Software tool for the design of event based PID controllers with events generated by crossing fixed thresholds

Los algoritmos de control PID basados en eventos tratan de aprovechar las conocidas ventajas del control PID a la vez que reducen el tráfico por las redes de comunicaciones que conectan las distintas unidades de hardware que forman los sistemas de control distribuidos: sensores, controladores, actuadores. En este trabajo se muestran resultados recientes en el ámbito de los PID basado en eventos por cruce de umbrales fijos y se presenta una herramienta de software que permite el análisis, diseño y simulación de este tipo de sistemas de control. La herramienta está programada en Python, es de código abierto y puede ser usada tanto con fines de investigación como docentes.Event-based PID control algorithms try to take advantage of the well-known benefits of PID controllers while reducing the traffic over the communications networks that connect the different devices in distributed control systems: sensors, controllers, actuators. This work shows recent results in the field of events based PID by crossing fixed thresholds and a software tool is presented for the analysis, design and simulation of this kind of control systems. The tool has been programmed in Python, it is open source and can be used for both research and teaching purposes

Identification of first and second order systems by reset control

[EN] The article presents a method for the identification of first and second order processes with time delay using reset controllers in the absence of disturbances. The method is based on compliance with the method of harmonic balance, which implies the use of an approximation of the control reset by its describing function. The FORE controller (First Order Reset Element) with fixed bandwidth has been chosen because it is the easiest reset driver that possesses all the inherent characteristics in this type of drivers and its descriptive function depends on the amplitude and frequency of its sinusoidal signal input. On the other hand, the fact that the behavior of this reset driver depends on of its reset band allows studying the impact of this parameter in the identification process and in its accuracy.[ES] El artículo presenta un método para la identificación de plantas de primer y segundo orden con retardo usando controladores reseteados en ausencia de perturbaciones. El método se basa en el cumplimiento del principio de equilibrio armónico, lo que implica el uso de una aproximación del controlador reseteado mediante su función descriptiva. Para la realización de este trabajo se ha elegido el controlador FORE (First Order Reset Element) con banda de reset porque es el controlador reseteado que posee todas las características intrínsecas de este tipo de controladores y presenta una función descriptiva que depende de la amplitud y frecuencia de la señal sinusoidal de su entrada. Por otro lado, el que el comportamiento de este controlador dependa de la anchura de la banda de reset que se haya fijado permite estudiar el impacto de este parámetro en el proceso de identificación y en su precisión.Este trabajo ha sido realizado parcialmente gracias al apoyo del Ministerio de Economía y Competitividad de España a través de los fondos asignados a los proyectos DPI2017-84259-C2-2-R y DPI2016-79278-C2-1-R.Zaragoza, S.; Sanchez, J.; Baños, A. (2020). Identificación de sistemas de primer y segundo orden mediante control basado en reset. Revista Iberoamericana de Automática e Informática industrial. 17(2):116-129. https://doi.org/10.4995/riai.2020.11598OJS116129172Bajarangbali, R., Majhi, S., Pandey, S., 2014. Identification of FOPDT and SOPDT Process Dynamics Using Closed Loop Test. ISA Trans. 53, 1223-1231. https://doi.org/10.1016/j.isatra.2014.05.014Bajarangbali, R., Majhi, S., 2017. Estimation of First and Second Order Systems. Proc. Natl. Acad. Sci., India, Sect. A Phys. Sci. https://doi.org/10.1007/s40010-017-0357-6Baños, A., Dormido, S., Barreiro, A., 2011. Limit Cycles Analysis of reset control systems with reset band. Nonlinear Analysis: Hybrid Systems, 5, 163-173. https://doi.org/10.1016/j.nahs.2010.07.004Baños, A., Barreiro, A., 2012a, Reset Control Systems, Springer, London, 2012. https://doi.org/10.1007/978-1-4471-2250-0Barreiro A., Baños, A., 2012b. Sistemas de Control Basados en Reset. RIAI 9, 329-346. https://doi.org/10.1016/j.riai.2012.09.007Baños, A., Vidal, A. , 2012. Design of Reset Control Systems: the PI+CI Compensator. Journal of Dynamic Systems, Measurement, and Control, 134. https://doi.org/10.1115/1.4004773Beschi, M., Dormido, S., Sánchez, J., Visioli, A., Yebra, L. J., 2014. Event-based PI plus Feedforward Control Strategies for a Distributed Solar Collector Field. IEEE Trans. Control Syst. Technol. 22, 1615-1622. https://doi.org/10.1109/TCST.2013.2279216Beschi, M., Dormido, S., Sánchez, J., Visioli, A., 2015a. Closed-Loop Automatic Tuning Technique for an Event-Based PI Controller. Ind. Eng. Chem. Res. 54, 6362-6370. https://doi.org/10.1021/acs.iecr.5b01024Beschi, M., Dormido, S., Sánchez, J., Visioli, A., 2015b. An Event-based PI Controller Autotuning Technique for Integral Processes. Proceedings of the 1st IEEE International Conference on Event-Based Control, Communication, and Signal Processing; Krakow, Poland. https://doi.org/10.1109/EBCCSP.2015.7300684Chang, R.C., Shen, S.H., Yu, C.C., 1992. Derivation of Transfer Function from Relay Feedback Systems. Ind. Eng. Chem. Res. 31, 855-860. https://doi.org/10.1021/ie00003a030Clegg, J.C., 1958. A Nonlinear Integrator for Servomechanisms. Trans A.I.E.E. 77, 41-42. https://doi.org/10.1109/TAI.1958.6367399Davo, M.A., 2015. Análisis y Diseño de Sistemas de Control Reseteados. Tesis Doctoral. Universidad de Murcia. http://hdl.handle.net/10201/46666Friman, M., Waller, K.V., 1997. A Two-Channel Relay for Autotunning. Ind. Eng. Chem. Res. 36, 2662-2671. https://doi.org/10.1021/ie970013uGelb, A., Van der Velde, W. E., 1968. Multiple-Input Describing Functions and Nonlinear System Design. McGraw-Hill, New York, NY.Gu, D., Ou, L., Wang, P., Zhang, W., 2006. Relay Feedback Autotuning Method for Integrating Processes with Inverse Response and Time Delay. Ind. Eng. Chem. Res. 45, 3119-3132. https://doi.org/10.1021/ie050739nHo, W.K., Feng, E.B., Gan, O.P., 1996. A Novel Relay Auto-Tuning Technique for Processes with Integration. Control Eng. Prac. 4, 923-928. https://doi.org/10.1016/0967-0661(96)00090-1Horowitz, I.M., Rosenbaum, P., 1975. Nonlinear Design for Cost of Feedback Reduction in Systems with Large Parameter Uncertainty. Int. J. Control 24, 977-1001. https://doi.org/10.1080/00207177508922051Kaya, I., 2006. Parameter Estimation for Integrating Processes Using Relay Feedback Control under Static Load Disturbances. Ind. Eng. Chem. Res. 45, 4726-4731. https://doi.org/10.1021/ie060270bKhalil, H. K., 2002. Nonlinear Systems, Prentice Hall, NJ.Li, W., Eskinat, E., Luyben, W.L., 1991. An Improved Autotune Identification Method. Ind. Eng. Chem. Res. 30, 1530-41. https://doi.org/10.1021/ie00055a019Liu, T., Wang, Q.G., Huang, H.P., 2013. A Tutorial Review on Process Identification from Step to Relay Feedback Test, J. Process Control, 23, 1597-1623. https://doi.org/10.1016/j.jprocont.2013.08.003Liu T, Gao F., 2012. Industrial Process Identification and Control: Design Step-Test and Relay-Experiment-based Methods. Springer-Verlag. London, UK.Luyben, W. L., 1987. Derivation of Transfer Functions for Highly Nonlinear Distillation Columns. Ind. Eng. Chem. Res. 26, 2490-2495. https://doi.org/10.1021/ie00072a017Sánchez, J., Guinaldo, M., Visioli, A., Dormido, S., 2018a. Identification of Process Transfer Function Parameters in Event-based PI Control Loops. ISA Trans. 75, 157-171. https://doi.org/10.1016/j.isatra.2018.01.033Sánchez, J., Guinaldo, M., Visioli, A., Dormido, S., 2018b. Enhanced Event-based Identification Procedure for Process Control. Ind. Eng. Chem. Res. 57, 7218-7231. https://doi.org/10.1021/acs.iecr.7b05239Scali, C., Marchetti, G., Semino, D, 1999. 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Event-Based PI Plus Feedforward Control Strategies for a Distributed Solar Collector Field

5This brief deals with the application of an event-based proportional-integral (PI) plus feedforward control strategy to a distributed solar collector field. In particular, a symmetric send-on-delta strategy is considered and an event based feedforward action to compensate for the disturbance represented by changes in the solar radiation is added to the PI control law. Furthermore, we propose a simple strategy, based on the describing function technique, to estimate the model parameters for tuning the controller. The obtained experimental results show that the proposed control strategy permits to obtain a very significant reduction of the events with only a slight decrement of the control performance.reservedmixedM. Beschi; S. Dormido; J. Sanchez; A. Visioli; L. J. YebraBeschi, Manuel; S., Dormido; J., Sanchez; Visioli, Antonio; L. J., Yebr

Contribuciones a la sintonía de controladores basados en eventos

Dentro del paradigma del control automático, las estrategias de control basado en eventos se postulan como una posible solución para satisfacer los requisitos de los actuales procesos de control distribuidos. La creciente descentralización, escala y número de dispositivos implicados, está demandando esquemas de muestreo más eficaces conforme a las nuevas necesidades. Los incipientes sistemas basados en red (tales como los sistemas de control en red) son una prueba de tal demanda. En estas aplicaciones el desafío consiste en reducir el intercambio de información entre dispositivos distribuidos con la menor pérdida de rendimiento y, para tal fin, los enfoques basados en eventos podrían aportar un compromiso satisfactorio entre el esfuerzo de muestro y el rendimiento del lazo, a través de un uso oportuno de los recursos y canales de comunicación. A pesar de las muchas ventajas potenciales del control basado en eventos, este campo de investigación se encuentra aún en sus primeros pasos. Aunque la última década ha sido prolífica en resultados analíticos, la carencia de una teoría comprensible es todavía evidente. El diseño de un esquema eficiente sigue siendo un problema difícil de resolver y cuestiones tales como la sintonía del controlador o las condiciones para la estabilidad global y la ausencia de ciclos límite son dificultades que todavía están lejos de ser completamente solventadas. En particular, la cuestión de la sintonía no ha sido tratada debidamente. En la mayoría de los sistemas de control propuestos por los autores, la sintonía o no es tratada o se terminan proponiendo reglas que por las propias condiciones de diseño restringen el espacio de parámetros y comprometen el rendimiento global del sistema. Ante tal escenario, la presente Tesis se centra en el diseño de controladores basados en eventos con ventajas prácticas desde el punto de vista del diseño y desarrollo de la sintonía. Para tal objetivo, la presente Tesis realiza tres principales aportaciones. En primer lugar, se propone un nuevo esquema de control basado en eventos. En su desarrollo se considera el diseño global del generador de eventos y del controlador, de manera que el sistema pueda tratar la problemática del retardo del proceso y el seguimiento de referencias y, a la vez, se obtenga un sistema basado en eventos de fácil diseño y ajuste. El enfoque se centra en sistemas de primer orden con retardo, pero puede ser extendido sistemas de orden mayor. Se ha desarrollado el análisis de estabilidad y robustez del sistema y los resultados experimentales y de simulación prueban la eficacia de la...In the paradigm of automatic control, event-based strategies are proposed as a solution to satisfy the current requirements of distributed process control. The increasing decentralization, large scale and the number of involved devices in current control applications demand more effective sampling schemes for signals. Systems based on networks (such as Networked Control Systems, NCS) are proof of this demand. In this context, the challenge is to reduce the exchange of information between distributed devices without losing performance and, to this aim, event-based approaches could provide a satisfactory trade-off between the sampling effort and the loop performance through an opportune use of sources and information channels. Despite many conceptual advantages of event-based control, this field is still in its infancy. Although last decade has been prolific in analytical results, the lack of a comprehensive theory is still evident. The design of an efficient scheme is a challenging problem and issues such as controller tuning, conditions for global stability and the absence of limit cycles are topics that are far from being fully solved yet. In particular, the question of controller tuning has not been properly addressed. In most control systems proposed for authors, the controller tuning task is omitted or the provided rules become complex and restrictive, compromising the overall system performance. In this context, this thesis is focused on the designing of event-based controllers with advantages from the point of view of a practical design and an intuitive tuning methodology. To this end, this thesis makes three main contributions. Firstly, a novel eventbased control scheme has been proposed. The overall design of the event generator and the controller is considered in order to cope with the problem of the process delay, the set-point tracking and to obtain an easy-to-tune event-based system. The approach is focused on FOPTD systems but can be easily extended to higher order systems. Stability and robustness analyses are conducted, and the experimental and simulation results verify the effectiveness of the approach. Secondly, the tuning framework is presented. The complexity of the design is simplified by using only two parameters with a very intuitive influence. The methodology is illustrated through the definition of the tuning regions and the guidelines for the tuning of parameters are provided. Thirdly, a new interactive software tool developed using Sysquake is described. By using the..