Supervisory control of timed discrete event systems under partial observation based on activity models and eligible time bounds

To avoid the state–space explosion by including tick events in timed discrete event systems (DESs) under partial observation, a notion of eligible time bounds is introduced and based on the notion, controllability and observability conditions of languages are presented. In particular, this paper shows that these controllability and observability conditions are necessary and sufficient for the existence of a supervisor to achieve the given language specification.     

Robust supervisory control of a class of timed discrete event systems under partial observation

This paper studies robust supervisory control of timed discrete event systems proposed by Brandin and Wonham. Given a set of possible models which includes the exact model of the plant, the objective is to synthesize a robust supervisor such that it achieves legal behavior for all possible models. We show that controllability for each possible model and observability for a suitably defined aggregate model are necessary and sufficient conditions for the existence of a solution to the robust supervisory control problem. Moreover, when there does not exist a solution, a maximally permissive robust supervisor is synthesized under the assumption that all controllable events are observable.     

Nonblocking supervisory control of timed discrete event systems under communication delays: The existence conditions

This paper addresses the problem of nonblocking supervisory control of timed discrete event systems under communication delays based on the framework proposed by Brandin and Wonham. For such a system, a supervisory control command could be applied to the system after some time-delay limited by a finite bound corresponding to the maximal number of tick occurrences, and some uncontrollable events may unexpectedly occur within this time-delay. This paper presents the necessary and sufficient conditions for the existence of a nonblocking supervisor that can achieve a given language specification in consideration of such delayed communications.     

Decentralized supervisory control of nondeterministic discrete event systems: The existence condition of a robust and nonblocking supervisor

This paper addresses a decentralized supervisory control problem for an uncertain discrete event system (DES) modeled by a set of possible nondeterministic automata with unidentified internal events. For a given language specification, we present the existence condition of a robust and nonblocking decentralized supervisor that achieves this specification for any nondeterministic model in the set. In particular, we show that the given language specification can be achieved based on the properties of its controllability and coobservability with respect to the overall nominal behavior of the uncertain DES. It is further shown that the existence of a nonblocking decentralized supervisor can be examined with a trajectory model of the language specification.     

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

In this paper, we examine the problem of robust nonblocking supervisory control. In the problem considered here, the exact model of the plant is not known but is assumed to be among a finite set of possible models. For each plant model a legal marked behavior is assumed given. We extend previous results for the case of control with full observation to the case of control under partial observation where only a subset of events are observable. Furthermore, we remove the limitations of previous results on ensuring the nonblocking property of the plant under supervision. We characterize the entire set of solutions of the robust control problem and obtain a set of necessary and sufficient conditions for the existence of a solution for the problem. As an illustrative example, we use our results on robust control to solve a fault recovery problem.     

Robust and fault-tolerant supervisory control of discrete event systems with partial observation and model uncertainty

This paper proposes the notions of faults and failures in discrete event systems (DESs) with partial observation. They are associated with controllability and an observability property. The proposed notions are used to address the notion of tolerable fault event sequences which represents fault-tolerant behaviour of systems as a desired specification. A robust and fault-tolerant supervisor is a controller which is robust to model uncertainty and guarantees fault-tolerant behaviour of a system. In this paper we present necessary and sufficient conditions for the existence of a robust and fault-tolerant supervisor. The developed conditions capture the concepts of controllability and observability which are cores in the control of DESs with partial observation     

Decentralized supervisory control of discrete event systems with communication delays based on conjunctive and permissive decision structures

In many practical discrete event systems (DESs), some unexpected and uncontrollable events can subsequently occur before a proper control action is actually applied to a plant due to communication delays. For such DESs, this paper investigates necessary and sufficient conditions for the existence of a nonblocking decentralized supervisor that can correctly achieve a given language specification when the decentralized supervisor is assumed to have a conjunctive and permissive decision structure. In particular, this paper presents a notion of delay-coobservability for a given language specification and shows that it is a key condition for the existence of such a decentralized supervisor.     

Real-time preemptive scheduling of sporadic tasks based on supervisory control of discrete event systems

This paper presents a preemptive scheduling scheme for real-time systems with sporadic tasks based on the supervisory control theory of discrete event systems. In particular, we present a systematic method of computing a schedulable language that includes all achievable sequences that meet the given deadlines of accepted sporadic tasks. A supervisor that achieves the schedulable language corresponds to a scheduler that can secure the deadlines of all accepted tasks. We further show that the schedulable language includes the decisions on whether a scheduler accepts or rejects a newly arrived sporadic task.     

Robust nonfragile observer‐based control of switched discrete singular systems with time‐varying delays: A sliding mode control design

This paper is devoted to the robust sliding mode control issue for a type of switched discrete singular systems with time‐varying delays under arbitrary switching. Since the system states are not available, the nonfragile observer strategy is used to generate the state estimation. By designing a novel sliding surface function, which is established on the estimation, new sufficient conditions via linear matrix inequalities are derived so that the closed‐loop system is admissible with an disturbance attenuation level γ. Furthermore, sliding mode controllers are given to guarantee the reachability of the quasi‐sliding mode and weaken the chattering. At last, examples are presented to verify the validity of our provided approach.     

Distributed reliable H∞ consensus control for a class of multi‐agent systems under switching networks: A topology‐based average dwell time approach

This paper investigates the problem of distributed reliable H_∞ consensus control for high‐order networked agent systems with actuator faults and switching undirected topologies. The Lipschitz nonlinearities, several types of actuator faults, and exogenous disturbances are considered in subsystems. Suppose the communication network of the multi‐agent systems may switch among finite connected graphs. By utilizing the relative state information of neighbors, a new distributed adaptive reliable consensus protocol is presented for actuator failure compensations in individual nodes. Note that the Lyapunov function for error systems may not decrease as the communication network is time‐varying; as a result, the existing distributed adaptive control technique cannot be applied directly. To overcome this difficulty, the topology‐based average dwell time approach is introduced to deal with switching jumps. By applying topology‐based average dwell time approach and Lyapunov theory, the distributed controller design condition is given in terms of LMIs. It is shown that the proposed scheme can guarantee that the reliable H_∞ consensus problem is solvable in the presence actuator faults and external disturbance. Finally, two numerical examples are given the effectiveness of the proposed theoretical results. Copyright © 2015 John Wiley & Sons, Ltd.