Abstract:Al procés d'identificació dels paràmetres d'un model nominal i la seua incertesa per a la seua utilització en Control Robust se'l coneix com a Identificació Robusta Paramètrica (IR).Un possible enfocament per a abordar l'IR, que resulta apropiat quan el desconeixement de les propietats estadístiques del soroll i/o la dinàmica no modelada invaliden els enfocaments estocàstics, és el determinístic (Set Membership Estimation). Aquest enfocament assumeix que l'error d'identificació (EI), diferència entre les eixid… Show more
“…ese parameters have been defined to obtain an adequate distribution in the objective space (divisions for each dimension, parameter n box), a sufficient number of new candidate solutions (Nind GA and Generations), and an adequate number of individuals Nind P of the population P(t) (population to explore the search space). For the definition of the remaining parameters, the values suggested in [41] for the original algorithm (ev-MOGA) are used. Figure 8 shows the discrete set P * Q,n obtained by nev-MOGA.…”
This paper presents a design for the multivariable control of a cooling system in a PEM (proton exchange membrane) fuel cell stack. This system is complex and challenging enough: interactions between variables, highly nonlinear dynamic behavior, etc. This design is carried out using a multiobjective optimization methodology. There are few previous works that address this problem using multiobjective techniques. Also, this work has, as a novelty, the consideration of, in addition to the optimal controllers, the nearly optimal controllers nondominated in their neighborhood (potentially useful alternatives). In the multiobjective optimization problem approach, the designer must make decisions that include design objectives; parameters of the controllers to be estimated; and the conditions and characteristics of the simulation of the system. However, to simplify the optimization and decision stages, the designer does not include all the desired scenarios in the multiobjective problem definition. Nevertheless, these aspects can be analyzed in the decision stage only for the controllers obtained with a much less computational cost. At this stage, the potentially useful alternatives can play an important role. These controllers have significantly different parameters and therefore allow the designer to make a final decision with additional valuable information. Nearly optimal controllers can obtain an improvement in some aspects not included in the multiobjective optimization problem. For example, in this paper, various aspects are analyzed regarding potentially useful solutions, such as (1) the influence of certain parameters of the simulator; (2) the sample time of the controller; (3) the effect of stack degradation; and (4) the robustness. Therefore, this paper highlights the relevance of this in-depth analysis using the methodology proposed in the design of the multivariable control of the cooling system of a PEM fuel cell. This analysis can modify the final choice of the designer.
“…ese parameters have been defined to obtain an adequate distribution in the objective space (divisions for each dimension, parameter n box), a sufficient number of new candidate solutions (Nind GA and Generations), and an adequate number of individuals Nind P of the population P(t) (population to explore the search space). For the definition of the remaining parameters, the values suggested in [41] for the original algorithm (ev-MOGA) are used. Figure 8 shows the discrete set P * Q,n obtained by nev-MOGA.…”
This paper presents a design for the multivariable control of a cooling system in a PEM (proton exchange membrane) fuel cell stack. This system is complex and challenging enough: interactions between variables, highly nonlinear dynamic behavior, etc. This design is carried out using a multiobjective optimization methodology. There are few previous works that address this problem using multiobjective techniques. Also, this work has, as a novelty, the consideration of, in addition to the optimal controllers, the nearly optimal controllers nondominated in their neighborhood (potentially useful alternatives). In the multiobjective optimization problem approach, the designer must make decisions that include design objectives; parameters of the controllers to be estimated; and the conditions and characteristics of the simulation of the system. However, to simplify the optimization and decision stages, the designer does not include all the desired scenarios in the multiobjective problem definition. Nevertheless, these aspects can be analyzed in the decision stage only for the controllers obtained with a much less computational cost. At this stage, the potentially useful alternatives can play an important role. These controllers have significantly different parameters and therefore allow the designer to make a final decision with additional valuable information. Nearly optimal controllers can obtain an improvement in some aspects not included in the multiobjective optimization problem. For example, in this paper, various aspects are analyzed regarding potentially useful solutions, such as (1) the influence of certain parameters of the simulator; (2) the sample time of the controller; (3) the effect of stack degradation; and (4) the robustness. Therefore, this paper highlights the relevance of this in-depth analysis using the methodology proposed in the design of the multivariable control of the cooling system of a PEM fuel cell. This analysis can modify the final choice of the designer.
“…Therefore, we have an MOP with two design objectives. To calculate the first objective f 1 the IAEs are added in both outputs relativized on the reference controller x R calculated using the S-IMC technique [36] for the definition of the remaining parameters, the values suggested in [39] are used for the original algorithm (ev-MOGA). Figure 5 shows a set of controllers found using nevMOGA (optimals and nearly optimals) for the problem posed.…”
Section: A Wood and Berry Distillation Columnmentioning
In this paper, we present the adjustment of controller parameters using multiobjective optimization techniques. Unlike other works, where only the Pareto optimal solutions are considered, we also consider the set of nearly optimal solutions nondominated in their neighborhood. These solutions are potentially useful for two reasons: 1) they are similar to the optimal solutions for the optimized objectives, and; 2) they differ significantly in their parameters. This last point makes them interesting, since they bring diversity and different characteristics to the set of solutions for analyzing in the decision stage. In problems of controller parameter adjustment, especially for multivariable processes, there are many conflicting objectives. To simplify the optimization problem and decision stage, it is common to aggregate some of the objectives, and so simplify the initial problem. In this scenario, some controllers that were optimal for the initial problem can become nearly optimal in the simplified case. When these controllers are nondominated in their neighborhood, they are especially interesting because they usually present a different trade-off for the initial objectives. For the calculation of nearly optimal solutions nondominated in their neighborhood, the evolutionary algorithm nevMOGA was used. In this paper, the usefulness of considering these solutions is revealed in two controller design problems: the Wood & Berry distillation column and the CIC2018 control benchmark. INDEX TERMS Multiobjective optimization, multivariable control systems, nearly optimal solutions.
“…for δ i > 0, and where f max Definition 10 (box dominance [19]). Given two decision vectors x 1 and x 2 whose boxes are box x 1 and box x 2 , respectively, x 1 is said to box dominate…”
Section: Discretization Of the New Set Ofmentioning
confidence: 99%
“…The parameter α i t is a random value uniformly distributed which belongs to interval −d t 1 + d t , and d t is a parameter which is adjusted by using an exponential decreasing function, as in simulated annealing [19]: (4) x P and x F are mutated by using a random mutation with Gaussian distribution:…”
Section: Complexitymentioning
confidence: 99%
“…The whole process is executed again and again until G t is full. In order to set the parameters which appear in the equations of the steps 3 and 4, the default values suggested by [19] for the original algorithm (evMOGA) are taken.…”
Traditionally, in a multiobjective optimization problem, the aim is to find the set of optimal solutions, the Pareto front, which provides the decision-maker with a better understanding of the problem. This results in a more knowledgeable decision. However, multimodal solutions and nearly optimal solutions are ignored, although their consideration may be useful for the decision-maker. In particular, there are some of these solutions which we consider specially interesting, namely, the ones that have distinct characteristics from those which dominate them (i.e., the solutions that are not dominated in their neighborhood). We call these solutions potentially useful solutions. In this work, a new genetic algorithm called nevMOGA is presented, which provides not only the optimal solutions but also the multimodal and nearly optimal solutions nondominated in their neighborhood. This means that nevMOGA is able to supply additional and potentially useful solutions for the decision-making stage. This is its main advantage. In order to assess its performance, nevMOGA is tested on two benchmarks and compared with two other optimization algorithms (random and exhaustive searches). Finally, as an example of application, nevMOGA is used in an engineering problem to optimally adjust the parameters of two PI controllers that operate a plant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.