Análisis de Perturbaciones de Sistemas de Tiempo Real en Aplicaciones de Control

Este proyecto plantea el desarrollo de técnicas y mecanismos de planificación de tiempo real flexibles, que permitan, de acuerdo a las condiciones de trabajo de una aplicación en determinado instante, modificar las características de tiempo real del sistema. Principalmente se abarcará la utilización de sistemas de tiempo real en aplicaciones de control y procesamiento de señales.Eje: Procesamiento de Señales y Sistemas en Tiempo RealRed de Universidades con Carreras en Informática (RedUNCI

Jitter Evaluation of Real-Time Control Systems

The implementation of industrial control applications typically introduces complexities like sampling jitter and control jitter, which have usually not been considered at the design stage. Consequently, the system behaves in a non-periodic manner and the real performance is degraded with regard to the expected response. This paper proposes a hybrid task model to reduce the impact of the scheduling on control performance. For a large batch of typical plants, we analyze how sensitive a control system is to jitter when the sampling rate is slow or fast compared to the bandwidth of the system

Combining Time-Triggered Plans with Priority Scheduled Task Sets

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-39083-3_13Time-triggered and concurrent priority-based scheduling are the two major approaches in use for real-time and embedded systems. Both approaches have their own advantages and drawbacks. On the one hand, priority-based systems facilitate separation of concerns between functional and timing requirements by relying on an underlying real- time operating system that takes all scheduling decisions at run time. But this is at the cost of indeterminism in the exact timing pattern of execution of activities, namely variable release jitter. On the other hand, time-triggered schedules are more intricate to design since all schedul- ing decisions must be taken beforehand in the design phase, but their advantage is determinism and more chances for minimisation of release jitter. In this paper we propose a software architecture that enables the combined and controlled execution of time-triggered plans and priority- scheduled tasks. We also describe the implementation of an Ada library supporting it. Our aim is to take advantage of the best of both ap- proaches by providing jitter-controlled execution of time-triggered tasks (e.g., control tasks), coexisting with a set of priority-scheduled tasks, with less demanding jitter requirements.This work has been partly supported by the Spanish Government’s project M2C2 (TIN2014-56158-C4-1-P-AR) and the European Commission’s project EMC2 (ARTEMIS-JU Call 2013 AIPP-5, Contract 621429).Real Sáez, JV.; Sáez Barona, S.; Crespo, A. (2016). Combining Time-Triggered Plans with Priority Scheduled Task Sets. En Reliable Software Technologies – Ada-Europe 2016. Springer. 195-212. https://doi.org/10.1007/978-3-319-39083-3_13S195212Liu, C., Layland, J.: Scheduling algorithms for multiprogramming in a hard real-time environment. J. ACM 20(1), 46–61 (1973)Martí, P., Fuertes, J., Fohler, G.: Jitter compensation for real-time control systems. In: Real-Time Systems Symposium (2001)Dobrin, R.: Combining off-line schedule construction and fixed priority scheduling in real-time computer systems. Ph.D. thesis. Mälardalen University (2005)Cervin, A.: Integrated control and real-time scheduling. Ph.D. thesis. Lund Institute of Technology, April 2003Balbastre, P., Ripoll, I., Vidal, J., Crespo, A.: A task model to reduce control delays. Real-Time Syst. 27(3), 215–236 (2004)Hong, S., Hu, X., Lemmon, M.: Reducing delay jitter of real-time control tasks through adaptive deadline adjustments. In: 22nd Euromicro Conference on Real-Time Systems - ECRTS, pp. 229–238. IEEE Computer Society (2010)ISO/IEC-JTC1-SC22-WG9: Ada Reference Manual ISO/IEC 8652:2012(E) (2012). http://www.ada-europe.org/manuals/LRM-2012.pdfBaker, T.P., Shaw, A.: The cyclic executive model and Ada. In: Proceedings IEEE Real Time Systems Symposium 1988, Huntsville, Alabama, pp. 120–129 (1988)Liu, J.W.S.: Real-Time Systems. Prentice-Hall Inc., Upper Saddle River (2000)Pont, M.J.: The Engineering of Reliable Embedded Systems: LPC1769. SafeTTy Systems Limited, Skelmersdale (2014). ISBN: 978-0-9930355-0-0Aldea Rivas, M., González Harbour, M.: MaRTE OS: an Ada kernel for real-time embedded applications. In: Strohmeier, A., Craeynest, D. (eds.) Ada-Europe 2001. LNCS, vol. 2043, pp. 305–316. Springer, Heidelberg (2001)Palencia, J., González-Harbour, M.: Schedulability analysis for tasks with static and dynamic offsets. In: 9th IEEE Real-Time Systems Symposium (1998)Wellings, A.J., Burns, A.: A framework for real-time utilities for Ada 2005. Ada Lett. XXVI XXVII(2), 41–47 (2007)Real, J., Crespo, A.: Incorporating operating modes to an Ada real-time framework. Ada Lett. 30(1), 73–85 (2010)Sáez, S., Terrasa, S., Crespo, A.: A real-time framework for multiprocessor platforms using Ada 2012. In: Romanovsky, A., Vardanega, T. (eds.) Ada-Europe 2011. LNCS, vol. 6652, pp. 46–60. Springer, Heidelberg (2011

A Quality-of-Service (QoS) based approach for the communication support in network-based control systems: an on-going project

Due to the increased availability of low cost network technology, the implementation ofNetwork-based Control Systems (NCS) is becoming widely accepted. Current NCS areusually supported by small-dedicated communication networks (known as fieldbusnetworks) operating in access-controlled mediums, which are able to guarantee thedelivery of control data within known and bounded delays.It is however foreseeable that, access-uncontrolled networks (such as packet-basednetworks) will play an important role in future NCS. In this paper, we present an ongoingproject, proposing the use of a QoS architecture to implement NCS built uponshared networks with uncontrolled access, i.e., considering communication environmentssubject to unknown disturbances.Within this project, several QoS architectures for packet-based networks are looked atcarefully, such as the IntServ and the DiffServ architectures and the Multi-ProtocolLabel Switching (MPLS) and the Constraint Based Routing strategies. Such multipleQoS architectures will be evaluated through the use of an experimental platform enablingthe implementation and evaluation of network-based control systems

The Continuous Stream Model of Computation for Real-Time Control

This paper presents a new Model of Computation (MoC) for real-time tasks used in control systems. This new model, named continuous stream task model, relaxes some of the constraints imposed by the traditional hard and soft real-time task models. A key advantage of the model is the possibility to easily analyse the probabilistic evolution of the delays. This leads to an easy formalisation of necessary and sufficient conditions for the stochastic stability of the closed loop system producing considerable savings in the amount of CPU bandwidth required to stabilise the system. This fact is confirmed by an extensive set of simulations. © 2013 IEEE

Algoritmo para disminución de degradación del rendimiento en sistemas de control con actuación periódica

Diseñar un algoritmo para disminución de degradación del rendimiento en sistemas de control considerando actuación periódicaLos sistemas de control modernos son implementados en sistemas microprocesados que se desempeñan en tiempo real, ejecutando simultáneamente múltiples tareas. Esto provoca que el rendimiento de la acción de control pueda verse deteriorado por problemas conocidos como: Retardos en los tiempos de muestreo/actuación, latencias de entrada/salida y la incertidumbre provocada por el ruido en el sistema. Como resultado, la acción de control es propensa a la degradación de su rendimiento y no cumple con la demanda de periodicidad. Existen trabajos realizados para enfrentar esta problemática, pero estos requieren que los retardos de control sean constantes. Estos requerimientos se vuelven difíciles de conseguir debido a la latencia existente entre la entrada y salida, además del ruido en el sistema. Contribuyendo a esta problemática se presenta un algoritmo de control, el cual basa su funcionamiento en la sincronización de los instantes de actuación para afrontar los retardos de tiempos y las latencias existentes entre la entrada y salida. Además, incorpora al modelo un filtro de Kalman para reducir la incertidumbre provocada por el ruido en el sistema. Los resultados obtenidos en las simulaciones confirman que el modelo propuesto presenta un rendimiento adecuado, frente a otros modelos de control.Ingenierí