3,137 research outputs found
Compositional synthesis of discrete event systems via synthesis equivalence
A two-pass algorithm for compositional synthesis of modular supervisors for largescale systems of composed finite-state automata is proposed. The first pass provides an efficient method to determine whether a supervisory control problem has a solution, without explicitly constructing the synchronous composition of all components. If a solution exists, the second pass yields an over-approximation of the least restrictive solution which, if nonblocking, is a modular representation of the least restrictive supervisor. Using a new type of equivalence of nondeterministic processes, called synthesis equivalence, a wide range of abstractions can be employed to mitigate state-space explosion throughout the algorithm
Generalised verification of the observer property in discrete event systems
The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system
Generalised verification of the observer property in discrete event systems
The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system
Verification of the observer property in discrete event systems
The observer property is an important condition to be satisfied by abstractions of Discrete Event System (DES) models. This technical note presents a new algorithm that tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure, called OP-Verifier, can be applied to (potentially nondeterministic) automata, with no restriction on the existence of cycles of 'non-relevant' events. This procedure has quadratic complexity in the number of states. The performance of the algorithm is illustrated by a set of experiments
Compositional synthesis of maximally permissive supervisors using supervision equivalence
This paper presents a general framework for efficient synthesis of supervisors for discrete event systems. The approach is based on compositional minimisation, using concepts of process equivalence. In this context, a large number of ways are suggested how a finite-state automaton can be simplified such that the results of supervisor synthesis are preserved. The proposed approach yields a compact representation of a least restrictive supervisor that ensures controllability and nonblocking. The method is demonstrated on a simple manufacturing example to significantly reduce the number of states constructed for supervisor synthesis
On the set of certain conflicts of a given language
Two concurrent processes are said to be in conflict if they can get trapped in a situation where they both are waiting or running endlessly, forever unable to complete their common task. In the design of reactive systems, this is a common fault which can be very subtle and hard to detect. This paper studies conflicts in more detail and characterises the most general set of behaviours of a process which certainly leads to a conflict when accepted by another process running in parallel. It shows how this set of certain conflicts can be used to simplify the automatic detection of conflicts and thus the verification of reactive systems
Modular nonblocking verification using conflict equivalence
This paper proposes a modular approach to verifying
whether a large discrete event system is nonconflicting.
The new approach avoids computing the synchronous
product of a large set of finite-state machines. Instead, the
synchronous product is computed gradually, and intermediate
results are simplified using conflict-preserving abstractions
based on process-algebraic results about fair testing. Heuristics
are used to choose between different possible abstractions.
Experimental results show that the method is applicable to
finite-state machine models of industrial scale and brings
considerable improvements in performance over other methods
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