Towards a concurrency theory for supervisory control

In this paper we propose a process-theoretic concurrency model to express supervisory control properties. In light of the present importance of reliable control software, the current work ow of direct conversion from informal specication documents to control software implementations can be improved. A separate modeling step in terms of controllable and uncontrollable behavior of the device under control is desired. We consider the control loop as a feedback model for supervisory control, in terms of the three distinct components of plant, requirements and supervisor. With respect to the control ow, we consider event-based models as well as state-based ones. We study the process theory TCP as a convenient modeling formalism that includes parallelism, iteration, communication features and non-determinism. Via structural operational semantics, we relate the terms in TCP to labeled transition systems. We consider the partial bisimulation preorder to express controllability that is better suited to handle non-determinism, compared to bisimulation-based models. It is shown how precongruence of partial bisimulation can be derived from the format of the deduction rules. The theory of TCP is studied under nite axiomatization for which soundness and ground-completeness (modulo iteration) is proved with respect to partial bisimulation. Language-based controllability, as the neccesary condition for event-based supervisory control is expressed in terms of partial bisimulation and we discuss several drawbacks of the strict event-based approach. Statebased control is considered under partial bisimulation as a dependable solution to address non-determinism. An appropriate renaming operator is introduced to address an issue in parallel communication. A case for automated guided vehicles (AGV) is modeled using the theory TCP. The latter theory is henceforth extended to include state-based valuations for which partial bisimulation and an axiomatization are dened. We consider an extended case on industrial printers to show the modeling abilities of this extended theory. In our concluding remarks, we sketch a future research path in terms of a new formal language for concurrent control modeling

On the use of observation equivalence in synthesis abstraction

In a previous paper we introduced the notion of synthesis abstraction, which allows efficient compositional synthesis of maximally permissive supervisors for large-scale systems of composed finite-state automata. In the current paper, observation equivalence is studied in relation to synthesis abstraction. It is shown that general observation equivalence is not useful for synthesis abstraction. Instead, we introduce additional conditions strengthening observation equivalence, so that it can be used with the compositional synthesis method. The paper concludes with an example showing the suitability of these relations to achieve substantial state reduction while computing a modular supervisor

Statistical Watermarking for Networked Control Systems

Watermarking can detect sensor attacks in control systems by injecting a private signal into the control, whereby attacks are identified by checking the statistics of the sensor measurements and private signal. However, past approaches assume full state measurements or a centralized controller, which is not found in networked LTI systems with subcontrollers. Since generally the entire system is neither controllable nor observable by a single subcontroller, communication of sensor measurements is required to ensure closed-loop stability. The possibility of attacking the communication channel has not been explicitly considered by previous watermarking schemes, and requires a new design. In this paper, we derive a statistical watermarking test that can detect both sensor and communication attacks. A unique (compared to the non-networked case) aspect of the implementing this test is the state-feedback controller must be designed so that the closed-loop system is controllable by each sub-controller, and we provide two approaches to design such a controller using Heymann's lemma and a multi-input generalization of Heymann's lemma. The usefulness of our approach is demonstrated with a simulation of detecting attacks in a platoon of autonomous vehicles. Our test allows each vehicle to independently detect attacks on both the communication channel between vehicles and on the sensor measurements

Supervisory Control System Architecture for Advanced Small Modular Reactors

This technical report was generated as a product of the Supervisory Control for Multi-Modular SMR Plants project within the Instrumentation, Control and Human-Machine Interface technology area under the Advanced Small Modular Reactor (SMR) Research and Development Program of the U.S. Department of Energy. The report documents the definition of strategies, functional elements, and the structural architecture of a supervisory control system for multi-modular advanced SMR (AdvSMR) plants. This research activity advances the state-of-the art by incorporating decision making into the supervisory control system architectural layers through the introduction of a tiered-plant system approach. The report provides a brief history of hierarchical functional architectures and the current state-of-the-art, describes a reference AdvSMR to show the dependencies between systems, presents a hierarchical structure for supervisory control, indicates the importance of understanding trip setpoints, applies a new theoretic approach for comparing architectures, identifies cyber security controls that should be addressed early in system design, and describes ongoing work to develop system requirements and hardware/software configurations

BASEL II: THE REVISED FRAMEWORK OF JUNE 2004

A major aim of Basel II has been to revise the rules of the 1988 Basel Capital Accord in such a way as to align banks´ regulatory capital more closely with their risks, taking account of progress in the measurement and management of risk and of the opportunities which these provide for strengthened supervision. Achievement of this aim has involved the incorporation in Basel II of methods for quantifying banking risks introduced since the late 1980s. The task of the designers of Basel II has been complicated by the way in which the BCBS´s rules for banks´ capital, originally intended for the internationally active banks of its member countries, have become a global standard widely applied in developing as well as developed countries. Acceptance of this role by the BCBS has entailed a global consultation process, whose results have been reflected in three consultative papers and the RF, and the different approaches and options for setting numerical capital requirements which are intended to accommodate banks and supervisors of different levels of sophistication. As well as providing a commentary on the main features of the RF this paper documents the response of the BCBS to some of the more important points which were raised during this consultation process, including the outcome of decisions taken at a meeting in Madrid in October 2003 following comments on the consultative paper of April 2003, and summarises the results of the most recent of the BCBS´s initiatives to estimate the quantitative impact of the Basel II rules on banks´ capital. This discussion includes a review of papers issued by the BCBS as part of the last stage of its work preceding the RF.

Systems of Systems: A Control Theoretic View

This paper considers the notion of SoS as an evolution of the standard notion of systems, provides a clear distinction to the standard notion of composite systems and aims to provide an abstract and generic definition that is detached from the particular domain as well as a classification of the families of SoS. We present a new abstract definition of the notion of System of Systems as an evolution of the notion of Composite Systems, empowered by the concept of autonomy and participation in tasks usually linked to games. Control theoretic concepts and methodologies are used to provide the characterization of the notion of "systems play" that is used as the evolution of the notion of the interconnection topology. In this set up the subsystems in SoS act as autonomous intelligent agents in a multi-agent system that is defined by a central task and possibly a game