Performance study of disturbance rejection in linear quadratic controllers: A practical adaptive tuning method

[EN] This paper proposes an adaptive tuning method for the Linear-Quadratic FeedForward (LQ-FF) optimal controller. The procedure aims to reject disturbances while maintaining the reference tracking performance of the conventional LQ controller. The adaptive mechanism is formulated by analyzing each element of the control signal LQ-FF concerning state regulation, reference change, and disturbance compensation. The disturbance rejection mechanism is based on the classical strategy used in Proportional-IntegralDerivative controllers and the theoretical analysis studied in previous works for predictive controllers, which aim to obtain the inverse dynamics of the disturbances and process inputs in relation to the outputs. In addition, a comparison is presented between an augmented state space model and a model with a polynomial delay approximation for treating delays associated with disturbances and process inputs in the controller formulation. The proposed method effectively controls a validated nonlinear temperature system, maintaining performance equivalent to the conventional LQ controller for reference tracking while entirely rejecting disturbance effects. The proposed tuning achieves 10 % less output error, with an increase of only 18 % in the control effort compared to conventional tuning in simulations.[ES] Este trabajo propone un metodo de ajuste adaptativo para la metodología de control cuadrático lineal con acción de control por adelanto (LQ-FF, por sus siglas en inglés, Linear-Quadratic FeedForward). El metodo tiene como objetivo rechazar las perturbaciones al mismo tiempo que mantiene el desempeno de seguimiento a referencias del controlador LQ convencional. El mecanismo adaptativo se formula analizando cada elemento de la senal de control LQ-FF en relación con la regulación de estados, el cambio de referencia y la compensacion de perturbaciones. Además, el rechazo de perturbaciones se basa en los controladores Proporcional-Integral-Derivativo y el análisis teórico para controladores predictivos, los cuales tienen como objetivo obtener la dinámica inversa de las perturbaciones y las entradas del proceso. Se presenta una comparativa entre un modelo de espacio de estados aumentado y un modelo con aproximación de retardo polinomial para el tratamiento de los retardos asociados a las perturbaciones y las entradas del proceso en la formulacion del controlador. El método propuesto demuestra su eficacia en el control de un sistema de temperatura no lineal validado, manteniendo el rendimiento similar al controlador LQ convencional en el seguimiento de referencias y rechazando por completo los efectos de las perturbaciones. Para el escenario de simulacion presentado, la sintonía propuesta logra un 10 % menos de error de salida, con un incremento de solo un 18 % en el esfuerzo de control en comparacion con la sintonía convencional.Este trabajo ha sido parcialmente desarrollado en el marco de los proyectos del Ministerio de Ciencia de España con número de subvenciones PID2020-112709RB-C21 y PID2021-122560OB-I00 (MCIN/AEI/10.13039/501100011033), y por la Fundaçao para a Ciência e a Tecnologia (Portugal) bajo el proyecto UIDB/50021/2020. Igor M. L. Pataro agradece el apoyo financiero del Consejo Nacional de Desarrollo Científico y Tecnológico (CNPq, Brasil) bajo la subvención 201143/2019−4.Pataro, IML.; D. Gil, J.; Guzmán, JL.; M. Lemos, J. (2023). Análisis de rendimiento del rechazo de perturbaciones en controladores cuadráticos lineales: un método práctico de sintonía adaptativo. Revista Iberoamericana de Automática e Informática industrial. 21(2):148-158. https://doi.org/10.4995/riai.2023.1970314815821

Linear quadratic tracking-feedforward controller with robust stability for solar furnaces

[EN] Solar energy represents a versatile renewable source that can be used in materials resistance experiments through solar furnaces. This article examines the application of optimal controllers based on linear quadratic tracking with feedforward control action (LQT-FF) to control solar furnaces used in material thermal stress tests. The proposed LQT-FF controller is based on previous studies thatoffer an analytical solution based on a linear model of the solar furnace, thereby reducing the computational cost of the optimalcontrol algorithm. The main contribution of this work lies in the incremental formulation of this model, incorporating an artificialintegrator to the original states. Additionally, robust stability analysis is used to tune the LQT-FF, considering the closed-loop stateestimator. The proper functioning of the proposed controller has been verified on a nonlinear model of the SF60 solar furnace at the Plataforma Solar de Almería. The obtained results represent a significant advance in existing optimal controllers in the literature, as the LQT-FF controller results in an optimal control law with disturbance rejection formulated through an incremental form of inputs, which eliminates reference tracking error with stable tuning for the entire operating range of the plant. On the other hand, this control law can be efficiently implemented with lower computational effort, which is crucial for its implementation.[ES] La energía solar representa una fuente renovable, versátil y confiable que puede emplearse en experimentos de resistencia de materiales mediante el uso de hornos solares. En este artículo se examina la aplicación de controladores óptimos basados en seguimiento cuadrático lineal con acción de control por adelanto (LQT-FF, por sus siglas en inglés, Linear Quadratic Tracking-FeedForward) para el control de hornos solares utilizados en pruebas de estrés térmico de materiales. El controlador LQT-FF propuesto se fundamenta en estudios previos que ofrecen una solución analítica basada en un modelo lineal del horno solar, reduciendo en este caso el coste computacional del algoritmo de control óptimo. La contribución principal de este trabajo radica en la formulación incremental de este modelo, incorporando un integrador artificial a los estados originales. Además, se utiliza el análisis de estabilidad robusta para sintonizar el LQT-FF considerando el estimador de estados en lazo cerrado. El correcto funcionamiento del controlador propuesto se ha verificado sobre un modelo no lineal del horno solar SF60 de la Plataforma Solar de Almería. Los resultados obtenidos suponen un avance significativo en los controladores óptimos existentes en la literatura, ya que el controlador LQT-FF resulta en una ley de control óptima con rechazo de perturbaciones formulada mediante una forma incremental de las entradas, la cual elimina el error de seguimiento de referencia con una sintonía estable para todo el rango de operación de la planta. Por otro lado, esta ley de control se puede implementar eficientemente y con menor esfuerzo computacional, lo que resulta crucial para su implementación.Los autores quieren agradecer el apoyo del personal de la Plataforma Solar de Almería en el desarrollo de esta línea de investigación, en especial a Lidia Roca, Inmaculada Cañadas y José Rodríguez. Igor M. L. Pataro agradece el soporte económico del Consejo Nacional de Desarrollo Científico y Tecnológico (CNPq, Brasil) que ha financiado parte de este trabajo bajo la beca con código 201143/2019−4. El trabajo de J. M. Lemos fue financiado por Fundacao para a Ciência e a Tecnologia (Portugal), proyecto UIDB/50021/2020. Además, este trabajo ha sido desarrollado el marco del proyecto PID2021-122560OB-I00 financiado por MCIN/AEI/10.13039/501100011033/ y por FEDER Una manera de hacer Europa.Pataro, IML.; Gil, JD.; Guzmán, JL.; Lemos, JM.; Berenguel, M. (2024). Controlador cuadrático lineal con acción de control por adelanto y estabilidad robusta para hornos solares. Revista Iberoamericana de Automática e Informática industrial. 21(4):306-317. https://doi.org/10.4995/riai.2024.2117930631721

Teachers Perception About Epilepsy.

To identify in a town of Brazil the knowledge, attitude and perception of epilepsy in teachers of elementary schools and to compare these before and after a training exercise. Teachers of nine public schools of Barão Geraldo, Campinas, Brazil completed a questionnaire. Two researchers had meetings with teachers, presenting the Global Campaign Epilepsy out of the shadows, when the questionnaire was first completed by all attendees. Twenty teachers of these schools were motivated to attend a training course entitled Epilepsy and Health as part of their continuous education programme. Two years later the same questionnaire was again completed (post-test) by these 20 teachers. 100 teachers originally completed the questionnaire (97 women, mean age 42 years, 64 married). Forty-three percent of teachers said that they had enough knowledge regarding epilepsy and 20% said that they had poor knowledge about the condition. Regarding the IQ of children with epilepsy, 45% of teachers believed that they had average IQ, 18% above average, six percent under average and 29% did not know. Teachers believed that children with epilepsy have a higher possibility of acquiring mental disease in the future (51%); that epilepsy is a disease (68%); that epilepsy is contagious (1%); epilepsy is treatable (90%). After the course, the teachers beliefs seem to have improved. This work with elementary school teachers identified difficulties related to epilepsy which, if addressed, may help promote better quality of life of people with epilepsy in the community and help to decrease stigma attached to the condition. Better informed teachers are likely to have a more positive attitude and this will be passed to others. Educational campaigns about epilepsy amongst teachers should be encouraged as this may improve the management of epilepsy, by helping to develop a well informed and tolerant community.65 Suppl 128-3

Optimal control based on a linear quadratic controller with feedforward action for solar furnace system

[Resumen] La energía solar es una fuente de energ´ıa renovable prometedora que se puede utilizar para experimentos de resistencia de materiales mediante el uso de hornos solares. Sin embargo, la operación manual de este tipo de sistemas requiere de operadores muy entrenados y capacitados. Este artículo analiza la aplicación de controladores óptimos basados en seguimiento cuadr´atico lineal con acción de control por adelanto (LQT-FF, por sus siglas en inglés, Linear Quadratic Tracking-FeedForward) para el control de hornos solares utilizados para pruebas de estrés térmico de materiales. El controlador LQT-FF propuesto se basa en estudios anteriores que proporcionan una solución analítica que utiliza un modelo lineal del horno solar, lo que reduce el costo computacional del algoritmo de control óptimo. La principal contribución del trabajo radica en la formulación de este modelo en forma incremental, añadiendo un integrador artificial a los estados originales, eliminando así el error de seguimiento para diferentes puntos de operación del sistema no lineal. El controlador propuesto ha sido implementado y validado sobre el modelo de horno solar SF60 de la Plataforma Solar de Almería. Los resultados obtenidos permiten establecer que las contribuciones del artículo avanzan el estado del arte de los controladores óptimos propuestos hasta ahora en la literatura, presentando una ley de control óptima con rechazo de perturbaciones formulada con una forma incremental de las entradas para eliminar el error de seguimiento de referencia. Además, la solución se resuelve de manera eficiente y presenta un esfuerzo computacional menor, lo que es fundamental para una implementación práctica real.[Abstract] Solar energy is a promising renewable energy source that can be used for material resistance experiments in solar furnace systems. However, the manual operation of such facilities requires highly experienced operators. Therefore, this paper discusses the application of optimal controllers based on Linear Quadratic Tracking with Feedforward action (LQT-FF) to control solar furnaces used for thermal stress testing of materials. Herein, the proposed LQT-FF controller builds on previous studies by providing an analytical solution that uses a linearized model of the solar furnace, reduces the computational cost of the optimal control algorithm, and a model formulation in the incremental form, including an artificial integrator to the original states, which eliminates the tracking error for different operating points of the nonlinear system. The proposed controller has been implemented and validated on the SF60 solar furnace model of the Plataforma Solar de Almer´ıa, southern Spain. The paper’s contributions advance the state of the art of optimal controllers proposed so far in the literature, presenting an optimal control law with disturbance rejection formulated with an incremental form of the inputs to eliminate the reference tracking error. Moreover, the solution is efficiently solved and presents a minor computational effort, promising for actual implementation.Brasil. Conselho Nacional de Desenvolvimento Científico e Tecnológico; 201143/2019 − 4Portugal. Fundação para a Ciência e a Tecnologia; UIDB/50021/2020Ministerio de Ciencia e Innovación; PID2021-122560OB-I0

Effect of post-harvest pulsed light treatment on the respiration rate of grapes: modelling and validation

Introduction. The quality and shelf-life of packed fresh produce is strictly related to the dynamic of the gas composition, namely O2, CO2, and ethylene, in the head space of the packages. Therefore, the challenge is to control the head space composition and, hence the respiration rate of fresh produce during storage. However, several factors can affect the dynamic of the head space gas composition including harvesting time, presence of injury due to handling, microbial infection level, type of sanitization technique, and storage conditions (e.g., temperature, humidity), among others. In this framework, numerical simulation could be applied to predict the dynamic of the head space composition, as well as to select optimal conditions to be adopted during post-harvest treatment, storage, and handling of fresh produce. The aim of this paper was to develop and validate a mathematical model describing the effects of both Pulsed Light (PL) treatment and film permeability on the dynamic of the concentration of O2 and CO2 in the head space of packages during the passive modified atmosphere packaging of fruit. Materials and Methods. A 2D numerical model describing the mass transport of O2, CO2 in the packages as a function of both diffusivity and film permeability was developed. Simulations were performed on three different films with high (MRX), medium (PPCX) and low (PSF530) permeability. The computation of both O2 and CO2 mass transport equations was performed using an implicit finite difference method (Crank Nicolson) solved with Matlab® (v.R2012b). For the validation of the model, experimental data on the respiration rate of table grape were collected. Samples of grapes were exposed to PL treatments at fluences from 1 to 12 J/cm2 before being packed in passive modified atmosphere packaging, and then stored 10°C for up to 10 days. Results. Results demonstrated that the model set up is able to predict the dynamic of the head space gas composition of either untreated and PL treated grape during storage in packages with films of different permeability. The concentration of O2 increased with storage time, while that of CO2 decreased accordingly. Changes in the head space composition were, besides the storage time, dependent on the film permeability and PL fluence applied. Conclusions. The developed model can represent a valuable tool to predict the concentration of O2 and CO2 in the head space of packages during the passive modified atmosphere packaging of fruit. Further work is necessary in order improve the capability of the model to predict the dynamics of the gas composition in more complex systems, where, for example, the influence of the ethylene production is also taken into accout

Effect of high-voltage electrical discharge (HVED) at high frequency on vacuum freeze-drying time and physicochemical properties of blueberries

Vacuum freeze-drying provides high-quality food products. However, it requires long operating times and high energy consumption. High voltage electrical discharge (HVED) is an emerging technology that could enhance freeze-drying rates and final product quality. This study aimed to evaluate the effect of HVED at high frequency (200 kHz) on freeze-drying kinetics of blueberries (effective moisture diffusivity, drying times) and the physicochemical properties of the resulting freeze-dried fruits. Blueberries were pretreated at different electric field strengths (10, 20, and 30 kV/cm) and operational times (10, 20, and 30 s) and freeze-dried until constant weight. The HVED treatment at 30 kV/cm and 30 s exhibited the best moisture diffusivity values and reduced drying time by at least 30% compared with untreated samples. Samples treated with HVED and freeze-dried preserved their shape and prevented shrinkage. Applying HVED as a pretreatment electrotechnology can help improve the efficiency of freeze-drying and the quality of dried food products

Testing of a new high voltage electrical discharge generator prototype at high frequencies to assist anthocyanin extraction from blueberries

Traditional extraction methods are based on high-temperature maceration with organic solvents, which are dangerous for human health. A viable alternative to overcome the issues associated with conventional extraction is to increase cell tissue permeability by applying high voltage electrical discharge (HVED) treatments. The objective of this work was to validate the electroporation of blueberry plant cells using a new HVED generator prototype at a high frequency, investigate the effect, intensity, and duration of the applied voltage, and recover anthocyanins from its electroporated cells. The electroporation level of the HVED-treated blueberries was measured qualitatively by transmission electron microscopy (TEM) analysis. Meanwhile, it was quantitatively measured by the cell permeabilization index (Zp) and anthocyanin extraction level. Results of the micrographs (TEM) showed electroporation in all treatments in which Zp was 0.24 when applying a 2 kV treatment for 2 s, whereas a 3-fold increase in tissue damage was revealed with the most powerful treatment (10 kV voltage, 30 s). In addition, anthocyanin values ranged from 83.09 ± 1.20 (control) to 136.82 ± 0.84 (HVED), which was 64.66% higher. The HVED treatment can increase mass transfer rates during conventional extraction processes. It should be noted that the validated prototype required a low specific energy requirement (31–204 kJ/kg) for proper tissue electropermeabilization. In conclusion, we demonstrated the capability of the developed HVED prototype to boost mass transfer phenomena and thus potentially increase its adaptability to assist dissimilar industrial processes or waste (e.g., peels and seeds) such as freeze-drying operations