Eckehard Schnieder

Integration of Software Specification Techniques for Applications in Engineering

Solid carbonaceous fossil fuels such as coal, lignite and peat are treated with an aqueous medium containing a novel catalyst to remove undesirable constituents and produce valuable products. The catalyst is prepared by steps including admixing a water soluble alkali metal silicate with an aqueous medium containing carefully controlled amounts of dissolved water soluble substances which are sources of calcium ion and magnesium ion, reacting the same to produce an aqueous colloidal suspension of the reaction product, admixing a micelle-forming surfactant with the aqueous medium, and agitating the aqueous medium containing the colloidal particles and surfactant to form catalyst-containing micelles. Particles of the fossil fuel, or components thereof, are treated and solubilized in the aqueous catalyst suspension to produce a novel aqueous solution which has highly unusual and unexpected properties. The resultant solution has important applications in agriculture and animal husbandry.

Formal Modelling and Simulation of Train Control Systems Using Petri Nets

A formal model was prepared on behalf of the German railways (Deutsche Bahn AG) starting from an informal (natural language) specifications of the European Train Control System (ETCS) system. Proceeding from the existing models of the system design - the waterfall and the spiral model - a model for the system design was developed so as to use Petri nets as a universal means of description for all the phases of the ETCS. Following a thorough and detailed comparison, it was decided to use Petri nets as a means of description for this procedure, as they permit universal application, the use of different methods and formal analysis. The method developed is an integrated event- and data-oriented approach, which shows the different aspects of the system on their own net levels. The model comprises three sub-models with a model of the environment developed next to the onboard and trackside systems. This environment model covers all the additional systems connected through the system interfaces, examples of which are interlocking or regulation. Starting from a net representing the system context, the process of the onboard and trackside sub-systems was modelled. Here, the different operations and processes are visualized in the form of scenarios, which in turn have access to additional refinements representing specific functions. System modelling was supported by the tool Design/CPN. It was chosen after a careful evaluation of several Petri net tools. ETCS system modelling was taken to a point permitting partial model simulation. On the basis of these models, additional options of the spiral model of the system design now appear: the train and trackside models may expand into specific visualizations, the algorithms can be further refined and compared, the models can be used for different kinds of tests and also for purposes of system quality assurance, which may go as far as furnishing proof of safety standards. Additional phases of system development may now be elaborated on the basis of the spiral model. Our experience has shown that it is possible to take real-life and operational systems specifications written in a natural language and express their content as a formal specification. Our experience has also demonstrated that it is possible to incorporate real life practices of software development cycles (spiral model, waterfall model) into formal models. The paper makes an overview of our experiences and highlights the various problems which were encountered and solved.

A Heuristic Approach to Railway Track Maintenance Scheduling

This paper on a heuristic approach to railway tract maintenance scheduling is from the proceedings of the 12th International Conference on Computer System Design and Operation in Railways and Other Transit Systems, held in Beijing, China, in 2010. The authors remind readers that traveling safely and comfortably on high speed railway lines that the whole railway infrastructure, particularly the railway track geometry, be in excellent condition. However, the maintenance process required to achieve such excellent conditions is largely complex and expensive, demanding an increased amount of both human and technical resources. The authors present a method for the optimization of the tamping scheduling using a heuristic algorithm, which finds a very detailed tamping schedule where each planned intervention is fully specified. Tamping is used to pack (or tamp) the track ballast under railway tracks to make the tracks more durable. The algorithm tries to maximize an objective function, which is a quantitative expression of the maintenance process’s objectives defined by the railway company. The method is validated by means of a case study based on real data of the 240 km track of a French high speed TGV line. The authors conclude that the value of the best solution found is very near to the upper bound (the difference is smaller than 1%), with a calculation time of under 1 second using a standard computer, thus, the heuristic algorithm has a great performance potential.

Verification of the safety communication protocol in train control system using colored Petri net

Abstract This paper deals with formal and simulation-based verification of the safety communication protocol in ETCS (European Train Control System). The safety communication protocol controls the establishment of safety connection between train and trackside. Because of its graphical user interface and modeling flexibility upon the changes in the system conditions, this paper proposes a composition Colored Petri Net (CPN) representation for both the logic and the timed model. The logic of the protocol is proved to be safe by means of state space analysis: the dead markings are correct; there are no dead transitions; being fair. Further analysis results have been obtained using formal and simulation-based verification approach. The timed models for the open transmit system and the application process are created for the purpose of performance analysis of the safety communication protocol. The models describe the procedure of data transmission and processing, and also provide relevant timed and stochastic factors, as well as time delay and lost packet, which may influence the time for establishment of safety connection of the protocol. Time for establishment of safety connection of the protocol in normal state is verified by formal verification, and then time for establishment of safety connection with different probability of lost packet is simulated. After verification it is found that the time for establishment of safety connection of the safety communication protocol satisfies the safety requirements.

UML-based safety analysis of distributed automation systems

HAZOP (hazard and operability) studies are carried out to analyse complex automated systems, especially large and distributed automated systems. The aim is to systematically assess the automated system regarding possibly negative effects of deviations from standard operation on safety and performance. Today, HAZOP studies require significant manual effort and tedious work of several costly experts. The authors of this paper propose a knowledge-based approach to support the HAZOP analysis and to reduce the required manual effort. The main ideas are (1) to incorporate knowledge about typical problems in automation systems, in combination with their causes and their effects, in a rule base, and (2) to apply this rule base by means of a rule engine on the description of the automated system under consideration. This yields a list of possible dangers regarding safety risks and performance reductions. These results can be used by the automation experts to improve the systems design. Within this paper, the general approach is presented, and an example application is dealt with where the system design is given in the form of a UML class diagram, and the HAZOP study is focused on hazards caused by faulty communication within the distributed system.

Performance Evaluation of GNSS for Train Localization

Global Navigation Satellite Systems (GNSS) are applicable to deliver train locations in real time. This train localization function should comply with railway functional safety standards; thus, the GNSS performance needs to be evaluated in consistent with railway EN 50126 standard [Reliability, Availability, Maintainability, and Safety (RAMS)]. This paper demonstrates the performance of the GNSS receiver for train localization. First, the GNSS performance and railway RAMS properties are compared by definitions. Second, the GNSS receiver measurements are categorized into three states (i.e., up, degraded, and faulty states). The relations between the states are illustrated in a stochastic Petri net model. Finally, the performance properties are evaluated using real data collected on the railway track in High Tatra Mountains in Slovakia. The property evaluation is based on the definitions represented by the modeled states.

Modeling market development of electric vehicles

Automobile powertrains are so far predominantly based on internal combustion engines burning fossil fuels so far. However, due to mandatory emission reduction and rising oil prices hybrid and full electric vehicles are about to be introduced in mass markets. Given their high costs, small range and missing recharging infrastructure, electric vehicles do not seem to be competitive enough compared to conventional powertrains to gain significant market share. This paper examines how such an infrastructure-dependent innovation can succeed on the long term in competition with an incumbent technology. A dynamic model is presented that contains cost, range, and infrastructure development as dynamic effects which drive adoption. The model is analyzed further in a simulation study, where the strength of feedback effects is evaluated. From this study it has to be concluded that it is primarily a quickly growing customer awareness that enables long-term market growth for electric vehicles. Quick cost reduction for batteries also has a significant effect, but it is less significant than awareness.

Formal Cognitive Resource Model: Modeling of human behavior in complex work environments

This paper presents a formal cognitive resource (FCR) model for the description of human behavior in complex work environments. As most important feature this model considers the motivated character of human work as related to the limitations of cognitive resources. The model is implemented with colored Petri nets. The formal description of colored Petri nets supports the simulation of the human-machine system in a completely consistent model structure. The mathematical basis of Petri nets allows a formal analysis of common systems. In a validation example the reasons for a specific behavior of human operators in a working environment are being identified depending on cognitive parameters of the FCR-model. It is shown how these parameters correspond to psychological performance properties

Knowledge-Based Decision Support System for Real-Time Train Traffic Control

Modern public transport and train traffic systems have to fulfill increasing demands on service reliability and availability. Train operators can only satisfy these requirements by quickly developing an efficient action in case of traffic disturbances. This paper describes a dispatching support system which is intended for use in railway operation control systems, but could also be useful for other kinds of public transport. The system consists of a knowledge-based decision support system, a simulation tool and a graphical user interface. The assistance consists of conflict detection, display of relevant information, prediction of certain dispatching measures’ impacts, and proposals for appropriate dispatching actions. Thus, the decision support system should significantly improve traffic performance, reliability, and customer satisfaction.

Control of DC-Drives by Microprocessors

Summary The possibility of employing microprocessors for direct digital control of thyristors depends on the required dynamics and the attainable resolution. This paper describes a firing-control-algorithm for a three phase thyristor AC/DC convertor. The scheme has been implemented on a commonly available microprocessor; it operates sufficiently fast, so that there is enough spare time to carry out the computations for superimposed current and speed control loops as well. Without further pulse forming the output of the processor initiates directly the gate firing amplifier. Current and speed control algorithms are of proportional-integral type with output limiting. The current signal is the only analogue variable requiring A/D conversion, since speed measurement can be performed by digital techniques thus disposing of analogue transmitters such as DC tachometers.