Supervisory Control of Discrete-Event Systems Under Attacks

We develop a process-theoretic approach for generally-dis-tributed discrete-event systems with unrestricted nondeterminism that is geared towards supervisory control. Supervisory control theory deals with synthesis of models of supervisory controllers that ensure safe and nonblocking behavior of the supervised system. The models are synthesized based on a model of the uncontrolled system and a formalization of the control requirements. Even though there exist extensions of supervisory control theory for timed and Markovian discrete-event systems, there are hardly any investigations of supervisory control of discrete-event systems with generally-distributed delays. General distributions provide for (convenient) modeling of important real-world phenomena that cannot be consistently modeled by means of real time or Markovian (exponentially-distributed) delays, like heavy-tail or uniformly distributed processes. Our theory relies on a behavioral preorder termed partial bisimulation, for which we provide a suitable extension. Based on the proposed theory we provide for an appropriate abstraction of the stochastic behavior, which enables us to employ standard supervisory controller synthesis tools. The synthesized supervisor can, thereafter, be coupled with the stochastic model of the unsupervised system and abstracted to a generalized semi-Markov process for the purpose of analysis and simulation.

In this paper we study suitability of using assignment based programming language for supervisory control of discrete event systems. We first show that the supervisory control problem in its general setting is undecidable. Next we show that the supervisory control problem for discrete event systems modeled by assignment based programs is decidable and develop techniques which reduce the supervisory control problem of such systems to that of solving arithmetic equations. We first apply these techniques for synthesis of static controllers.

The signed real measure of regular languages has been introduced and validated in recent literature for quantitative analysis and synthesis of discrete-event supervisory (DES) control systems, where all events are assumed to be observable. This paper presents a modification of the language measure for supervisory control under partial observation and shows how to generalize the analysis when some of the events may not be observable at the supervisory level. Thus, for synthesis of DES control systems, the language measure of partially observable discrete-event processes is expressed in a closed form, which is structurally similar to that of completely observable discrete-event processes.

This paper proposes a solution to the electric Vehicle Scheduling Problem (eVSP) based on the framework of Discrete Event System (DES). A supervisory control is synthesized using the theory of Supervisory Control of Discrete Event System (SCDES) to manage the power admission control of a group of local Plug-in Electric Vehicles (PEV). The PEVs are categorized based on their level of priority to be charged and an algorithm is developed to allocate power to PEVs according to their priority and available capacity. The proposed algorithm and supervisor validates the schedulability of charging of PEVs while meeting the constraint of the grid to achieve peak demand reduction. Simulation studies are carried out using MATLAB/Simulink and STATEFLOW toolkit and the result validates the effectiveness of the control scheme to reduce peak demand while providing fair charging schedules to PEVs.

In this paper the Supervisory Control Problem (SCP) for discrete event systems (DES) is generalized to a class of probabilistic discrete event systems (PDES). Necessary and sufficient conditions for the existence of a solution to the probabilistic SCP for a class of nonterminating PDES are developed. Methods of representing probabilistic supervisors for PDES are described and the computation of supervisors is briefly discussed. Finally, we discuss how the results may be extended to terminating probabilistic languages. >

As railway platforms expand in size, complexity, and traffic volume, ensuring efficiency and safety of train entrance and exit a station becomes increasingly critical. This study presents a scheduling approach for monorail one-way stations that minimises reliance on the train timetable while validating scheduling decisions against it, thereby enhancing the feasibility and safety of the scheduling process. For multi-platform stations, where switches are organised into partial binary trees, this paper introduces a modular discrete event system (DES) modelling approach to design and implement train entrance and exit schedules. The fundamental modelling unit of a multi-platform station consists of a single module, comprising an entrance/exit switch and its associated sensors. The complete DES model of the train station is then constructed as the synchronous product of multiple such modular units. In addressing train scheduling, the proposed approach incorporates fair train entrance/exit specifications, platform capacity constraints, and crossover capacity limitations. Through the supervisory control of DES, an optimal supervisor is synthesised to prevent collision incidents. This innovative methodology and accompanying algorithm facilitate seamless and equitable scheduling for train entrances and exits, without distinguishing between individual trains traversing the station.

In the context of supervisory control of discrete-event systems, decentralized control is a well-established area of research. In this paper we present an implementation of such controllers for an assembly cell with two-assembly stations (SCARA robots), in a laboratory scale computer integrated manufacturing (CIM) system. Step by step implementation, conflict avoidance between local supervisors and difficulties encountered are discussed. Petri nets are used as the modelling tool and Lin and Wonham framework is used as the control architecture. Assembly stations are modelled as intelligent agents. A separate software module called order processing module (OPM) is used to handle orders into and out of the system and to schedule the two-assembly stations

In this paper we develop a data-driven approach for supervisory control of discrete-event systems (DES). We consider a setup in which models of DES to be controlled are unknown, but a set of data concerning the behaviors of DES is available. We propose a new concept of data-informativity, which captures the notion that the available data set contains sufficient information such that a valid supervisor may be constructed for a family of DES models that all can generate the data set. We then characterize data-informativity with a necessary and sufficient condition, based on which we design an algorithm for its verification.

Supervisory control of discrete event systems with distinguishers

Human performance in problem solving in the context of supervisory control of discrete-event systems is discussed. Software packages for such problems usually offer only rudimentary support in the form of visual data entry and algorithmic computations. Other activities such as system modeling and verification of the solution have to be done without computer support. This work is a first step in understanding how humans approach discrete-event control problems. An observational study is described, where subjects are video-taped solving supervisory control problems. One video recording is used to construct a taxonomy of the task and then the different activities of the subject are encoded accordingly. The data are analysed to discover patterns of human activity. These results can be used to guide the design of software for computer-aided problem solving in this context.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents supervisory control of a dynamic flow controller (DFC) based on the discrete-event systems (DES) theory. A DFC can be considered as a flexible ac transmission system controller and includes a mechanically-switched phase-shifting transformer, a multimodule thyristor-switched capacitor, a multimodule thyristor-switched reactor, and a mechanically switched capacitor. Owing to the inherent discrete switching nature of a DFC, its components are modeled as finite automata; then, a DES supervisory control is designed to implement the control logic of the DFC system in different modes of operation (i.e., “automatic” and “auto/manual”). It is shown that the specifications are controllable and the synthesized supervisors are nonblocking in both modes and the modular supervisors nonconflict in auto/manual mode. </para>

Robust nonblocking supervisory control of discrete-event systems under partial observation

Modern engineering systems and cyber‐physical systems often consist of many distributed and networked physical plants, control units, and other devices with wired or wireless communication networks to exchange information between controllers and plants. These systems are called networked systems. In this article, we review supervisory control of networked discrete‐event systems. We first discuss how to model networked discrete‐event systems and how to obtain state estimates using a networked observer. We then introduce and solve the following supervisory control problems of networked discrete‐event systems: (i) (nondeterministic) supervisory control problem, (ii) deterministic supervisory control problem, (iii) nonblocking supervisory control problem, (iv) robust supervisory control problem, (v) robust deterministic supervisory control problem, (vi) deterministic decentralized supervisory control problem, and (vii) nonblocking decentralized supervisory control problem. We present and prove necessary and sufficient conditions for solving the above problems. Finally, we list the open problems in supervisory control of networked discrete‐event systems.

Supervisory control of discrete-event systems: A brief history

In this paper, we study the supervisory control problem of Timed Networked Discrete Event Systems (TNDES) subject to delays and losses of observations. We assume that the plant is distributed, having, therefore, several communication channels for the transmission of the event observations to the supervisor. We propose a timed model based on, a priori, knowledge of the minimal transition activation time and on the maximal time delay (possible packet loss also) of the communication channels. We then, obtain an equivalent untimed one and, based on this model we formulate a supervisory control problem (here referred to as networked supervisory control), and present a necessary and sufficient existence condition and a method for the synthesis of networked supervisors.