Model-based closed-loop control

Figure 8.11 Schematic representation of the model-based closed-loop control strategy.

Model-based closed-loop control and real-time optimization... 

Song Q, Zhu G (2002) Model-based Closed-loop Control of Urea SCR Exhaust Aftertreatment System for Diesel Engine. SAE Technical Paper 2002-01-0287... 

Song Q, Zhu G. (2002) Model-based closed-loop control of urea SCR exhaust aftertreatment system for Diesel engine, SAE 2002 World Congress, 2002-01-028... 

Amodel-based closed-loop controller was designed for maximization of polymer production under safe process condition in emulsion copolymerization processes, while keeping the copolymer composition constant [195]. The interesting feature of the proposed controller was the use of a fuzzy model for design of the optimum reference trajectories. 

Considerable work has been done on mathematic models of the extmsion process, with particular emphasis on screw design. Good results are claimed for extmsion of styrene-based resins using these mathematical methods (229,232). With the advent of low cost computers, closed-loop control of... 

The dynamic model was used to study and design closed-loop control systems for the kiln. Various ideas as to how to achieve effective control existed before the study began and new ideas were conceived during the study. Two systems based upon the control of combustion air temperature will illustrate this use of the model. 

The most widely distributed methodology of complex control systems SA is based on computer modeling and simulation (M S) using special methods and software for stability analysis. The typical phases of closed-loop control systems SA by means of M S are the following ... 

In Figure 1 are shown the closed loop results for the proposed measurement-driven calorimetric controller (Eq. 46) (continuous plots) and for its exact model-based nonlinear SF counterpart (discontinuous plots) (Eq. 43). As it can be seen, the difference in behavior between the two controllers is almost imperceptible. The small differences are due to the estimation error dynamics. In other words, as expected from the theoretical developments, the calorimetric controller basically recovers the behavior of its exact model-based nonlinear SF controller (Eq. 43) counterpart, without needing the kinetics and heat exchange models. As... 

Optimal control strategy based on a mechanistic model Closed-loop control... 

Foxboro developed a self-tuning PID controller that is based on a so-called expert system approach for adjustment of the controller parameters. The on-line tuning of K, Xi, and Xo is based on the closed-loop transient response to a step change in set point. By evaluating the salient characteristics of the response (e.g., the decay ratio, overshoot, and closed-loop period), the controller parameters can be updated without actually finding a new process model. The details of the algorithm, however, are proprietary... 

New research advances in control theory that are bringing it closer to practical problems are promising dramatic new developments and attracting widespread industrial interest. One of these advances is the development of "robust" systems. A robust control system is a stable, closed-loop system that can operate successfully even if the model on which it is based does not adequately describe the plant. A second advance is the use of powerful semiempirical formalisms in control problems, particularly where the range of possible process variables is constrained. 

In the present study, we propose a tuning method for PID controllers and apply the method to control the PBL process in LG chemicals Co. located in Yeochun. In the tuning method proposed in the present work, we first find the approximated process model after each batch by a closed-loop Identification method using operating data and then compute optimum tuning parameters of PID controllers based on GA (Genetic Algorithm) method. 

The identification of plant models has traditionally been done in the open-loop mode. The desire to minimize the production of the off-spec product during an open-loop identification test and to avoid the unstable open-loop dynamics of certain systems has increased the need to develop methodologies suitable for the system identification. Open-loop identification techniques are not directly applicable to closed-loop data due to correlation between process input (i.e., controller output) and unmeasured disturbances. Based on Prediction Error Method (PEM), several closed-loop identification methods have been presented Direct, Indirect, Joint Input-Output, and Two-Step Methods. 

Model-based) Direct synthesis For a given system, synthesize the controller function according to a specified closed-loop response. The system time constant, xc, is the only tuning parameter. 

The system dynamics uncertainty A(s) contains parametric and model uncertainties, and its L2 gain bounded as A(s) oo < 1/7- Based on the L2"gain control theory, the first task of a robust controller for stabilizing perturbed plants is to endow the closed-loop system with the following property ... 

A closed loop optimization experiment was presented in order to investigate the ability to control the ionization of NaK clusters in a molecular beam. The analysis of the optimized pulse shows that the maximum intensity of the ion signal was obtained with a pulse structure containing intensity maxima separated by a multiple of half vibrational periods. The proposed simple model in order to explain the pulse structure is based on previously performed pump-probe experiments [6]. 

The most general approach to model-based nonlinear control is the so-called Feedback Linearization (FL) [35], In fact, FL control approaches use the model of the plant to achieve a global linearization of the closed-loop systems, so as well-established linear controllers can be adopted for the globally linearized model. In... 

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