Matteo Sartini

A fault tolerant architecture for supervisory control of discrete event systems

Abstract In this paper the problem of Fault Tolerant Control (FTC) in the framework of Discrete Event Systems (DES) modeled as automata is considered. The approach we follow is the so-called active approach in which the supervisor actively reacts to the detection of a malfunctioning component in order to eventually meet degraded control specifications. Starting from an appropriate model of the system, we recall the notion of safe diagnosability as a necessary step in order to achieve fault tolerant supervision of DES. We then introduce two new notions: (i) “safe controllability”, which represents the capability, after the occurrence of a fault, of steering the system away from forbidden zones and (ii) “active fault tolerant system”, which is the property of safely continuing operation after faults. We show how it is possible to define a general control architecture to deal with the FTC problem by introducing a special kind of automaton, called a “diagnosing-controller”.

Hierarchical control architectures in industrial automation: a design approach based on the generalized actuator concept

Abstract In this paper an effective design approach to the design of hierarchical control architectures for the automation industrial plants is presented. The main characteristic of the solution is the clear and structural separation between “policies” and “actions” deriving from the use of a novel abstract entity in modelling automation plants: the Generalized Actuator. Particular attention is paid to illustrate how to define generalized actuators starting from a “bare plant”. The potentialities of this method are emphasized by means of a case study.

Architectural design patterns for logic control of manufacturing systems: The generalized device

In all automated manufacturing systems the design of the control system plays a key role for the achievement of the targeted performance. A valuable support is provided by industrial technologies vendors in terms of computational platforms, smart I/O devices, networking infrastructures, integrated development and run-time environments. What is still lacking is a reference framework comprising a comprehensive set of highly reusable logic control components that, focusing on cross-cutting functionalities characterizing the automation domain, may help the designers in the process of modeling and structuring their applications according to the specific needs. As a first step in this direction, the paper introduces a set of new components that abstractly model the behavior of manifold field devices commonly used within automated manufacturing systems, regardless their nature, intrinsic features and specific functional purposes. These components, called Generalized Devices, are basic logic controllers/diagnosers, which play, in our architectural multilayer organization of the overall control logic, the fundamental role of keeping cleanly distinct higher-level control policies from low-level mechanisms dealing with actuators and sensors.

Rapid prototyping of automated manufacturing systems by software-in-the-loop simulation

Nowadays automated manufacturing systems are designed as the complex interconnection of components belonging to different engineering domains. Actually high performances are required in order to satisfy market needs and standards. In this framework the validation via simulation plays a crucial role as it allows to verify the system during the design phase. Software-in-the-loop architectures represent a good practice to take into account also technological side-effects that represent a classical cause of long time-to-market or, in the worst case, to project failure. In this paper we present a mathematical simulator to be used within a software-in-the-loop prototyping system.

A methodology for modular model-building in discrete automation

Our objective is to develop a general and versatile approach for building structured formal models of complex automated systems in order to facilitate their control and diagnosis. For this purpose, we present a methodology that builds the complete model of a system by composing models of the individual hardware components, their physical coupling, and the associated control logic. We choose to employ a hierarchical decomposition that separates the control logic into a high level that manages the sequence of control actions and a low level that implements the control actions. The low level is composed of control logic and physical components (sensors and actuators) grouped into a device. In order to capture the physical constraints between the components in a device, we propose the notion of a physical constraint automaton, which is composed with the generic component automata to generate the complete model of the device. We also show how the methodology allows the introduction of component faults into the overall model. The effectiveness of the proposed approach is demonstrated on a micro flexible manufacturing system.

Modular model building for vehicular traffic systems with macroscopic dynamics

Abstract Vehicular traffic modeling, analysis and supervision has became in the last year very attractive both for engineers and mathematicians with the aim of understanding, controlling and forecasting traffic phenomena. In this framework, the use of simulation tools has spread rapidly both to adequately perform the design of a road infrastructure, and as a support to simulate and verify the road infrastructure. Currently available simulators are in general closed systems where designers have no access to the implemented models, do not permit the integration of macroscopic and microscopic models together and are usually separated from design and verification tools. This paper presents a preliminary study on how to fill these gaps by using a modular model building approach. The developed elementary traffic models have been implemented into Matlab/Simulink environment and collected into a sort of library. The approach has been tested and validated using a real scenario and the available traffic measurements. Copyright ©2011 IFAC.

Mathematical Modeling for Software-in-the-Loop Prototyping of Automated Manufacturing Systems

Nowadays automated manufacturing systems are designed as the complex interconnection of components belonging to different engineering domains. Actually high performances are required in order to satisfy market needs and standards. In this framework the validation via simulation plays a crucial role as it allows to verify the system during the design phase. Software-in-the-loop architectures represent a good practice to take into account also technological side-effects that represent a classical cause of long time-to-market or, in the worst case, to project failure. In this paper we present a mathematical simulator to be used within a software-in-the-loop prototyping system.

Parameters Optimization in a Production Line Using Genetic Algorithms

In this work we present an optimization algorithm based on a discrete event simulation engine driven by a metaheuristic genetic-like search machinery; this algorithm is used to tune logical as well as physical settings in a production line. In this paper the production line and its simulation model will be described and, after a short theoretical review on genetic algorithms, the tool will be presented. Finally its use, as well as the obtained results, will be shown.