Networked Supervisory Control Research Articles

A New Approach for Verification of Delay Co-observability of Discrete-Event Systems

In decentralized networked supervisory control of discrete-event systems (DESs), the local supervisors observe event occurrences subject to observation delays to make correct control decisions. Delay coobservability describes whether these local supervisors can make sufficient observations. In this paper, we provide an efficient way to verify delay coobservability. For each controllable event, we partition the specification language into a finite number of sets such that strings in different sets have different lengths. For each of the sets, we construct a verifier to check if delay coobservability holds for the controllable event. The computational complexity of the proposed approach is polynomial with respect to the number of states, the number of events, and the upper bounds on observation delays and only exponential with respect to the number of local supervisors. It has lower complexity order than the existing approaches. In addition, we investigate the relationship between the decentralized supervisory control of networked DESs and the decentralized fault diagnosis of networked DESs and show that delay <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> -codiagnosability is transformable to delay coobservability. Thus, techniques for the verification of delay coobservability can be leveraged to verify delay <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> -codiagnosability.

Overview of networked supervisory control with imperfect communication channels

This paper presents an overview of the networked supervisory control frameworks for discrete event systems with imperfect communication networks, which are divided into the centralized setup, the decentralized setup and the distributed setup. The state-of-the-art works on networked supervisory control of discrete-event systems addressing the channel imperfections that are caused by channel delays, data losses or non-FIFO channels are discussed. By presenting the key concepts and main results of each representative work, we analyze the pros and cons of different approaches. Finally, we also provide a summary of the existing works, which roughly follow two different lines of thinking and result in two different verification or synthesis approaches. The first approach utilizes simple, non-networked plant models but relies on the development of sophisticated concepts of network controllability and observability to capture network imperfections, while the second approach embeds relatively complex yet verifiable channel models into the model of the networked plant and adopts the standard concepts of controllability and observability for the (verification and) synthesis of networked supervisors. Some future research topics are also presented.

Deterministic supervisory control with flexible upper-bounds on observation delay and control delay

This paper considers supervisory control of discrete event systems with observation delay and control delay. We first extend the formulation of networked supervisory control in the literature by allowing both the upper bound of observation delay and the upper bound of control delay to vary among different event strings, and accommodating dynamic observation in which the past influences whether or not an occurrence of an event is observable. We then combine observation delay and control delay and prove that satisfying both controllability and delay observability over the combined delay is necessary and sufficient for the existence of a supervisor by which the desired language can be obtained deterministically. After that, we reduce the type of problems concerning the networked supervisory control to the corresponding type of problems concerning traditional supervisory control without any delay on observation or control. As an immediate application, the verifier of observability can be used to test the corresponding delay observability. Finally, this reduction is used to leverage methods for minimizing sensor activations for supervisory control without control delay to minimize sensor activations with control delay.

Research on a hybrid controller combining RBF neural network supervisory control and expert PID in motor load system control

Considering the contradiction among the response speed, overshoot and stability of system when the motor load system adopts PID control, a control strategy combining RBF (Radial Basis Function) neural network supervisory control and expert PID control is designed to effectively improve this problem in this paper. First of all, the related algorithms of RBF neural network supervisory control composed of RBF neural network and PID control (RSC-PID) is introduced. This method can make the motor load system reach a steady state faster than simple PID control. But RSC-PID is also unsatisfactory in terms of overshoot. Based on the RSC-PID control method, a hybrid controller combining RBF neural network supervisory control and expert PID control (RSC-EPID) is proposed. This method combines RSC-PID control theory with expert PID control ideas, further improves the stability and rapidity of the system, reduces the overshoot. Moreover, when the input signal is a time-varying signal with interference, the motor load system shows better anti-interference performance after using RSC-EPID. The simulation results show that RSC-EPID control improves the tracking effect of the output signal of the motor load system, ensures the stability of the system, and improves the performance of the system.

Supervisory Control of Networked Discrete Event Systems With Timing Structure

In this article, we study the supervisory control problem of networked discrete event systems with timing structure assuming bounded communication delays and intermittent loss of observations. The communication between the plant and the supervisor is through a network that can have several channels, and so communication delays may change the order of event observations by the supervisor. We assume a priori knowledge of the minimal activation time of the plant transitions and the maximum communication delays, and propose an equivalent untimed model that takes into account all possible observation delays and also loss of observations. Based on this model, we formulate a networked supervisory control problem and show that it can be converted into an equivalent range control problem. We also address implementation, and, to this end, we present a representation for networked supervisors that is able to deal with possible loss of synchronization between event occurrence and its observation.

Opacity of Networked Supervisory Control Systems Over Insecure Communication Channels

In this article, we investigate security and privacy issues in networked supervisory control systems over multiple channel networks. We consider a networked discrete-event system controlled by a supervisor that receives information from sensors and sends control decisions to actuators via observation channels and control channels, respectively. The security problem is studied for the scenario where some of the communication channels are insecure in the sense there exists a passive intruder (eavesdropper) that can access the information-flow in those insecure communication channels. We adopt the concept of opacity, an information flow security property, to characterize the security status of the supervisory control system. Specifically, we assume that the system has a secret and the system is said to be opaque if the intruder can never determine the secret of the system unambiguously based on the information-flow in the insecure channels. We consider the notions of current-state opacity, K-step opacity, and infinite-step opacity in the networked control setting. New network observers are proposed to estimate the state of the system with two-side incomparable channel information. We show that the opacity verification problems for the networked setting can be effectively solved using the proposed network observers.

New Results on Deterministic Networked Supervisory Control and Relative Delay Observability

This paper considers supervisory control of discrete event systems with observation delays and control delays, which is termed deterministic networked supervisory control. Delay observability, together with delay controllability, is required for obtaining a networked supervisor so that the language generated by the supervised system is deterministic and is equal to a given specification language. In this article, we simplify this existence condition and prove such a networked supervisor also exists if controllability and delay observability are satisfied. A new language property called relative delay observability, which accommodates observation delays in relative observability, is further defined. Relatively delay observability implies delay observability and enjoys an important property that is closed under union. We then show how to check the relative delay observability in polynomial time complexity. A general algorithm used to calculate the supremal sublanguage satisfying controllability and another user-defined language property in a solution space of interest, is presented. As a special case, we calculate the supremal controllable and relatively delay observable sublanguage. Finally, a practical example is given to illustrate the application of relative delay observability.

Research on Information Resources Sharing Patterns Based on Cloud Computing

Based on the principle and characteristics of cloud computing, we put forward the detailed introduction of the constitution and function of cloud information resource flow architecture. Therefore, the problems of network source information management, supervisory control, exploitation and utilization can be solved.

Team performance in networked supervisory control of unmanned air vehicles: effects of automation, working memory, and communication content.

Assess team performance within a net-worked supervisory control setting while manipulating automated decision aids and monitoring team communication and working memory ability. Networked systems such as multi-unmanned air vehicle (UAV) supervision have complex properties that make prediction of human-system performance difficult. Automated decision aid can provide valuable information to operators, individual abilities can limit or facilitate team performance, and team communication patterns can alter how effectively individuals work together. We hypothesized that reliable automation, higher working memory capacity, and increased communication rates of task-relevant information would offset performance decrements attributed to high task load. Two-person teams performed a simulated air defense task with two levels of task load and three levels of automated aid reliability. Teams communicated and received decision aid messages via chat window text messages. Task Load x Automation effects were significant across all performance measures. Reliable automation limited the decline in team performance with increasing task load. Average team spatial working memory was a stronger predictor than other measures of team working memory. Frequency of team rapport and enemy location communications positively related to team performance, and word count was negatively related to team performance. Reliable decision aiding mitigated team performance decline during increased task load during multi-UAV supervisory control. Team spatial working memory, communication of spatial information, and team rapport predicted team success. An automated decision aid can improve team performance under high task load. Assessment of spatial working memory and the communication of task-relevant information can help in operator and team selection in supervisory control systems.

Team Performance and Communication within Networked Supervisory Control Human-Machine Systems

The effects of task load, automation reliability and team communication on supervisory control performance were examined using a multi-UAV simulation with two operators. Performance was degraded by high task load and improved with an automated decision aid. In addition, team working memory, defined as the average of individual working memory capacity scores, was associated with superior team performance. Higher levels of task load increased the amount of information communicated by teams whereas the presence of an automated decision aid decreased the amount of information communicated by teams. The results are discussed in relation to models of team cognition for teams performing similar tasks in a shared, networked human-machine system.

PI architecture functionally distributed system for power network supervisory control

In recent years, the sizes of Energy Management Systems (EMS) and Supervisory Control and Data Acquisition (SCADA) systems have grown to huge proportions for two reasons: The power systems to which they are applied have grown in size and complexity; and Their own functions have become more diverse and sophisticated. This raises the following problems: degradation of response time; decreased reliability; limited expandability; less maintainability; and increased costs. A functionally distributed system that is characterized by parallel processing and independent subsystems (parallel-independent architecture) will solve these problems. The system is comprised of a group of functional units, each of which runs in parallel, independently and asynchronously. Copies of some programs and power system status data are stored in the relevant functional units, and data-driven architecture is adopted, which eliminates the need for a centralized control mechanism. The feasibility of a functionally distributed system was tested through construction of a prototype. The results were satisfactory.