In this paper, we study decentralized supervisory control of timed discrete event systems, where we adopt the OR rule for fusing local enablement decisions and the AND rule for fusing local enforcement decisions. Under these rules, necessary and sufficient conditions for the existence of a decentralized supervisor that achieves a given specification language are easily obtained from the result of literature. If a given specification language does not satisfy these existence conditions, we must compute its sublanguage satisfying them. The main contribution of this paper is proposing a method for computing such a sublanguage.

In the framework of decentralized supervisory control of timed discrete event systems (TDESs), each local supervisor decides the set of events to be enabled to occur and the set of events to be forced to occur under its own local observation in order for a given specification to be satisfied. In this paper, we focus on fusion rules for the enforcement decisions and adopt the combined fusion rule using the AND rule and the OR rule. We first derive necessary and sufficient conditions for the existence of a decentralized supervisor under the combined fusion rule for a given partition of the set of forcible events. We next study how to find a suitable partition.

In the framework of supervisory control of timed discrete event systems (TDESs), a supervisor decides the set of events to be enabled to occur and the set of events to be forced to occur in order for a given specification to be satisfied. In this paper, we consider decentralized supervisory control of TDESs where enforcement decisions of local supervisors are fused by the AND rule or the OR rule. We derive existence conditions of a decentralized supervisor under these decision fusion rules.

In this paper, we study opacity-enforcing supervisory control of discrete event systems. We consider the case that the secrete behavior of the system is specified by multiple secret languages, and synthesize a maximally permissive supervisor that enforces opacity for all secret languages. We prove that, under a certain assumption on observable and uncontrollable events, a maximally permissive opacity-enforcing supervisor can be synthesized in a modular fashion.

This paper presents an approach to implementing simulation models for SAM fuzzy controllers without the use of external components. The approach represents a fuzzy controller as a composition of simple simulation models which involve only basic operations.

Software model checking is typically applied to components of large systems. The assumption generation is the problem of finding the least restrictive environment in which the components satisfy a given safety property. There is an algorithm to compute the environment for properties given as a regular language. In this paper, we propose a general scheme for computing the assumption even for non-regular properties, and show the uniqueness of the least restrictive assumption for any class of languages. In general, dealing with non-regular languages may fall into undecidability of problems. We also show a method to compute assumptions based on visibly pushdown automata and their finite-state abstractions.

In human-machine systems, a user gets abstracted information of a machine via an interface and operates it referring to a manual. If a manual has an erroneous description leading to automation surprises, the user may be lost in his/her operations so that he/she may make a serious human error. In this paper, we propose an algorithm for generating a manual by which automation surprises never occur. We model the machine and the interface as a discrete event system and a mapping from machine's state to a display of the interface, respectively. First, we represent a manual as a finite language and model behavior of the system operated by the user with the manual as a tree called an operational tree. Next, we characterize three automation surprises using the tree. Finally, we propose an algorithm for generating an operational tree by which the machine reaches a target state.

In networked control systems, uncontrollable events may unexpectedly occur in a plant before a proper control action is applied to the plant due to communication delays. In the area of supervisory control of discrete event systems, Park and Cho [5] proposed the notion of delay-nonconflictingness for the existence of a supervisor achieving a given language specification under communication delays. In this paper, we present the algebraic properties of delay-nonconflicting languages which are necessary for solving supervisor synthesis problems under communication delays. Specifically, we show that the class of prefix-closed and delay-nonconflicting languages is closed under intersection, which leads to the existence of a unique infimal prefix-closed and delay-nonconflicting superlanguage of a given language specification.

A dynamically reconfigurable device is a device that can change its hardware configuration arbitrarily often in order to achieve the desired performance and functions. Since several tasks are executed on the device concurrently, scheduling of both task execution and reconfiguration is an important problem. In our model, the dynamically reconfigurable device is represented by a two-level hierarchical automaton, and execution of each periodic task is represented by a timed discrete event system. We propose a composition rule to get an automaton, which represents non-preemptive execution of periodic tasks on the dynamically reconfigurable device. We introduce a method to get a feasible execution sequence of tasks by using state feedback control.

A supervisor proposed by Ramadge and Wonham controls a discrete event system (DES) so as to satisfy logical control specifications. However a precise description of both the specifications and the DES is needed for the control. This paper proposes a synthesis method of the supervisor for decentralized DESs based on reinforcement learning. In decentralized DESs, several local supervisors exist and control the DES jointly. Costs for disabling and occurrence of events as well as control specifications are considered. By using reinforcement learning, the proposed method is applicable under imprecise specifications and uncertain environment.

The conventional decentralized supervisory control architectures for discrete event systems assume that default control of controllable events is static. In this paper, we propose a new decentralized supervisory control architecture using dynamic default control of controllable events. We present necessary and sufficient conditions for the existence of a decentralized supervisor in the proposed architecture. Then, we give an example of a language that is achieved in the proposed architecture, but not in the conventional architectures using static default control.

This paper considers a motion planning method for humanoid robots. First, we review a modular state net which is a state net representing behavior of a part of the humanoid robots. Each whole body motion of the humanoid robots is represented by a combination of modular state nets for those parts. In order to obtain a feasible path of the whole body, a timed Petri net is used as an abstracted model of a set of all modular state nets. Next, we show an algorithm for constructing nonlinear dynamics which describes a periodic motion. Finally, we extend the state net in order to represent primitive periodic motions and their transition relation so that we can generate a sequence of primitive periodic motions satisfying a specified task.

A batch process is a typical concurrent system in which multiple interacting tasks are carried out in parallel on several batches at the same time. A major difficulty in designing a batch control system is the lack of modeling techniques. This paper aims at developing a method of constructing batch control system models in a hierarchical manner and operating batch processes using the constructed models. For this purpose, it first defines process and plant specifications described by partial languages, next presents a procedure for constructing hierarchical Petri net based models, and states the verification of models based on reachability analysis. It also discusses the detection of faults and conflicts in batch processes based on place-invariant analysis.

In this paper, we study supervisory control of a class of discrete event systems with simultaneous event occurrences, which we call concurrent discrete event systems. The behavior of the system is described by a language over the simultaneous event set. We introduce a notion of concurrent well-posedness of languages. We then prove that Lm(G)-closure, controllability, and concurrent well-posedness of a specification language are necessary and sufficient conditions for the existence of a nonblocking supervisor. We address the computational complexity for verifying the existence conditions.

In this paper, we study reliable decentralized supervisory control of discrete event systems with a control architecture where certain controllable events are controlled under the conjunctive fusion rule, and certain others are controlled under the disjunctive fusion rule. We first introduce a notion of reliable co-observability with respect to such a partition of the controllable event set. We then prove that reliable co-observability together with Lm(G)-closure and controllability is a necessary and sufficient condition for the existence of a reliable decentralized supervisor under a given partition. Moreover, we present necessary and sufficient conditions for the existence of a partition of the controllable event set under which a given specification language is reliably co-observable.

In this paper, we study nonblocking supervisory control of discrete event systems under partial observation. We introduce a weak normality condition defined in terms of a modified natural projection map. The weak normality condition is weaker than the original one and stronger than the observability condition. Moreover, it is preserved under union. Given a marked language specification, we present a procedure for computing the supremal sublanguage which satisfies Lm(G)-closure, controllability, and weak normality. There exists a nonblocking supervisor for this supremal sublanguage. Such a supervisor is more permissive than the one which achieves the supremal Lm(G)-closed, controllable, and normal sublanguage.

This paper deals with the decentralized supervisory control problems of uncertain discrete event systems which are represented as a set of some possible models. For a given global specification, this paper provides the necessary and sufficient conditions for the existence of local supervisors to achieve the specification under model uncertainty.

We consider a discrete event system controlled by a decentralized supervisor consisting of n local supervisors. Given a nonempty and closed language as the upper bound specification, we consider a problem to synthesize a reliable decentralized supervisor such that the closed-loop behavior is still legal under possible failures of any less than or equal to n-k (1 k n) local supervisors. We synthesize two such reliable decentralized supervisors. One is synthesized based on a suitably defined normal sublanguage. The other is the fully decentralized supervisor induced by a suitably defined centralized supervisor. We then show that the generated languages under the control actions of these two decentralized supervisors are incomparable.

In this paper, we study decentralized supervisory control of discrete event systems where local disabling actions are fused by the OR rule. We generalize an on-line procedure for synthesizing decentralized supervisors proposed by Prosser. By using the generalized procedure, we can achieve a sublanguage of a specification which is not achieved by a class of decentralized supervisors synthesized by the Prosser's procedure.

Recently, many on-line control methods of partially observed discrete event systems(DES's) have been proposed. This paper proposes an algorithm for on-line control based on a supervisor under complete observation. It is shown that DES's controlled by the proposed on-line controller generate maximally controllable and observable sublanguages which include the supremal normal sublanguages. Moreover, computational complexity of the proposed algorithm is polynomial with respect to the numbers of the unobservable events and the state of the supervisor under complete observation.