On Conditional Decomposability

The requirement of a language to be conditionally decomposable is imposed on a specification language in the coordination supervisory control framework of discrete-event systems. In this paper, we present a polynomial-time algorithm for the verification whether a language is conditionally decomposable with respect to given alphabets. Moreover, we also present a polynomial-time algorithm to extend the common alphabet so that the language becomes conditionally decomposable. A relationship of conditional decomposability to nonblockingness of modular discrete-event systems is also discussed in this paper in the general settings. It is shown that conditional decomposability is a weaker condition than nonblockingness.Comment: A few minor correction

Supervisory control of discrete-event systems with output : application to hybrid systems

In this thesis, the problem of supervisory control of Discrete-Event Systems (DES) with output is presented and discussed at length. In such systems, causal output functions are employed to assign each sequence of inputs with a corresponding sequence of outputs. When the specification of the desired behavior is given by a formal language over the output alphabet, necessary and sufficient conditions are derived for the existence of nonblocking input as well as nonblocking output supervisory controls. An algorithm is presented to extend the results of nonblocking input/output supervisory control from language-based framework into finite automata framework, making the proposed results applicable to large scale discrete-event systems. The idea of siblings is introduced to solve the problem of nondeterminism in discrete-event abstractions of hybrid systems, giving rise to the development of a theory for nonblocking supervisory control of hybrid systems. Our results enable one to apply classical supervisory control theory to design supervisors for DES approximations of hybrid systems, and to import many interesting concepts from classical theory such as modular and hierarchical control

Supervisory Control of Asynchronous and Hierarchical Finite State Machines

International audienceIn this paper, modular supervisory control of a class of Discrete Event Systems is investigated. Discrete event systems are modeled by a Hierarchical Finite State Machine. The basic problem of interest is to solve the State Avoidance Control Problem. We provide algorithms that, based on a particular decomposition of the set of forbidden configurations, locally solve the control problem (i.e. on each component without computing the whole system) and produce a global supervisor ensuring the desired property. This kind of objectives may be useful to perform dynamic interactions between different parts of a syste

PLC Implementation of Supervisory Control for a Dynamic Power Flow Controller using a Modular Approach

Dynamic Power Flow Controller (DPFC) provides steady-state and dynamic power flow control for power lines and is considered as a Flexible AC Transmission System (FACTS) controller. This paper deals with control of a standard DPFC using a Discrete Event System model. The Supervisory Control of DES has been used to implement Modular supervisors for the DPFC. Despite the fact that the SCT is well consolidated, with a large number of publications focusing on the theoretical aspects, the industrial application is unknown. It is mainly due to the complexity of the theory. The numbers of states and events to be controlled are very large even for the seemingly simple systems. In recent years, a model for modular approach to the Supervisory Control for performing the formal synthesis of Supervisors has been proposed. Programmable Logic Controllers are used for the physical implementation of the controllers. Some problems in physical realization of Supervisors in PLCs are dealt with

Supervisory control of fuzzy discrete event systems with applications to mobile robotics

Fuzzy Discrete Event Systems (FDES) were proposed in the literature for modeling and control of a class of event driven and asynchronous dynamical systems that are affected by deterministic uncertainties and vagueness on their representations. In contrast to classical crisp Discrete Event Systems (DES), which have been explored to a sufficient extent in the past, an in-depth study of FDES is yet to be performed, and their feasible real-time application areas need to be further identified. This research work intends to address the supervisory control problem of FDES broadly, while formulating new knowledge in the area. Moreover, it examines the possible applications of these developments in the behavior-based mobile robotics domain. An FDES-based supervisory control framework to facilitate the behavior-based control of a mobile robot is developed at first. The proposed approach is modular in nature and supports behavior integration without making state explosion. Then, this architecture is implemented in simulation as well as in real-time on a mobile robot moving in unstructured environments, and the feasibility of the approach is validated. A general decentralized supervisory control theory of FDES is then established for better information association and ambiguity management in large-scale and distributed systems, while providing less complexity of control computation. Furthermore, using the proposed architecture, simulation and real-time experiments of a tightly-coupled multi-robot object manipulation task are performed. The results are compared with centralized FDES-based and decentralized DES-based approaches. -- A decentralized modular supervisory control theory of FDES is then established for complex systems having a number of modules that are concurrently operating and also containing multiple interactions. -- Finally, a hierarchical supervisory control theory of FDES is established to resolve the control complexity of a large-scale compound system by modularizing the system vertically and assigning multi-level supervisor hierarchies. As a proof-of-concept example to the established theory, a mobile robot navigation problem is discussed. This research work will contribute to the literature by developing novel knowledge and related theories in the areas of decentralized, modular and hierarchical supervisory control of FDES. It also investigates the applicability of these contributions in the mobile robotics arena

Modular supervisory controller for complex systems

Automation for the oil and gas industry is driven by the need to improve efficiency, productivity, consistency, and personnel safety, while reducing cost. Fully automated systems alleviate the physical toll on human operators and allow them to focus on monitoring unsafe well events and machinery maintenance. Complex systems like drilling rigs and snubbing units require supervisory controllers that can safely coordinate equipment and processes, overcome interoperability challenges and allow for functional scalability without sacrificing safety, security, and consistency of operations. The primary objective of this report is to explore the feasibility of developing a modular supervisory controller architecture which addresses these concerns by modifying and extending existing architectures. Such modifications include the use of non-homogeneous models in sub-system modules, including discrete event models for control and physics-based models for collision avoidance, addition of a system compilation module (Meta Module) to identify simple design errors, and implementation of an algorithm for synthesis of modules and filters to replace missing sub-systems. This report discusses the implementation results of the modular supervisory control architecture (modMFSM) on a simplified two-machine drilling system for assessment of design practices. Simulations for three test cases were executed to assess the ability of the controller to correctly perform error-free operations, detect and react to possible collisions, and adapt to missing equipment. The report then discusses the possibilities of extending the modMFSM architecture to control large complex systems such as drilling rigs, using snubbing operations as an example.Mechanical Engineerin

Model Properties for Efficient Synthesis of Nonblocking Modular Supervisors

Supervisory control theory provides means to synthesize supervisors for systems with discrete-event behavior from models of the uncontrolled plant and of the control requirements. The applicability of supervisory control theory often fails due to a lack of scalability of the algorithms. We propose a format for the requirements and a method to ensure that the crucial properties of controllability and nonblockingness directly hold, thus avoiding the most computationally expensive parts of synthesis. The method consists of creating a control problem dependency graph and verifying whether it is acyclic. Vertices of the graph are modular plant components, and edges are derived from the requirements. In case of a cyclic graph, potential blocking issues can be localized, so that the original control problem can be reduced to only synthesizing supervisors for smaller partial control problems. The strength of the method is illustrated on two case studies: a production line and a roadway tunnel.Comment: Submitted to Journal of Control Engineering Practice, revision