Nathalie Dangoumau

Reactive mode handling of flexible manufacturing systems

This paper deals with a new modeling approach for mode handling of flexible manufacturing systems (FMS). Based on a review of the modeling methods and the specification formalisms in the existing approaches, we show that the mutual benefit of functional modeling and synchronous languages is very convenient for mode handling problem. We start by introducing the context of our work and the basic concepts of the proposed modeling approach. Then we present the steps of functional modeling and we illustrate them through an example of a flexible manufacturing cell. Functional modeling is completed by generic behavioral specifications representing the states of a subsystem or the whole system. The specification method is modular, hierarchical and supports reuse concept. The established model is generic and well adapted to our control system context. Mode handling function role within the control system is then studied. This function enables a reactive update of the availability of the resources and functions and the transmission of high level control and reconfiguration orders.

A Petri Net based approach for the Synthesis of Parts' Controllers for Reconfigurable Manufacturing Systems

The goal of this work is to address the problem of the synthesis of Petri nets controllers to design reconfigurable manufacturing systems. Our approach is inspired by supervisory control but proposes to use Petri nets (PN) to model both the plant model and the user specifications. Since Ramadge and Wonham original works, many authors have investigated supervisory control problems based on automata formalism. However, finite automata present some drawbacks such as the difficulty to model parallelism, synchronization and resource sharing. The approaches based on this formalism are generally limited by the combinatorial explosion that occurs when attempting to model complex systems. On the other hand, Petri net is a more powerful tool for modeling parallelization or synchronization, but its uses for synthesis has not been largely investigated. The method developed here is based on the Ghaffaris region theory to synthesis control places that are added to the original plant model in order to obtain a closed-loop PN that respect the user specifications. In this study one assumes that the system production is based on cyclic scheduling performed by sharing resources. More specifically the goal is to synthesis online resources allocators based on the scheduling of operations that is established offline by the scheduling task

A formal approach for reactive mode handling

The purpose of this study is the formal verification and validation of a model used for the reconfiguration process of a production system. This process is ensured by a function within the control framework named mode handling. For the needs of reactivity of this function, a synchronous approach using the formal specification formalism safe state machine (SSM) is adopted. We explain firstly what the required properties are, the methods used to check them are presented, and then we propose the specifications in SSM, which guarantee their verification and their validation. This study is mainly concerned with safety properties ensuring mode coherence.

Modes Management for Safe Production Systems

Abstract In a fault tolerant framework, in order to obtain safe production systems, it is necessary to know, at each time and under a given configuration, the set of authorised and reachable states. This is the role of the Modes Management function. Another role is to manage the commutation states that are not planned by the current control. In this paper, a modelling approach is proposed in view of the modes management for safe production systems. Two used models are described. The Model of Function allows knowing the state of a function. The Model of Component allows knowing the state of a resource. Finally, the existing interactions between these two models are presented.

An iterative method for the design process of mode handling models

This paper deals with a multi level modular approach for the design process of a model dedicated to mode handling of flexible manufacturing systems. This model was proposed in our earlier work. It is characterized by a strong hierarchy and concurrency that is why within the design process an iterative approach for specification, verification and validation is introduced in order to improve this process. The main properties being verified are presented and the approach is illustrated through an example of a manufacturing production cell. The formal analysis tools integrated into the development environment Esterel Studio are used within the proposed design process.

Verification and validation of a SSM model dedicated to mode handling of flexible manufacturing systems

This paper focuses on verification and validation of a model dedicated to mode handling of flexible manufacturing systems (FMSs). This model is specified using the synchronous formalism safe state machines (SSMs). The rigorous semantics that characterize such formalism enable to provide formal verification mechanisms ensuring determinism and dependability. A structured framework for verification and validation of the model dedicated to mode handling is proposed. The main properties being verified within this framework and the corresponding verification methods are presented. The approach is illustrated using an example of a manufacturing production cell. The formal analysis tools integrated into the development environment Esterel Studio are used within the design process.

Reconfiguration through a component oriented hybrid architecture

In this article, we present a new methodology for the reconfiguration of a hybrid system that relies on component- oriented hybrid architecture. Each component is described through a hybrid behavioural automaton, and is controlled through continuous and discrete entries that are injected by the controller. The latter is used until the objectives specifications are not respected. In this case, a central reconfiguration module updates the controller according to a components description database. This architecture is applied in the case of a system of communicating tanks.

A functional modeling approach for mode handling of flexible manufacturing systems

Abstract a new modeling approach for mode handling of Flexible Manufacturing Systems (FMS) is presented in this paper. At first the basic concepts of this modeling approach are introduced. Then the modeling steps of the FMS functional model are presented and illustrated through an example of a flexible manufacturing cell. The proposed method is modular, hierarchical and supports re-use concept. The established model is generic and well adapted to our control system context. Integration within this control system in particular within the supervision framework, is studied in the last paragraph.

FAULT RECOVERING TASKBLOCKS AND CONTROL SYNTHESIS FOR A CLASS OF CONDITION SYSTEMS

Abstract In this paper, we define fault recovery in terms of condition system languages, and show how to modify a component model to represent a fault that limits the functionality of a component. We also show under what conditions a control can be synthesized to work around such a fault. Finally, we consider the propagation of faulty behavior throughout the system and present an algorithm to evaluate whether some target specification is achievable by utilizing existing control synthesis techniques.

A Component Based Architecture for the Reconfiguration of Hybrid Systems Using Control Description

Abstract Control systems are required to satisfy increasingly severe safety and performance criteria (reliability, security***…) mainly in the case of large scale systems. Such systems have to be described with a multiple abstraction levels paradigms such as hybrid systems (implementing both discrete and continuous dynamics). We present and formalize a new strategy for the reconfiguration of a hybrid system that relies on the specification of a region-based component-oriented model which is updated whenever the system dynamics are modified. The standard controller is modified whenever a fault is detected and identified by use of an objectives automaton : Failing standard controls are replaced by a new sequence of controls chosen from an input space. Finally, we illustrate this method in the case of a system of communicating tanks.