Estimación de estados para una clase de sistemas no lineales con retardo en la medición. Caso de estudio: mecanismo homeostático de la glucosa en pacientes con DMT1

Los sistemas dinámicos pueden representarse mediante modelos matemáticos no lineales para diferentes fin es, entre ellos el control de sistemas, aplicación para la cual se hace necesario medir las variables relevantes o estados para realizar la debida corrección cuando no se este en el punto de operación deseado. No obstante, salvo algunas excepciones, no es posible acceder a una medición directa de todos los estados ya sea porque no existen elementos primarios para algunas variables, porque los sensores disponibles operan en rangos restrictivos, su operación y mantenimiento es delicado y complejo, o porque estos tienen costos prohibitivos, por lo que se hace necesaria la implementación de estimadores de estado. En este sentido, a partir de la revisión del estado del arte, se pudo identificar que los retardos en la medición son un problema que aparece en la salida del sistema y que ingresa directamente al estimador afectando la calidad de la estimación y por ende las acciones de control que dependen de ella. Para dar solución a lo anterior, en esta tesis se propone una metodología de diseño de estimadores de estado para una clase de sistemas no lineales sobre los cuales se obtienen mediciones con un retardo desconocido pero acotado. La metodología propuesta integra la técnica de análisis de correlación máxima para la estimación del tiempo de retardo, un Filtro de Kalman Unscented como esquema de estimación de estados y el Predictor de Smith como herramienta para la corrección del tiempo de retardo. Mediante la integración de los tres métodos ya mencionados, fue posible proponer un nuevo esquema de estimación en cascada que permite obtener un mejor desempeño en comparación con un estimador convencional que no tiene en cuenta el retardo en la medición.Dynamic systems can be represented by non-linear mathematical models for di erent purposes, including system control, the application for which it is necessary to measure the relevant variables or states to perform the correct correction when not in the point of operation wanted. No, except for some exceptions, it is not possible to access a direct measurement of all states and the sea because there are no primary elements for some variables, because the available sensors operate in restrictive ranges, their operation and maintenance is delicate and complex, or because they have prohibitive costs, so the implementation of state estimators is needed. In this sense, from the review of the state of the art, it can be identi ed that the delays in the measurement are a problem that appears in the output of the system and that enters directly into the estimator a recting the quality of the estimate and therefore the actions of control that depends on it. To give a solution to the above, this test proposes a design methodology for state estimators for a class of non-linear systems on which it can be measured with an unknown but limited delay. The proposed methodology was carried out with the technique of maximum correlation analysis for the estimation of the delay time, a Kalman lter without fragrance as a state estimation scheme and the Smith predictor as a tool for the correction of the delay time. By integrating the three methods, it is possible to propose a new cascade estimation scheme that allows obtaining a better performance in comparison with a conventional estimator that does not take into account the delay in the measurement.Magister en Automatización y Contro

Monitoring Plasma Glucose Concentration from Interstitial Glucose Measurements for Patients at the Intensive Care Unit

The glucose homeostasis is responsible for regulating the blood glucose concentration around 100 mg / dl. When this physiological mechanism is broken due to the inability of the pancreas to produce insulin, an increase of the blood glucose levels is produced and patients are diagnosed with Diabetes Mellitus. In recent years, some research has directed towards the creation of an artificial pancreas that allows automatically the regulation of glucose levels in blood. However, one of the greatest difficulties in achieving this objective, is that not all internal variables of the mathematical model associated with the controller can be measured directly by physical sensors, either because there are no sensors for all variables, because existing sensors are not commercial, or because they are not viable from the economic point of view. Therefore, it is necessary to use estimation schemes to reconstruct the unknown states by measuring the interstitial glucose , in the case of the glucose-insulin system. However, the delay between plasma glucose and interstitial glucose has a negative effect on the performance of state estimators, so the treatment of this delay is necessary either from the modeling process of the glucose-insulin system or by a modification of the estimation techniques. According to the results it can be inferred that in the scenario at which the concentration of blood glucose is assumed, the estimated values have upper and lower peaks that are unrealistic from a physiological point of view, this due to the negative effect of the delay in measurement. Otherwise, in the scenario where the interstitial glucose concentration is considered as the measured variable, including dynamics of the interstitial glucose, the estimator exhibits better performance and rapid convergence to the real states

Monitoring Plasma Glucose Concentration from Interstitial Glucose Measurements for Patients at the Intensive Care Unit

The glucose homeostasis is responsible for regulating the blood glucose concentration around 100 mg / dl. When this physiological mechanism is broken due to the inability of the pancreas to produce insulin, an increase of the blood glucose levels is produced and patients are diagnosed with Diabetes Mellitus. In recent years, some research has directed towards the creation of an artificial pancreas that allows automatically the regulation of glucose levels in blood. However, one of the greatest difficulties in achieving this objective, is that not all internal variables of the mathematical model associated with the controller can be measured directly by physical sensors, either because there are no sensors for all variables, because existing sensors are not commercial, or because they are not viable from the economic point of view. Therefore, it is necessary to use estimation schemes to reconstruct the unknown states by measuring the interstitial glucose , in the case of the glucose-insulin system. However, the delay between plasma glucose and interstitial glucose has a negative effect on the performance of state estimators, so the treatment of this delay is necessary either from the modeling process of the glucose-insulin system or by a modification of the estimation techniques. According to the results it can be inferred that in the scenario at which the concentration of blood glucose is assumed, the estimated values have upper and lower peaks that are unrealistic from a physiological point of view, this due to the negative effect of the delay in measurement. Otherwise, in the scenario where the interstitial glucose concentration is considered as the measured variable, including dynamics of the interstitial glucose, the estimator exhibits better performance and rapid convergence to the real states

A model-based supersaturation estimator (inferential or soft-sensor) for industrial sugar crystallization process

The degree of supersaturation of the mother liquor is a key factor in improving the monitoring and control of the final stage of industrial sugar crystallization. However, the difficulty of obtaining online supersaturation measurements is one of the challenges associated with monitoring and controlling sugar crystallization. There is no direct method or single instrument for measuring supersaturation. It can only be calculated or inferred from other measurements. In the literature, estimators of mother liquor supersaturation are reported, typically focused on the first stage of crystallization. The SeedMaster series transmitters are the sole industrial instruments that provide online supersaturation information by calculating it from external measurements. The purpose of this study is to design a first-principles model-based soft-sensor as a practical alternative to obtain real-time information about supersaturation in the last stage of sugar crystallization. The proposed estimator relies on two models: a supersaturation model and a second simplified model of the last stage of crystallization. The parameters of both models were estimated based on real industrial data. The estimation is performed in three steps: 1. An Unscented Kalman Filter estimates the states of the crystallization model and their variance. 2. The estimated supersaturation value is obtained by substituting the estimated states into the supersaturation model. 3. The estimator's bias, and variance are calculated to establish error bounds. The main characteristics of the obtained estimator are: practical unbiasedness, nearly minimum variance and robustness. The performance and behavior of the supersaturation estimator are contrasted using real data from an industrial crystallization plant (Urbano Noris factory, Holguín, Cuba). Regardless of its initial conditions, the estimator converges to the three standard deviation error band in less than three minutes. The exact time may vary depending on how much the estimator's initial conditions deviate from those of the process. After this time (Reach Time), the estimates remain within the calculated error limits of three standard deviations. The maximum absolute errors obtained were less than 0.019 units, corresponding to a maximum relative error of less than 1.5%. These values are favorable since they are well below critical values (0.125 units of absolute error). Moreover, the error bands are much smaller than the operating zone width (approximately 0.25 units), which is a necessary condition for any supersaturation estimator to be useful. Finally, it should be noted that the errors have been reduced compared to the values reported in previous research focused on the sugar industry using other techniques.Fil: Morales Gonzalez, Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; ArgentinaFil: Di Sciascio, Fernando Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; ArgentinaFil: Aguirre Zapata, Estefanía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; ArgentinaFil: Amicarelli, Adriana Natacha. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentin

La voz de octubre

Decidimos detenernos en la pregunta que indaga por la emoción. ¿Cuál fue la emoción que experimentamos con el suceso y qué sentimiento la describe? La pregunta por la emoción y el sentimiento que la nombra es la pregunta que surge de lo vivido, que por su fuerza se trasforma en una vivencia, cuyo significado tejido con las posibles respuestas será duradero. Nos preguntamos, entonces, ¿qué fue lo que sentimos durante lo vivido? ¿Qué produjo en nuestro espíritu esos 12 días? Nos detuvimos en la pregunta, teníamos que hospedarnos en ella, hundirnos en su vacío y quebrar ahí cualquier certeza previa, cualquier respuesta mecánica que la aniquile. Detenerse en la cadencia de la pregunta nos devuelve a nuestra circunstancia de indigencia, de seres que aparecimos en el cosmos sin respuestas. Solo desde allí es posible el surgimiento de la voluntad que imagine las respuestas que tejan el sentido de nuestra vida, de los acontecimientos que la constituyen y nos proyecten un destino común