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  • Distributed reactive power control methods to avoid voltage rise in grid-connected photovoltaic power generation systems

     Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª; Camacho Santiago, Antonio; Miret Tomas, Jaume; Castilla Fernandez, Miguel
    IEEE International Symposium on Industrial Electronics
    Presentation of work at congresses

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    A high density of grid-connected photovoltaic (PV) power generation systems is expected to occur in urban areas. The connection of distributed generation (DG) may cause serious problems in the distribution system such as voltage rise. Several voltage control strategies exist to avoid the over-voltage at the power grid. In particular, reactive power control methods have been proved to successfully bring DGs voltages within the admissible voltage range without reducing the production of active power. In addition, the possible use of communication infrastructure to link DGs opens up the development of new reactive power control methods where control actions at each DG may be decided using both local and global information. This paper presents a comparative study of existing and novel distributed reactive power control methods that have been designed exploiting the information exchange facility provided by a communication infrastructure.

    A high density of grid-connected photovoltaic (PV) power generation systems is expected to occur in urban areas. The connection of distributed generation (DG) may cause serious problems in the distribution system such as voltage rise. Several voltage control strategies exist to avoid the over-voltage at the power grid. In particular, reactive power control methods have been proved to successfully bring DGs voltages within the admissible voltage range without reducing the production of active power. In addition, the possible use of communication infrastructure to link DGs opens up the development of new reactive power control methods where control actions at each DG may be decided using both local and global information. This paper presents a comparative study of existing and novel distributed reactive power control methods that have been designed exploiting the information exchange facility provided by a communication infrastructure.

  • Mixing local and distributed reactive power control for balancing inverters¿ effort in grid-connected photovoltaic systems

     Velasco Garcia, Manuel; Marti Colom, Pau; Camacho Santiago, Antonio; Miret Tomas, Jaume; Castilla Fernandez, Miguel
    International Conference on Systems and Control
    Presentation's date: 2013-10-29
    Presentation of work at congresses

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  • On the use of communication infrastructure in distributed power generation: a preliminary case study

     Marti Colom, Pau; Velasco Garcia, Manuel; Castilla Fernandez, Miguel; Miret Tomas, Jaume; Camacho Santiago, Antonio
    IEEE International Conference on Emerging Technologies and Factory Automation
    Presentation's date: 2012-09-19
    Presentation of work at congresses

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    Penetration of distributed power generation poses new problems in energy distribution. For example, photovoltaic generation systems may difficult the voltage management in distribution lines and voltage rise may occur. To overcome this problem, several voltage control strategies are available and they can be classified as autonomous or distributed regarding whether communication is available between dispersed generators. Through a preliminary case study, this paper investigates the impact that the communication infrastructure has for a given distributed voltage control strategy. Communication issues like transmission rate, delays, and losses are analyzed with respect to the voltage control application performance.

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    Designing a practical course in networked control systems  Open access

     Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza, Jordi; Mares Marti, Pere; Marti Colom, Pau; Velasco Garcia, Manuel; Yepez, J.; Torres, Gina; Perelló, Miquel
    Jornadas de Tiempo Real
    Presentation's date: 2012-02-02
    Presentation of work at congresses

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    This paper presents a hands-on course in networked control systems (NCS) to be integrated in the education of embedded control systems engineers. The course activities have a strong practical component and most of them are applied exercises to be implemented in a NCS setup. The paper describes the experimental setup and then proposes several activities that can be shaped into a course program according to the needs and diverse background of the targeted audience.

  • Hands-on course in networked control systems

     Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Mares Marti, Pere; Marti Colom, Pau; Velasco Garcia, Manuel; Yepez, J.; Torres Guerrero, Gina; Perello, M.
    Mediterranean Conference on Control and Automation
    Presentation's date: 2012
    Presentation of work at congresses

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    In many industrial robotic applications there is a need to track periodic reference signals and/or reject periodic disturbances. This paper presents a novel repetitive control design for systems with constant time-delays in both forward and feedback control channels. An additional delay is introduced together with plant delays to construct an internal model for periodic signals, and a simple proportional control is utilized to stabilize the closed-loop system. Sufficient stability conditions of the closed-loop system and the robustness analysis under modeling uncertainties are studied. Experimental results are included to evaluate the validity and effectiveness of the proposed method.

  • Resource and performance trade-offs in real-time embedded control systems

     Lozoya Gámez, Rafael Camilo; Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª; Martin Rull, Enric Xavier
    Real-time systems
    Date of publication: 2012-12-28
    Journal article

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    Design of a hands-on course in networked control systems  Open access

     Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza, Jordi; Mares Marti, Pere; Marti Colom, Pau; Velasco Garcia, Manuel; Yepez, J.; Torres Guerrero, Gina
    Date: 2012-01-17
    Report

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    This report presents a hands-on course in networked control systems (NCS) to be integrated in the education of embedded control systems engineers. The course activities have a strong practical component and most of them are ap- plied exercises to be implemented in a NCS setup. The report containts four parts: a) a report that describes the experimental setup, proposing several activities that can be shaped into a course program according to the needs and diverse background of the targeted audience, b) a tentative program ex- ample for master students, c) a user manual to help setting up the hardware and software from a Live CD, and d) a quick guide to start working with the programming environment.

  • Performance evaluation framework (PEF) for real-time embedded control systems

     Lozoya Gámez, Rafael Camilo; Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    Date: 2012-03-14
    Report

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    This report presents a performance evaluation framework (PEF) designed to simulate and implement diverse theoretical results on control and resource performance optimization that has recently appeared in the literature

  • Lowering traffic without sacrificing performance in networked control systems

     Marti Colom, Pau; Velasco Garcia, Manuel; Yepez Castillo, Jose Gregorio; Martin Rull, Enric Xavier
    IEEE International Conference on Emerging Technologies and Factory Automation
    Presentation's date: 2011-09-06
    Presentation of work at congresses

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    In Networked Control Systems (NCS), the amount of control data exchanged between sensors, controllers and actuators nodes highly depends on the control performance specifications given to each networked control loop. The periodic execution of each loop helps meeting the control specifications while imposing a static network traffic. This paper presents an alternative execution mechanism for each networked control loop that permits to dynamically lower the traffic while ensuring the same or better control performance than the achieved by the periodic case. Simulation results illustrate the theoretical analysis.

  • Qualitative analysis of a one-step finite-horizon boundary for event-driven controllers

     Velasco Garcia, Manuel; Marti Colom, Pau; Yepez Castillo, Jose Gregorio; Ruiz Vegas, Francisco Javier; Fuertes Armengol, José Mª; Bini, Enrico
    IEEE Conference on Decision and Control and European Control Conference
    Presentation's date: 2011-12-13
    Presentation of work at congresses

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    Performance optimization for networked and embedded control systems refers to the ability of minimizing controllers’ resource utilization and/or improving control performance. Event-driven control has been shown to be a promising technique for minimizing controllers’ computational demands. However, optimization of control performance for event-driven control has not been fully addressed. For LTI plants, this paper presents a boundary for event-driven controllers that determines at each job execution when the next job execution should occur in order to minimize a continuous-time quadratic cost function while minimizing controllers’ computational demand. Simulation results illustrate the qualitative shape of this boundary.

  • Lab Proposal for Integrated Real-Time and Control

     Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Mares Marti, Pere; Marti Colom, Pau; Velasco Garcia, Manuel; Yepez Castillo, Jose Gregorio; Camacho, Antonio
    Jornadas de Tiempo Real
    Presentation's date: 2011-02-04
    Presentation of work at congresses

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    One-step finite horizon boundary with varying control gain for event-driven networked control systems  Open access

     Yepez Castillo, Jose Gregorio; Velasco Garcia, Manuel; Marti Colom, Pau; Martin Rull, Enric Xavier; Fuertes Armengol, José Mª
    Annual Conference of the IEEE Industrial Electronics Society
    Presentation's date: 2011-11-09
    Presentation of work at congresses

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    Recent research has shown that event-driven control requires less samples than time-driven (periodic) control. Consequently, event-driven control applied to Networked Control Systems (NCS) is a good approach for alleviating controllers bandwidth demands and reducing overall network traffic. Following this trend, this paper presents an execution rule for event-driven networked controllers that at each job execution aims at postponing the next job execution while applying an appropriated controller gain considering each varying sampling interval that applies at run time. This method permits to dynamically lower the generated traffic for each networked control loop while ensuring the same or better control performance than the achieved by the periodic case. In addition, an implementation strategy capable of dealing with network induced time delays is also presented. Simulation results illustrate the operation and benefits of the presented approach.

    Postprint (author’s final draft)

  • Networked sliding mode control of the double integrator system using the event-driven self-triggered approach

     Marti Colom, Pau; Velasco Garcia, Manuel; Camacho Santiago, Antonio; Martin Rull, Enric Xavier; Fuertes Armengol, José Mª
    IEEE International Symposium on Industrial Electronics
    Presentation's date: 2011-06-28
    Presentation of work at congresses

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    Sliding mode control (SMC) methods rely on applying a high-frequency switching control. In networked control systems (NCS), high-frequency operations/transactions are not desirable because communication bandwidth consumption increases dramatically. This paper studies the application of event-driven self-triggered techniques to sliding mode control over networks as a means for reducing the bandwidth utilization. To this end, sliding mode control with hysteresis is adopted and control updates are forced to only occur at the hysteresis band boundary. This paper elaborates on the conditions that must be fulfilled in order to ensure such operation for the case of the double integrator system. Simulation results illustrate the presented concepts.

  • Optimal online sampling period assignment: theory and experiments

     Cervin, Anton; Velasco Garcia, Manuel; Marti Colom, Pau; Camacho Santiago, Antonio
    IEEE transactions on control systems technology
    Date of publication: 2011-07
    Journal article

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  • Resource and performance trade-offs in real-time embedded control systems  Open access

     Lozoya Gámez, Rafael Camilo
    Defense's date: 2011-07-19
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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    The use of computer controlled systems has increased dramatically in our daily life. Microprocessors are embedded in most of the daily- used devices. Due to cost constraints, many of these devices that run control applications are designed under processing power, space, weight, and energy constraints, i.e., with limited resources. Moreover, the embedded control systems market demands new capabilities to these devices or improvements in the existing ones without increasing the resource demands. Enabling devices with real-time technology is a promising step toward achieving cost-effective embedded control systems. Recent results of real-time systems theory provide methods and policies for an efficient use of the computational resources. At the same time, control systems theory is starting to offer controllers with varying computational load. By combining both disciplines, it is theoretically feasible to design resource-constrained embedded control systems capable of trading-off control performance and resource utilization. This thesis focuses on the practical feasibility of this new generation of embedded control systems. To this extend, two issues are addressed: 1) the effective implementation of control loops using real-time technology and 2) the evaluation of resource/performance- aware policies that can be applied to a set of control loops that concurrently execute on a microprocessor. A control task generally consists of three main activities: input, control algorithm computation, and output. The timing of the input and output actions is critical to the performance of the controller. The implementation of these operations can be conducted within the real- time task body or using hardware functions. The former introduces considerable amounts of jitters while the latter forces delays. This thesis presents a novel task model as a computational abstraction for implementing control loops that is shown to remove the endemic problems caused by jitters and delays. This model is synchronized at the output instants rather than at the input instants. This has been shown to provide interesting properties. From the scheduling point of view, the new task model can be seamlessly integrated into existing scheduling theory and practice, while improving task set schedulability. From a control perspective, the task model absorbs jitters because it allows irregular sampling by incorporating predictors, and improves reactiveness in front of perturbations. In addition, Kalman techniques have been also investigated to deal with the case of noisy measurements. The effective implementation of simple control algorithms making use of this new task model does not guarantee the feasibility of implementing state-of-the-art resource/performance-aware policies. These policies, which can be roughly divided into feedback scheduling and event-driven control, have been mainly treated from a theoretical point of view while practical aspects have been omitted. Conversely to the initial problem targeted by these policies, that is, to minimize or keep resource requirements to meet the tight cost constraints related with mass production and strong industrial competition, research advances seem to require sophisticated procedures that may impair a cost-effective implementation. This thesis presents a performance evaluation framework that permits to assess these policies in terms of the potential benefits offered by the theory as well as the pay-off in terms of complexity and overhead. The framework design is the result of a taxonomical analysis of the related state-of-the-art. Among other specifications, the framework, which is composed by a simulation and an experimental platform, supports both event/time triggered paradigms, allows different sort of control and optimization algorithms, and flexibly evaluates control performance and resource utilization.

    El uso de sistemas controlados por computadora ha incrementado dramáticamente en nuestra vida cotidiana. En la mayor parte de los dispositivos que usamos diariamente encontramos microprocesadores. Debido a restricciones de coste muchos de estos dispositivos ejecutan aplicaciones de control diseñadas bajo restricciones de potencia, espacio, peso y energía, esto es, con recursos limitados. Además, el mercado de sistemas de control embebido demanda nuevas capacidades a estos dispositivos o mejoras en los dispositivos ya existentes sin incrementar las demandas de recursos. Incluir en estos dispositivos tecnología de tiempo real es un prometedor paso para conseguir sistemas de control embebido de bajo coste. Resultados recientes en sistemas de tiempo real proporcionan métodos y políticas para un uso eficiente de los recursos. Al mismo tiempo, los sistemas de control empiezan a ofrecer controladores con carga computacional variable. Al combinar estas dos disciplinas, es teóricamente posible diseñar sistemas de control embebido con recursos restringidos capaces de balancear el rendimiento de control y la utilización de recursos. El objetivo de esta tesis es determinar la viabilidad de la implementación práctica de esta nueva generación de sistemas de control embebidos. En este sentido, dos problemas principales son abordados: 1) la efectiva implementación de lazos de control usando tecnología de tiempo real, y 2) la evaluación de políticas de mejoras en recursos y rendimiento que pueden ser aplicados a un conjunto de lazos de control que se ejecutan concurrentemente en un microprocesador. Una tarea de control consiste generalmente en tres actividades principales: entrada, cómputo del algoritmo de control y salida. El tiempo en el que se ejecutan las acciones de entrada y salida es crítico con respecto al rendimiento del controlador. La implementación de estas operaciones puede ser ejecutada dentro del cuerpo de la tarea de tiempo real o a través de funciones hardware como interrupciones. La primera opción introduce una considerable cantidad de jitters (variaciones), mientras que la segunda introduce retardos. Esta tesis presenta un nuevo modelo de tareaspara la implementación de lazos de control que es capaz de eliminar los problemas endémicos causados por los jitters y los retardos. En este modelo la sincronización se realiza en los instantes de salida, en lugar de los instantes de entrada. Esto ha demostrado tener propiedades interesantes. Desde el punto de vista de planificación de tareas, el nuevo modelo puede ser integrado en forma directa a la teoría y práctica de planificación de tareas, mejorando la capacidad de planificación. Desde una perspectiva de control, el modelo de tareas absorbe los jitters al permitir muestreos irregulares mediante el uso de predictores, y además mejora la capacidad de reacción del sistema frente a perturbaciones. Adicionalmente, técnicas basadas en filtros de Kalman han sido también investigadas para tratar situaciones en que se tengan mediciones con ruido. La efectiva implementación de algoritmos simples de control haciendo uso de este nuevo modelo de tarea no garantiza la factibilidad de implementar políticas más avanzadas, aparecidas recientemente en el estado del arte, para mejorar el rendimiento del control y el uso eficiente de recursos. Estas políticas, que pueden ser divididas en planificación con retroalimentación (feedback scheduling) y control guiado por eventos (event-driven control), han sido principalmente abordadas desde una perspectiva teórica mientras los aspectos prácticos usualmente son omitidos. Contrariamente al problema inicial al que se enfocan estas políticas, que es minimizar o mantener los requerimientos de uso de recursos para lograr las restricciones de coste debidas a la producción en masa y a la fuerte competencia industrial, los avances en las investigaciones parecen requerir procedimientos sofisticados que van en detrimento de una implementación de bajo coste. Esta tesis presenta una plataforma de evaluación de rendimiento que permite valorar estas políticas en términos de los beneficios potenciales ofrecidos por la teoría, además de valorar los costes en términos de complejidad y uso adicional de recursos. El diseño de la plataforma es el resultado de un análisis taxonómico de distintos métodos que forman parte del estado del arte. Entre otras especificaciones, la plataforma, que está compuesta por una plataforma de simulación y una experimental, soporta tanto los paradigmas basados en tiempo como los basados en eventos, permite la implementación de distintos algoritmos de optimización y control, y es capaz de evaluar tanto el rendimiento de control como el uso de recursos.

  • Sistemas de control empotrados y en red guiados por eventos

     Villa Millaruelo, Ricardo; Griful Ponsati, Eulalia; Ayza Graells, Jordi; Marti Colom, Pau; Yepez Castillo, Jose Gregorio; Lozoya, Camilo; Guardia Oliveras, Josep; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    Participation in a competitive project

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    Self-triggered networked control systems: an experimental case study  Open access

     Camacho Santiago, Antonio; Marti Colom, Pau; Velasco Garcia, Manuel; Lozoya, Camilo; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª; Griful Ponsati, Eulalia
    IEEE International Conference on Industrial Technology
    Presentation's date: 2010-03-14
    Presentation of work at congresses

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    A self-triggered controller is characterized, in general, by a non-periodic sequence of job activations. And each job execution, apart from performing sampling, control algorithm computation and actuation, calculates the next job activation time as a function of the plant state. This paper describes the implementation of self-triggered controllers in networked control systems (NCS). The implementation corroborates that self-triggered control can be used for minimizing bandwidth utilization while providing similar control performance than periodic controllers.

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    Minimizing control cost in resource-constrained control systems: from Feedback scheduling to event-driven control  Open access

     Lozoya, Camilo; Marti Colom, Pau; Velasco Garcia, Manuel
    Mediterranean Conference on Control and Automation
    Presentation's date: 2010-06-23
    Presentation of work at congresses

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    This paper evaluates approaches aimed at minimizing aggregated control cost of a set of controllers that concurrently execute sharing limited computing resources. The evaluation focuses on feedback scheduling and event-driven control methods. The performance results drive the analysis to explore self-triggered controllers in the context of minimizing control cost when given a fixed amount of computing resources. This leads to the formulation of an optimization problem, that for given example, is numerically solved. The solution helps understanding the behavior of self-triggered controllers.

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    Embedding Kalman techniques in the one-shot task model when non-uniform samples are corrupted by noise  Open access

     Lozoya, Camilo; Romero, Julio; Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    Mediterranean Conference on Control and Automation
    Presentation's date: 2010-06-23
    Presentation of work at congresses

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    The performance of several closed-loop systems whose controllers concurrently execute in a multitasking realtime system may be deteriorated due to timing uncertainties in tasks´executions, problem known as scheduling jitters. Recently, the one-shot task model, that combines irregular sampling, a predictor observer, and strictly periodic actuation, was presented in order to remove the negative effects of jitters. However, its successful application required noise-free samples. In this paper we extend the one-shot task model to the case of noisy measurements. In particular, we embed a Kalman filter into the model taking into account that the available measurements are not periodic. This poses the problem of adapting the standard discrete-time Kalman filter to the case under study, and decide when to apply the prediction and the correction phase. Two different strategies are presented, and their control performance and computation demand are analyzed through real experiments.

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    Invariant manifolds as boundaries for event-driven control systems  Open access

     Velasco Garcia, Manuel; Marti Colom, Pau
    International Conference on Hybrid Systems: Computation and Control
    Presentation's date: 2010-04-13
    Presentation of work at congresses

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    In event-driven control approaches, control updates are triggered by event conditions that are often characterized by different types of boundaries defined in the state-space domain. In this paper we define an event-driven control approach where boundaries are manifolds characterized as invariant sets. With such a boundary, a control update will only be activated when the system trajectory intersects the boundary. And the system trajectory must intersect again the boundary to activate the next control update. For linear systems, we derive an scaling property for these boundaries that permit to regulate the accuracy of the control without altering the timing offered by the scaled boundary.

    Postprint (author’s final draft)

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    Efficient utilization of bus idle times in CAN-based networked control systems  Open access

     Marti Colom, Pau; Camacho Santiago, Antonio; Velasco Garcia, Manuel; El Mongi Ben Gaid, Mohamed
    IFAC Workshop on Distributed Estimation and Control in Networked Systems
    Presentation's date: 2010-09-13
    Presentation of work at congresses

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    This paper presents a novel approach to networked control systems (NCS) analysis and design that provides increased control performance for a set of control loops that exchange control data over the Controller Area Network (CAN). This is achieved by enabling the following functionality for each control loop: first, standard periodic messaging is guaranteed to ensure stability, and second, non-periodic additional messaging is added whenever the bus is idle in such a way that the aggregated control performance for all control loops is improved. The proposed approach, named Maximum Difference (MD) policy, is computable in a distributed manner, and is practically feasible (computationally efficient and CAN-implementable). We theoretically prove that the MD policy behaves better than static strategies. Simulation results complement the theoretical derivations and show that the MD policy outperforms static, random and Largest Error First policies.

    Postprint (author’s final draft)

  • Synchronizing sampling and actuation in the absence of global time in networked control systems

     Marti Colom, Pau; Camacho Santiago, Antonio; Velasco Garcia, Manuel; Mares Marti, Pere; Fuertes Armengol, José Mª
    IEEE International Conference on Emerging Technologies and Factory Automation
    Presentation's date: 2010-10-15
    Presentation of work at congresses

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    The successful operation of Networked Control Sys- tems (NCS) requires employing appropriate approaches for dealing with network induced time delays, i.e. time intervals elapsed from consecutive sampling and actua- tion operations. Effective approaches often require to im- pose periodic execution for the sampling and/or actuation operations, enforcing synchronized constant time delays. And considering that sampling and actuation is performed in different nodes, global time between nodes achieved by clock synchronization is the standard assumption or strat- egy that enables such synchronized operations. This pa- per presents a technique that permits to implement these synchronized operations in NCS in the absence of global time. Experimental results corroborate the effectiveness of the presented approach.

  • SimpleRTK: Minimal Real-Time Kernel for Time/Event-Driven Control Applications

     Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Marti Colom, Pau; Velasco Garcia, Manuel; Yepez Castillo, Jose Gregorio; Lozoya, Camilo; Camacho Santiago, Antonio; García, Daniel
    Jornadas de Tiempo Real
    Presentation's date: 2010-02-05
    Presentation of work at congresses

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  • Achieving periodic execution of networked control systems in the absence of global time

     Marti Colom, Pau; Velasco Garcia, Manuel; Camacho Santiago, Antonio; Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Yepez Castillo, Jose Gregorio; Lozoya, Camilo; Griful Ponsati, Eulalia
    Simposio en Ingeniería de Sistemas y Automática en Bioingeniería
    Presentation's date: 2010-09-09
    Presentation of work at congresses

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  • Experimental evaluation of slack management in real-time control systems: Coordinated vs. self-triggered approach

     Velasco Garcia, Manuel; Marti Colom, Pau; Fuertes Armengol, José Mª; Lozoya Gamez, Camilo; Brandt, S A
    Journal of systems architecture
    Date of publication: 2010-01
    Journal article

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    Design of an embedded control system laboratory experiment  Open access

     Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª; Camacho Santiago, Antonio; Buttazzo, Giorgio
    IEEE transactions on industrial electronics
    Date of publication: 2010-02-08
    Journal article

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    This paper presents a prototype laboratory experiment to be integrated in the education of embedded control system engineers. The experiment, a real-time control of a dynamical system, is designed to drive students to a deeper understanding and integration of the diverse theoretical concepts that often come from different disciplines such as real-time systems and control systems. Rather than proposing the experiment for a particular course within an embedded system engineering curriculum, this paper describes how the experiment can be tailored to the needs and diverse background of both undergraduate and graduate students education.

  • Simulation study of a remote wireless path tracking control with delay estimation for an autonomous guided vehicle

     Lozoya, Camilo; Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª; Martin Rull, Enric Xavier
    International journal of advanced manufacturing technology
    Date of publication: 2010-06-05
    Journal article

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    Industrial applications involving mobile systems can benefit from the use of wireless technology. However, wireless communication has not been widely accepted on the factory floor due to its difficulty in achieving the timely and reliable transmission of messages over error-prone wireless channels. This paper presents an autonomous guided vehicle (AGV) path tracking wireless control system where an accurate delay estimation scheme is shown to be the key for successful operation. The control architecture consists on an AGV connected through a wireless network to a controller. To mitigate the negative effects that varying time delays in data transfer have in the networked control loop, the controller performs two tasks at each loop operation. First, it uses a Kalman filter to produce an optimal delay estimate considering a simple stochastic model of the wireless delay dynamics. Second, each delay estimate is employed to infer the real AGV position which permits to compute the appropriate control commands. Results show that the proposed technique provides more efficient and effective operation for path tracking control compared to similar previously proposed solutions.

  • Runtime Allocation of Optional Control Jobs to a Set of CAN-Based Networked Control Systems

     Marti Colom, Pau; Camacho Santiago, Antonio; Velasco Garcia, Manuel; El Mongi Ben Gaid, Mohamed
    IEEE transactions on industrial informatics
    Date of publication: 2010-09-23
    Journal article

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  • Design of an embedded control system laboratory experiment

     Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª; Camacho Santiago, Antonio; Buttazzo, Giorgio
    IEEE transactions on industrial electronics
    Date of publication: 2010-10-01
    Journal article

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    This paper presents a prototype laboratory experiment to be integrated in the education of embedded control system engineers. The experiment, a real-time control of a dynamical system, is designed to drive students to a deeper understanding and integration of the diverse theoretical concepts that often come from different disciplines such as real-time systems and control systems. Rather than proposing the experiment for a particular course within an embedded system engineering curriculum, this paper describes how the experiment can be tailored to the needs and diverse background of both undergraduate and graduate students education.

  • Draco: Efficient Resource Management for Resource-Constrained Control Tasks

     Marti Colom, Pau; Caixue, L; Brandt, Sa; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    IEEE transactions on computers
    Date of publication: 2009-01
    Journal article

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  • Schedulability analysis for CAN-based networked control systems with dynamic bandwidth management

     Velasco Garcia, Manuel; Marti Colom, Pau; Yepez Castillo, Jose Gregorio; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª
    IEEE International Conference on Emerging Technologies and Factory Automation
    Presentation's date: 2009-09-22
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    This paper presents the schedulability analysis for control messages when networked control loops, built on top of the controller area network (CAN), are dynamically allocating bandwidth in terms of their controlled plants' dynamics. The bandwidth allocation policy is theoretically described by an optimization problem and practically solved by the distributed bitwise arbitration of CAN messages when message identifiers, i.e., priorities, reflect control applications demands. This poses the problem of assessing whether the set of real-time messages will meet their deadlines regardless of run-time priority changes. This is solved by a schedulability analysis based on recent results on worst-case response time techniques for real-time CAN applications. The analysis ends up with the schedulability test for this type of applications.

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    Preliminary approach to Lyapunov sampling in CAN-based networked control systems  Open access

     Yepez Castillo, Jose Gregorio; Lozoya, Camilo; Velasco Garcia, Manuel; Marti Colom, Pau; Fuertes Armengol, José Mª
    Annual Conference of the IEEE Industrial Electronics Society
    Presentation's date: 2009-11-03
    Presentation of work at congresses

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    This paper presents a preliminary approach to networked control systems (NCS) that relies on an event-driven control method based on Lyapunov sampling. The goal is to study and develop approaches for NCS capable of offering controllers with low bandwidth demands. The paper starts by presenting the theoretical framework required for applying Lyapunov sampling to a set of closed-loop systems that share a serial bus line. The discussion permits identifying which requirements must be fulfilled in order to guarantee overall stability. In addition, the feasibility of the theoretical framework in terms of implementation requires to address problems caused by the implicit distributed architecture of the NCS. In particular, an efficient implementation approach is described for the CAN network. Simulation results illustrate the operation and benefits of the presented approach.

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    On Lyapunov sampling for event-driven controllers  Open access

     Velasco Garcia, Manuel; Marti Colom, Pau; Bini, Enrico
    IEEE Conference on Decision and Control and Chinese Control Conference
    Presentation's date: 2009-12-17
    Presentation of work at congresses

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    This paper investigates an event condition for event-driven controllers based on Lyapunov functions. Considering that constant values of a Lyapunov function define contour curves that form closed regions around the equilibrium point, in this paper we present a sampling mechanism that enforces job executions (sampling, control algorithm computation and actuation) each time the system trajectory reaches a given contour curve. By construction, the sequence of generated samples is stable in the discrete Lyapunov sense. However, in order to ensure that the system trajectory will tend to zero as time tends to infinity, it must be ensured that the sequence of samples is infinite. We provide conditions to ensure this property. The approach is illustrated by simulated examples.

  • Implementation of event-driven control systems: a real-time systems engineering approach

     Camacho Santiago, Antonio; Marti Colom, Pau; Velasco Garcia, Manuel; Yepez Castillo, Jose Gregorio; Lozoya, Camilo; Ayza Graells, Jordi; Fuertes Armengol, José Mª
    Jornadas de Tiempo Real
    Presentation's date: 2009-02-05
    Presentation of work at congresses

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  • Sistemas de control en red basados en eventos: estudio preliminar al muestreo disparado por funciones de Lyapunov

     Yepez Castillo, Jose Gregorio; Velasco Garcia, Manuel; Marti Colom, Pau; Camacho Santiago, Antonio; Ayza Graells, Jordi; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª
    Jornadas de Automática
    Presentation's date: 2009-09-03
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  • Equilibrium sampling interval sequences for event-driven controllers

     Velasco Garcia, Manuel; Marti Colom, Pau; Bini, Enrico
    European Control Conference
    Presentation's date: 2009-08-24
    Presentation of work at congresses

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    Standard discrete-time control laws consider periodic execution of control jobs. Although this assumption simplifies the control design and the resource utilization analysis for later implementation, it leads to a conservative usage of computing resources. On the contrary, event-driven control offers controllers with a tighter resource utilization. However, job executions are no longer periodic, and predicting their computing requirements is crucial for efficient implementation in severely limited computing systems. Sampling intervals for event-driven control systems show different patterns, ranging from chaotic behaviors to periodic oscillatory patterns, named equilibrium sampling interval sequences (ESIS). Focusing on resource demands predictability, in this paper we identify the conditions for event-driven controllers to exhibit ESIS, and provide methods to characterize and compute them. Finally, we study the transitions from ESIS to chaotic sampling. Simulated experiments illustrate the paper contributions.

  • The Optimal Boundary and Regulator Design Problem for Event-Driven Controllers

     Marti Colom, Pau; Velasco Garcia, Manuel; Bini, E
    Lecture notes in computer science
    Date of publication: 2009-01
    Journal article

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  • Proposal for an embedded control systems laboratory activity

     Marti Colom, Pau; Velasco Garcia, Manuel; Lozoya, C; Ayza Graells, Jordi; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª
    Jornadas de Automática
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  • Taxonomy on Prior Work on Sampling Period Selection for Resource-Constrained Real-Time Control Systems

     Camilo, Lozoya; Velasco Garcia, Manuel; Marti Colom, Pau; Yépez, José; Frederic, Pérez; Guàrdia, Josep; Ayza Graells, Jordi; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª
    XI Jornadas de Tiempo Real
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  • A Taxonomy on Prior Work on Sampling Period Selection for Resource-Constrained Real-Time Control Systems

     Camilo, Lozoya; Velasco Garcia, Manuel; Marti Colom, Pau; Yepez Castillo, Jose Gregorio; Frederic, Pérez; Guàrdia, Josep; Ayza Graells, Jordi; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª
    XI Jornadas de Tiempo Real
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  • Clock Synchronization for Networked Control Systems Using Low-Cost Microcontrollers

     Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    Date: 2008-04
    Report

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  • Schedulability Analysis for CAN-based Control Applications with Dynamic Bandwidth Management

     Velasco Garcia, Manuel; Marti Colom, Pau; Fuertes Armengol, José Mª
    Date: 2008-11
    Report

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  • An Embedded Real-Time Control Systems Laboratory Activity

     Marti Colom, Pau; Velasco Garcia, Manuel; Buttazzo, and Giorgio
    Date: 2008-08
    Report

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  • Analysis and Design of Networked Control Loops with Synchronization at the Actuation Instants

     Lozoya Gamez, Camilo; Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    Annual Conference of the IEEE Industrial Electronics Society
    Presentation's date: 2008-11-12
    Presentation of work at congresses

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  • Control Performance Evaluation of Selected Methods of Feedback Scheduling of Real-time Control Tasks

     Camilo, Lozoya; Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª
    World Congress of the International Federation of Automatic Control
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  • On the Timing of Discrete Events in Event-Driven Control Systems

     Velasco Garcia, Manuel; Marti Colom, Pau; Lozoya Gamez, Camilo
    11th International Conference on Hybrid Systems: Computation and Control
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  • Control-driven Tasks: Modeling and Analysis

     Velasco Garcia, Manuel; Marti Colom, Pau; Enrico, Bini
    29th IEEE Real-Time Systems Symposium
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    On the timing of discrete events in event-driven control systems  Open access

     Velasco Garcia, Manuel; Marti Colom, Pau; Lozoya, Camilo
    Lecture notes in computer science
    Date of publication: 2008-04-01
    Journal article

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    This paper presents an analysis method to determine offline at what intervals have to be taken the samples for various types of event- driven control systems.

    Postprint (author’s final draft)

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    Performing flexible control on low cost microcontrollers using a minimal real-time kernel  Open access

     Marau, Ricardo; Leite, Paulo; Velasco Garcia, Manuel; Marti Colom, Pau; Almeida, Luis; Pedreiras, Paulo; Fuertes Armengol, José Mª
    IEEE transactions on industrial informatics
    Date of publication: 2008-05-01
    Journal article

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    In recent years, approaches to control performance and resource optimization for embedded control systems have been receiving increased attention. Most of them focus on theory, whereas practical aspects are omitted. Theoretical advances demand flexible real-time kernel support for multitasking and preemption, thus requiring more sophisticated and expensive software/ hardware solutions. On the other hand, embedded control systems often have cost constraints related with mass production and strong industrial competition, thus demanding low-cost solutions. In this paper, it is shown that these conflicting demands can be softened and that a compromise solution can be reached. We advocate that recent research results on optimal resource management for control tasks can be implemented on simple multitasking preemptive real-time kernels targeting low-cost microprocessors, which can be easily built in-house and tailored to actual application needs. The experimental evaluation shows that significant control performance improvement can be achieved without increasing hardware costs.

  • One-shot task model for implementing real-time control tasks

     Marti Colom, Pau; Velasco Garcia, Manuel; Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Yépez, J; Lozoya, C
    II Congreso Español de Informática
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