Showing papers on "Supervisory control published in 1987"

Supervisory control of a class of discrete event processes

Abstract: This paper studies the control of a class of discrete event processes, i.e. processes that are discrete, asynchronous and possibly nondeter-ministic. The controlled process is described as the generator of a formal language, while the controller, or supervisor, is constructed from the grammar of a specified target language that incorporates the desired closed-loop system behavior. The existence problem for a supervisor is reduced to finding the largest controllable language contained in a given legal language. Two examples are provided.

GT-MSOCC - A domain for research on human-computer interaction and decision aiding in supervisory control systems. [Georgia Tech - Multisatellite Operations Control Center]

Abstract: Modeling and aiding operators in supervisory control environments are necessary prerequisites to the effective use of automation in complex dynamic systems. A research program is described that explores these issues within the context of the Georgia Tech-Multisatellite Operations Control Center (GT-MSOCC). GT-MSOCC is a real-time interactive simulation of the operator interface to a NASA ground control system for unmanned Earth-orbiting satellites. GT-MSOCC is a high fidelity domain in which a range of modeling, decision aiding, and workstation design issues addressing human-computer interaction may be explored. GT-MSOCC is described in detail. The use of high-fidelity domains as research tools is also discussed, and the validity and generalizability of such results to other domains are examined. In addition to a description of GT-MSOCC, several other related parts are included. A GT-MSOCC operator function model (OFM) is presented. The GT-MSOCC model illustrates an enhancement to the general operator function modeling methodology that extends the model's utility for design applications. The proposed methodology represents operator actions as the lowest level discrete control network nodes. Actions may be cognitive or manual; operator action nodes are linked to information needs or system reconfiguration commands. Thus augmented, the operator function model provides a formal representation of operator interaction with the controlled system and serves as the foundation for subsequent theoretical and empirical research. A brief overview of experimental and methodological studies using GT-MSOCC is also given.

GT-MSOCC: A Domain for Research on Human - Computer Interaction and Decision Aiding in Supervisory Control Systems

Abstract: Modeling and aiding operators in supervisory control environments are necessary prerequisites to the effective use of automation in complex dynamic systems. A research program is described that explores these issues within the context of the Georgia Tech-Multisatellite Operations Control Center (GT-MSOCC). GT-MSOCC is a real-time interactive simulation of the operator interface to a NASA ground control system for unmanned Earth-orbiting satellites. GT-MSOCC is a high fidelity domain in which a range of modeling, decision aiding, and workstation design issues addressing human-computer interaction may be explored. GT-MSOCC is described in detail. The use of high-fidelity domains as research tools is also discussed, and the validity and generalizability of such results to other domains are examined. In addition to a description of GT-MSOCC, several other related parts are included. A GT-MSOCC operator function model (OFM) is presented. The GT-MSOCC model illustrates an enhancement to the general operator function modeling methodology that extends the model's utility for design applications. The proposed methodology represents operator actions as the lowest level discrete control network nodes. Actions may be cognitive or manual; operator action nodes are linked to information needs or system reconfiguration commands. Thus augmented, the operator function model provides a formal representation of operator interaction with the controlled system and serves as the foundation for subsequent theoretical and empirical research. A brief overview of experimental and methodological studies using GT-MSOCC is also given.

Supervisory control and data acquisition

Abstract: The acquisition of data, the processing of those data for use by the operator, and operator control of remote devices are the fundamental building blocks upon which all modern utility control systems are based The systems to accomplish these functions are known as Supervisory Control and Data Acquisition (SCADA) systems This paper provides an overview of the functions of SCADA and the fundamentals of operation of SCADA systems, including a brief description of the key man-machine interface Several of the key issues and problems in modern SCADA systems, ie, message standards, system performance testing, and system obsolescence are discussed The paper concludes with the current trends toward distributed processing, improved man-machine interface, standard systems, smarter RTUs, and standard software The authors' view of the future, using interchangeable system parts, is provided

Use of Model-Based Qualitative Icons and Adaptive Windows in Workstations for Supervisory Control Systems

Abstract: Model-based qualitative icons and adaptive window display interfaces may be valuable tools to enhance the effectiveness of operators in real-time data-intensive supervisory control systems. Qualitative icons may be used to integrate low-level quantitative data into high-level qualitative error detection mechanisms. Using windowing technology, multiple data sources that reflect different aspects of system state can be displayed simultaneously on a single screen. Both technologies were combined and implemented to design an operator interface to the Georgia Tech-Multisatellite Operation Control Center (GT-MSOCC). An operator function model for GT-MSOCC was used to derive workstation features, including hardware configuration, the function of qualitative icons for monitoring, fault detection and identification, and the contents and placement of computer windows. The model also determined sets of windows needed by the operator to undertake major operator control functions. An experiment was performed to evaluate the effectiveness of a workstation incorporating model-based qualitative icons and dynamic operator function window sets. Subjects controlled GT-MSOCC via either a conventional operator interface or the model-based interface. Eleven measures that reflected operator performance were analyzed. Subjects using the model-based workstation operated the system significantly better on nine of these measures. On all measures, performance with the model-based workstation was uniformly better on average and had less variability than performance with the conventional workstation.

Master station apparatus for remote supervisory control system with touch panel video display

Abstract: The inventive master station apparatus for a remote supervisory control system makes poke points for selecting remote stations displayed on a video display (3) by an output control circuit (24), so that, when an operator touches one of the poke points on a touch panel (4), a CPU (21) makes the pattern and the current status of a monitored/controlled device of the corresponding remote station and a poke point for a control command displayed. When the poke point for the control command is touched, the CPU (21) transmits a control command to the monitored/controlled device of the corresponding one of remote stations (11, 12, . . . , 1n) through a line interface (5). When control of the corresponding device is executed, the remote station transmits a signal indicating the operation thereof to the master station apparatus (1). On the basis of the operation indicating signal, the CPU (21) updates the content of a status memory (23), and the status indication displayed on the video display (3) through the output control circuit (24).

Supervisory control architecture for underwater teleoperation

Abstract: An overall concept and specific system elements for teleoperated vehicles and manipulators are presented. The approach emphasizes continuous, real-time sharing of control between both the human operator and the computer system and is intended for application to the JASON underwater vehicle now in development. As JASON will have extremely high communications bandwidth available through a fiber optic cable, the emphasis will be on aiding and extending the capabilities of the human operator. Specific elements presented include task-resolved motion specification, rule-based inverse kinematics, and robust and adaptive nonlinear tracking control.

Multimodal User Input to Supervisory Control Systems: Voice-Augmented Keyboard

Abstract: The use of a voice-augmented keyboard input modality is evaluated in a supervisory control application. An implementation of voice recognition technology in supervisory control is proposed: voice is used to request display pages, while the keyboard is used to input system reconfiguration commands. Twenty participants controlled GT-MSOCC, a highfidelity simulation of the operator interface to a NASA ground control system, via a workstation equipped with either a single keyboard or a voice-augmented keyboard. Experimental results showed that in all cases where significant performance differences occurred, performance with the voice-augmented keyboard modality was inferior to and had greater variance than the keyboard-only modality. These results suggest that, current moderately priced voice recognition systems are an inappropriate human-computer interaction technology in supervisory control systems.

Power Substation Automation Using a Knowledge Based System - Justification and Preliminary Field Experiments

Abstract: Conventional automation and control devices are passive and responsive. These devices typically "respond" to changes in the power system as measured against fixed thresholds and preset limits. These systems are designed to prevent catastrophic failures and incorrect operations and work well for general data acquisition and remote supervisory control. How ever, feedback control, system diagnostics, advanced protection, and contingency control are difficult to implement on the ever changing power system with these conventional approaches. Knowledge based systems have the potential for following the changes in the power system and adjusting decision criteria accordingly. Decisions can be made on a more complete data base which is constantly adjusted to changes ir system parameters and operation. This paper describes the various functions where knowledge based systems could ideally be used. The use of a knowledge based, adaptive system approach for diagnosing distribution system disturbances and equipment failures is presented. Two field experiments are described.

On the limits of expert systems and engineering models in process control

Abstract: The review is based on an analysis of current literature of expert systems and of system engineering models in dynamic process control. It starts with an analysis of the mental operations and cognitive requirements needed for supervisory control. Mental models are discussed as a function of situational requirements as well as of personal strategies. Systems engineering models and expert systems are briefly described and their function as decision support tools evaluated. Criteria are the overall functionality, similarity of knowledge bases and reasoning strategies of the human and the support system, adaptability to the operator's skill level and self-explanation of the support system in the interaction mode. As a result, system engineering models are only of limited value for knowledge-based process control. Expert systems seem to be very valuable tools for augmenting human decision making in process control, if the interaction problem can be solved.

A real-time interactive computer model of a flexible manufacturing system

Abstract: A real-time interactive model of a flexible manufacturing system (FMS) is described, with emphasis given to the system's structure and to the model's interactive component. An attempt is made to illustrate how the model can be used to extract knowledge concerning human strategies at supervisory control of an FMS, knowledge that would otherwise be largely inaccessible. This knowledge is considered essential for the development of expert systems that would serve as supervisory controllers of FMSs.

On Supervisory Control of Real-Time Discrete-Event Systems

Abstract: A discrete-event system G is modelled as the controlled generator of a formal language L(G), in the framework of Ramadge and Wonham. By means of the concepts of well-posed language and well-posed supervisor, it is suggested how this framework can accommodate certain real-time control constraints. Then it is shown that a closed-loop supervisory control has `correct' real-time behavior if and only if the supervisor is well-posed (with respect to time delay).

On the control of discrete-event dynamical systems

Abstract: We study a class of problems related to the supervisory control of a discrete-event system (DES), as formulated by Wonham and we focus on the computational effort required for their solution. While the problem of supervisory control of a perefetcly observed DES may be easily solved by dynamic programming, the problem becomes intractable (in the sense of complexity theory) when a supervisor with a minimal number of states is sought. Furthermore, supervisory control is an intractable problem, in general, when imperfectly observed systems are considered. Finally, some negative results are obtained for the control of interconnected systems consisting of a large number of subsystems.

MIT research in telerobotics

Abstract: Ongoing MIT research in telerobotics (vehicles capable of some autonomous sensing and manipulating, having some remote supervisory control by people) and teleoperation (vehicles for sensing and manipulating which are fully controlled remotely by people) is discussed. The current efforts mix human and artificial intelligence/control. The idea of adjustable impedance at either end of pure master-slave teleoperation, and simultaneous coordinated control of teleoperator/telerobotic systems which have more than six degrees of freedom (e.g., a combined vehicle and arm, each with five or six DOF) are discussed. A new cable-controlled parallel link arm which offers many advantages over conventional arms for space is briefly described. Predictor displays to compensate for time delay in teleoperator loops, the use of state estimation to help human control decisions in space, and ongoing research in supervisory command language are covered. Finally, efforts to build a human flyable real-time dynamic computer-graphic telerobot simulator are described. These projects represent most, but not all, of the telerobotics research in our laboratory, supported by JPL, NASA Ames and NOAA.

Finitely recursive processes

Abstract: We present a new class of discrete event models called Finitely Recursive Processes (FRP). These models are motivated by problems in supervisory control while some of the formal structure is based on Hoare's Communicating Sequential Processes. Although our work is preliminary we believe that for many problems it offers a formalism that is superior to that of Finite State Machines recently introduced in control theory.

Positioniersystem der qualitaetsfuehrungsfunktionen in rotationsdruckmaschinen

Abstract: Each unit of the press has a control system (1) comprising a primary station (3) which receives nominal values of working parameters from a central control system (11), each primary station (3) being connected to at least one application converter (5) which receives nominal values from the station (3) and actual values from a respective actuator (22) in order to regulate the actuator. As shown, the central control system (11) receives inputs from a control panel (13) or an external computer or servicing device (12). The arrangement also includes supervisory control systems (2) and secondary stations (4). The invention enables the system (1) to be standardised, regardless of the supervisory control system (2).

Human supervisor modelling: some new developments

Abstract: Three levels of human behavior can be distinguished: skill-, rule- and knowledge-based behavior. It has been stated before, Stassen (1986) , that modelling of this behaviour can only be successfully achieved at the skill- and rule-based level. Knowledge-based behavior is quantitatively difficult to model. Recent developments in our research group have made the sharp boundary to what can or cannot be modelled, more or less fuzzy. This fact is illustrated by some new developments on the application of fuzzy set theory in modelling the navigator's behavior during the maneuvring of large vessels, on the use of expert systems in diagnostic problems, on human reliability analyses and on the influence of flow modelling on human supervisory control behavior.

Expert Fuzzy Process Control of a Rotary Dryer

Abstract: The expert fuzzy process control system consists of both precise and imprecise state descriptions and decision rules. The control system uses a supervising expert system, deterministic or crisp controllers and fuzzy logic controllers. The supervisor task is based on appropriate criteria which maintains the overall application objective. The selected system structure allows for use of both fuzzy and crisp controllers and encourages optimum allocation of the overall process control hardware and software resources. The control system is applied to a simulated rotary dryer process whose variables are nonlinear and exhibit interaction effects which typically require constant monitoring by skilled operators. Control automation is performed with the proposed system by implementation of the appropriate controller type under expert system supervisory control. The supervisory tasks include those which aid in improving the performance of control.

Building managing device

Abstract: PURPOSE:To make air-conditioning supervisory control and burglar prevention supervisory control to act in close cooperation with each other and to make said control easy and convenient to use without giving any burden to a central unit, by providing a supervisory controller constituted of an air-conditioning controlling means, burglar prevention managing means, and communication controlling means which controls the communication between the above-mentioned means and communicates with the central unit. CONSTITUTION:An air-conditioning controlling means 1a in a supervisory controller 1 controls an air-conditioning machine in accordance with the state of air conditioning loads and a burglar prevention managing means 1b in the controller 1 controls locking and unlocking of a door in accordance with the reading input of a card reader, etc., and, at the same time, performs burglar prevention monitoring by detecting any invaders by means of a man-sensitive sensor 2 after office hour. The means 1a communicates with the means 1b to stop an air-conditioning machine at the time of locking the door and actuate the machine at the time of unlocking the door. A central device 9 is connected with the supervisory controller 1 and facility controllers 10a and 10a through a data transmission line 8. Therefore, the optimum interlocked control can be attained.

Advanced Teleoperation (II) The Generalized Information Feedback Concept in Computer-Aided Teleoperation

Abstract: This paper sets the problem of information feedback in computer aided teleoperation from the point of view of supervisory control. Section 1 deals with telepresence versus generalised information feedback (G.I.F.) concepts and the associated perception-action loops in C.A. teleoperation. Section 2 presents the design and implementation of the IRIS experimental system where we underline the contribution of sophisticated technologies: we briefly summarize how force control may be extended to the “remote touch” feeling using proximity sensors. Section 3 focuses on the importance of world model based information for generating realistic or/synthetic, visual or/force feedback. A simulator is firstly used to provide 3D graphic displays. Then it is extended to include a potential field description, which allows the operator to feel in real time artificial magnetic-like forces.

Centralized supervisory control system

Abstract: PURPOSE:To reduce the cable materials cost and the wiring cost by arranging each transmission terminal equipment and each distribution transformer closely and using a composite cable being the combination of an optical fiber signals wire and a high voltage power wire so as to connect the equipments. CONSTITUTION:In the titled centralized supervisory control system, the composite cable 12 comprising the optical fiber signal wire 10 and the high voltage power wire 11 is provided between plural sets of transmission terminal equipments 13 and distribution transformers 14 arranged closely, the signal of the equipment 13 is sent through the signal line 10 and the power to the transformer 14 is supplied through the power wire 11. The loop data transmission line between a central control unit 15 and each terminal equipment 13 is constituted by the said cable 12 and a loop reception/distribution path between a high voltage electric room 16 and each transformer 14 is constituted thereby. Each transformer is provided to supply a low voltage power to an installation equipment subject to supervisory control in the system.

Device for automatizing distribution line

Abstract: PURPOSE:To prevent the remote supervisory control of other sound slave stations from troubling due to a fault slave station by providing response time supervisory circuits stopping forcibly the transmission of supervisory return signals when a response time of the supervisory return signals transmitted from the slave stations exceeds a specified value. CONSTITUTION:When the action of a slave station R1 is normal, a transmission time by the slave station terminates in t1. When the supervisory return signals 71 are continuously transmitted due to the fault and the like, a timer 81 in the response time supervisory circuit 41 times out after t2 hours, and a switching circuit 51 is forcibly switched OFF, whereby the transmission of the supervisory return signals 71 are stopped. Consequently, the slave station R1 is detached from a transmission line (l). Thus, the fault is not given to communication between the other sound slave stations R2-Rn and the master station 1. The slave stations R2-Rn are similarly detached from the transmission line (l) When the supervisory return signals continue.

Method for a remote supervisory control system

Abstract: The apparatus has a touch panel (4), for a video display (3) controlled by an output control circuit (24), so that, when an operator touches a point on a touch panel (4), a CPU (21) causes the display to display: a representation of, and the current status of, a monitored/controlled device of the corresponding remote station; and a touch point for a control command. When the touch point for the control command is touched, the CPU (21) transmits a control command to the monitored/controlled device of the corresponding one of remote stations (11, 12...,1n) through a line interface (5). When control of the corresponding device is executed, the remote station transmits a signal indicating the operation thereof to the master station apparatus (1). On the basis of the operation indicating signal, the CPU (21) updates the content of a status memory (23), and the status indication displayed on the video display (3) through the output control circuit (24).