Real-time Issues Research Articles

Summary of the 6th International Workshop on real-time Ada issues

article Summary of the 6th International Workshop on real-time Ada issues Share on Editors: Alan Burns View Profile , Andy Wellings View Profile Authors Info & Claims ACM SIGAda Ada LettersVolume XIIIIssue 2March/April 1993 pp 21–36https://doi.org/10.1145/152827.152828Online:15 March 1993Publication History 0citation33DownloadsMetricsTotal Citations0Total Downloads33Last 12 Months0Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Real-time issues of transputers in high-performance motion control systems

The real-time issues related to using transputers to implement high-performance AC motor drive controllers because of their direct support for parallel processing are addressed. They include event response time, scheduling strategies, I/O, and real-time kernel performance. The implementation of part of a real-time kernal consisting of a multiple event handler and an efficient scheduler, to improve the transputer's real-time performance, is described. In addition to supporting high-performance controller tasks, the real-time kernel implements features such as parameter sampling and user interaction. The kernel is intended to be a platform to support a highly programmable and configurable controller suitable for a wide range of motion control applications. Test results are presented to show the performance of the kernel. >

Computer-aided design of a generic robot controller handling reactivity and real-time control issues

An original system, Open Robot Controller Computer-Aided Design (ORCCAD), for the computer-aided design of robot controllers is described. Accessed by three different user levels (system, control, and application), it provides a coherent approach from a high-level specification down to its implementation, and offers several tools for design, display, and test. Following a critical study of the main architectures reported in the literature, the basic principles and underlying concepts of ORCCAD are presented. The main entity considered is the robot task, an elementary control action associated with a local behavior controlled by a set of observers and modeled by a finite-state automaton. It is made of a set of real-time communicating tasks, called module tasks. The module task which handles the behavior of the robot task, is described using the synchronous language ESTEREL. The application level is defined as a set of synchronized robot tasks, also described using ESTEREL. Two detailed examples are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Dice: A Real-Time Toolbox

In this paper research the DICE toolbox is described. This toolbox has been developed for real-time AI issues. DICE offers progressive reasoning as a way to handle time critical situations. DICE is a multitasking environment developed for a VAX/VMS environment. It offers both boolean and multivalued logic implementations. Some examples concerning the syntax are given.

Dice: A real-time toolbox

In this paper research the DICE toolbox is described. This toolbox has been developed for real-time AI issues. DICE offers progressive reasoning as a way to handle time critical situations. DICE is a multitasking environment developed for a VAX/VMS environment. It offers both boolean and multivalued logic implementations. Some examples concerning the syntax are given.

An overview of real-time issues and Ada

The Ada programming language (ANSI/MIL-STD-1815A) is the result of a design competition by the United States Department of Defense in response to the realization that billions of dollars was being spent annually on military' software, with the largest portion being spent for the maintenance of real-time and embedded systems. This paper provides an overview of several issues concerning real-time programming in general, and how they are addressed in Ada. These issues are: Scheduling, Interaction with Hardware, Concurrency, Dealing with Time, Priority Inversion, and Asynchronous Transfer of Control.

An approach to the evaluation of microcomputer operating systems with respect to real-time issues

This paper gives an overview of the approach used for the assessment of several operating systems for microcomputers. The operating systems are all commercial products and cover a spectrum ranging from general purpose operating systems to small, real-time operating systems. The criteria used for the evaluation are discussed and the approach used is discussed in detail. The results of the evaluation are not discussed in this paper.

Knowledge Modularization for Adaptive Decision Modeling

Existing research has shown that theorem proving techniques of predicate calculus can be used as effective tools for query resolution in decision support systems. Implementation of these techniques however require searching large axiom sets leading to dead ends and backtracking. In this paper we use a mathematical programming approach to partition axiom sets into modules for efficient query resolution. The method is based on a two-stage analysis of the domain specific knowledge regarding queries types. The first stage analyzes the queries to determine the information requirement on the axiom set. The second stage determines the optimal modularization of the axiom set using this information. The advantage of our approach is that by selecting the appropriate modules for query resolution only a subset of axioms are considered in the resolution process. This approach works significantly better than the traditional methods when the axiom set can be partitioned into non-overlapping modules based on the commonality of a given query set. In the case of module overlap, the math program assigns the axioms to one of the overlapping modules maximizing overall query resolution efficiency of the system. An adaptive component performs dynamic reorganization of the modules when the query set is time variant. Real time issues of query resolution with modularized axiom set are briefly discussed. INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.

Object-oriented real-time language design: constructs for timing constraints

We propose a new object-oriented programming language called RTC++ for programming real-time applications. RTC++ is an extension of C++ and its features are to specify i) a real-time object which is an active entity, ii) timing constraints in an operation as well as in statements, and iii) a periodic task with rigid timing constraints. In this paper, we first discuss real-time programming issues and what language support should be provided for building real-time applications. Then, the key features of RTC++ are described. Some programming examples are shown to demonstrate RTC++'s expressive power. A comparison to other programming languages are also discussed.

Monitoring process control systems

Recently, there has been considerable interest in the applications of artificial intelligence to process control. To date, most work has been focused on how to enhance the process control loop itself or how to interact directly with the process and the control system. For near term applications, we claim that artificial intelligence should be used purely in a monitoring role. Rather than being involved in the active control of the system, artificial intelligence should be used to identify and assist with rapidly correcting any problems which cause the process control system to fail. We also claim that it is too early to be concerned with real time issues. Rather, the emphasis should be on on-line systems, with particular emphasis placed on aids in knowledge base development and trending capabilities to provide early prediction of failure. We have developed a system called Annie that embodies these principles into a working process monitoring system.

Distributed communications

Communications among multiple Ada programs is a must, either as an explicit link or as an invisible link hidden beneath a distributed Ada veneer. Unisys has defined two Ada package specifications for inter-program communications, that are derived from the requirements developed at the Third International Workshop on Real-Time Ada Issues (RTAW3). Unisys is implementing these packages on several embedded real-time testbeds, both as standalone capabilities for application developers and as the communication layer supporting a distributed Ada system. These specifications are proposed as a basis for a secondary standard for inter-program communication for Ada9X. This paper describes how these specifications match the RTAW3 requirements and the motivation for their features. Some details of the specifications are interspersed throughout the text, with a full specification contained in the appendix.

Time-constrained reasoning under uncertainty

Dynamic classification problems present unique challenges beyond those of more traditionalstatic knowledge-based systems. Uncertain and incomplete input data, unpredictable event sequences, and critical time and resource constraints require new approaches and techniques for automated reasoning. Our work toward addressing these complex requirements has concentrated on developing an integrated software architecture which supports the knowledge engineering process from development to deployment. The approach we are using to deal with real-time issues in the deployment environment involves the use of a fast knowledge representation scheme, efficient forward and backward chaining mechanisms, and a meta-controller which handles asynchronous inputs, prioritized task requests, and hard performance deadlines.

Real-Time issues in distributed data bases for Real-Time control

This paper takes a pragmatic application-oriented view of distributed data bases to be used in Real-Time Process and Manufacturing Control. It acknowledges the strides that have been made in the development of distributed data base techniques in general, but is concerned with the problem of mapping these techniques into the Real-Time Control world. The paper takes the view that distributing data in a control system is not only an essential feature of integrated systems, but indeed is the key to their success or otherwise. However, this distribution of data has characteristics which differentiate it from other areas in which distributed data bases are used — such as air line bookings, etc. The paper discusses the essential nature of these differences and goes on to discuss how distributed data bases have to fit in with the overall control strategy, which in turn calls heavily on the use of integrated communication systems. These latter systems are themselves often based on rapidly emerging standardised systems (primarily for economic reasons), and are increasingly OSI-based. The paper concludes that to be of value, a distributed data base in a real-time control system must be designed from the viewpoint of the user rather than from that of the data base designer!

Issues in Ada compiler technology

The key technical issues involved in producing high-quality Ada compilers and related support tools are discussed. These include real-time issues, programming tools and environments, and code optimization. Also addressed are some important problems that compiler designers face, for example, determining which deficiencies of existing Ada systems can be attributed to the language and which are simply hard-to-implement features or unresolved issued in Ada compiler technology. >

A heuristic algorithm for real-time application allocation to multimicrocomputer

Multimicrocomputers, due mainly to their low cost and large potential for high throughput, better reliability and incremental system growth, have emerged as an attractive computing means for critical real-time control applications. In developing real-time multimicrocomputer many design issues must be addressed. As it has a great impact on response time, the allocation of workload to processors is one of the most important issues, which must be properly resolved in order to meet very severe performance requirements. Without careful considerations, a module allocation can cause computer saturation due to excessive interprocessor communication. The major contribution of this paper is the solution of the task allocation problem in the presence of real-time constraints. Our static, deterministic, heuristic algorithm iteratively searches for task allocation with appropriate precedence relationships, which yield a lower response time by reducing interprocessor communication, while balancing processor load.

A testbed for investigating real-time Ada issues

A testbed for investigating real-time Ada issues

Real-time knowledge-based systems

Real-time domains present a new and challenging environment for the application of knowledge-based problem-solving techniques. However, a substantial amount of research is still needed to solve many difficult problems before real-time expert systems can enhance current monitoring and control systems. In this article, we examine how the real-time problem domain is significantly different from those domains which have traditionally been solved by expert systems. We conduct a survey on the current state of the art in applying knowledge-based systems to real-time problems and describe the key issues that are pertinent in a real-time domain. The survey is divided into three areas: applications, tools, and theoretic issues. From the results of the survey, we identify a set of real-time research issues that have yet to be solved and point out limitations of current tools for real-time problems. Finally, we propose a set of requirements that a real-time knowledge-based system must satisfy.

International workshop on real-time Ada issues: summary report

This workshop, sponsored by Ada U. K. in cooperation with ACM SIGAda, was held in Devon, England, during 13--15 May 1987. It comprised five main sessions on the broad and overlapping topics of Application Requirements, Tasking, Issues in Distributed Processing, Run-Time System Issues, and Design and Development Techniques. A summary session at the end established a set of conclusions and recommendations.Participants in the workshop were selected on the basis of submitted position papers. There were 37 attendees, with 16 representing organizations that are users/implementors of real-time software, 11 representing academic institutions or research laboratories, 6 representing vendors of Ada compilers, and 4 representing hardware manufacturers. The users were principally concerned with avionics and other "hard" real-time applications, as opposed to plant processing control or similar systems with "soft" real-time constraints. Partitioned by country, there were 20 from the U. S., 7 from the U. K., 4 from France, and 1 each from Denmark, Finland, Germany, Italy, Spain and Sweden. (Five from the U. S. were in fact natives of the U.K., so there were more British accents than might be apparent from these figures.)This paper is a summary of the three-day workshop. Complete proceedings including position papers by the participants have been published as a special issue of Ada Letters (Volume VII, Number 6, Fall 1987).

Real-time Ada issues

Real-time Ada issues