Showing papers presented at "Computer Aided Systems Theory in 1999"

Simulation of Gaussian Processes and First Passage Time Densities Evaluation

Abstract: Motivated by a typical and well-known problem of neurobiological modeling, a parallel algorithm devised to simulate sample paths of stationary normal processes with rational spectral densities is implemented to evaluate first passage time probability densities for time-varying boundaries. After a self-contained outline of the original problem and of the involved computational framework, the results of numerous simulations are discussed and conclusions are drawn on the effect of a periodic boundary and a Butterworth-type covariance on determining quantitative and qualitative features of first passage time probability densities.

Modeling Complex Systems by Multi-agent Holarchies

Abstract: Arthur Koestler (1967, 1969, 1978) introduced into science the concepts of a “holon” and of a “holarchy” A holarchy is according to A Koestler a tree-like hierarchy where the nodes of the tree – the components of the hierarchy – are autonomous intelligent acting I/O systems

Floating Car Data Anaylsis of Urban Road Networks

Abstract: A model for the analysis of floating car data (FCD) in urban road networks is proposed. In contrast to freeway traffic, structural features such as traffic lights are shown to dominate the dynamics – in a quasistationary picture – of such a network. Principles for obtaining a segment travel time depending on the mean vehicle density are discussed. Some remarks for the determination of this state variable are given, also on several segments.

HEDES: A System Theory Based Tool to Support Evolutionary Software Systems

Abstract: Software systems evolve over time. Traditional software development methods and tools support partial aspects of this evolving process. Over the last few years we have researched into theoretical evolution search models which might be applied to the development of software systems. The Theory of Systems and biology have interesting views on the evolution process, very different from genetic algorithms, which may aid in the development of software systems and CASE tools. Our aim in this paper is to present a first version of a tool (HEDES) which includes these models and implements them in an object-oriented language (VisualWorks 3.0), using first-order temporal logic as support. In addition, some lessons learnt in the development of these complex and changing tools will be outlined, especially the importance of an iterative lifecycle in object-oriented development, a high degree of cohesion of the develop- ment team and the need for flexible and rapid ways of communicating new ideas using discussion meetings, Internet facilities and development support tools.

Floating car data analysis of urban road networks

Abstract: A model for the analysis of floating car data (FCD) in urban road networks is proposed. In contrast to freeway traffic, structural features such as traffic lights are shown to dominate the dynamics – in a quasistationary picture – of such a network. Principles for obtaining a segment travel time depending on the mean vehicle density are discussed. Some remarks for the determination of this state variable are given, also on several segments.

Uncertain Variables in the Computer Aided Analysis of Uncertain Systems

Abstract: The paper is concerned with static uncertain systems described by a function or by a relation Unknown parameters in the mathematical models are considered as so called uncertain variables described by certainty distributions given by an expert Two versions of the uncertain variables based on two versions of uncertain logics are defined In the second part of the paper the formulations of the analysis and decision making problems adequate to the description of uncertainty are presented and the general procedures of the problem solving are described Simple examples and an algorithm of the decision problem solving for a discrete case illustrate the computational aspects of the approach based on the uncertain variables and the possibility of the application to computer-aided analysis and decision making

Mobile Robot Path Planning Among Weighted Regions Using Quadtree Representations

Abstract: An approach to the mobile robot path planning among heterogeneous regions is presented. Proper weight factors are associated with the regions of different kind (rock, sand, grass) to characterize the amount of the difficulty required to travel through that particular region, as compared to traveling over a flat, smooth surface (corresponding to a minimum weight). The weighted regions are represented in the form of modified matrix quadtree. The technique of distance transform is extended to the weighted regions and applied to the robot path planning. Illustrative examples are included.

Vertical Partitioning Algorithms in Distributed Databases

Abstract: Data distribution is a crucial problem affecting the cost and efficient use of these systems. The problem is further exacerbated by the lack of methods and support tools for the design of distributed databases. This paper outlines some of the main techniques currently used for data distribution, such as vertical partitioning and replication. Two vertical fragmentation methods are described, the classic NAVATHE method and the newer FURD method, as well as the two proposed in this paper, the FURD-FDEZ and the FURD WITH REPLICATION methods.

Representation of the RCS Reference Model Architecture Using an Architectural Description Language

Abstract: The Real-Time Control System (RCS) Reference Model Architecture provides a well-defined strategy for development of software components for applications in robotics, automated manufacturing, and autonomous vehicles. ADLs are formally defined languages for specification of software system’s designs. In this report, we describe the results of an investigation into the use of an ADL to specify RCS software systems, and assess the potential value of ADLs as specification and development tools for RCS domain experts. The report also discusses potential influence of ADLs for commercial software development tools and component-based development.

Electronic Performance Support Systems Challenges and Problems

Abstract: After a short introduction to the concept of automation and computer based systems, chapter 2 presents the the concepts of Electronic Performance Support Systems (EPSS). Chapter 3 specifically discusses process-centered EPSS and their realization in software engineering and office automation. Different attitudes and requirements are pointed out. Chapter 4 argues that computer support makes it necessary to extend Scheer’s Y (well-known in the CIM-area) to accomodate additional granularity. This discussion is carried over into chapter 5 where we map the relevant processes of software engineering and office automation to the processes identified in the extended Y from chapter 4.

A Formalisation of the Evolution of Software Systems

Abstract: One of the most interesting and probably more difficult challenges in developing Software Systems is the modelling of their evolutionary capacity, that is to say, to gather the possibility that the Software Systems will go ahead in the future with the necessary changes to adapt to the environment using a different and new functionality. Modelling this evolution requires to have into account what kind of changes and modifications could follow and support a Software System during its life and also during its development. The evolutionary characteristics of a Software System can be approached by abstract evolutionary models, which can be further formalised. This formalisation makes operational the abstract evolutionary models and allows a kind of representation of the evolutionary process that could support the specification and mapping into concrete specification and implementation tools. These tools further allow us to obtain concrete and functional Software Systems.

Multiagent Approach to Intelligent Control of Robot

Abstract: Within the last years the paradigm of intelligent software agents became an emerging topic in computer science research and development. Intelligent software agents are computational systems that populate complex dynamic environment, act and react there in an autonomous way in order realize a specific task based on a set of goals given to them. In multi agent systems (= MAS) intelligent software agents are grouped together and represent a network of problem solvers designed to achieve a common goal, which would be too large for a single centralized software agent. The member agents of such a multi agent system have a sufficient degree of decision-making autonomy and interact with other agents by explicit communication. Therefore the main fields of interest in multi agent based system design cover coordination, communication and negotiation based on uncertain data and knowledge of each member agent of the multi agent system. This article proposes s system theoretical approach towards the design and synthesis of a multi agent system for controlling a robotic agent.

Integrating Two Dynamic Models of Business-Logistics Plant

Abstract: In order to engineer business processes a model is needed that allows us to analysis and design of the dynamic properties of the processes. This paper shows a unified framework for data flow diagrams (DFD, for short) and Petri nets in modeling business processes. Introducing the concept of business transaction Petri net, we provide a firm mathematical basis for a comparison of a such Petri net to a business process modeled by a DFD. It will be turned out that the behavior of a business transaction Petri net is simulated by the corresponding business transaction system.

Computer Aided Planning System of a Flexible Microrobot-Based Microassembly Station

Abstract: The assembly of complex microsystems consisting of several single components (i.e. hybrid microsystems) is a task which has to be solved to make mass production of microsystems possible. Therefore, it is necessary to introduce flexible, highly precise and fast microassembly methods. In this paper, the control system of a microrobot-based microassembly desktop station that has been developed at the University of Karlsruhe, will be presented from the lower to the planning levels. This comprises vision-based closed-loop control, user interfaces, a re-configurable computer-array, execution planning and assembly planning algorithms tailored to the needs of the microassembly station.

The Supervision of Hybrid Control Systems-A Layered Architecture

Abstract: The scenario treated in this paper concerns the discrete event control and supervision of two decoupled continuous systems. The theoretical framework is based on the hybrid control system architecture, developed by P.J. Antsaklis and his co-workers and on the supervised control concept, proposed by the Sylodi Group from Grenoble. The main contribution of this paper is an algorithm for building the discrete event approximation of a continuous system with unknown, constant and constrained parameters. The Antsaklis formalism is extended to a disturbed continuous first order system.

Development of a Precision Assembly System Using Selective Assembly and Micro Machining

Abstract: In this paper we propose a new combinatorial optimization method for parts matching in a precision assembly system. This method combines selective assembly with micro machining so as to produce high precision assembled units. From the simulation results, it is presented that the system is effective in a small lot production, where higher assembly rates can not be attained with conventional methods, in such that a higher rate is obtained if micro machining is used alongside.

Conceptual Desin, Functional Decomposition, Mathematical Modelling, and Perturbation Analysis

Abstract: Conceptual Design methods place some intermediate solution steps between problem definition and final technical solution. Functional Decomposition is such a method which aims at finding solution concepts in terms of functions first and, after that, technical realisations for the individual functions. The role of mathematical models in conceptual design is to provide some coarse quantitative assessment of certain solution concepts, and furthermore, to clarify the relationship between the Functional Requirements and the Design Parameters. Later on, in the more detailed design steps refined mathematical models are used. What is their relation to the early models used in conceptual design? The concept of perturbation analysis seems to provide a framework for defining and understanding these relationships.

Multi-processor Design of Non-linear Robust Motion Control for Rigid Robots

Abstract: The research activities carried out in the framework of the proposed paper have been directed to the development of nonlinear control techniques, algorithms and architectures for the free motion of robots having rigid links, that provide the following global control performances: global asymptotic stability, precision for time varying trajectory tracking, robustness at external disturbances, nonlinear coupling between motion axes and uncertainties of the dynamic model of the manipulator with drives structure, for closed-loop robot systems with n ≥ 5 degrees of freedom. Thus, there is proposed a solution for nonlinear motion control based on adaptive control techniques. The control method that is proposed provides high dynamic performances for the ensemble manipulator – drive systems – internal transducers – controller – user interface, that is: high displacement speed and tracking precision on desired time varying trajectories, rejection of disturbances of the type: variable masses carried by the arm, modeling errors, measuring noise. In the framework of this paper, the authors designed and simulated a library of procedures, algorithms and software control modules to be further implemented in a generic parallel multiprocessing architecture, as a robot controller. In this respect, the structural design was directed towards VME – based bus oriented multimaster structures.

Patterns for Embedded Systems Design

Abstract: This paper deals with embedded systems architecture components called as application patterns, and with their employment for design reuse. The first part of this contribution introduces the concepts of application patterns and relates them to the well-known object-oriented design abstractions. Employing application patterns that demonstrate the concrete examples of reusability, the kernel of this contribution presents two case studies, which are based on real design projects: petrol pumping station dispenser controller and multiple lift control system. To reuse an architectural component whose implementation usually consists both of software and hardware, it means to reuse its formal specification. The paper deals with behavioral specifications employing state or timed-state sequences and with their closed-form descriptions by finite-state or timed automata. The contribution focuses on identification, creation, and initial classification of reusable application patterns while retrieval, adaptation, and storage reuse tasks with case-based reasoning support are treated briefly at the conclusion as an introductory information about launching research.

Decision Based Adaptive Model for Managing Software Development Projects

Abstract: The article is about the management of an important part of the development process of a software system: the phase of incremental implementation Implementation is based on the design of the system architecture and its components, its main task is the production of modules and their integration

Variable-Structure Learning Controllers

Abstract: In this paper, a direct sliding control learning strategy is combined with a fuzzy system with variable granularity to achieve different precision requirements in different zones of the state-space; non-local basis functions are also added. A coordinate transformation gives a clearer meaning over performance evaluation and the fuzzy system operates on this transformed space.

Parallel Processor Array for Tomographic Reconstruction Algorithms

Abstract: In this paper we derive exemplarily a parallel processor array for algorithms of commonly used tomographic reconstruction methods by using the tools of the design system DESA. The algorithms represent a group of computationally intensive image processing algorithms requiring high throughput and real-time processing.

Towards Verifying Distributed Systems Using Object-Oriented Petri Nets

Abstract: The article discusses the notion of state spaces of object-oriented Petri nets (OOPNs) associated to the tool called PNtalk and the role of identifiers of dynamically appearing and disappearing instances within these state spaces. Methods of working with identifiers based on sophisticated naming rules and mechanisms for abstracting names are described and compared. Some optimizations of state space generating algorithms for the context of OOPNs are mentioned, as well. Finally, some possibilities of specifying properties of systems to be checked over the state spaces of their OOPN-based models are discussed.

A Fractal Software Complexity Metric Analyser

Abstract: As we try to fulfill the requirements upon quality of the software products we cannot avoid the use of the complexity metrics. There is a lot of different metrics and also there are hundreds of tools for analyzing the software with some of those metrics. However, since all tools available are concentrated only on some specific programming metrics, for a comprehensive analysis one has to use a lot of different tools. We wanted to derive an environment that would include all of the mostly used metrics, and since we are also developing new metrics ourselves, we developed a tool called Software Complexity Analyzer, that beside classical metrics incorporates also more universal fractal metrics.

Computer-Aided Analysis and Validation of Heterogeneous System Specifications

Abstract: In applications of formal methods, the problem of how to establish the correctness of the initial formalization step is an often underestimated aspect of the system design process. We propose a methodology based on the construction of a mathematical model which reflects the given system so closely that the correctness can be established by observation and experimentation (ground model). Complex technical systems are often heterogeneous, so that different system aspects are best modelled by means of different techniques. This leads to heterogeneous ground models. To achieve a consistent and coherent view of heterogeneous behavioural models, which is a prerequisite for any systematic analysis and validation, we introduce a common semantic framework (meta-model) based on the notion of Abstract State Machines. We exemplify our methodology by an industrial case study from automated manufacturing, the distributed control for a material flow system (MFS).

Design for Disassembly and Recycling for Small and Medium Sized Companies for the Next Generation

Abstract: As we left the 20th century the industry has paid particular attention to the ecological impacts of new facilities, energy use, number of used materials and several other very important environmental issues. Now many impacts to design and recycle facilities as “life cycle” (planning, design, development, supply, manufacture, use, recycling) have not been systematically and comprehensively studied and analysed. Engineers, operators, professionals and other people who works in this area together maybe in different firms should understand the environmental and interactions of management, team behavior and methods because their everyday decisions carry substantial social implications.

Cast Methods in Biocybernetics

Abstract: The systematic use of what we now call Systems Theory in the description of biological systems, and more precisely, the nervous system, took off in the Forties although many of the basic ideas had been being managed in philosophic and scientific circles almost since the Ancient Greeks. From 1943 to 1945, a kind of synergetic process was started up, triggered as the result of three basic works. First, Norbert Wiener, Arthur Rosemblueth and Julian Bigelow’s study (1943) on the nature of teleological processes where the crucial idea was that what was relevant in a homeostatic process was the information return and not theenergy return via the feedback links. It is representative of the analytical approach.

Simulating Social Grouping: An Interactive Team-Building Tool (ITBT)

Abstract: The paper presents the concept of an interactive team-building tool for simulating social grouping. It shows how decisions whom to assign which task can be supported from a game-theoretic perspective. Thus the group member are modeled as social entities following their preferences and being able to resist against work distributions they do not want. The features of ITBT are deduced from the decision situation of a team leader being in charge for the work distribution and are described in more detail in the paper.

Distributed Simulation with Multimedia Interface

Abstract: The training of the personnel plays a major role in the security and reliability of many industrial processes. In order to fulfil this objective it is necessary to develop applications that support distributed interactive simulation with an interface near the real world. This paper describes such type of application during the development of a training simulator prototype for a nuclear power plant. The simulator is based on a client/server architecture that allows the execution on different machines in a network and many users to participate in the same simulation. The interface was designed to support the interaction of the operators with the simulator through touch screens with high fidelity displays of the control room developed using the component technology. The main features of the simulator are the distributed execution of the models using inexpensive hardware and the flexibility of design and maintenance of the interface.

Development of a Precision Assembly System Using Selective Assembly and Micro Machining (Evaluation of Combinatorial Optimization Method for Parts Matching)

Abstract: In this paper we propose a new combinatorial optimization method for parts matching in a precision assembly system. This method combines selective assembly with micro machining so as to produce high precision assembled units. From the simulation results, it is presented that the system is effective in a small lot production, where higher assembly rates can not be attained with conventional methods, in such that a higher rate is obtained if micro machining is used alongside.