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Manipulated Variables (manipulated + variable)
Selected AbstractsCavity pressure control during cooling in plastic injection moldingADVANCES IN POLYMER TECHNOLOGY, Issue 3 2006B. Pramujati Abstract Cavity pressure control during filling, packing, and cooling phases is imperative for maintaining product quality in injection molding process. This paper presents the design and implementation of a strategy to control cavity pressure profile during the cooling phase. In order to do this, a controlled variable parameter was defined to be the time constant , of the pressure profile. This parameter can be used effectively to control the shape of the cavity pressure over the cooling cycle. The coolant flow rate through the mold was used as the manipulated variable. A predictive control system was designed and implemented successfully to allow monitoring and control of , at several setpoints ,sp resulting in good and effective cavity pressure control. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25:170,181, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20068 [source] A generic controller for part surface temperature on a plastic injection molding machineADVANCES IN POLYMER TECHNOLOGY, Issue 1 2006R. Dubay A new approach for controlling part cooling in plastic injection molding is developed using a PI controller and coolant flow rate as the manipulated variable. The method uses an average part surface temperature within the mold as the setpoint parameter. A mechatronic control system was developed for providing variable coolant flow rates. The control strategy was simulated using plant models, implemented and tested on a 50-tonne plastic injection-molding machine with good closed loop responses. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 1,12, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20053 [source] Feedback control design for an anaerobic digestion processJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2002Jose Alvarez-Ramirez Abstract An approach for the design of linear feedback controllers for anaerobic digestion systems is presented. The effluent chemical oxigen demand (COD) concentration and the dilution rate are taken respectively as the regulated and the manipulated variables. The control design is based on simple step-response models of the process endowed with an input delay to account for dead-times induced by measurement devices. The resulting feedback controller has a traditional proportional-integral (PI) control structure, so it can be easily implemented with conventional control technologies. Since the concentration of volatile fatty acids can be easily and quickly measured as compared with COD concentration, it is used as a secondary measurement that is incorporated into the feedback loop scheme to enhance the robustness of the control scheme with respect of influent disturbances. The performance of the proposed control scheme is illustrated via numerical simulations and experimental work. © 2002 Society of Chemical Industry [source] Enhancing Controller Performance via Dynamic Data ReconciliationTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2005Shuanghua Bai Abstract Measured values of process variables are subject to measurement noise. The presence of measurement noise can result in detuned controllers in order to prevent excessive adjustments of manipulated variables. Digital filters, such as exponentially weighted moving average (EWMA) and moving average (MA) filters, are commonly used to attenuate measurement noise before controllers. In this article, we present another approach, a dynamic data reconciliation (DDR) filter. This filter employs discrete dynamic models that can be phenomenological or empirical, as constraints in reconciling noisy measurements. Simulation results for a storage tank and a distillation column under PI control demonstrate that the DDR filter can significantly reduce propagation of measurement noise inside control loops. It has better performance than the EWMA and MA filters, so that the overall performance of the control system is enhanced. Les valeurs mesurées des variables de procédé sont affectées par les bruits de mesure. La présence de bruit de mesure force de régler à la baisse les régulateurs afin de prévenir des mouvements excessifs des variables manipulées. Des filtres numériques, tels que les filtres à moyenne mobile pondérée exponentiellement (EWMA) et les filtres à moyenne mobile (MA), sont communément utilisés pour atténuer le bruit de mesure avant les régulateurs. On présente dans cet article une autre approche, soit un filtre dynamique de réconciliation de données (DDR). Ce filtre emploie des modèles dynamiques discrets qui peuvent être phénoménologiques ou empiriques comme contraintes pour réconcilier les mesures bruitées. Les résultats de simulation pour un réservoir de stockage et une colonne à distiller utilisant un régulateur PI montrent que le filtre DDR peut réduire de manière significative la propagation du bruit de mesure dans les boucles de régulation. Sa performance est meilleure que celles des filtres EWMA ou MA, et par conséquent la performance globale du système de commande s'en trouve accrue. [source] Modelling the continuous drying of a thin sheet of fibres on a cylinder heated by electric inductionTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2001Sergio Pérez Abstract The derived model predicts the evolution of the humidity and temperature of a thin web of fibrous material during drying on the surface of a metal cylinder heated by electric induction. The model explicitly considered heat conduction, convection and radiation, and thermal induction as well as energy transfer caused by the evaporation of the water. It also predicted the process responses to perturbations in the manipulated variables and in the initial humidity of the web entering a small-scale induction dryer. The manipulated variables included the rotational speed of the cylinder, the electric power fed to the inductors, and the area of the web in contact with the cylinder. The simulations carried out showed a high degree of correspondence between the model predictions and the experimental data. Un modèle prévisionnel de l'évolution de l'humidité et de la température au cours du séchage d'une nappe mince de fibres en contact avec un cylindre méallique chauffé par induction électrique a été dérivé. Les processus de conduction, de convection, de radiation, d'induction thermique ainsi que le transfert d'énergie dû à la vaporisation de l'eau furent considérés explicitement. Le modèle calcule la réponse du procédé face à des perturbations dans les variables manipulées ainsi que dans l'humidité de la nappe à l'entrée d'un banc d'essai. Les variables manipulées étaient la vitesse de rotation du cylindre, la puissance électrique fournie aux inducteurs et la surface de contact entre la nappe et le cylindre. Les simulations effectuées indiquent une bonne correspondance entre les calculs et les résultats expérimentaux. [source] Nonlinear parametric predictive control.ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009Application to a continuous stirred tank reactor Abstract This paper presents a nonlinear model-based controller based on the ideas of parametric predictive control applied to a continuous stirred tank reactor (CSTR) process unit. Controller design aims at avoiding the complexity of implementation and long computational times associated with conventional NMPC while maintaining the main advantage of taking into account process nonlinearities that are relevant for control. The design of the parametric predictive controller is based on a rather simplified process model having parameters that are instrumental in determining the required changes to the manipulated variables for error reduction. The nonlinear controller is easy to tune and can operate successfully over a wide range of operating conditions. The use of an estimator of unmeasured disturbances and process-model mismatch further enhances the behavior of the controller. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||