Design and implementation of event-based multi-rate controllers for networked control systems

Tesis por compendio[ES] Con esta tesis se pretende dar solución a algunos de los problemas más habituales que aparecen en los Sistemas de control basados en red (NCS) como son los retardos variables en el tiempo, las pérdidas y el desorden de paquetes, y la restricción de ancho de banda y de recursos computacionales y energéticos de los dispositivos que forman parte del sistema de control. Para ello se ha planteado la integración de técnicas de control multifrecuencial, de control basado en paquetes, de control basado en predictor y de control basado en eventos. Los diseños de control realizados se han simulado utilizando Matlab-Simulink y Truetime, se ha analizado su estabilidad mediante LMIs y QFT, y se han validado experimentalmente en un péndulo invertido, un robot cartesiano 3D y en robots móviles de bajo coste. El artículo 1 aborda el control basado en eventos, el cual minimiza el ancho de banda consumido en el NCS mediante un control basado en eventos periódicos y presenta un método para obtener sus parámetros óptimos para el sistema específico en que se utilice. Los artículos 2, 4 y 6 añaden el control basado en paquetes, así como el control multifrecuencia, que aborda problemas de falta de datos por bajo uso del sensor y los retardos, pérdidas y desórdenes de paquetes en la red. También afrontan, mediante tecnicas de predicción basadas en un filtro de Kalman multifrecuencia variable en el tiempo, los problemas de ruido y perturbaciones, así como la observación de los estados completos del sistema. El artículo 7 hace frente a un modelo no lineal que utiliza las anteriores soluciones junto con un filtro de Kalman extendido para presentar otro tipo de estructura para un vehículo autónomo que, gracias a la información futura obtenida mediante estas técnicas, puede realizar de forma remota tareas de alto nivel como es la toma de decisiones y la monitorización de variables. Los artículos 3 y 5, presentan una forma de obtener y analizar la respuesta en frecuencia de sistemas SISO multifrecuencia y estudian su comportamiento ante ciertas incertidumbres o problemas en la red haciendo uso de procedimientos QFT.[CA] Amb aquesta tesi es pretén donar solució a alguns dels problemes més habituals que apareixen als Sistemes de Control Basats en xarxa (NCS) com son els retards d'accés i transferència variables en el temps, les pèrdues y desordenament de paquets, i la restricció d'ampli de banda així com de recursos computacionals i energètics dels dispositius que foment part del sistema de control. Per tal de resoldre'ls s'ha plantejat la integració de tècniques de control multifreqüencial, de control basat en paquets, de control basat en predictor i de control basat en events. Els dissenys de control realitzats s'han simulat fent ús de Matlab-Simulink i de TrueTime, s'ha analitzat la seua estabilitat mitjançant LMIs i QFT, i s'han validat experimentalment en un pèndul invertit, un robot cartesià 3D i en robots mòbils de baix cost. L'article 1 aborda el control basat en events, el qual minimitza l'ampli de banda consumit a l'NCS mitjançant un control basat en events periòdics i presenta un mètode per a obtindré els seus paràmetres òptims per al sistema específic en el qual s'utilitza. Els articles 2, 4 i 6 afegeixen el control basat en paquets, així com el control multifreqüència, que aborda problemes de falta de dades per el baix us del sensor i els retards, pèrdues i desordre de paquets en la xarxa. També afronten, mitjançant tècniques de predicció basades en un filtre de Kalman multifreqüència variable en el temps. Els problemes de soroll i pertorbacions, així com la observació dels estats complets del sistema. L'article 7 fa referència a un model no lineal que utilitza les anteriors solucions junt a un filtre de Kalman estès per a presentar altre tipus d'estructura per a un vehicle autònom que, gracies a la informació futura obtinguda mitjançant aquestes tècniques, pot realitzar de manera remota tasques d'alt nivell com son la presa de decisions i la monitorització de variables. Els articles 3 y 5 presenten la manera d'obtindre i analitzar la resposta en frequencia de sistemes SISO multifreqüència i estudien el seu comportament front a certes incerteses o problemes en la xarxa fent us de procediments QFT.[EN] This thesis attempts to solve some of the most frequent issues that appear in Networked Control Systems (NCS), such as time-varying delays, packet losses and packet disorders and the bandwidth limitation. Other frequent problems are scarce computational and energy resources of the local system devices. Thus, it is proposed to integrate multirate control, packet-based control, predictor-based control and event-based control techniques. The control designs have been simulated using Matlab-Simulink and Truetime, the stability has been analysed by LMIs and QFT, and the experimental validation has been done on an inverted pendulum, a 3D cartesian robot and in low-cost mobile robots. Paper 1 addresses event-based control, which minimizes the bandwidth consumed in NCS through a periodic event-triggered control and presents a method to obtain the optimal parameters for the specific system used. Papers 2, 4 and 6 include packet-based control and multirate control, addressing problems such as network delays, packet dropouts and packet disorders, and the scarce data due to low sensor usage in order to save battery in sensing tasks and transmissions of the sensed data. Also addressed, is how despite the existence of measurement noise and disturbances, time-varying dual-rate Kalman filter based prediction techniques observe the complete state of the system. Paper 7 tackles a non-linear model that uses all the previous solutions together with an extended Kalman filter to present another type of structure for an autonomous vehicle that, due to future information obtained through these techniques, can remotely carry out high level tasks, such as decision making and monitoring of variables. Papers 3 and 5, present a method for obtaining and analyzing the SISO dual-rate frequency response and using QFT procedures to study its behavior when faced with specific uncertainties or network problems.This work was supported by the Spanish Ministerio de Economía y Competitividad under Grant referenced TEC2012-31506.Alcaina Acosta, JJ. (2020). Design and implementation of event-based multi-rate controllers for networked control systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159884TESISCompendi

Dual-rate sampled-data systems. Some interesting consequences from its frequency response analysis

This is an Accepted Manuscript of an article published by Taylor & Francis in International Journal of General Systems on JUL 4 2019, available online: http://www.tandfonline.com/10.1080/03081079.2019.1608984[EN] The main goal of this contribution is to introduce a new procedure in order to analyse properly SISO dual-rate systems (DRS) and to provide straightforward answers to some common general questions about this kind of systems. Frequency response analysis based on DRS lifting modelling can lead to interesting results about stability margins or performance prediction. As a novelty, it is explained how to understand DRS frequency response and how to handle it for an easy computation of magnitude and phase margins keeping classical frequency domain methods. There are also some repetitive questions about DRS that can be analysed and answered properly using the results from this contribution: what the optimum relation between sampling periods is or what effects does delay have in a DRS. Every step is illustrated with examples that should clarify the understanding of the text.Salt Llobregat, JJ.; Alcaina-Acosta, JJ. (2019). Dual-rate sampled-data systems. Some interesting consequences from its frequency response analysis. International Journal of General Systems. 48(5):554-574. https://doi.org/10.1080/03081079.2019.1608984S55457448

Delay-independent dual-rate PID controller for a packet-based networked control system

[EN] In this paper, a novel delay-independent control structure for a networked control system (NCS) is proposed, where packet-based control strategies with predictor-based and dual-rate control techniques are integrated. The control solution is able to cope with some networked communication problems such as time-varying delays, packet dropouts and packet disorder. In addition, the proposed approach enables to reduce network load, and usage of connected devices, while maintaining a satisfactory control performance. As a delay-independent control solution, no network-induced delay measurement is needed for controller implementation. In addition, the control scheme is applicable to open-loop unstable plants. Control system stability is ensured in terms of linear matrix inequalities (LMIs). Simulation results show the main benefits of the control approach, which are experimentally validated by means of a Cartesian-robot-based test-bed platform. (C) 2019 Elsevier Inc. All rights reserved.This work is funded by European Commission as part of Project H2020-SEC-2016-2017, Topic: SEC-20-BES-2016 Id: 740736 C2 Advanced Multi-domain Environment and Live Observation Technologies (CAMELOT). Part WP5 supported by Tekever ASDS, Thales Research & Technology, Viasat Antenna Systems, Universitat Politècnica de València, Fundação da Faculdade de Ciências da Universidade de Lisboa, Ministério da Defesa Nacional Marinha Portuguesa, Ministério da Administração Interna Guarda Nacional Republicana.Alcaina-Acosta, JJ.; Cuenca, Á.; Salt Llobregat, JJ.; Casanova Calvo, V.; Pizá, R. (2019). Delay-independent dual-rate PID controller for a packet-based networked control system. Information Sciences. 484:27-43. https://doi.org/10.1016/j.ins.2019.01.059S274348

A packet-based dual-rate PID control strategy for a slow-rate sensing Networked Control System

[EN] This paper introduces a packet-based dual-rate control strategy to face time-varying network-induced delays, packet dropouts and packet disorder in a Networked Control System. Slow-rate sensing enables to achieve energy saving and to avoid packet disorder. Fast-rate actuation makes reaching the desired control performance possible. The dual-rate PID controller is split into two parts: a slow-rate PI controller located at the remote side (with no permanent communication to the plant) and a fast-rate PD controller located at the local side. The remote side also includes a prediction stage in order to generate the packet of future, estimated slow-rate control actions. These actions are sent to the local side and converted to fast-rate ones to be used when a packet does not arrive at this side due to the network-induced delay or due to occurring dropouts. The proposed control solution is able to approximately reach the nominal (no-delay, no-dropout) performance despite the existence of time-varying delays and packet dropouts. Control system stability is ensured in terms of probabilistic Linear Matrix Inequalities (LMIs). Via real-time control for a Cartesian robot, results clearly reveal the superiority of the control solution compared to a previous proposal by authors. (C) 2018 ISA. Published by Elsevier Ltd. All rights reserved.This work is funded by European Commision as part of Project H2020-SEC-2016-2017 Topic: SEC-20-BES-2016 Id: 740736 C2 Advanced Multi-domain Environment and Live Observation Technologies (CAMELOT). Part WP5 supported by Tekever ASDS, Thales Research & Technology, Viasat Antenna Systems, Universitat Politècnica de València, Fundação da Faculdade de Ciências da Universidade de Lisboa, Ministério da DefesaNacional Marinha Portuguesa, Ministério da Administração Interna Guarda Nacional Republicana.Cuenca, Á.; Alcaina-Acosta, JJ.; Salt Llobregat, JJ.; Casanova Calvo, V.; Pizá, R. (2018). A packet-based dual-rate PID control strategy for a slow-rate sensing Networked Control System. ISA Transactions. 76:155-166. https://doi.org/10.1016/j.isatra.2018.02.022S1551667

Control of the rotary inverted pendulum through threshold-based communication

[EN] This paper deals with the real implementation of an event-based control structure for the classical rotary inverted pendulum. The communication between controller and plant is performed through Ethernet (TCP/IP) which leads to a Networked Control System. The bandwidth used by the control loop is reduced, compared with the one that needs a conventional control, by using a threshold-based communication. The values of the thresholds have been determined by means of simulation techniques. The results over the real plant show how this technique can reach a significant reduction of the bandwidth consumed with a negligible worsening of the performance.This work was supported by the Spanish Ministerio de Economía y Competitividad under Grant referenced TEC2012-31506.Casanova Calvo, V.; Alcaina-Acosta, JJ.; Salt Llobregat, JJ.; Pizá, R.; Cuenca Lacruz, ÁM. (2016). Control of the rotary inverted pendulum through threshold-based communication. ISA Transactions. 62:357-366. https://doi.org/10.1016/j.isatra.2016.01.0093573666

Técnicas de ahorro energético en un sistema de control basado en red

[EN] In this project the goal will be to apply multirate event control techniques in order to contol an unstable system[ES] En este proyecto se va a emplear técnicas de control multifrecuencia basado en eventos para ahorrar ancho de banda y mantener las prestaciones del control de un sistema inestableAlcaina Acosta, JJ. (2015). Técnicas de ahorro energético en un sistema de control basado en red. http://hdl.handle.net/10251/56210TFG

Diseño e implementación de un control para el péndulo invertido a través de una realimentación basada en umbrales por TCP/IP

Consulta en la Biblioteca ETSI Industriales (Riunet)[ES] En el proyecto se pretende desarrollar una estructura de control, partiendo de un controlador discreto convencional de un péndulo invertido, una estrategia de control para que, a través de una red de comunicación, se decida cuándo enviar o no enviar los nuevos datos de lectura o control según estos difieran de los obtenidos en instantes anteriores un umbral establecido y cómo obtener ese umbral. En el capítulo de Justificación de la solución adoptada se hace hincapié en qué significa el término umbral, pero básicamente, el término umbral hace referencia al valor que tiene que cambiar una variable que va a ser comunicada a través del medio de comunicación para que el sistema considere que el cambio ha sido significativo, tenerlo en cuenta y comunicarlo. Mientras ese valor no es superado, el sistema considera que no ha cambiado lo suficiente y no usa el medio de comunicación manteniéndolo libre. El objetivo es obtener una técnica de control basado en red que no difiera en prestaciones de un control convencional pero que minimice el ancho de banda consumido por la red. El presente estudio también pretende defender la utilidad de dicha técnica de control, por lo tanto se puede separar dicho proyecto en dos partes diferenciadas.Alcaina Acosta, JJ. (2015). Diseño e implementación de un control para el péndulo invertido a través de una realimentación basada en umbrales por TCP/IP. http://hdl.handle.net/10251/48257.Archivo delegad

A Remote Control Strategy for an Autonomous Vehicle with Slow Sensor Using Kalman Filtering and Dual-Rate Control

[EN] This work presents a novel remote control solution for an Autonomous Vehicle (AV), where the system structure is split into two sides. Both sides are assumed to be synchronized and linked through a communication network, which introduces time-varying delays and packet disorder. An Extended Kalman Filter (EKF) is used to cope with the non-linearities that appear in the global model of the AV. The EKF fuses the data provided by the sensing devices of the AV in order to estimate the AV state, reducing the noise effect. Additionally, the EKF includes an h-step-ahead state prediction stage, which, together with the consideration of a packet-based control strategy, enables facing the network-induced delays. Since the AV position is provided by a camera, which is a slow sensing device, a dual-rate controller is required to achieve certain desired (nominal) dynamic control performance. The use of a dual-rate control framework additionally enables saving network bandwidth and deals with packet disorder. As the path-tracking control algorithm, pure pursuit is used. Application results show that, despite existing communication problems and slow-rate measurements, the AV is able to track the desired path, keeping the nominal control performance.This research work has been developed as a result of a mobility stay funded by Spanish Ministry of Education under "Programa Estatal de Promocion del Talento y su Empleabilidad en I+D+i, Subprograma Estatal de Movilidad, del Plan Estatal de Investigacion Cientifica y Tecnica y de Innovacion 2013-2016". In addition, the research was funded in part by Grant RTI2018-096590-B-I00 from the Spanish government and by the European Commission as part of Project H2020-SEC-2016-2017, Topic: SEC-20-BES-2016, ID: 740736, "C2 Advanced Multi-domain Environment and Live Observation Technologies" (CAMELOT). Part WP5 supported by Tekever ASDS, Thales Research and Technology, Viasat Antenna Systems, Universitat Politecnica de Valencia, Fundacao da Faculdade de Ciencias da Universidade de Lisboa, Ministerio da Defensa Nacional, Marinha Portuguesa, and Ministerio da Administracao Interna Guarda Nacional Republicana.Cuenca, Á.; Zhan, W.; Salt Llobregat, JJ.; Alcaina-Acosta, JJ.; Tang, C.; Tomizuka, M. (2019). A Remote Control Strategy for an Autonomous Vehicle with Slow Sensor Using Kalman Filtering and Dual-Rate Control. Sensors. 19(13):1-21. https://doi.org/10.3390/s19132983121191