Search

The development of power electronics in the past century and the current state of the art of power electronics converters are briefly reviewed, before giving an insight into the deficiencies of the conventional current-source and voltage-source converters and into the superiority of impedance-source converters and, then, proposing a design methodology for impedance-source converters aimed to replace the traditional tedious, manual and experience-dependent design methods. Some examples for their deployment in renewable-energy applications are discussed, and the direction into which power electronic converters will develop in the future is indicated.

Preventing power transmission failures in its network of electrical terminal stations is a major concern for the infrastructure of the Thai capital Bangkok and its vicinity. Towards this objective the present study aims to analyse the network and its reliability under conditions of increased demand. The analysis is based on a representation of the network as a graph allowing to identify the most important terminal stations by graph-theoretical terms. These are, in particular, the centrality measures Degree Centrality (DC) giving the number of a station’s one-hop neighbours, Closeness Centrality (CC) describing the efficiency of power transmission from one station to others, shortest-path Betweenness Centrality (BC) indicating the number of a station’s occurrences on the shortest paths between indirectly connected stations, Hub describing stations that are connected to a large number of important stations, and Authority indicating the stations that connect many important stations. Experimental results revealed that the Bangkok Noi station was most significant when the measures DC, CC and BC were considered and, on the other hand, that the North Bangkok station was vital in terms of CC, Hub and Authority. Therefore, these stations need to be closely monitored and their operation to be carried out with extreme care in order to prevent the occurrence of power transmission failures within the Bangkok metropolitan area.

Two novel boost converters with three active Z-networks are to be designed in this chapter.

When run, most traditional clustering algorithms require the number of clusters sought to be specified beforehand, and all clustered items to be present. These two, for practical applications very serious shortcomings are overcome by a straightforward sequential clustering algorithm. Its most crucial constituent is a distance measure whose suitable choice is discussed. It is shown how sequentially obtained cluster sets can be improved by reclustering, and how items considered as outliers can be removed. The method’s feasible applicability to text analysis is shown.

SUMMARY In recent years, several large blackouts have drawn much attention to security problems in electric power transmission systems all over the world, which were triggered by initial minor disturbances and caused by cascading failures. Many models for cascading failures in power grids based on node attacks have been proposed, where only one kind of load is involved. In real power systems, however, strict measures are normally taken to protect the nodes, i.e. the power stations, so that failures at the nodes can hardly occur. It is much easier for transmission lines to break down, which may lead to cascading failures in entire power systems. Hence, a new model involving active and reactive loads and considering transmission line failures instead of node failures is proposed to understand cascading failures of power grids. When a transmission line breaks down, its load is redistributed to its neighbouring lines according to their respective capacities. It is well known that a power grid's topology and connectivity play a key role in determining its dynamic behaviour. Therefore, cascading failures of power grids with typical topologies, i.e. random, small-world and scale-free networks, are investigated using the model proposed and considering transmission line breakdowns. Finally, the model's effectiveness is validated employing real data of the European power grid. Copyright © 2014 John Wiley & Sons, Ltd.

Two huge blackouts, occurred separately on 30 and 31 July 2012 in India, spread over half the country when three of its five regional grids collapsed, leaving hundreds of millions of people without government-supplied electricity and ringing once again alarm bells with security problems in electric power grid systems. The first investigation reveals that the outage of the second (backup) 400 kV Bina–Gwalior–Agra line on 29 July 2012 led to the cascading failure through the grid, which can be simulated and explained from the perspective of the complex networks theory. In this paper, a new model of a power grid involving the active and reactive power loads is proposed and then used to analyze the cascading behavior of power grids, which is also used to explain the reason of the blackout happening in India. Furthermore, some strategic advices are given for improving the stability and security of power grids, especially Indian power grids.

As recommender systems have proven their usefulness in e-commerce by providing personalised recommendations, the approach is to be transferred to medicine. Particularly, the diagnoses made by physicians in rural hospitals of developing countries, in remote areas or in situations of uncertainty are to be complemented by machine recommendations drawing on large bases of expert knowledge to reduce the risk to patients. To this end, a database of patients' medical history and a cluster model is maintained centrally. The model is constructed incrementally by a combination of collaborative and knowledge-based filtering, in the course of which it permanently widens its knowledge base on a medical area given. To give a recommendation, the model's cluster matching the diagnostic pattern of a considered patient best is sought. The therapy actually applied after the recommendation and its subsequently observed consequences are fed back for model updating. Readily available personal digital accessories can be used for remote data entry and recommendation display as well as for communication with the central site. The approach is validated in the area of obstetrics and gynecology using data on cephalopelvic disproportion.

A modulation technique based on mathematical chaos is introduced and investigated with respect to suppress electromagnetic inference (EMI) in power electronics converters with replacing or complementing traditional filtering and schielding technologies in mind. The technique allows for parameter modulation and for chaos-based pulse width modulation (PWM). The latter can be implemented both in analogue or digital ways. To facilitate industrial applications, a novel chaotic modulation interface circuit to serve as a plug-in component for commercial power supplies is designed. Its effectiveness is verified theoretically and experimentally.

The security risks of network connectivity include malware intrusion into servers and sabotage such as denial-of-service attacks. It will be shown here how these security risks can, in contrast to employing firewalls, effectively be coped with by an adequate network interface whose architecture combines two malware-proof programmable controllers with specific software functions. By design and physical separation, the interface behaves in a fail-secure way, i.e. there is never open access from a network to a computer even if the interface fails itself.

As ontology usage becomes more prevalent in e-business decision support systems, it is essential to establish interoperation between agents or web services with different ontologies. Ontology matching represents a promising technique in information integration, agent communication and web services. Here, an ontology similarity assessment algorithm is proposed to map concepts and properties between ontologies of semantic web services. It has the two phases (1) syntactic analysis based on string tokenisation, and (2) semantic analysis employing the WordNet thesaurus and tree-structured graphs with the Tversky model. Promising experimental results indicate that this algorithm can find matching results with relatively high precision.

An analogue chaotic carrier is designed to be embedded in a chaotic pulse width modulation (PWM) boost converter, and to be used for reducing electromagnetic interference (EMI) in dc-dc converters. The analogue chaotic PWM has its advantages over the digital one in its low costs and easy-to-design, making it suitable for high-frequency operation and situations when design flexibility and low cost are required. Finally, simulations and experiments are conducted to illustrate the effectiveness of the proposed analogue chaotic PWM in reducing EMI.

Spatiotemporal chaotic systems have been applied to design pseudo-random-bit generators or ciphers for better cryptographic performance, where spatiotemporal chaos is desirable. This paper presents a chaotification method (or anti-chaos control) for creating spatiotemporal systems, which are originally either nonchaotic or chaotic, strongly chaotic. Sufficient conditions on the system parameters for chaotification are obtained. A mathematically rigorous proof shows that the chaotified system satisfying the parameter conditions is chaotic in the sense of Li–Yorke and Devaney, respectively. Moreover, the chaotification method is applicable to other spatiotemporal systems even with different configurations. Simulation results have illustrated the effectiveness of the proposed chaotification method. Additionally, the statistical properties of the spatiotemporal systems and their chaotified counterparts are analyzed and compared, showing that the chaotification method endows the spatiotemporal systems with good statistical properties. Therefore, the chaotification method can be used for applications of spatiotemporal systems in cryptography.

A novel chaotic pulse-width-modulation (PWM) boost converter has been previously proposed to reduce electromagnetic interference (EMI) in DC–DC converters, where the circuit design and simulations have been conducted, but the problems such as the mean value estimation of state variables for circuit parameter design, the ripple estimation of the input current and the stability analysis have been remained to be addressed in this paper. Here, a mean value estimation method is first proposed, which is used to estimate the mean values of state variables of chaotic PWM boost converters for facilitating the circuit parameter design and selection of circuit components. Although ripples are slightly increased, caused by adopting chaotic carriers, the DC–DC converter with reduced EMI is still stable under the chaotic PWM control. This work provides a theoretic verification of the effectiveness and practicability of the proposed chaotic PWM DC–DC converters. Copyright © 2010 John Wiley & Sons, Ltd.

A safety shell for real-time applications to be developed with UML is defined based on a re-configuration management pattern. Inspired by the architectural specifications in the Specification PEARL methodology, the pattern is parameterised by defining the properties of its components as well as by defining how the software is to be mapped to the hardware architecture. The initial and alternative scenarios are defined as well as the method for switching between them. This article includes the description of the UML pattern and of its parameterisation method, with the goal to obtain clearly specified operation scenarios with well-defined transitions among them. In order to achieve safe and timely operation, the pattern must provide a safety shell for all scenarios, i.e., enable their deterministic, temporally predictable operation, and transitions between them.

A safety shell pattern was defined based on a re-configuration management pattern and inspired by the architectural specifications in Specification PEARL. It is meant to be used for real-time applications to be developed with UML-RT as described. The implementation of the safety shell features as defined in Kornecki and Zalewski (Software Development for Real-Time Safety—Critical Applications. Software Engineering Workshop—Tutorial Notes, 29th Annual IEEE/NASA 03, pp 1–95, 2005), namely, its timing and state guards as well as I/O protection and exception handling mechanisms, is explained. The pattern is parameterised by defining the properties of its components as well as by defining the mapping between software and hardware architectures. Initial and alternative execution scenarios as well as the method for switching between them are defined. The goal pursued with the safety shell is to obtain clearly specified operation scenarios with well-defined transitions between them. To achieve safe and timely operation, the pattern must provide safety shell mechanisms for an application designed, i.e., enable its predictable deterministic and temporally predictable operation now and in the future.

Since James Clerk Maxwell established the electromagnetic field theory in 1865, multifarious electrical and electronic products have been invented, designed, produced, and widely deployed, such as wireless communication devices, electrical machines and motors. This has profoundly changed our world and our lives. Now we cannot live without electrical products anymore and, thus, we are surrounded with electromagnetic fields generated. On the other side, especially in the past few decades, the rapid development and wide deployment of electrical products have caused lots of troubles, among which the most prominent one is electromagnetic interference (EMI), which may impact other devices' performance and harm human beings' health. Therefore, fighting EMI has become a stringent, difficult problem faced by engineers and scientists. The sources of EMI include natural sources, like atmospheric charge/discharge phenomena and extraterrestrial radiation, and man-made sources, like power lines, auto ignition, radio frequency interference, and radiation hazards, to name just a few. As important components, direct current (DC-DC) converters are embedded and employed in various electrical devices, thus forming main sources of EMI. Some measures, such as filters and electromagnetic shielding, have been taken to suppress EMI, but these methods have various drawbacks with respect to cost, volume, weight, and efficiency. Therefore, new theories and methodologies are desired to cope with the EMI problem, and chaos theory is a candidate due to the continuous spectrum feature of chaos. This paper aims to provide an overview on the state of the art of traditional EMI suppression technologies, and to introduce the use of chaos theory and chaos control to reduce EMI, as well as to motivate more efforts in theoretical research and engineering practice.

The security problems raised by using standard technologies for both wired and wireless communication in industrial automation have a high potential to endanger safety. To counteract them, an encryption and authentication system was designed based on chaostheoretical cryptography, on post-processing of pseudo-random bit sequences to enhance their randomness, and on a general ciphering device adding redundancy to and blurring symbol boundaries in transmission units. The system features packet-length encryption and frequent modification of the employed pseudo-random bit generators’ parameters to come close to one-time-pad encryption.

A reconfiguration pattern for UML-based projects of embedded (real-time) systems is defined. It enables to set up hardware/software configurations, and to specify conditions and methods for dynamic reconfiguration. The reconfiguration pattern was inspired by the reconfiguration management solution of the Specification PEARL methodology, which is based on the standard for Multiprocessor PEARL whose original idea it was to extend the language to enable the programming of distributed real-time applications in PEARL. In Specification PEARL, the possibility for abstract descriptions of hardware and software architectures and for defining mappings from software to hardware components has been enhanced in correspondence with the standard. Here, a UML pattern for reconfiguration management in distributed embedded applications based on concepts from Specification PEARL is presented. Its behavioural, structural and functional aspects are outlined. It addresses stereotype entities from the Specification PEARL language, which were joined in a UML profile, and outlines the related reconfiguration management mechanisms, which were carried over to the mentioned UML pattern. The proposed reconfiguration pattern is to facilitate the development of distributed embedded application in UML with consistent and temporally predictable reconfiguration support. It should also support and enhance the applications’ flexibility and portability.

Only recently have methodical tools adequate to design real-time systems been formally introduced in design methodologies. Naturally, they were present from the beginning, but due to the large diversity of embedded systems’ areas of deployment, specially dedicated formalisms have been developed and used. High-level language programming and integration of modeling formalisms into design methods eased the development of more complex real-time applications. With the emerging object-oriented programming languages and design methods, their integration into larger information systems has become more transparent. It was the UML methodology, however, which eventually merged also the design methods and concepts of real-time systems into a consistent whole. It took a large consortium and a long process to persuade industry of the benefits the new integral methodology can offer. On the other hand, there are some trade-offs, and there are some features not completely covered, yet. Here, a different, more straightforward approach to program and design (embedded) real-time systems is presented. Since it emerged from the real-time community, it includes most features relevant there. Independent of the UML profile for schedulability, performance and time specification, a profile was devised for use in PEARL-oriented UML design. The strengths of the mentioned language and design methods for QoS-oriented design of (embedded) real-time systems are emphasised throughout this article.

Conventional measures do not sufficiently protect embedded systems against intruders and malware attacks of any kind. The main reason for this is that the system architectures are based on highly insecure and error-prone foundations. Whereas some time ago this shortcoming could still be partially coped with by swift counteraction, due to the fast data networks there are no reactive measures anymore that could compensate for the aggressors’ temporal advantage. Since computers employed for purposes of safety-related automation and control or in critical infrastructures are more and more connected to networks and are, thus, endangered by malware, new architectures for their hardware and software as presented here are necessary, which completely solve the security problems by their intrinsic properties.

It is known from information theory that eavesdropping and gaining unauthorised access to computers can be prevented by cryptography employing one-time keys. Regarding this fact, a practically feasible data encryption and user authentication scheme is presented, whose two stages are already information-theoretically secure each on its own. The first stage generates packet-long one-time keys by a chaos-theoretical method, and the second one adds redundancy in form of allowing to encrypt any plaintext by a randomly selected element out of a large set of possible ciphertexts. Obliterating the symbol boundaries in transmission units, this cryptosystem removes a toehold for cryptanalysis not addressed before.

A novel multiple-output pseudo-random-bit generator (PRBG) based on a coupled map lattice (CML) consisting of skew tent maps, which generates spatiotemporal chaos, is presented. In order to guarantee PRBG highly effective, avoiding synchronization among the sites in the CML is discussed. The cryptographic properties, such as probability distribution, auto-correlation and cross-correlation, of the PRBG with various parameters, are investigated numerically. The randomness of the PRBG is verified via FIPS 140-2. In addition, as compared with the PRBG based on the CML consisting of the logistic maps, which are often used in chaos-based PRBGs by many other researchers, the ranges of the parameters within which this multiple-output PRBG have good cryptographic properties are much bigger in terms of their cryptographic properties. It lays a foundation for designing a faster and more secure encryption.

An implementation of the disjunctive datafiow execution model for distributed control applications is presented. In this model, a control application is divided into independently executable function blocks. To achieve shorter response times, each function block is only executed when there is a significant change in any of its input data valum. To this end, an implementation hased on a field programmahle gate array (FPGA) was designed. Based on the requirements of a specific control application, VHDL code expressing the necessary firmware support is generated, compiled, and loaded into the FPGA before execution.

A new approach in control engineering (“Information Processing for Action”) is presented, in which control, computers, communication and cognition play equal roles in addressing real-life problems from very small-scale devices to very large-scale industrial processes and non-technical applications. Thus, the C2 paradigm of “Computers for Control” is shifting towards the C4 paradigm of “Computers, Communication and Cognition for Control” providing an integrated perspective on the role computers play in control systems and control plays in computer systems. This change is mainly due to new developments in computers and knowledge management, and the rapidly emerging field of telecommunications providing a number of possible applications in control. Control engineers will have to master computer and software technologies to be able to build the systems of the future, and software engineers need to use control concepts to master the ever-increasing complexity of computing systems.

An approach to generate multiple pseudorandom-bit sequences from a single spatiotemporal chaotic system is proposed in this Letter. A coupled map lattice is adopted as a prototype of a spatiotemporal chaotic system. The cryptographic properties of the pseudorandom-bit generator based on the coupled map lattice (CML–MPRBG) are analyzed. It is observed from simulation results that the CML–MPRBG has good cryptographic properties. Basic security analysis of a stream cipher based on the CML–MPRBG is also discussed. The results show that the CML–MPRBG can be a good candidate for constructing a secure cipher.

A stream cipher based on a spatiotemporal chaotic system is proposed. A one-way coupled map lattice consisting of logistic maps is served as the spatiotemporal chaotic system. Multiple keystreams are generated from the coupled map lattice by using simple algebraic computations, and then are used to encrypt plaintext via bitwise XOR. These make the cipher rather simple and efficient. Numerical investigation shows that the cryptographic properties of the generated keystream are satisfactory. The cipher seems to have higher security, higher efficiency and lower computation expense than the stream cipher based on a spatiotemporal chaotic system proposed recently.

Programmable Electronic Systems (PESs) for real-time applications that cannot immediately be transferred to safe states must provide especially high degrees of fault-tolerance. Conventionally, this reqirement is satisfied not only by configuring multiple PESs redundantly but also by applying redundant structures within each PES. Only few systems provide the capability to re-start PES units at runtime. Re-starting units must copy the internal state from their redundant counterparts, and then - when state equivalence has been reached - rejoin redundant processing. This State Restoration at Runtime prevents redundancy attrition due to transient faults, since failed channels can be brought back on line. Here, the associated problems are explained, the advantages and disadvantages of existing techniques are discussed, and a hardware-supported state restoration concept is introduced.

Cryptography as an ancient subject is endowed with new vigor by chaos theory. Cryptography protects the security of today's ubiquitous Internet communication, which as an open network is vulnerable to attack. In this paper, chaos-based cryptography is surveyed with focus on designing chaotic pseudo-random number generators (CPRNGs) for stream cipher and their chip implementation. The properties of the proposed CPRNG are analyzed.

A new approach in control engineering (“Information Processing for Action”) is presented, in which control, computers, communication and cognition play equal roles in addressing real-life problems from very small-scale devices to very large-scale industrial processes and non-technical applications. Thus, the C2 paradigm of “Computers for Control” is shifting towards the C4 paradigm of “Computers, Communication and Cognition for Control” providing an integrated perspective on the role computers play in control systems and control plays in computer systems. This change is mainly due to new developments in computers and knowledge management, and the rapidly emerging field of telecommunications providing a number of possible applications in control. Control engineers will have to master computer and software technologies to be able to build the systems of the future, and software engineers need to use control concepts to master the ever-increasing complexity of computing systems.

In this article, the usability of genetic algorithms for signal approximation is discussed. Due to recent developments in the field of signal approximation by wavelets, this work concentrates on signal approximation by wavelet-like functions. Signals are approximated by a finite linear combination of elementary functions and a genetic algorithm is employed to find the coefficients to such an approximation. The algorithm maintains a population of different approximations, encoded in the form of 'chromosomes'. From this population 'parents' are selected according to their 'fitness', and the 'children' that constitute the next generation are produced from these parents using mutation and crossover operators.Fitness functions employed to evaluate different approximations are the L1, L2, L4, and L∞ norms. Experiments are carried out on several test signals, using Gabor and spline wavelets, both to evaluate the quality of different fitness functions, encoding schemes, and operators, and to assess the usefulness of genetic algorithms in the realm of signal approximation.Although other existing methods are faster while providing comparable approximation quality, the algorithm offers a great deal of flexibility in terms of different elementary functions, fitness criteria, etc.

Programmable electronic systems are being used in almost all application sectors to perform non-safety and increasingly to perform safety functions as well. Although software based solutions are usually superior to hard wired ones for reasons of efficiency and flexibility, there is a certain reluctance of the certification authorities when it comes to licensing computer based systems which are classified as safety critical. Despite many attempts to overcome problems of software safety (IEC 61508, IEC 880, VDE 0801, IDS 00-55, RTCA/DO-178), up to now neither precise guidelines supporting the software development process are available, nor are there serious efforts being made to develop programming languages dedicated to the implementation of safety critical functions. To improve this unsatisfactory situation, i.e., to meet both economic and safety requirements, it is necessary to design appropriate language concepts with consequent regard to safety aspects. Accordingly, four subsets of a real time language suitable for the implementation of safety related systems are proposed, whose definitions fulfil the respective requirements of the four Safety Integrity Levels.

This paper gives an overview of a holistic project dealing with the consistent design of embedded control systems falling into the first level of safety integrity requirements (SIL l) (IEC, 1998). It shows how existing methods can be adapted and reasonably employed, whenever possible, without having to resort to new innovations. Firstly, the hardware issues are dealt with and extensively elaborated, particularly the peripheral interfaces with integrated processing capabilities. Secondly, the proven correct real-time operating system executing on its own dedicated processor is briefly addressed, and finally, programming issues including descriptions of the specific programming language, time bounded handling of exceptions, and how to deal with temporal overload.

Faculty of Information Technology and systems, Delft University of Technology, Delft, the Netherlands *Department of Automation Engineering, Inha University, Inchon, Korea **Faculty of Electrical Engineering, Fern Universitat, Hagen, Germany ***Intelligent Control and Systems Group, School of Electrical and Electronic Engineering, Queen’s University, Belfast, UK ****Department of Electrical and Computing Engineering, University of Central Florida, Orlando, USA

Applying an LC network into a half-bridge converter, a novel Z-source half-bridge converter is presented, in which less LC components are needed compared to the conventional one. This Z-source half-bridge converter can solve not only the problems of the shoot-through and limited voltage but also the problem of imbalance at the midpoint voltage of input capacitors. Furthermore, it can generate a broader range of output voltage values and much more kinds of waveforms, such as the varied positive or negative output voltages and the varied time ratio between positive and negative voltages, which are particularly desirable for some special power supplies, like the electrochemical power supply. Finally, the proposed converter is implemented in a prototype, and the experimental results can verify the effectiveness of the proposed converter.

The security risks of cloud computing include loss of control over data and programs stored in the cloud, spying out these data and unnoticed changing of user software by the cloud provider, malware intrusion into the server, eavesdropping during data transmission as well as sabotage by attackers able to fake authorised users. It will be shown here how these security risks can effectively be coped with. Only for preventing the cloud provider from wrong-doing no technical solution is available. The intrusion of malware into cloud servers and its malicious effects can be rendered impossible by hardware-supported architectural features. Eavesdropping and gaining unauthorised access to clouds can be prevented by information-theoretically secure data encryption with one-time keys. A cryptosystem is presented, which does not only work with one-time keys, but allows any plaintext to be encrypted by a randomly selected element out of a large set of possible ciphertexts. By obliterating the boundaries between data items encrypted together, this system removes another toehold for cryptanalysis.

A field bus architecture particularly designed for real time applications is described, in which the runtime performance cannot only be determined a priori, but also controlled during the entire process duration. Basically, it consists of a dual ring bus, in which two telegrams are transmitted on both channels in opposite directions, thus making delay measurements feasible. An ASIC timer module with an accuracy of 100μs is used for time synchronisation, which is fed by a GPS receiver. Only one GPS receiver is required in a system, because the timers of the bus nodes are synchronised via the field bus. By additional Hamming encoding of the telegrams, in each receiver errors can be corrected without requiring repetition of transfer. Additionally, the transfer of short data nibbles ensures high flexibility at different terminal equipment. Even in the presence of strong disturbances on the transmission channel, the Signal encoding by a modified "Frequency Shift Keying" method enables the receivers to securely recognise the input signals.

A programmable (logic) controller especially suited for automation applications of highest safety criticality, i.e., on Safety Integrity Level 4, is presented. Its main characteristics are input conditioning by low resolution analogue-to-digital converters and inference by look-up in cause/effect tables or rule set tables. This programmable electronic system consists of a few industry standard components, only. Thus, it is reliable, safe, verifiable, cheap and small. Owing to the simplicity of both its hardware and software, safety licensing of the controller is facilitated. With regard to software, this can easily be carried out by inspection of the table content. As a result, the approach is particularly cost effective with respect to software development. The controller is very fast, with its speed mainly determined by the table access time, and works almost jitter free. Operating in a strictly cyclic fashion, the controller exhibits fully predictable real time behaviour. Its hardware operation is supervised by a fail safe logic immediately initiating an emergency shut-down in case of a malfunction.

The concept of Distance Laboratory is presented. Based based on the widespread availability of personal computers and telecommunication networks as well as on utilising multimedia technology, this is an innovative approach for the automation of laboratory practicals as constituent of university teaching, and for both the spatial and temporal separation of students and experimental rigs and experimentation, respectively. An environment for the design of digital circuits was developed as the first realisation of the concept. A number of further experiments is in preparation.

The periodic sampling and acquisition of experimental continuous time functions by integrating analogue-to-digital conversion is discussed. With special regard to intrinsic suppression of disturbances, the theoretical justification of the superiority of this approach over point measurement schemes, and an appropriate mathematical method based on positive spline approximation operators for the computer internal representation and processing of empirical functions are established. Then, the hardware design of a corresponding multichannel interfacing unit, its physical interconnection with computers, and the required software support are described. The technique yields considerable complexity and workload reductions, and eases the time constraints imposed on process control computers.

Programs employed for purposes of safety critical control must be verified rigorously, i.e., subjected to formal safety licensing, which constitutes a very difficult and hitherto not satisfactorily solved problem. The essential issues and fundamental principles of safety related programs and computer applications are elaborated, and the importance of the human element in their development process is pointed out. At any time, utmost simplicity should be strived for, and self-discipline should be exercised. To each of the four safety integrity levels as defined by 1EC 61508-1 is assigned, respectively, a set of static and inherently safe language constructs, as well as a typical programming language or method, whose syntax enforces observation of the prevailing restrictions and rules. This is done in accordance with simplicity and comprehensibility of the verification methods available for the selected programming paradigms to meet the requirements of the individual safety integrity levels and, thus, the trustworthiness of the corresponding results. The programming methods cause/effect tables and function block diagrams on the basis of verified libraries assigned to the two upper safety integrity levels SIL 4 and SIL 3 are the only ones so far allowing, at the present state of the art, to verify automation software, which has to meet high safety requirements, in easy and economic ways. For the lower safety integrity levels, textual languages are introduced, viz., for SIL 2 a partial language enabling formal program verification, and for SIL 1 a static language with safe constructs for asynchronous multitasking. To formulate sequential function charts, an inherently safe language is defined.

The engineering life cycle is being supported by more or less isolated methods and tools. For the application area of automation technology for hybrid processes in plant engineering, this paper discusses newly developed and upcoming standards covering more than just interfaces. They refer to the entire life cycle, the infrastructure, or to the lowest level of data structures. As practice in this manufacturing industry shows, not only the users' view on the tools needs integration, but also the underlying methodologies that give rise to appearance as well as to functionality. By extending methodologies to adjacent processes or pooling methods with consistent contexts, breaks can be avoided in using these tools during the life cylce stages.

This paper introduces ADOORATA an object-oriented approach for developing large and complex real-time industrial automation systems (for example, production control systems, flexible manufacturing systems, robot control, etc.). The task of developing modern real-time systems cost-effectively, on time, and fulfilling prescribed quality criteria, can only be satisfactorily met by applying adequate system engineering approaches. All development phases, from requirements engineering through design, implementation, testing, until maintenance are covered within the ADOORATA approach. The paper discusses strategies for structuring the software and hardware components of industrial automation applications using real-time autonomous objects. Such structuring approach allows a representation of the application world at a very high level of abstraction. Timing requirements and behavioral specification is made within the context of application objects. Besides system's timeliness, special emphasis is cared on aspects such as maintainability, extensibility, and reusability.

A large part of real time and computer control applications are safety related. Hence, the software involved must be rigorously verified, i.e., safety licensed, which is extremely critical, since it is far from being as dependable as hardware. This task, however, is very difficult and not satisfactorily solved, yet. In this paper, the intrinsic problems and fundamental principles of safety licensing software are worked out. The importance of the human element in this process is emphasised. Striving for simplicity, the use of two software development paradigms especially suitable for safety critical control systems and trustworthy verification, viz., cause effect tables and function block diagrams, is advocated for. The presented approaches deviate from classical techniques by enforcing the re-use of pre-engineered and a priori verified off-the-shelf application oriented standard software function modules, and by employing diagrammatic and graphical programming paradigms. The methods effectively cope with complexity by simplification, and meet the need of society for safe and dependable computerised automation systems.

A novel design for a computer control system to be employed in safety critical applications, as found in medical environments, is presented. It features a low complexity, fault detecting hardware architecturally supporting a strictly cyclic operating mode, as known from programmable logic controllers, and a specification level, graphical programming technique based on the interconnection of application oriented standard software function modules. By design, there is no semantic gap between the programming and machine execution levels. Thus enabling the safety licensing of application software by an extremely simple but rigorous method, the software verification problem is satisfactorily solved for a large application area, where failures may cause hazards to, or even loss of, human safety and lives.

Although the domain of hard real-time systems has been thoroughly elaborated in the academic sphere, embedded computer control systems –- being an important component in mechatronic designs –- are seldom dealt with consistently. Often, off-the-shelf computer systems are used, with no guarantee that they will be able to meet the requirements specified. In this paper, a design for embedded control systems is presented. Particularly, the paper deals with the hardware architecture and design details, the operating system, and high-level real-time language support. It is shown how estimates of process run-times necessary for schedulability analysis can be acquired on the basis of deterministic behavior of the hardware platform.

This paper summarizes the discussion held among members of the IFAC TC on Real-Time Software Engineering on the distinctive features of real-time computing. It discusses the internal and external factors that characterize real-time computing as an area of science and presents some ideas about the balance between theory, abstraction, and design in the process of instruction. It also attempts to answer the question whether realtime computing is a fundamental or an applied subject area.

A computer organisation suitable to improve the performance of embedded systems encountered in hard real-time environments is described, which enhances dependability and efficiency by exploiting possibilities for parallel processing inherent to real-time systems. It is shown that internal data transmissions due to context-switching can be eliminated and that CPUs can be relieved from a considerable amount of routine work by providing a separate module for major functions of real-time operating systems, viz., for interrupt and signal recognition, for time management, and for the administration of task execution plans and states. Considering the layer model of contemporary real-time operating systems, these functions constitute kernel and first layer. The hardware implementation of typical hard real-time support features provides a clear physical separation of the intrinsically independent functions event reaction and (user) task processing. While minimising response times in general, the architecture enables to guarantee predefined, short upper bounds for them. It also incorporates a new approach for and hardware realisation of timers characterised by utmost precision and high handling comfort. Such timers are particularly well-suited to serve in distributed real-time systems, since, by employing the exact UTC received from the satellites of GPS (the global navigation and positioning system), synchronisation is not needed anymore.