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Versión del autor This paper presents a new methodology to design multivariable Smith predictor for n×n processes with multiple time delays based on the centralized inverted decoupling structure. The controller elements are calculated in order to achieve good reference tracking and decoupling response. Independently of the system size, very simple general expressions for the controller elements are obtained. The realizability conditions are provided and the particular case of processes with all of its elements as first order plus time delay systems is discussed in more detail. A diagonal filter is added to the proposed control structure in order to improve the disturbance rejection without modifying the nominal set-point response and to obtain a stable output prediction in unstable plants. The effectiveness of the method is illustrated through different simulation examples in comparison with other works.

Refrigerant compressors are relatively complex products that require a wide variety of tests to be performed for both product development and quality control. Performance tests are an example of such tests and they are typically performed using test rigs with calorimeters. This paper presents the experimental results of the use of a multivariable dead-time compensating structure to control the conditions at the calorimeter inlet and outlet. Besides the control results themselves, the paper presents the identification of the multivariable model used for control purposes, as well as it discusses tuning and implementation of the proposed controller. The closed-loop experimental results are compared to the ones obtained by using PID controllers and they demonstrate the good performance of the implemented controller. As a result, both the test time and the result uncertainties have been reduced. Besides presenting an important contribution from the point of view of industrial application, this study presents experimental results of dead-time compensators, which are generally analyzed just towards simulation.

[EN] This paper presents an analysis of dead-time compensating controllers for processes exhibiting a dead time. The robustness and performance of several dead-time compensating control structures are analysed and the effect of the predictor on the closed-loop is studied. A unified approach is used considering ideas from “Model Pedictive Control” (MPC) and “Dead-time Compensators” (DTC). The main papers in the area are revised and the relationships between MPC and DTC are shown. The paper shows that the predictors designed to produce optimal open-loop predictions are not optimal when operating in closed loop. Furthermore, structures based on the Smith predictor offer more robust controllers and similar nominal performance even when the process exactly matches the situation required by optimal controllers. A new concept "Predicción para Control" is introduced where predictors should be designed as an integral part of the controller in order to produce better closed-loop response., [ES] Este trabajo analiza el control de sistemas con retardo cuando se utilizan estructuras de control basadas en predictores. Se estudia la robustez de diversas estrategias de compensación de retardo y los efectos producidos por el predictor en el comportamiento en bucle cerrado del sistema. Esta problemática se trata de forma unificada utilizando ideas provenientes de dos grandes áreas dentro del control: el área del control predictivo basado en modelo (“Model Predictive Control”, mpc) y el área de los compensadores de tiempos muertos (“Dead Time Compensators”, dtc). Se revisan los trabajos publicados en los últimos años sobre el tema y se muestra que existe una relación muy íntima entre las estructuras de dtc y mpc. Se propone así el concepto de ”Predicción para Control” que considera los efectos de las características de la estructura del predictor utilizado en el controlador en la robustez y comportamiento del sistema en bucle cerrado., Trabajo financiado por CICYT Contrato DPI 2005-4568 y CAPES-BRASIL Contrato BEXO 0828/05-0.

This paper presents a new approach for non-linear predictive control based on the local model ideas. The algorithm uses a non-linear (NL) model of the plant for internal simulation. When a change in the operating point is required this NL model is used to identify a linear ARX model of the process. The optimization procedure is then executed using this linear model and a control weighting factor adapted to the nonlinear model static gain obtained from the inverse static characteristic. The proposed controller is applied to some simulated NL process and the obtained results compared to some MPC algorithms recently presented in literature to show the main advantages of this new approach: simplicity, low processing time and uniform dynamic behaviour in the operating range. Este artigo apresenta uma nova abordagem para o controle preditivo não linear no contexto dos modelos locais. O algoritmo de controle proposto usa um modelo não linear (MNL) da planta para simular internamente o comportamento do processo. Quando se aplica uma mudança de set-point no processo, o algoritmo usa o MNL para identificar um modelo ARX linear. O procedimento de otimização é então executado usando este modelo linear e uma penalização variável do controle, determinada em função do ganho não linear do modelo identificado. O controle proposto é aplicado em al-guns processos simulados e também se apresentam comparações com outras técnicas de controle preditivo aplicadas a plantas não lineares disponíveis na literatura para ilustrar as principais vantagens da metodologia proposta: simplicidade, baixo tempo de processamento computacional e comportamento dinâmico uniforme em todo o intervalo de operação da planta.

This paper presents the integrated design and control of a buck boost converter (BBC). In the proposed methodology the design tool provides simultaneously the controller tuning and BBC design parameters in such a way that some closed-loop pre-specified static and dynamic behavior is obtained. This approach contrasts with the traditional methodology, where the design of BBC is performed without taking into account its dynamical behavior. An optimization procedure is used to obtain the electronic components of the BBC and the tuning parameters of the controller, minimizing an objective function that considers the set of performance specifications. Although the methodology can be applied to any converter and any control strategy, in this particular case an ideal BBC and a Sliding Model Control (SMC) strategy are used. Some simulation results show the advantages and principally the flexibility that can be obtained with this approach.