Comparison of Riemann and Lebesque sampling for first order stochastic systems
01 Jan 2002-Vol. 2, pp 2011-2016
TL;DR: In this article, it is shown that Lebesgue sampling gives better performance for some simple systems than traditional Riemann sampling, which is an analog of integration theory and is called event-based sampling.
Abstract: The normal approach to digital control is to sample periodically in time. Using an analog of integration theory we can call this Riemann sampling. Lebesgue sampling or event based sampling is an alternative to Riemann sampling. It means that signals are sampled only when measurements pass certain limits. In this paper it is shown that Lebesgue sampling gives better performance for some simple systems.
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12 citations
01 Jan 2009
TL;DR: In this article, a plate heat exchanger of new design, where one side is used as a chemical continuous reactor and the other side is filled with a cooling/heating medium, is presented.
Abstract: The project is aiming at improving process control of chemical reactors, especially the new Alfa Laval Plate Reactor. Innovative process design leads to vastly improved control capabilities, allowing increased productivity, efficiency and safety. Background and process description In the chemical industry of today, the batch reactor is the most common reactor type. However is it unsuitable for highly exothermic reactions due to its limited heat transfer capacity. The reactant solutions have to be diluted with water to reduce the amount of energy released during the reaction. After the reaction, separation is necessary to remove the excess water of the product solution. Alfa Laval AB is currently developing a new kind of reactor technology, a plate heat exchanger of new design, where one side is used as a chemical continuous reactor and the other side is filled with a cooling/heating medium. See Figure 5.8 A typical reaction can be stated as: A + B -> C + D. The primary reactant A enters the main inlet of the reactor. The secondary reactant B is then added in multiple inlet ports along the reactor, to distribute the heat from the exothermic reaction. See Figure 5.9. The process has a much higher heat transfer capacity, so solutions of higher concentrations can be used leading to less separation need. The process will also have higher productivity, more efficient reaction and a safer process.
7 citations
01 May 2017
TL;DR: In this article, the authors define a set of metodologias of localizacion for robot moviles in interiores that mejoran de forma considerable the esquemas tradicionales.
Abstract: Resumen Los sistemas de control basados en tiempo continuo y discreto se utilizan de forma masiva para resolver los problemas de navegacion en robots moviles. Estas tecnicas de control gozan de una base teorica solida y de metodologias que facilitan su diseno y sintonia en este tipo de aplicaciones. Por otro lado, en los ultimos anos, las tecnicas de control basadas en eventos estan ganando relevancia y se estan posicionando como una alternativa a los esquemas clasicos por sus ventajas diferenciales respecto al consumo de recursos.
En esta tesis, se profundiza en el estudio de las tecnicas de control basadas en eventos y se aplican estos metodos a los algoritmos de navegacion en robotica movil. Los esquemas de control planteados resuelven el problema de navegacion con una precision similar a los metodos clasicos basados en tiempo continuo/discreto. Por otro lado, se definen los criterios que deben cumplir estos nuevos sistemas para garantizar su estabilidad. Como resultado, estas nuevas estructuras obtienen grandes eficiencias en el consumo de recursos, convirtiendose asi, en una alternativa a los esquemas tradicionales.
Se hace un analisis exhaustivo de los algoritmos de navegacion mas comunes usados en robotica movil y se define su implementacion en los nuevos esquemas de control planteados. Seguidamente, se desarrollan estos mecanismos de control para robot moviles diferenciales. Gracias a la flexibilidad de las estructuras planteadas, estas soluciones son de aplicacion directa en cualquier otro tipo de robot movil.
Se demuestra que el ruido en estos sistemas de control tiene un alto impacto en el consumo de recursos. En este sentido, se plantean mecanismos dinamicos de sintonia que minimizan estos efectos, consiguiendo ademas hacer estos nuevos esquemas mas inmunes a las perturbaciones.
Dada la alta dependencia que estos algoritmos tienen con la informacion de posicionamiento, en esta tesis se plantean nuevas metodologias de localizacion para robots moviles en interiores que mejoran de forma considerable los esquemas tradicionales.
Por ultimo, a partir de este trabajo se abren nuevas lineas de investigacion. Estas van dirigidas a experimentar estos esquemas de control en vehiculos moviles mas complejos, analizar nuevos tipos de perturbaciones y plantear desarrollos teoricos para analizar la estabilidad de las arquitecturas de control aqui plateadas.
Palabras clave: Robots Moviles, Sistemas de Control en Red, Control Basado en Eventos, Algoritmos de Navegacion, Ajuste Dinamico de Umbrales, Eficiencia en el Consumo de Recursos, Modelos de Ruido, Odometria, Algoritmos de Posicionamiento, Navegacion Inercial, Robots mOway.
6 citations
Cites background from "Comparison of Riemann and Lebesque ..."
...[13] Karl Johan Åström and Bo Bernhardsson....
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...[121]) y muestreo de Lebesgue (Åström and Bernhardsson [13])....
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...En este nuevo contexto de los sistemas de control, las técnicas de control basadas en eventos (Event-Based Control EBC) pueden resolver multitud de problemas en sistemas de control en red (NCS) (Åström and Bernhardsson [13], Åström [12])....
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DOI•
26 Feb 2018
TL;DR: The purpose of this thesis is to study how to guarantee pre-designed stability and performance under limitations of bandwidth and energy supplies, with the goal to enrich the control approaches for resource-aware industrial applications.
Abstract: Wireless networked control systems, as the name indicates, employ wireless networks to interconnect their components, e.g. sensors, computing units, and actuators, in their implementation. Removing wires from control system implementations, the components can be more easily installed in spatial positions that are hard to access, and facilitate their deployment within large physical scales. This enables the expansion of control applications to new domains or objectives previously not attainable. However, as a trade-off, in a wireless networked control system, the transmission bandwidth is much smaller compared to a wired one. Besides, to achieve flexibility and mobility, some nodes may have energy supplies from batteries, which have limited capacity and are usually costly to replace. The limitations in bandwidth and energy supplies is a major problem when designing wireless networked control systems. The purpose of this thesis is to study how to guarantee pre-designed stability and performance under limitations of bandwidth and energy supplies, with the goal to enrich the control approaches for resource-aware industrial applications.
6 citations
Cites background from "Comparison of Riemann and Lebesque ..."
...6: System evolution and event intervals when w = 2sin(πt ), t ∈ [3,8]: state evaluation and perturbance, event intervals with the bounds....
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...There are many results already available studying ETC, see [8], [31], [32], [48], [70], [72], [95], [110], [111], and references therein....
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...In [8], Åström and Bernhardsson present the comparison between periodical sampling (Riemann sampling) and event-based sampling (Lebesgue sampling)....
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Dissertation•
19 Feb 2014
TL;DR: Les travaux developpes dans cette these portent sur la "co-conception diagnostic / ordonnancement des mesures dans un systeme controle en reseau" qui est un sujet multidisciplinaire necessitant des competences en theorie du controle et en theories des reseaux.
Abstract: Les travaux developpes dans cette these portent sur la "co-conception diagnostic / ordonnancement des mesures dans un systeme controle en reseau" qui est un sujet multidisciplinaire necessitant des competences en theorie du controle et en theorie des reseaux. La these a pour but de developper, dans le contexte des systemes controles en reseau, une approche de co-conception qui integre de facon coordonnee les caracteristiques qui expriment la performance du diagnostic des defauts et les parametres de l'ordonnancement temps-reel des messages. L'interet de cette approche coordonnee reside essentiellement dans la minimisation des ressources necessaires pour atteindre la performance du diagnostic requise, minimisation qui prend tout son sens dans le contexte des systemes embarques. Nous nous sommes interesses plus particulierement a l'etude des problemes lies a l'elaboration d'algorithmes de diagnostic efficaces et adaptes aux caracteristiques de l'application de facon tout en prenant en compte differents types de contraintes liees au reseau. En conjonction avec ces algorithmes, deux ensembles de techniques d'ordonnancement des mesures ont ete developpes : i) ordonnancement hors ligne, ii) ordonnancement evenementiel en ligne. Pour l'ordonnancement hors ligne, les sequences de communication sont concues en amont, prealablement a la mise en oeuvre de l'algorithme de diagnostic (implementation). D'autre part, nous proposons aussi des techniques d'ordonnancement en ligne basees sur l'echantillonnage evenementiel developpe au cours de la derniere decennie. Au contraire de la plupart des recherches en automatique classique, considerant que l'echantillonnage des signaux continus est realise d'une maniere periodique, les mesures dans cette approche sont transmises si et seulement si la condition de transmission (evenement) est verifiee. Ceci permet d'economiser les ressources fournies par le reseau tout en gardant une performance du diagnostic acceptable. L'objectif de ces algorithmes est de minimiser le nombre de transmission d'informations ce qui signifie moins de consommation d'energie.
5 citations
Cites methods from "Comparison of Riemann and Lebesque ..."
...For dealing with abrupt changes in the output signal due to perturbations, the integral of the innovation signal can be used for event generation [4], this technique is named « integral sampling »....
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...To deal with random and unknown network-induced delay, [4] formulates the design of observer based robust fault detection filters for NCS as an H∞ filtering problem by introducing a new optimization performance index, and [5] proposes a parity space fault detection system robust to the random delay....
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...Compared with the approaches in [4] and [5], the new approach is not restricted to the condition that the delay has to be less than one sampling period....
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References
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05 Mar 2007
TL;DR: This work reviews several recent results on estimation, analysis, and controller synthesis for NCSs, and addresses channel limitations in terms of packet-rates, sampling, network delay, and packet dropouts.
Abstract: Networked control systems (NCSs) are spatially distributed systems for which the communication between sensors, actuators, and controllers is supported by a shared communication network. We review several recent results on estimation, analysis, and controller synthesis for NCSs. The results surveyed address channel limitations in terms of packet-rates, sampling, network delay, and packet dropouts. The results are presented in a tutorial fashion, comparing alternative methodologies
3,748 citations
TL;DR: This note investigates a simple event-triggered scheduler based on the paradigm that a real-time scheduler could be regarded as a feedback controller that decides which task is executed at any given instant and shows how it leads to guaranteed performance thus relaxing the more traditional periodic execution requirements.
Abstract: In this note, we revisit the problem of scheduling stabilizing control tasks on embedded processors. We start from the paradigm that a real-time scheduler could be regarded as a feedback controller that decides which task is executed at any given instant. This controller has for objective guaranteeing that (control unrelated) software tasks meet their deadlines and that stabilizing control tasks asymptotically stabilize the plant. We investigate a simple event-triggered scheduler based on this feedback paradigm and show how it leads to guaranteed performance thus relaxing the more traditional periodic execution requirements.
3,695 citations
Book•
01 Jan 1970
2,565 citations
"Comparison of Riemann and Lebesque ..." refers background or methods in this paper
...The traditional way to design digital control systems is to sample the signals equidistant in time, see Åström and Wittenmark (1997). A nice feature of this approach is that analysis and design becomes very simple....
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...The output variance is then minimized by the minimum variance controller, see Åström (1970). The sampled system becomes x(t+ h) = x(t) + u(t) + e(t)...
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TL;DR: The controller updates considered here are event-driven, depending on the ratio of a certain measurement error with respect to the norm of a function of the state, and are applied to a first order agreement problem.
Abstract: Event-driven strategies for multi-agent systems are motivated by the future use of embedded microprocessors with limited resources that will gather information and actuate the individual agent controller updates. The controller updates considered here are event-driven, depending on the ratio of a certain measurement error with respect to the norm of a function of the state, and are applied to a first order agreement problem. A centralized formulation is considered first and then its distributed counterpart, in which agents require knowledge only of their neighbors' states for the controller implementation. The results are then extended to a self-triggered setup, where each agent computes its next update time at the previous one, without having to keep track of the state error that triggers the actuation between two consecutive update instants. The results are illustrated through simulation examples.
1,876 citations
Book•
01 Jan 1978
TL;DR: An electric dynamically operated storage element comprises two energy stores and circuitry is provided for applying periodically repeating phase clock pulses simultaneously to the energy stores through the charging circuits.
Abstract: An electric dynamically operated storage element comprises two energy stores. Each store has a charging circuit including a rectifying element and a discharging circuit including a controlled respectively variable resistance connected in series with the rectifying element. Also, circuitry is provided for applying periodically repeating phase clock pulses simultaneously to the energy stores through the charging circuits.
1,802 citations