J.M. van de Mortel-Fronczak

Analyzing a Chi model of a turntable system using Spin, CADP, and Uppaal

Nowadays, due to increasing system complexity and growing competition and costs, industry makes high demands on powerful techniques used to design and analyze manufacturing systems. One of the most popular techniques to do performance analysis is simulation. However, simulation-based analysis cannot guarantee the correctness of a system, so it is less suitable for functional analysis. Our research focuses on examining other methods to do performance analysis and functional analysis, and trying to combine the two. One of the approaches is to translate a simulation model that is used for performance analysis to a model written in an input language of an existing verification tool. We translate a χ [D.A. van Beek, K.L. Man, M.A. Reniers, J.E. Rooda, R.R.H. Schiffelers, Syntax and Consistent Equation Semantics of Hybrid Chi, CS-Report 04-37, Eindhoven University of Technology, 2004] simulation model of a turntable system into models written in the input languages of the tools CADP [J.-C. Fernandez, H. Garavel, A. Kerbrat, L. Mounier, R. Mateescu, M. Sighireanu, CADP—a protocol validation and verification toolbox, in: Proceedings of the 8th Conference on Computer Aided Verification (CAV’96), Lecture Notes in Computer Science, vol. 1102, 1996, pp. 437–440], Spin [G.J. Holzmann, The SPIN Model Checker, Addison-Wesley, 2003] and Uppaal [K.G. Larsen, P. Pettersson, W.Yi, Uppaal in a nutshell, Int. J. Software Tools for Technology Transfer 1 (1–2) (1997) 134–152] and do a functional analysis with each of them. This allows us to evaluate the usefulness of these tools for the functional analysis of χ models. We compare the input formalisms, the expressiveness of the temporal logics, and the algorithmic techniques for model checking that are used in those tools.

Specification of a Flexible Manufacturing System Using Concurrent Programming

Because of the growing complexity, the design of and reasoning about modern industrial systems becomes increasingly difficulty. In order to understand and estimate the dynamic system behaviour, appropriate models have to be used. In many cases, existing mathematical models like queuing networks, Markov chain models, or perturbation analysis cannot be applied. In such cases, usually a model is constructed that can be validated by means of computer simulation. Since industrial systems exhibit concurrency, formalisms developed to reason about con current systems are also well suited for developing models in this specific application area. Models of systems can be expressed, for instance, in terms of Petri nets or in terms of programs written in a concurrent programming language, like Timed CSP. Both approaches, originating from computer science, are increasingly often applied in modelling of manufacturing systems. In this paper, we present a simple modular approach to the specification of (discrete) industrial systems that is based on concurrent programming. As an illustration, we present a model of a flexible manufacturing cell. The specification language used is modular and, therefore, allows for hierarchical modelling. To specify the information and control flows, a VDM-like notation is used.

Test Sequencing in Complex Manufacturing Systems

Testing complex manufacturing systems, such as an ASML lithographic machine, takes up to 45% of the total development time of a system. The problem of which tests must be executed in what sequence to ensure in the shortest possible test time that the system works, which is the test-sequencing problem, was already solved by Pattipati et al. for the diagnosis of systems during operation. Test-sequencing problems during the development and manufacturing phases of systems, however, require a different approach than the test-sequencing problems during operation. In this paper, the test problem description and algorithms developed by Pattipati et al. are extended to solve test-sequencing problems for the development and manufacturing of manufacturing systems. For a case study in the manufacturing process of an ASML lithographic machine, it is shown that solving a test-sequencing problem with this method can reduce the test time by 15% to 30% compared to experts that solve this problem manually.

A Model-based Integration and Testing Method to Reduce System Development Effort⋆

Abstract New methods and techniques are needed to reduce the very costly integration and test effort (in terms of lead time, costs, resources) in the development of high-tech multi-disciplinary systems. To facilitate this effort reduction, we propose a method called model-based integration. This method allows to integrate formal executable models of system components that are not yet physically realized with available realizations of other components. The combination of models and realizations is then used for early analysis of the integrated system by means of validation, verification, and testing. This analysis enables early detection and prevention of problems that would otherwise occur during real integration, resulting in a significant reduction of effort invested in the the real integration and test phases. This paper illustrates how models of components, developed for model-based integration, can be used for automated model-based testing, which allows time-efficient determination of the conformance of component realizations with respect to their requirements. The combination of model-based integration and model-based testing is practically illustrated in a realistic industrial case study. Results obtained from this study encourage further research on model-based integration as a prominent method to reduce the integration and test effort.

Heterarchical control systems for production cells - a case study

Abstract Most control systems of flexible production cells have a hierarchical structure. They become very complicated and difficult to maintain and modify when the underlying production cells grow in size and complexity. Moreover, they are characterized by a relatively high sensitivity to failures. As opposed to that, heterarchical control systems are flexible, modular, easy to modify, and — to some extent — faulttolerant. In this paper, a heterarchical control system of a flexible production cell is formally specified in the CSP-based language χ. This language is well suited for the description of autonomous components cooperating with each other by exchanging information.

Hierarchical Test Sequencing for Complex Systems

Testing complex systems, such as the ASML TWINSCAN lithographic machine, is expensive and time consuming. In a previous work, a test sequencing method to calculate time-optimal test sequences has been developed. Because complex systems are composed of several subsystems, which are again composed of several modules, there exists a need to hierarchically model test sequencing problems. Such a hierarchical test sequencing problem consists of a high-level model that describes a test sequencing problem at the system level, and one or more low-level models that describe the test sequencing problems at the subsystem or module level. The tests at the system level correspond to the solutions of low-level problems. This paper describes a hierarchical test sequencing model and proposes two algorithms to compute an optimal test sequence. The benefits of hierarchically modeling a problem are less computational effort and less modeling effort, because not all relations are needed. This is illustrated by a small example. The industrial relevance of this method is illustrated on a case study related to a manufacturing testing phase of a lithographic machine.

Integration and Test Sequencing for Complex Systems

The integration and test phase of complex manufacturing machines, like an ASML lithographic manufacturing system, is expensive and time consuming. The tests that can be performed at a certain point in time during the integration phase depend on the modules that are integrated and, therefore, on the preceding integration sequence. In this paper, we introduce a mathematical model to describe an overall integration and test sequencing problem, and we propose an algorithm to solve this problem. The method is a combination of integration sequencing and test sequencing. Furthermore, we introduce several strategies that determine when test phases should start. With a case study within the development of a software release that is used to control an ASML lithographic machine, we show that the described method and strategies can be used to solve real-life problems.

Model-based system analysis using Chi and Uppaal: An industrial case study

Abstract New methods and techniques are needed to reduce the integration and test effort (lead time, costs, resources) in the development of high-tech multi-disciplinary systems. To facilitate this effort reduction, a method called model-based integration and testing is being developed. The method allows to integrate formal and executable models of system components that are not yet physically realized with available realizations of other components. The combination of models and realizations is then used for early analysis of the integrated system by means of validation, verification, and testing. The analysis enables early detection and prevention of problems that would otherwise occur during real integration, resulting in a significant reduction of effort invested in the real integration and testing phases. This paper illustrates the application of the method to a realistic industrial case study, focusing on verification of the models obtained. We show how a system model has been developed for model-based integration and testing in the timed process algebra χ (Chi), and how certain behavioral properties of this model have been verified by the Uppaal model checker.

Estimating and quantifying the impact of using models for integration and testing

Industrial trends show that the lead time and costs of integrating and testing high-tech multi-disciplinary systems are becoming critical factors for commercial success. In our research, we developed a method for early, model-based integration and testing to reduce this criticality. Although its benefits have been demonstrated in industrial practice, the method requires certain investments to achieve these benefits, e.g. time needed for creating models. Making the necessary trade-off between investments and potential benefits to decide when modeling is profitable is a difficult task that is often based on personal intuition and experience. In this paper, we describe a method based on integration and test sequencing techniques that can be used to make quantitative impact estimations of using models for integration and testing. An industrial case study application of this method shows that it is feasible to quantify the costs and benefits of using models in terms of risk, time, and costs, such that the profitability can be determined.

Modeling, analysis and implementation of infrastructure for model-based integration and testing

To reduce the lead time and the costs of integrating and testing high-tech multi-disciplinary systems, we use formal and executable models of components for early system analysis and for early integration and testing with available component realizations. In this paper, we investigate the role of the infrastructure that establishes the interaction between the components. We include a model of the infrastructure for early system analysis and we implement a corresponding integration infrastructure to integrate and test models and realizations. Application of this approach to examples of typical interaction types proves to be rather straightforward, allowing proper analysis of system and infrastructure properties, which remain valid during model-based integration and system testing.