Showing papers in "Real-time Systems in 2004"
TL;DR: This 25th year anniversary paper for the IEEE Real Time Systems Symposium reviews the key results in real-time scheduling theory and the historical events that led to the establishment of the current real- time computing infrastructure.
Abstract: In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key results in real-time scheduling theory and the historical events that led to the establishment of the current real-time computing infrastructure. We conclude this paper by looking at the challenges ahead of us.
636 citations
TL;DR: This paper contains both a survey of mode change protocols for single-processor, fixed-priority, preemptively scheduled real-time systems, and a proposal of several new protocols along with their corresponding schedulability analysis and configuration methods.
Abstract: This paper contains both a survey of mode change protocols for single-processor, fixed-priority, preemptively scheduled real-time systems, and a proposal of several new protocols along with their corresponding schedulability analysis and configuration methods. First, a classification of the protocols found in the literature is given and a set of requirements is proposed for their evaluation. Then, the new protocols are introduced and discussed in the light of the stated requirements. A number of mode change protocols are based on delaying the initiation of the new mode by applying an offset to the initial release of tasks in the destination mode. We tackle the problem of how to obtain these offsets for the proposed protocols. The issue of consistently sharing resources during the mode change by means of a priority inheritance protocol is also dealt with.
268 citations
TL;DR: The utilization bound for earliest deadline first EDF scheduling is extended from uniprocessors to homogeneous multiprocessor systems with partitioning strategies, and the basic task model is extended to include resource sharing, release jitter, deadlines less than periods, aperiodic tasks, non-preemptive sections, context switches, and mode changes.
Abstract: The utilization bound for earliest deadline first (EDF) scheduling is extended from uniprocessors to homogeneous multiprocessor systems with partitioning strategies. First results are provided for a basic task model, which includes periodic and independent tasks with deadlines equal to periods. Since the multiprocessor utilization bounds depend on the allocation algorithm, different allocation algorithms have been considered, ranging from simple heuristics to optimal allocation algorithms. As multiprocessor utilization bounds for EDF scheduling depend strongly on task sizes, all these bounds have been obtained as a function of a parameter which takes task sizes into account. Theoretically, the utilization bounds for multiprocessor EDF scheduling can be considered a partial solution to the bin-packing problem, which is known to be NP-complete. The basic task model is extended to include resource sharing, release jitter, deadlines less than periods, aperiodic tasks, non-preemptive sections, context switches, and mode changes.
202 citations
TL;DR: Besides robotics, applications such as medical patient monitoring, programmed stock trading, and military command and control systems like submarine contact tracking require timely actions as well as the ability to access and store complex data that reflects the state of the application's environment.
Abstract: Typically, a real–time system consists of a a controlling system and a controlled system. In an automated factory, the controlled system is the factory floor with its robots, assembling stations, and the assembled parts, while the controlling system is the computer and human interfaces that manage and coordinate the activities on the factory floor. Thus, the controlled system can be viewed as the environment with which the computer interacts. The controlling system interacts with its environment based on the data available about the environment, say from various sensors, e.g. temperature and pressure sensors. It is imperative that the state of the environment, as perceived by the controlling system, be consistent with the actual state of the environment. Otherwise, the effects of the controlling systems’ activities may be disastrous. Hence, timely monitoring of the environment as well as timely processing of the sensed information is necessary. The sensed data is processed further to derive new data. For example, the temperature and pressure information pertaining to a reaction may be used to derive the rate at which the reaction appears to be progressing. This derivation typically would depend on past temperature and pressure trends and so some of the needed information may have to be fetched from archival storage. Based on the derived data, where the derivation may involve multiple steps, actuator commands are set. For instance, in our example, the derived reaction rate is used to determine the amount of chemicals or coolant to be added to the reaction. In general, the history of (interactions with) the environment are also logged in archival storage. In addition to the timing constraints that arise from the need to continuously track the environment, timing correctness requirements in a real–time (database) system also arise because of the need to make data available to the controlling system for its decision-making activities. If the computer controlling a robot does not command it to stop or turn on time, the robot might collide with another object on the factory floor. Needless to say, such a mishap can result in a major catastrophe. Besides robotics, applications such as medical patient monitoring, programmed stock trading, and military command and control systems like submarine contact tracking require timely actions as well as the ability to access and store complex data that reflects the state of the application’s environment. That is, data in these applications must be valid, or fresh, when it is accessed in order for the application to perform correctly. In a patient monitoring system, data such as heart rate, temperature, and blood pressure must be collected periodically. Transactions that monitor the danger level of a patient’s status must be performed within a specified time, and the data must be accessed within an interval that defines the validity of the data. If not, the computations made by the transactions do not reflect the current state of the patient’s health. A traditional database provides some of the functionality required by these applications, such as coordination of concurrent actions and consistent access to shared data. But they do not provide for enforcement of the
177 citations
TL;DR: The ultimate goal is to design performant systems with sharp upper and lower bounds on execution times, and proposed design principles that support timing predictability are described.
Abstract: A large part of safety-critical embedded systems has to satisfy hard real-time constraints. These need sound methods and tools to derive run-time guarantees that are not only reliable but also precise. The achievable precision highly depends on characteristics of the target architecture, the implementation methods and system layers of the software. Trends in hardware and software design run contrary to predictability. This article describes threats to timing predictability of systems, and proposes design principles that support timing predictability. The ultimate goal is to design performant systems with sharp upper and lower bounds on execution times.
175 citations
TL;DR: The proposed constant bandwidth server allows real-time tasks to execute in a dynamic environment under a temporal protection mechanism, so that each task will never exceed a predefined bandwidth, independently of its actual requests.
Abstract: This paper focuses on the problem of providing efficient run-time support to multimedia applications in a real-time system, where different types of tasks (characterized by different criticality) can coexist. Whereas critical real-time tasks (hard tasks) are guaranteed based on worst-case execution times and minimum interarrival times, multimedia tasks are served based on mean parameters. A novel bandwidth reservation mechanism (the constant bandwidth server) allows real-time tasks to execute in a dynamic environment under a temporal protection mechanism, so that each task will never exceed a predefined bandwidth, independently of its actual requests. The paper also discusses how the proposed server can be used for handling aperiodic tasks efficiently and how a statistical analysis can be applied to perform a probabilistic guarantee of soft tasks. The performance of the proposed method is compared with that of similar service mechanisms (dynamic real-time servers and proportional share schedulers) through extensive simulation experiments.
146 citations
TL;DR: It is argued that the small, proprietary kernels are predictable, but offer little help to the real-time systems designer and implementor in producing predictable applications.
Abstract: Real-time operating systems are an integral part of complex real-time systems. Three general categories of real-time operating systems exist: small, proprietary kernels, real-time extensions to commercial timesharing operating systems, and research kernels. This paper discusses each of these areas focusing on how each of these classes deal with predictability. It is argued that the small, proprietary kernels are predictable, but offer little help to the real-time systems designer and implementor in producing predictable applications. Real-time versions of commercial operating systems like UNIX and Mach offer greater implementation support, but are, in general, NOT predictable themselves nor offer enough support to applications which require predictability. This, of course, does not mean that there is no way to achieve predictability with these operating systems. It is possible to achieve predictability by very careful design, by using a very limited subset of the overall features provided, and by proving that the features being used for predictability cannot in any way be impacted by any other part of the system. Finally, research kernels are attempting to provide greater design, implementation and evaluation support together with predictability for both the operating system and the application.
141 citations
TL;DR: An adaptive and object-based middleware, called reconfigurable context-sensitive middleware (RCSM) is presented to facilitate context- sensitive communications in ubicomp environments, which is adaptive in the sense that depending on the context-ensitive behavior of the applications, it adapts its object discovery and connection management mechanisms.
Abstract: Context-sensitivity is an important expected capability in applications in ubiquitous computing (ubicomp) environments. These applications need to use different contextual information from the user, host device, on board sensors, network, and the ambient environments to systematically adapt their actions. In addition, some context-sensitive applications may use specific contextual conditions to trigger impromptu and possibly short-lived interactions with applications in other devices. This property, referred to as context-sensitive or context-aware communications, allows applications to form short-range mobile ad hoc networks consisting of mobile and stationary devices, sensors, and other computing resources. Real-time applications, especially those having reactive behavior, running on embedded devices and requiring context-sensitive communications support, pose new challenges related to systematic representation of specific contexts, associations of contexts with real-time actions, timely context data collection and propagation, and transparent context-sensitive connection establishment. An object-based middleware can be effective to meet these challenges if such a middleware can provide a well-defined development framework as well as lightweight runtime services. In this paper, an adaptive and object-based middleware, called reconfigurable context-sensitive middleware (RCSM) is presented to facilitate context-sensitive communications in ubicomp environments. To facilitates context-sensitive communications, RCSM provides a context-aware interface definition language for specifying context-sensitive interfaces of real-time objects, an object container framework for generating interfaces-specific context-analyzers, and a context-sensitive object request broker for context-sensitive object discovery and impromptu connection management. RCSM is adaptive in the sense that depending on the context-sensitive behavior of the applications, it adapts its object discovery and connection management mechanisms.
95 citations
TL;DR: An analysis for the communication delays with four different message scheduling policies over a time-triggered communication channel is developed, Optimization strategies for the synthesis of communication are developed, and the four approaches to message scheduling are compared.
Abstract: We present an approach to static priority preemptive process scheduling for the synthesis of hard real-time distributed embedded systems where communication plays an important role. The communication model is based on a time-triggered protocol. We have developed an analysis for the communication delays with four different message scheduling policies over a time-triggered communication channel. Optimization strategies for the synthesis of communication are developed, and the four approaches to message scheduling are compared using extensive experiments.
72 citations
TL;DR: A new task model is proposed in order to reduce the CAI and DAI parameters, which implies an improvement in the control performance, and this work shows how to evaluate these delays under static and dynamic scheduling policies.
Abstract: Industrial control applications are usually developed in two phases: control design and real-time system implementation. In the control design stage a regulator is obtained and later it is translated into an algorithm in the implementation phase. Traditionally, these two phases have been developed in separate ways. Recently, some works have pointed out the necessity of the integration of the control design and its implementation. One of these works reduce the delay variance of control tasks (defined as the control action interval (CAI) and data acquisition interval (DAI) parameters) splitting every task into three parts. The CAI reduction method highly reduces the delay variance and improves the control performance. This work shows how to evaluate these delays under static and dynamic scheduling policies. A new task model is proposed in order to reduce the CAI and DAI parameters, which implies an improvement in the control performance. The new task model will be implemented in a real process, and the experimental measurements will show how, effectively, the control performance is highly improved with the methods presented in this paper.
37 citations
TL;DR: A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are presented and the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched.
Abstract: This paper addresses the issue of improving the performance of memory management for real-time Java applications, building upon the real-time specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a collecting dynamic memory solution including both a real-time garbage collector and region-based memory management, is proposed. A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are then presented. Finally, the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched.
TL;DR: Two new garbage collection algorithms that are dedicated to real-time garbage collection on a multithreaded Java microcontroller are introduced and it is shown that these algorithms require only about 5–10% of the processor time for an effective garbage collection concerning the authors' real- time benchmarks.
Abstract: We envision the upcoming of microcontrollers and systems-on-chip that are based on multithreaded processor kernels due to the fast context switching ability of hardware multithreading. Moreover we envision an extensive market for Java-based applications in embedded real-time systems. This paper introduces two new garbage collection algorithms that are dedicated to real-time garbage collection on a multithreaded Java microcontroller. Our garbage collector runs in a thread slot in parallel to real-time applications. We show that our algorithms require only about 5–10% of the processor time for an effective garbage collection concerning our real-time benchmarks.
TL;DR: This work presents a new method, which it is called dynamic update for real-time systems, which can be used to update real- time applications using rate-monotonic scheduling, while preserving the original deadline guarantees.
Abstract: Updating application software is a common occurrence for modern computing systems Software updates stem from the need to correct coding errors or to enhance the functionality of an application Updating an application typically requires taking the current application offline and restarting a new application This method of updating an application is perfectly acceptable for many general purpose-computing environments However, in real-time environments that require high availability and have stringent timing constraints, taking a process offline for updates may be unacceptable or pose unnecessary risks Some examples of these environments include telecommunications, air traffic control, railway control and medical patient monitoring We present a new method to dynamically update a real-time application without having to take it offline Our new method, which we call dynamic update for real-time systems, can be used to update real-time applications using rate-monotonic scheduling, while preserving the original deadline guarantees
TL;DR: This paper proposes a method called service classes configuration to address the QoS problem with dynamic arrival and departure of tasks by offline designing templates (called service classes) of resource allocation, which will be adaptively used depending on online situations.
Abstract: Many application level qualities are functions of available computation resources. Recent studies have handled the computation resource allocation problem to maximize the overall application quality. However, such QoS problems are fundamentally multi-dimensional optimization problems that require extensive computation. Therefore, online usage of optimization procedures may significantly reduce the computation resource available for applications. This raises the question of how to best use the optimization procedures for dynamic real-time task sets. In dynamic real-time systems, it is important to improve the performance by re-allocating the resources adapting to dynamic situations. However, the overhead of changing task parameters (i.e., algorithms and frequencies) for resource re-allocation is non-negligible in many applications. Thus, too frequent change of resource allocation may not be desirable. This paper proposes a method called service classes configuration to address the QoS problem with dynamic arrival and departure of tasks. The method avoids online usage of optimization procedures by offline designing templates (called service classes) of resource allocation, which will be adaptively used depending on online situations. The service classes are designed by best trading-off the accuracy of dynamic adaptation against the overhead of resource re-allocation. A simplified radar application is used as an illustrative example.
TL;DR: This paper presents the proposed framework, and demonstrates how it can be used to support the transparent replication of software components, within the DEAR-COTS architecture.
Abstract: Building reliable real-time applications on top of commercial off-the-shelf (COTS) components is not a straightforward task. Thus, it is essential to provide a simple and transparent programming model, in order to abstract programmers from the low-level implementation details of distribution and replication. However, the recent trend for incorporating pre-emptive multitasking applications in reliable real-time systems inherently increases its complexity. It is therefore important to provide a transparent programming model, enabling pre-emptive multitasking applications to be implemented without resorting to simultaneously dealing with both system requirements and distribution and replication issues. The distributed embedded architecture using COTS components (DEAR-COTS) architecture has been previously proposed as an architecture to support real-time and reliable distributed computer-controlled systems (DCCS) using COTS components. Within the DEAR-COTS architecture, the hard real-time subsystem provides a framework for the development of reliable real-time applications, which are the core of DCCS applications. This paper presents the proposed framework, and demonstrates how it can be used to support the transparent replication of software components.
TL;DR: This paper intends to present a comprehensive review on recent advances in hard real-time communication with the timed token protocol and several challenging problems are identified.
Abstract: With the increasing use of distributed real-time systems, the ability of communication networks to handle real-time traffic is becoming more and more important. The timed token medium access control protocol, which has been now incorporated into several network standards such as FDDI and SAFENET due to its special timing property of bounded medium access time, is one of the most suitable and attractive candidate communication protocols for supporting distributed hard real-time applications. Extensive research has been conducted on using the timed token protocol to guarantee timely transmission of messages in a communication environment with hard real-time requirements. This paper intends to present a comprehensive review on recent advances in hard real-time communication with the timed token protocol. In addition, several challenging problems are identified.
TL;DR: This paper presents a comparison of methods for industrial on-line sensor calibration monitoring for redundant sensors using both simulated data and data sets from an operating nuclear power plant, finding that under most conditions ICA outperforms PCA.
Abstract: This paper presents a comparison of methods for industrial on-line sensor calibration monitoring for redundant sensors. Principal component analysis (PCA) and independent component analysis (ICA) techniques are developed and compared using both simulated data and data sets from an operating nuclear power plant. The performance is dependent on the types of noise sources; however, under most conditions ICA outperforms PCA, based on the bias and variance of their respective parameter estimates. A case study is included to demonstrate the usefulness of both techniques for the early detection of sensor drift.
TL;DR: The parallels between MSET and more traditional kernel techniques, namely kernel regression, are drawn and it is shown that MSET is a special type of kernel regression algorithm.
Abstract: This paper presents an analytical derivation and analysis of the uncertainty of the Multivariate State Estimation Technique (MSET). Like all other nonparametric techniques, MSET uncertainty consists of two parts: bias and variance. Bias is a systematic error in MSET inference and practically not computable and non-removable, but when properly regularized it is usually very small with respect to the variance when properly regularized. Variance, on the other hand, represents variability of the MSET estimate due to random noise in the data and can be estimated in real time. All the derivations and results are obtained for the inferential case. The MSET cost function is also derived which shows that MSET minimizes a weighted least squares cost function with weighting affected by the MSET memory matrix. The parallels between MSET and more traditional kernel techniques, namely kernel regression, are drawn and it is shown that MSET is a special type of kernel regression algorithm. The final section presents the results of the MSET uncertainty analysis for real world data obtained from a commercial nuclear power plant.
TL;DR: This paper evaluates the development of a rapid prototype for an air condition controller with the popular CASE tool Rational Rose/RT® and proposes an extension toRose/RT®, which overcomes the weaknesses by combining Rose/ RT’s UML dialect with data flow equations.
Abstract: Object-oriented (OO) modeling languages, tools, and methods more and more attract the interest of embedded (real-time) system developers. This is especially true if embedded (real-time) system software has to cooperate with interactive multimedia software, as it is more and more the case in automotive systems. It is still an open question whether and how the standard OO modeling language UML and its accompanying tools have to be adapted to the regarded application domain. This paper evaluates the development of a rapid prototype for an air condition controller with the popular CASE tool Rational Rose/RT®. We point out some weaknesses of the presented solution and propose an extension to Rose/RT®, which overcomes the weaknesses by combining Rose/RT’s UML dialect with data flow equations.
TL;DR: Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues.
Abstract: Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.
TL;DR: Through applying the proposed lifting technique to sampled-data systems with input time delays, the time-invariant discrete-time system with infinite-dimensional input and output spaces is obtained and can satisfy the problem of H2 sampled- data control systems withinput time delays.
Abstract: This paper presents a general framework based on lifting technique for sampled-data systems with input time delays. By analyzing the properties of operator-valued matrices of lifted systems with input time delays, an extended lifting technique is obtained. It is then shown that, with the proposed lifting technique, the complex behavior of the system can be illustrated by two simple lifted systems, which construct the extended lifted system. The extended lifted system has the same induced norm as that of the original system with an input time delay, since the proposed lifting technique is an isometric isomorphism. Through applying the proposed lifting technique to sampled-data systems with input time delays, the time-invariant discrete-time system with infinite-dimensional input and output spaces is obtained. The equivalent discrete-time system, which is derived from the extended lifted system, can satisfy the problem of H2 sampled-data control systems with input time delays. Simulation results are given to show that the proposed method can guarantee a more stable system response than the conventional H2 sampled-data controller for the sampled-data systems with the various input time delays.
TL;DR: A highly reliable control system using modular and temporal redundancy, called dual-modular temporal redundancy (DMTR), and an efficient recursive computation algorithm for rapidly obtaining the probabilistic schedulability of the overall system are proposed.
Abstract: To improve reliability of real-time control systems, various fault-tolerance methods have been designed and implemented. We propose a highly reliable control system using modular and temporal redundancy, called dual-modular temporal redundancy (DMTR). Assuming that transient faults occur and recover with exponential probability distributions, we analyze the probabilistic schedulability of DMTR for multiple tasks with harmonic periods (DMTR-HP). After formulating a discrete-time reliability model for DMTR-HP, we formulate an efficient recursive computation algorithm for rapidly obtaining the probabilistic schedulability of the overall system. Considering the overhead for checkpointing in a DMTR-HP control system, we obtain the optimal number of subslots for maximum reliability using our DMTR-HP reliability model. In addition, we compare the reliabilities of DMTR-HP, DMTR using GCDP scheduling (DMTR-GCDP), and conventional dual-modular redundancy (DMR).
TL;DR: Simulation results show that FHRN outperforms these existent real-time schedulers such as random priority (RP), earlier deadline (ED), highest value (HV), hierarchical earliest deadline (HED), and highest reward and urgency (HRU) when an application requires a nested transaction model.
Abstract: Many noticeable studies have focussed on scheduling flat transactions in a distributed real-time database system (RTDBS). However, a nested transaction model has been widely adopted in many real-life applications such as Internet stock trading systems and telecommunications. This work concerns efficiently scheduling real-time nested transactions in a distributed RTDBS. A new real-time scheduler called flexible high reward for nested transactions (FHRN) is proposed. FHRN consists of (1) FHRNp1 policy to schedule real-time nested transactions and (2) 2PLlHPN to resolve the concurrent data-accessing problem among interleaved nested transactions. Simulation results show that FHRN outperforms these existent real-time schedulers such as random priority (RP), earliest deadline (ED), highest value (HV), hierarchical earliest deadline (HED), and highest reward and urgency (HRU) when an application requires a nested transaction model.
TL;DR: An overview on existing approaches for assessing the reliability of complex software with safety demands and proposes to adopt a procedure supporting the re-usability of component certification when licensing software systems for new safety applications.
Abstract: This article offers an overview on existing approaches for assessing the reliability of complex software with safety demands. It addresses both inherent difficulties as well as observable trends towards international standardized procedures. The contribution distinguishes between product-based and process-based quality indicators and comments on the applicability of existing techniques to evaluate them qualitatively and quantitatively. In particular, it focusses on licensing the re-use of pre-developed software components. In the light of lessons learnt from real-world accidents it proposes to adopt a procedure supporting the re-usability of component certification when licensing software systems for new safety applications.
TL;DR: A method is proposed which supports both functional and timing verification of the specified system, which integrates the extended specification and description language (SDL) and message sequence chart (MSC) specifications with the task allocation and schedulability analysis algorithms.
Abstract: The correctness of hard real-time systems depends not only on the correct functional behavior but also on the correct temporal behavior. That is, the designed hard real-time system should meet all its functional and timing requirements even in the worst case. By performing timing analysis in early stages of the system life cycle, it is possible to reduce the overall development costs. This is due to the fact that the detection of the deadline violation in hard real-time systems will often lead to a complete redesign. Therefore the integration of system specification and timing analysis will be very helpful in the design of hard real-time systems. In this paper a method is proposed which supports both functional and timing verification of the specified system. The method integrates the extended specification and description language (SDL) and message sequence chart (MSC) specifications with the task allocation and schedulability analysis algorithms. The extensions of SDL and MSC are annotations in form of embedded comments in the original languages. They are used to describe the timing requirements of the specified system. The usability of the proposed method is illustrated through a case study.
TL;DR: The developed algorithm enables real-time applications such as fast tube defects classification systems and visualization of ECT signal feature prototypes, which may improve the speed of time-critical decision making during power plant maintenance outages.
Abstract: A new classification method, for isolating steam generator tube defects in nuclear power plants using Eddy Current Test (ECT) signals, has been developed. The method uses Self-Organizing maps (SOM) with different data signatures to identify and classify these defects. A multiple inference system is proposed which evaluates different extracted characteristic SOMs to infer the defect type. Wavelet zero-crossing representation, a linear predictive coding (LPC), and other basic signal representations, such as magnitude and phase, are used to construct characteristic vectors that combine one or more of these features. These vectors are evaluated for their ability to classify tube defects and the ones with the best performance are used in the multiple inference system. The effectiveness of the method is demonstrated by applications of the characteristic maps to ECT data from various cases of tube defects in pressurized water reactor plant steam generators. The developed algorithm enables real-time applications such as fast tube defects classification systems and visualization of ECT signal feature prototypes, which may improve the speed of time-critical decision making during power plant maintenance outages.
TL;DR: The artificially intelligent monitoring system (AIMS), a framework for power plants real-time monitoring systems (RT/MS), developed at Federal University of Rio de Janeiro (COPPE/UFRJ) and applied to the Brazilians Angra-1 and AngRA-2 nuclear power plants is described.
Abstract: In this paper, we describe the artificially intelligent monitoring system (AIMS), a framework for power plants real-time monitoring systems (RT/MS), developed at Federal University of Rio de Janeiro (COPPE/UFRJ) and applied to the Brazilians Angra-1 and Angra-2 nuclear power plants. The kernel of AIMS is an object-oriented knowledge-base system, in which acquired and calculated variables, as well as their interdependencies, are mapped into a hierarchical objects network where the rules and real-time constraints are implicit in objects operators and network topology. The state of monitored variables updates a fact-base, which is used by a real-time inference-machine (RT/IM) to activate and synchronize the fire of the knowledge-base (KB) rules. The operators man–machine interface (MMI) are, then, updated. Besides, also following the object-oriented paradigm, AIMS provides many facilities for building and maintaining the KB and the operators MMI. In order to illustrate the use of AIMS, we show part of a real application in Angra-2 NPP.
TL;DR: Preliminary results of a computational intelligence approach to the enhancement of the accuracy of cross-correlation flow measurements as a potential solution to the problem of Venturi fouling are reported on.
Abstract: One of the primary cost-saving objectives of the power plant industry, including the nuclear industry, has long been the efficient operation of plant systems. Since the maximum operating thermal power of any nuclear plant is bounded by the specific licensing requirements of the competent national nuclear authorities, the amount of uncertainty in its calculation has a direct effect on the maximum energy that can be produced. The feedwater flow rate is one of the major quantities used in the thermal power calculations, and Venturi flow meters are traditionally used to measure this flow rate. Venturi flow meters are subject to known drifting problems, mainly originating from the gradual fouling of the Venturi constriction, which leads to an overestimation of the flow, and, consequently, of the produced thermal power. This overestimation has then to be balanced by a reduction of the operating power in order to stay within authority limits. This paper reports on preliminary results of a computational intelligence approach to the enhancement of the accuracy of cross-correlation flow measurements as a potential solution to the problem of Venturi fouling.
TL;DR: This paper reviews some process signal analysis and representation methods that can be used during reactor operation such that they are suitable for real-time applicatons.
Abstract: This paper reviews some process signal analysis and representation methods that can be used during reactor operation such that they are suitable for real-time applicatons. All listed methods have been tested on data from operating plant. The objective is to detect and interpret changes in the plant or core status at an early stage, such that appropriate measures can be taken immediately. The methods that are discussed and demonstrated in the paper can be divided into two categories. The first is the use of fast and intelligent computing methods such as neural networks and fast wavelet transform, in combination with a diagnostic unfolding procedure which would be computationally rather demanding with traditional methods. The second type is based on direct representation of the system state through visualization of large complex data, showing the space–time behavior of the system. This latter is not associated with any unfolding procedure, it uses only a moderate signal preprocessing for filtering out redundant information, but otherwise showing the process status directly. Such methods have been made possible with the development of powerful computer visualization techniques. The potentials represented by this second alternative do not seem to have been explored fully yet in reactor diagnostics. Methods corresponding to both categories will be demonstrated and discussed in the paper.
TL;DR: The UML has demonstrated potential for modeling real-time and embedded systems, but this potential can be greatly enhanced with the use of DORIS, a method extensively used in the aerospace industry.
Abstract: Real-time and embedded systems have widespread use in industrial, commercial and defence applications. They tend to be large and complex and need to focus on non-functional aspects such as performance, throughput and dependability. The UML has demonstrated potential for modeling real-time and embedded systems, but this potential can be greatly enhanced with the use of DORIS, a method extensively used in the aerospace industry. This paper considers how the two can be used in combination to model complex systems.