Utilization Control And Optimization Of Real Time Embedded Systems

Real-time embedded systems have been widely deployed in mission-critical applications, such as avionics mission computing, highway traffic control, remote patient monitoring, wireless communications, navigation, etc. These applications always require their real-time and embedded components to work in open and unpredictable environments, where workload is volatile and unknown. In order to guarantee the temporal correctness and avoid severe underutilization or overload, it is of vital significance to measure, control, and optimize the processor utilization adaptively. A key challenge in this mission is to meet real-time requirements even when the workload cannot be accurately characterized a priori. Traditional approaches of worst-case analysis may cause underutilization of resources, while Model Predictive Control (MPC) based approaches may suffer severe performance deterioration when large estimation errors exist. To address this challenging problem and provide better system performance, we have developed several important online adaptive optimal control approaches based on advanced control techniques. Our approaches adopt Recursive Least Square (RLS) based model identification and Linear Quadratic (LQ) optimal controllers to guarantee that the systems are neither overloaded, nor underloaded. These proposed approaches, as well as the associated tools, can quickly adapt to volatile workload changes to provide stable system performance. To minimize the impact of modeling errors, we adopt the Adaptive Critic Design (ACD) technique and develop an improved solution that requires little information of the system model. To deal with the discrete task rates, we further propose to utilize the frequency scaling technique to assist the utilization control and optimization.

Ubiquitous in today's consumer-driven society, embedded systems use microprocessors that are hidden in our everyday products and designed to perform specific tasks. Effective use of these embedded systems requires engineers to be proficient in all phases of this effort, from planning, design, and analysis to manufacturing and marketing.Taking a sys

Today, many embedded or cyber-physical systems, e.g., in the automotive domain, comprise several control applications, sharing the same platform. It is well known that such resource sharing leads to complex temporal behaviors that degrades the quality of control, and more importantly, may even jeopardize stability in the worst case, if not properly taken into account. In this thesis, we consider embedded control or cyber-physical systems, where several control applications share the same processing unit. The focus is on the control-scheduling co-design problem, where the controller and scheduling parameters are jointly optimized. The fundamental difference between control applications and traditional embedded applications motivates the need for novel methodologies for the design and optimization of embedded control systems. This thesis is one more step towards correct design and optimization of embedded control systems. Offline and online methodologies for embedded control systems are covered in this thesis. The importance of considering both the expected control performance and stability is discussed and a control-scheduling co-design methodology is proposed to optimize control performance while guaranteeing stability. Orthogonal to this, bandwidth-efficient stabilizing control servers are proposed, which support compositionality, isolation, and resource-efficiency in design and co-design. Finally, we extend the scope of the proposed approach to non-periodic control schemes and address the challenges in sharing the platform with self-triggered controllers. In addition to offline methodologies, a novel online scheduling policy to stabilize control applications is proposed.

Embedded computer systems are now everywhere: from alarm clocks to PDAs, from mobile phones to cars, almost all the devices we use are controlled by embedded computers. An important class of embedded computer systems is that of hard real-time systems, which have to fulfill strict timing requirements. As real-time systems become more complex, they are often implemented using distributed heterogeneous architectures. Analysis and Synthesis of Distributed Real-Time Embedded Systems addresses the design of real-time applications implemented using distributed heterogeneous architectures. The systems are heterogeneous not only in terms of hardware components, but also in terms of communication protocols and scheduling policies. Regarding this last aspect, time-driven and event-driven systems, as well as a combination of the two, are considered. Such systems are used in many application areas like automotive electronics, real-time multimedia, avionics, medical equipment, and factory systems. The proposed analysis and synthesis techniques derive optimized implementations that fulfill the imposed design constraints. An important part of the implementation process is the synthesis of the communication infrastructure, which has a significant impact on the overall system performance and cost. Analysis and Synthesis of Distributed Real-Time Embedded Systems considers the mapping and scheduling tasks within an incremental design process. To reduce the time-to-market of products, the design of real-time systems seldom starts from scratch. Typically, designers start from an already existing system, running certain applications, and the design problem is to implement new functionality on top of this system. Supporting such an incremental design process provides a high degree of flexibility, and can result in important reductions of design costs. STRONGAnalysis and Synthesis of Distributed Real-Time Embedded Systems will be of interest to advanced undergraduates, graduate students, researchers and designers involved in the field of embedded systems.

Embedded computing systems play an important and complex role in the functionality of electronic devices. With our daily routines becoming more reliant on electronics for personal and professional use, the understanding of these computing systems is crucial. Embedded Computing Systems: Applications, Optimization, and Advanced Design brings together theoretical and technical concepts of intelligent embedded control systems and their use in hardware and software architectures. By highlighting formal modeling, execution models, and optimal implementations, this reference source is essential for experts, researchers, and technical supporters in the industry and academia.

Real-time and embedded systems are essential to our lives, from controlling car engines and regulating traffic lights to monitoring plane takeoffs and landings to providing up-to-the-minute stock quotes. Bringing together researchers from both academia and industry, the Handbook of Real-Time and Embedded Systems provides comprehensive covera

A real-time system is a complex system which is an integral part of an industrial or experimental system, a vehicle or a construction machine. The peculiarity of these systems is that they are driven by real-time targets in distributed environments. Command-control for Real-time Systems presents the calculation of correction for industrial systems of different physical natures, their implementation on real-time target industrial systems (PLC-SCADA, embedded systems with distributed networks, Networked Control Systems) and their validation by simulation. It optimizes industrial processes by the use of automatic tools, industrial computing and communications networks and aims to successively integrate new control laws (linear, nonlinear and fuzzy controllers) so that users can leverage the power of engineering science as an automatic service process optimization while maintaining their high maintainability facilities. Contents 1. Introduction. 2. Modeling Tools, Sébastien Cabaret and Mohammed Chadli. 3. Control Tools, Mohammed Chadli and Hervé Coppier. 4. Application to Cryogenic Systems, Marco Pezzetti, Hervé Coppier and Mohammed Chadli. 5. Applications to a Thermal System and to Gas Systems, Sébastien Cabaret and Hervé Coppier. 6. Application to Vehicles, Elie Kafrouni and Mohammed Chadli. 7. Real-time Implementation, Marco Pezzetti and Hervé Coppier. About the Authors Mohamed Chadli is a senior lecturer and research supervisor at the University of Picardie Jules Verne (UPJV) in France. His main research interests lie in robust control, the diagnosis and fault tolerant control of polytopic systems and applications for automobiles. He is a senior member of the IEEE, and Vice President of the AAI Club as part of SEE-France. He is the author/co-author of 3 books, book chapters and more than 100 articles published in international journals and conferences. Hervé Coppier is a lecturing researcher at ESIEE-Amiens in France. He has collaborated with industrialists in the field of automation and industrial computing, particularly with CERN, and has spearheaded various international European projects.

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.

This book integrates new ideas and topics from real time systems, embedded systems, and software engineering to give a complete picture of the whole process of developing software for real-time embedded applications. You will not only gain a thorough understanding of concepts related to microprocessors, interrupts, and system boot process, appreciating the importance of real-time modeling and scheduling, but you will also learn software engineering practices such as model documentation, model analysis, design patterns, and standard conformance. This book is split into four parts to help you learn the key concept of embedded systems; Part one introduces the development process, and includes two chapters on microprocessors and interrupts---fundamental topics for software engineers; Part two is dedicated to modeling techniques for real-time systems; Part three looks at the design of software architectures and Part four covers software implementations, with a focus on POSIX-compliant operating systems. With this book you will learn: The pros and cons of different architectures for embedded systems POSIX real-time extensions, and how to develop POSIX-compliant real time applications How to use real-time UML to document system designs with timing constraints The challenges and concepts related to cross-development Multitasking design and inter-task communication techniques (shared memory objects, message queues, pipes, signals) How to use kernel objects (e.g. Semaphores, Mutex, Condition variables) to address resource sharing issues in RTOS applications The philosophy underpinning the notion of "resource manager" and how to implement a virtual file system using a resource manager The key principles of real-time scheduling and several key algorithms Coverage of the latest UML standard (UML 2.4) Over 20 design patterns which represent the best practices for reuse in a wide range of real-time embedded systems Example codes which have been tested in QNX---a real-time operating system widely adopted in industry