A re-configurable multi-agent system architecture for error recovery in production systems

Multi-agent systems for manufacturing systems appear to provide adequate response to abrupt disturbances on the shop floor. To date, most of the work has been focused on planning and scheduling but very little work has been done on issues pertaining to monitoring, diagnostics and error recovery. Our approach addresses the issue of combining the discipline of hierarchical systems with the agility of multi-agent systems. Within the context of a hierarchy, the focus is on the workstation level and, in particular, the construction of a re-configurable system having production agents, error recovery agents, and a mediator agent structure connecting production and recovery agent hierarchies. In addition, the relationship to a multi-level, multi-layer hierarchy control is established. This latter hierarchy, based on Petri Net constructs, serves, in one sense, as a retrieval based resource for process planning and generation of recovery plans for production and recovery agents within the proposed multi-agent system. An objective of this effort is to provide a test-bed for comparison of hierarchical systems, heterarchical, and a hybrid combination which is the focus of the investigation presented here.     

FASA: A software architecture and runtime framework for flexible distributed automation systems

Modern automation systems have to cope with large amounts of sensor data to be processed, stricter security requirements, heterogeneous hardware, and an increasing need for flexibility. The challenges for tomorrow’s automation systems need software architectures of today’s real-time controllers to evolve.This article presents FASA, a modern software architecture for next-generation automation systems. FASA provides concepts for scalable, flexible, and platform-independent real-time execution frameworks, which also provide advanced features such as software-based fault tolerance and high degrees of isolation and security. We show that FASA caters for robust execution of time-critical applications even in parallel execution environments such as multi-core processors.We present a reference implementation of FASA that controls a magnetic levitation device. This device is sensitive to any disturbance in its real-time control and thus, provides a suitable validation scenario. Our results show that FASA can sustain its advanced features even in high-speed control scenarios at 1 kHz.     

GSPN models of Markovian multiserver multiqueue systems

The paper presents exact results for the average customer waiting and sojourn times in Markovian systems comprising a number of finite-capacity queues cyclically attended by several servers. The system behaviour is described using generalized stochastic Petri nets (GSPN), and the performance indices are obtained numerically by means of GreatSPN, the software tool for the analysis of GSPN. The average waiting and sojourn times of customers in Markovian multiserver multiqueue systems are computed exactly in this paper for the first time: they were previously estimated for similar systems by other authors only through approximate models.     

An agent-based framework for cooperating expert systems in concurrent engineering

This paper describes an agent-based framework with a tandem integration architecture for cooperating distributed, heterogeneous, and autonomous concurrent engineering systems. The approach has been experimented with using the prototype AGENTS system. It is demonstrated that design tools can be dynamically connected and configured to construct highly complex systems on an incremental basis, designing and proving one system at a time without bothering the rest. A major advantage of the approach is the balance between the interoperability and the autonomy of individual systems.     

RealNet: a neural network architecture for real-time systems scheduling

Real-time embedded systems are spreading to more and more new fields and their scope and complexity have grown dramatically in the last few years. Nowadays, real-time embedded computers or controllers can be found everywhere, both in very simple devices used in everyday life and in professional environments. Real-time embedded systems have to take into account robustness, safety and timeliness. The most-used schedulability analysis is the worst-case response time proposed by Joseph and Pandya (Comput J 29:390–395,1986). This test provides a bivaluated response (yes/no) indicating whether the processes will meet their corresponding deadlines or not. Nevertheless, sometimes the real-time designer might want to know, more exactly, the probability of the processes meeting their deadlines, in order to assess the risk of a failed scheduling depending on critical requirements of the processes. This paper presents RealNet, a neural network architecture that will generate schedules from timing requirements of a real-time system. The RealNet simulator will provide the designer, after iterating and averaging over some trials, an estimation of the probability that the system will not meet the deadlines. Moreover, the knowledge of the critical processes in these schedules will allow the designer to decide whether changes in the implementation are required.This revised version was published online in November 2004 with a correction to the accepted date.     

T-CREST: Time-predictable multi-core architecture for embedded systems

Real-time systems need time-predictable platforms to allow static analysis of the worst-case execution time (WCET). Standard multi-core processors are optimized for the average case and are hardly analyzable. Within the T-CREST project we propose novel solutions for time-predictable multi-core architectures that are optimized for the WCET instead of the average-case execution time. The resulting time-predictable resources (processors, interconnect, memory arbiter, and memory controller) and tools (compiler, WCET analysis) are designed to ease WCET analysis and to optimize WCET performance. Compared to other processors the WCET performance is outstanding.The T-CREST platform is evaluated with two industrial use cases. An application from the avionic domain demonstrates that tasks executing on different cores do not interfere with respect to their WCET. A signal processing application from the railway domain shows that the WCET can be reduced for computation-intensive tasks when distributing the tasks on several cores and using the network-on-chip for communication. With three cores the WCET is improved by a factor of 1.8 and with 15 cores by a factor of 5.7.The T-CREST project is the result of a collaborative research and development project executed by eight partners from academia and industry. The European Commission funded T-CREST.     

The HORSE framework: A reference architecture for cyber-physical systems in hybrid smart manufacturing

In the Industry 4.0 era, manufacturers strive to remain competitive by using advanced technologies such as collaborative robots, automated guided vehicles, augmented reality support and smart devices. However, only if these technological advancements are integrated into their system context in a seamless way, they can deliver their full potential to a manufacturing organization. This integration requires a system architecture as a blueprint for positioning and interconnection of the technologies. For this purpose, the HORSE framework, resulting from the HORSE EU H2020 project, has been developed to act as a reference architecture of a cyber-physical system to integrate various Industry 4.0 technologies and support hybrid manufacturing processes, i.e., processes in which human and robotic workers collaborate. The architecture has been created using design science research, based on well-known software engineering frameworks, established manufacturing domain standards and practical industry requirements. The value of a reference architecture is mainly established by application in practice. For this purpose, this paper presents the application and evaluation of the HORSE framework in 10 manufacturing plants across Europe, each with its own characteristics. Through the physical deployment and demonstration, the framework proved its goal to be basis for the well-structured design of an operational smart manufacturing cyber-physical system that provides horizontal, cross-functional management of manufacturing processes and vertical control of heterogeneous technologies in work cells. We report on valuable insights on the difficulties to realize such systems in specific situations. The experiences form the basis for improved adoption, further improvement and extension of the framework. In sum, this paper shows how a reference architecture framework supports the structured application of Industry 4.0 technologies in manufacturing environments that so far have relied on more traditional digital technology.     

Fluid Stochastic Petri Nets for Computing Transfer Time Distributions in Peer-to-Peer File Sharing Applications

This paper presents an application of the Fluid Stochastic Petri Net (FSPN) formalism for the analysis of the transfer time distribution in peer-to-peer (P2P) file sharing applications.The transfer of the resource follows a successful search; the transfer time is mainly dominated by network characteristics, application characteristics, resource characteristics, and user behavior.The proposed analytical modeling technique accounts all these aspects and provides an estimation of the transfer time distribution after the search for a given resource has been performed.Some numerical results are presented to prove the flexibility and the potential of the proposed technique.     

基于多视图的信息物理融合系统体系结构研究

美国将信息-物理融合系统（Cyber-Physical Systems,CPS）列为八个重要信息技术领域之首,CPS亦成为国内当前研究热点。通过对国内外CPS研究现状分析,针对系统、功能和技术三个视图角度,提出了三种新型基于视图的CPS体系结构,说明了三种视图间的关系,利用微电网CPS实例论证了基于不同视图的CPS体系结构分析方法的优点。同时,对于CPS未来的研究方向进行了展望。     

Socio-technical systems: From design methods to systems engineering

It is widely acknowledged that adopting a socio-technical approach to system development leads to systems that are more acceptable to end users and deliver better value to stakeholders. Despite this, such approaches are not widely practised. We analyse the reasons for this, highlighting some of the problems with the better known socio-technical design methods. Based on this analysis we propose a new pragmatic framework for socio-technical systems engineering (STSE) which builds on the (largely independent) research of groups investigating work design, information systems, computer-supported cooperative work, and cognitive systems engineering. STSE bridges the traditional gap between organisational change and system development using two main types of activity: sensitisation and awareness; and constructive engagement. From the framework, we identify an initial set of interdisciplinary research problems that address how to apply socio-technical approaches in a cost-effective way, and how to facilitate the integration of STSE with existing systems and software engineering approaches.     

PROTOB: An object-oriented case tool for modelling and prototyping distributed systems

The PROTOB object-oriented methodology for the executable specification of large-scale event-driven systems is introduced and described. Two supporting features of PROTOB are also presented: the graphic and textual language that formally describes the behaviour of objects, which is based on high-level Petri nets called “PROT nets” and which is demonstrated to be more powerful than SA/RT dataflows; and a CASE environment with tools for specification, modelling, simulation and prototyping. Use of PROTOB is illustrated by discussion of the automated generation of distributed systems running on a network of VMS and UNIX computers.     

一种利用UML的Petri网软件实现方法

Petri网既是一种图形化建模工具,又是一种形式化数学工具。Petri网具有对并发、并行、分布、异步系统进行验证仿真的能力。但是,Petri网是用来描述和分析要开发的系统模型的工具。不是计算机的实现工具,必须要通过一定的方法才能将Petri网用软件来实现。由于UML(统一建模语言)具有友善的用户界面,易于编程实现,故提出一种利用UML作为过渡的Petri网软件实现方法。     

A framework for meta-level control in multi-agent systems

Sophisticated agents operating in open environments must make decisions that efficiently trade off the use of their limited resources between dynamic deliberative actions and domain actions. This is the meta-level control problem for agents operating in resource-bounded multi-agent environments. Control activities involve decisions on when to invoke and the amount to effort to put into scheduling and coordination of domain activities. The focus of this paper is how to make effective meta-level control decisions. We show that meta-level control with bounded computational overhead allows complex agents to solve problems more efficiently than current approaches in dynamic open multi-agent environments. The meta-level control approach that we present is based on the decision-theoretic use of an abstract representation of the agent state. This abstraction concisely captures critical information necessary for decision making while bounding the cost of meta-level control and is appropriate for use in automatically learning the meta-level control policies.     

A combined queueing network and stochastic Petri-net approach for evaluating the performability of fault-tolerant computer systems

In this paper the performability analysis of fault-tolerant computer systems using a hierarchical decomposition technique is presented. A special class of queueing network (QN) models, the so-called BCMP [4], and generalized stochastic Petri nets (GSPN) [1] which are often used to separately model performance and reliability respectively, have been combined in order to preserve the best modelling features of both.

A conceptual model is decomposed into GSPN and BCMP submodels, which are solved in isolation. Then, the remaining GSPN portion of the model is aggregated with flow-equivalents of BCMP models, in order to compute performability measures. The substitutes of BCMP models are presented by means of simple GSPN constructs, thereby preserving the 1st and 2nd moments of the throughput. A simple example of a data communication system where failed transmissions are corrected, is presented.     

Fundamentals of systems ergonomics/human factors

Ergonomics/human factors is, above anything else, a systems discipline and profession, applying a systems philosophy and systems approaches. Many things are labelled as system in today's world, and this paper specifies just what attributes and notions define ergonomics/human factors in systems terms. These are obviously a systems focus, but also concern for context, acknowledgement of interactions and complexity, a holistic approach, recognition of emergence and embedding of the professional effort involved within organization system. These six notions are illustrated with examples from a large body of work on rail human factors.     

面向方面软件体系结构编织的形式化描述方法

面向方面的规范描述在软件体系结构建模和分析中起着重要的作用,但目前已有的方法不能对体系结构方面及其编织逻辑的详细描述提供足够的支持,也缺乏行之有效的方法对方面的编织逻辑进行推理和评价。本文以Petri网作为行为描述和结构描述的统一基础,提出了一种描述软件体系结构方面及其编织逻辑的形式化方法,并通过实例对相关的概念和模型进行了说明。应用研究表明,该方法描述能力强,不仅能描述复杂的方面结构、行为以及相应的编织逻辑,还可对编织效果进行推理和评价。     

Smart grid coordination in building HVAC systems: EMPC and the impact of forecasting

Energy consumption by heating, ventilation, and air conditioning (HVAC) systems exhibits a clear correlation with electricity prices. The method of economic model predictive control (EMPC) can be used in conjunction with thermal energy storage (TES) to time-shift power consumption away from periods of high demand to periods of low energy cost. Dynamic electricity pricing and weather condition forecasts can be readily incorporated within this methodology. Unfortunately, the receding horizon nature of this control strategy makes it very susceptible to the quality of the forecasts used. To this end, the development and implementation of several forecasting methods will be discussed. Finally, the EMPC performance of these methods will be assessed on a simple building example using active TES.