enough to include it in the group of meteorological variables that are forecast daily. This work focusses on the comparison of different forecasting systems for daily maximum ozone levels at Santiago, Chile. The modelling tools used for these systems were linear time series, artificial neural networks and fuzzy models. The structure of the forecasting model was derived from basic principles and it includes a combination of persistence and daily maximum air temperature as input variables. Assessment of the models is based on two indices: their ability to forecast well an episode, and their tendency to forecast an episode that did not occur at the end (a false positive). All the models tried in this work showed good forecasting performance, with 70-95% of successful forecasts at two monitor sites: Downtown (moderate impacts) and Eastern (downwind, highest impacts). The number of false positives was not negligible, but this may be improved by expressing the forecast in broad classes:low, average, high, very high impacts; the fuzzy model was the most reliable forecast, with the lowest number of false positives among the different models evaluated. The quality of the results and the dynamics of ozone formation suggest the use of a forecast to warn people about excessive exposure during episodic days at Santiago. (C) 1998 Elsevier Science Ltd. All rights reserved.
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    Modelling and simulation of a direct contact rotary dryer
    (MARCEL DEKKER INC, 1996) Shene, C; Cubillos, F; Perez, R; Alvarez, PI
    A mathematical model able to predict solid and drying gas temperature and moisture content axial profiles along a direct contact rotary dryer was developed. The study was focused on the drying kinetics based on phenomenological models. Two different drying mechanisms in the decreasing drying rate period were tested: proportional to the unbound moisture content and moisture diffusion inside the particle. Experimental data collected in a pilot-scale direct contact rotary dryer was used to validate the model. Soya and fish meals were used as drying material.