This paper deals with the model re-identification in closed-loop systems with already existing MPC controllers. lt is assumed that the controller has a two-layer structure where the upper layer performs a simplified economic optimization in which the economic objective is represented as a linear combination of the process inputs. This is the case of several commercial MPC packages applied in industry. This work focuses on the case where the existing process model shows signs of deterioration and there is benefit in obtaining a new model. It is proposed a methodology where the test signal is introduced in the coefficients of the objective function of the economic layer. The approach allows the continuous operation of the system as the process constraints and product specification can be satisfied during the test. The application of the method is illustrated by simulation on a C3/C4 splitt...

This paper deals with the model re-identification in closed-loop systems with already existing MPC controllers. lt is assumed that the controller has a two-layer structure where the upper layer performs a simplified economic optimization in which the economic objective is represented as a linear combination of the process inputs. This is the case of several commercial MPC packages applied in industry. This work focuses on the case where the existing process model shows signs of deterioration and there is benefit in obtaining a new model. It is proposed a methodology where the test signal is introduced in the coefficients of the objective function of the economic layer. The approach allows the continuous operation of the system as the process constraints and product specification can be satisfied during the test. The application of the method is illustrated by simulation on a C3/C4 splitt...

The purpose of this paper is to optimiza the operation of an upflow anaerobic sludge blanket (UASB) reactor. In this kind of processes, besides to maximiza organic matter removal, it is attractive to capture the biogas and to use it to provide energy services. For this purpose, the biogas has to be produced in large quantities. Thus, we have two clear objectives to be achieved: to maximiza both the organic matter removal and the biogas production. Three multiobjective optimization techniques are used to solve this problem. The first optimization approach is multiplex, which is based on the simplex method for single objective optimization. Other used approach is an interior point method, which is proved to be an efficient linear programming technique. Finally, it is applied an evolutionary algorithm, namely the elitist non-dominated sorting genetic algorithm (NSGA 11), which is considerad...

The purpose of this paper is to optimiza the operation of an upflow anaerobic sludge blanket (UASB) reactor. In this kind of processes, besides to maximiza organic matter removal, it is attractive to capture the biogas and to use it to provide energy services. For this purpose, the biogas has to be produced in large quantities. Thus, we have two clear objectives to be achieved: to maximiza both the organic matter removal and the biogas production. Three multiobjective optimization techniques are used to solve this problem. The first optimization approach is multiplex, which is based on the simplex method for single objective optimization. Other used approach is an interior point method, which is proved to be an efficient linear programming technique. Finally, it is applied an evolutionary algorithm, namely the elitist non-dominated sorting genetic algorithm (NSGA 11), which is considerad...

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El objetivo de este trabajo es la re-identificación del modelo de proceso que se utiliza en controladores predictivos (MPC) ya existentes usando datos de operación en lazo cerrado. Se asume que el controlador tiene una estructura en dos capas, donde en la capa superior un simple algoritmo optimización económica determina un conjunto de valores óptimos en estado estacionario (“targets ”), los cuales son pasados al MPC para su implementación. Este es el caso de varios paquetes comerciales MPC aplicados en la industria. El presente trabajo enfoca el caso donde el modelo del proceso presenta signos de deterioro, por lo que obtener un nuevo modelo representa beneficios significativos en el procedimiento de re-comisionamiento del MPC. Se propone una nueva metodología para excitar el sistema en lazo cerrado, introduciendo señales de excitación persistente en la función objetivo de...

The objective of this work is the re-identification of the process model that is used in existing predictive controllers (MPC) using closed-loop operation data. The controller is assumed to have a two-layer structure, where in the upper layer a simple economic optimization algorithm determines a set of optimal steady-state values ​​("targets"), which are passed to the MPC for implementation. This is the case for several commercial MPC packages applied in the industry. This paper focuses on the case where the model represents significant benefits in the MPC re-commissioning procedure. A new methodology is proposed to excite the system in closed loop, introducing persistent excitation signals in the objective function of the upper layer of the MPC. This strategy allows the continuous operation of the system, respecting the constraints of the process and meeting the specifications of th...