Author
Gary J. Powers
Bio: Gary J. Powers is an academic researcher from Carnegie Mellon University. The author has contributed to research in topics: Process control & Control system. The author has an hindex of 14, co-authored 30 publications receiving 834 citations.
Papers
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TL;DR: An algorithm is presented for the synthesis of fault-trees which is deduced directly from a digraph (directed graph) model of the system being analyzed, and a computer program which uses this algorithm is illustrated for a chemical processing system.
Abstract: An algorithm is presented for the synthesis of fault-trees. The fault-tree is deduced directly from a digraph (directed graph) model of the system being analyzed. The digraph describes the normal, failed, and conditional relationships which exist between variables and events in the system. A computer program which uses this algorithm is illustrated for a chemical processing system.
298 citations
TL;DR: A model-based verification method is developed and applied to validation of VLSI circuits and to reveal discrete event errors, the method is applied to a simple combustion system and an alarm acknowledge system.
Abstract: Clarke et al. (1986) have developed a model-based verification method and have applied it to validation of VLSI circuits. We have used the method to test automatically the safety and operability of discrete chemical process control systems. The technique involves: (1) a “system model” describing the process and its software; (2) “assertions” in temporal logic expressing user-supplied questions about the system behavior with respect to safety and operability; and (3) a “model checker” that determines if the system model satisfies each of the assertions and provides a counterexample to locate the error if one exists. Temporal logic is used for reasoning about occurrence of events over time. To reveal discrete event errors, we have applied the verification method to a simple combustion system and an alarm acknowledge system.
88 citations
TL;DR: In this paper, the authors apply non-numerical problem-solving techniques to the problem of synthesizing process control structures based on the cause-and-effect representation of the process.
Abstract: This paper is concerned with an important aspect of process control design—synthesis of the control structure. Synthesis of control structures has long been practiced by experienced control engineers, who relied on intuition, insight and judgment to pick a feasible solution from the vast number of alternatives that were possible. This paper describes a systematic procedure to generate these alternatives based on the cause-and-effect representation of the process. The final product is a set of control schemes from which the final system may be selected or evolved. The work is significant in that it is the first attempt to apply non-numerical problem-solving techniques to the problem of synthesizing process control structures. As such, it gives a new way of studying and teaching chemical process control.
57 citations
TL;DR: In this paper, a strategy is proposed for the systematic synthesis of operating procedures for chemical processing facilities, which is based on artificial intelligence techniques, most importantly planning with constraints, and the concept of stationary states are used as targets during procedure planning and real-time operations.
52 citations
TL;DR: A modelling method is presented which combines local causal models for identifying unit manipulations with numerical models to verify effects of process manipulations and to determine feasibility of this systematic synthesis of operating procedures for chemical processing systems.
42 citations
Cited by
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TL;DR: This three part series of papers is to provide a systematic and comparative study of various diagnostic methods from different perspectives and broadly classify fault diagnosis methods into three general categories and review them in three parts.
2,263 citations
TL;DR: This part of the paper reviews qualitative model representations and search strategies used in fault diagnostic systems and broadly classify them as topographic and symptomatic search techniques.
1,415 citations
TL;DR: A discrete-event systems (DES) approach to the failure diagnosis problem is proposed, applicable to systems that fall naturally in the class of DES; moreover, for the purpose of diagnosis, continuous-variable dynamic systems can often be viewed as DES at a higher level of abstraction.
Abstract: Detection and isolation of failures in large, complex systems is a crucial and challenging task. The increasingly stringent requirements on performance and reliability of complex technological systems have necessitated the development of sophisticated and systematic methods for the timely and accurate diagnosis of system failures. We propose a discrete-event systems (DES) approach to the failure diagnosis problem. This approach is applicable to systems that fall naturally in the class of DES; moreover, for the purpose of diagnosis, continuous-variable dynamic systems can often be viewed as DES at a higher level of abstraction. We present a methodology for modeling physical systems in a DES framework and illustrate this method with examples. We discuss the notion of diagnosability, the construction procedure of the diagnoser, and necessary and sufficient conditions for diagnosability. Finally, we illustrate our approach using realistic models of two different heating, ventilation, and air conditioning (HVAC) systems, one diagnosable and the other not diagnosable. While the modeling methodology presented here has been developed for the purpose of failure diagnosis, its scope is not restricted to this problem; it can also be used to develop DES models for other purposes such as control.
699 citations
TL;DR: This paper reviews and classifies fault-tree analysis methods developed since 1960 for system safety and reliability and classified the literature according to system definition, fault- Tree construction, qualitative evaluation, quantitative evaluation, and available computer codes for fault-Tree analysis.
Abstract: This paper reviews and classifies fault-tree analysis methods developed since 1960 for system safety and reliability. Fault-tree analysis is a useful analytic tool for the reliability and safety of complex systems. The literature on fault-tree analysis is, for the most part, scattered through conference proceedings and company reports. We have classified the literature according to system definition, fault-tree construction, qualitative evaluation, quantitative evaluation, and available computer codes for fault-tree analysis.
582 citations
14 Dec 1994
TL;DR: A discrete event systems (DES) approach to the failure diagnosis problem is proposed and the notion of diagnosability is discussed, and the construction procedure of the diagnoser is presented.
Abstract: We propose a discrete event systems (DES) approach to the failure diagnosis problem. We present a methodology for modeling physical systems in a DES framework. We discuss the notion of diagnosability and present the construction procedure of the diagnoser. Finally, we illustrate our approach using a heating, ventilation and air conditioning (HVAC) system. >
505 citations