Arquitecturas de Sistemas Embebidos de Tiempo-Real para Aplicaciones de Control

Este proyecto plantea el desarrollo de técnicas y mecanismos de planificación de tiempo real flexibles. Estos deben permitir adaptarse a las diferentes condiciones de trabajo de una aplicación, al mismo tiempo de minimizar el impacto en el resto de los requerimientos de diseño. Principalmente se abarcará la utilización de sistemas de tiempo real en aplicaciones de control y procesamiento de señales.Eje: Procesamiento de Señales y Sistemas de Tiempo RealRed de Universidades con Carreras en Informática (RedUNCI

Arquitecturas de Sistemas Embebidos de Tiempo-Real para Aplicaciones de Control

Este proyecto plantea el desarrollo de técnicas y mecanismos de planificación de tiempo real flexibles. Estos deben permitir adaptarse a las diferentes condiciones de trabajo de una aplicación, al mismo tiempo de minimizar el impacto en el resto de los requerimientos de diseño. Principalmente se abarcará la utilización de sistemas de tiempo real en aplicaciones de control y procesamiento de señales.Eje: Procesamiento de Señales y Sistemas de Tiempo RealRed de Universidades con Carreras en Informática (RedUNCI

Arquitecturas de Sistemas Embebidos de Tiempo-Real para Aplicaciones de Control

Este proyecto plantea el desarrollo de técnicas y mecanismos de planificación de tiempo real flexibles. Estos deben permitir adaptarse a las diferentes condiciones de trabajo de una aplicación, al mismo tiempo de minimizar el impacto en el resto de los requerimientos de diseño. Principalmente se abarcará la utilización de sistemas de tiempo real en aplicaciones de control y procesamiento de señales.Eje: Procesamiento de Señales y Sistemas de Tiempo RealRed de Universidades con Carreras en Informática (RedUNCI

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

Tutorial on arbitrary and state-dependent sampling

International audienceThis tutorial, presents basic concepts and recent research directions about sampled-data systems. We focus mainly on the stability of systems with time-varying sampling intervals. Without being exhaustive, which would be neither possible nor useful, we try to give a structural survey of what we think to be the main results and issues in this domain

실시간 멀티코어 플루이드 스케줄링에서 전체 시스템의 시간 · 밀도 트레이드오프

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 이창건.Recent parallel programming frameworks such as OpenCL and OpenMP allow us to enjoy the parallelization freedom for real-time tasks. The parallelization freedom creates the time vs. density tradeoff problem in fluid scheduling, i.e., more parallelization reduces thread execution times but increases the density. By system-widely exercising this tradeoff, this dissertation proposes a parameter tuning of real-time tasks aiming at maximizing the schedulability of multicore fluid scheduling. The experimental study by both simulation and actual implementation shows that the proposed approach well balances the time and the density, and results in up to 80% improvement of the schedulability.1 Introduction 1 1.1 Motivation and Objective 1 1.2 Approach 3 1.3 Organization 4 2 Related Work 6 2.1 Real-Time Scheduling 6 2.1.1 Workload Model 6 2.1.2 Scheduling on Multicore Systems 7 2.1.3 Period Control 9 2.1.4 Real-Time Operating System 10 2.2 Parallel Computing 10 2.2.1 Parallel Computing Framework 10 2.2.2 Shared Resource Management 12 3 System-wide Time vs. Density Tradeoff with Parallelizable Periodic Single Segment Tasks 14 3.1 Introduction 14 3.2 Problem Description 14 3.3 Motivating Example 21 3.4 Proposed Approach 26 3.4.1 Per-task Optimal Tradeoff of Time and Density 26 3.4.2 Peak Density Minimization for a Task Group with the Same Period 27 3.4.3 Heuristic Algorithm for System-wide Time vs. Density Tradeoff 38 3.5 Experimental Results 45 3.5.1 Simulation Study 45 3.5.2 Actual Implementation Results 51 4 System-wide Time vs. Density Tradeoff with Parallelizable Periodic Multi-segment Tasks 64 4.1 Introduction 64 4.2 Problem Description 64 4.3 Extension to Parallelizable Periodic Multi-segment Task Model 70 4.3.1 Peak Density Minimization for a Task Group of Multi-segment Tasks with Same Period 71 4.3.2 Heuristic Algorithm for System-wide Time vs. Density Tradeoff 78 5 Conclusion 81 5.1 Summary 81 5.2 Future Work 82 References 84 Appendices 100 A Period Harmonization 100Docto

Adaptive Quality of Service Control in Distributed Real-Time Embedded Systems

An increasing number of distributed real-time embedded systems face the critical challenge of providing Quality of Service (QoS) guarantees in open and unpredictable environments. For example, such systems often need to enforce CPU utilization bounds on multiple processors in order to avoid overload and meet end-to-end dead-lines, even when task execution times deviate significantly from their estimated values or change dynamically at run-time. This dissertation presents an adaptive QoS control framework which includes a set of control design methodologies to provide robust QoS assurance for systems at different scales. To demonstrate its effectiveness, we have applied the framework to the end-to-end CPU utilization control problem for a common class of distributed real-time embedded systems with end-to-end tasks. We formulate the utilization control problem as a constrained multi-input-multi-output control model. We then present a centralized control algorithm for small or medium size systems, and a decentralized control algorithm for large-scale systems. Both algorithms are designed systematically based on model predictive control theory to dynamically enforce desired utilizations. We also introduce novel task allocation algorithms to ensure that the system is controllable and feasible for utilization control. Furthermore, we integrate our control algorithms with fault-tolerance mechanisms as an effective way to develop robust middleware systems, which maintain both system reliability and real-time performance even when the system is in face of malicious external resource contentions and permanent processor failures. Both control analysis and extensive experiments demonstrate that our control algorithms and middleware systems can achieve robust utilization guarantees. The control framework has also been successfully applied to other distributed real-time applications such as end-to-end delay control in real-time image transmission. Our results show that adaptive QoS control middleware is a step towards self-managing, self-healing and self-tuning distributed computing platform

Dynamics analysis and integrated design of real-time control systems

Real-time control systems are widely deployed in many applications. Theory and practice for the design and deployment of real-time control systems have evolved significantly. From the design perspective, control strategy development has been the focus of the research in the control community. In order to develop good control strategies, process modelling and analysis have been investigated for decades, and stability analysis and model-based control have been heavily studied in the literature. From the implementation perspective, real-time control systems require timeliness and predictable timing behaviour in addition to logical correctness, and a real-time control system may behave very differently with different software implementations of the control strategies on a digital controller, which typically has limited computing resources. Most current research activities on software implementations concentrate on various scheduling methodologies to ensure the schedulability of multiple control tasks in constrained environments. Recently, more and more real-time control systems are implemented over data networks, leading to increasing interest worldwide in the design and implementation of networked control systems (NCS). Major research activities in NCS include control-oriented and scheduling-oriented investigations. In spite of significant progress in the research and development of real-time control systems, major difficulties exist in the state of the art. A key issue is the lack of integrated design for control development and its software implementation. For control design, the model-based control technique, the current focus of control research, does not work when a good process model is not available or is too complicated for control design. For control implementation on digital controllers running multiple tasks, the system schedulability is essential but is not enough; the ultimate objective of satisfactory quality-of-control (QoC) performance has not been addressed directly. For networked control, the majority of the control-oriented investigations are based on two unrealistic assumptions about the network induced delay. The scheduling-oriented research focuses on schedulability and does not directly link to the overall QoC of the system. General solutions with direct QoC consideration from the network perspective to the challenging problems of network delay and packet dropout in NCS have not been found in the literature. This thesis addresses the design and implementation of real-time control systems with regard to dynamics analysis and integrated design. Three related areas have been investigated, namely control development for controllers, control implementation and scheduling on controllers, and real-time control in networked environments. Seven research problems are identified from these areas for investigation in this thesis, and accordingly seven major contributions have been claimed. Timing behaviour, quality of control, and integrated design for real-time control systems are highlighted throughout this thesis. In control design, a model-free control technique, pattern predictive control, is developed for complex reactive distillation processes. Alleviating the requirement of accurate process models, the developed control technique integrates pattern recognition, fuzzy logic, non-linear transformation, and predictive control into a unified framework to solve complex problems. Characterising the QoC indirectly with control latency and jitter, scheduling strategies for multiple control tasks are proposed to minimise the latency and/or jitter. Also, a hierarchical, QoC driven, and event-triggering feedback scheduling architecture is developed with plug-ins of either the earliest-deadline-first or fixed priority scheduling. Linking to the QoC directly, the architecture minimises the use of computing resources without sacrifice of the system QoC. It considers the control requirements, but does not rely on the control design. For real-time NCS, the dynamics of the network delay are analysed first, and the nonuniform distribution and multi-fractal nature of the delay are revealed. These results do not support two fundamental assumptions used in existing NCS literature. Then, considering the control requirements, solutions are provided to the challenging NCS problems from the network perspective. To compensate for the network delay, a real-time queuing protocol is developed to smooth out the time-varying delay and thus to achieve more predictable behaviour of packet transmissions. For control packet dropout, simple yet effective compensators are proposed. Finally, combining the queuing protocol, the packet loss compensation, the configuration of the worst-case communication delay, and the control design, an integrated design framework is developed for real-time NCS. With this framework, the network delay is limited to within a single control period, leading to simplified system analysis and improved QoC