Expert systems for real-time monitoring and fault diagnosis

Methods for building real-time onboard expert systems were investigated, and the use of expert systems technology was demonstrated in improving the performance of current real-time onboard monitoring and fault diagnosis applications. The potential applications of the proposed research include an expert system environment allowing the integration of expert systems into conventional time-critical application solutions, a grammar for describing the discrete event behavior of monitoring and fault diagnosis systems, and their applications to new real-time hardware fault diagnosis and monitoring systems for aircraft

Comparison of QPE and QSIM as Qualitative Reasoning Techniques

Qualitative reasoning predicts and explains the behavior of physical systems using the system's structure through modeling and simulation. There are several approaches to qualitative reasoning. Two of the most prominent software implementations are QPE (Qualitative Process Engine) by Forbus and QSIM (Qualitative Simulation) by Kuipers. A comparison of the two systems is done on the basis of representation and reasoning ability of physical systems. The standard examples in qualitative reasoning and examples in fatigue and fracture in metals are used in the comparison. The fatigue and fracture domain of study can serve as a prototype for other related models of material behavior. A thorough comparison of QSIM and QPE identifies future directions of qualitative reasoning development

Utilization of the MVL system in qualitative reasoning about the physical world

Ankara : Department of Computer Engineering and Information Science and Institute of Engineering and Science, Bilkent Univ., 1993.Thesis (Master's) -- Bilkent University, 1993.Includes bibliographical references leaves 60-63An experimental progra.m, QRM, has been implemented using the inference mechanism of the Multivalued Logics (MVL) Theorem Proving System of Matthew Ginsberg. QRM has suitable facilities to reason about dynamical systems in qualitative terms. It uses Kenneth Forbus’s Qualitative Process Theory (QPT) to describe a physical system and constructs the envisionment tree for a given initial situation. In this thesis, we concentrate on knowledge representation issues, and basic qualitative reasoning tasks based on QPT. We offer some insights about what MVL can provide for writing Qualitative Physics programs.Şencan, Mine ÜlküM.S

Model-based scientific discovery--a study in space bioengineering

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1992.Includes bibliographical references (leaves 130-138).by Nicolas Groleau.Ph.D

Solution monitoring as a nuclear materials safeguards tool

The work presented in this thesis describes a solution monitoring system that has been developed to assist United Nations' inspectors performing nuclear materials safeguards, primarily pertaining to plutonium storage and nuclear fuel reprocessing facilities. Based on the concept of the 'event', which is essentially any process that occurs on the plant, it aims to construct a hypothesis of which events have actually occurred, and to decide if any of these have safeguards implications. The package developed is robust, portable, and easy to use. The system has been implemented in G2 with extensive call-outs to FORTRAN and C routines. Sensor data from the plant is first analysed, and salient features (sub-events) are extracted. A model based diagnostic algorithm is then used to determine all possible causes of these sub-events; based on topographical knowledge of the plant, this makes extensive use of a simulation model. A rule based system then examines permutations of these sub-events and diagnoses, to find all possible events which could explain the data. From the possibilities generated, the most likely events are chosen on the basis of user specified subjective probabilities and on supporting evidence; these probabilities reflect the view that some events are more likely to be acceptable to the operator than others. Bayesian evidential updating methods are used to achieve this. An automatic model generator is presented, which extends the portability and applicability of the diagnostic aid, and makes implementation a great deal easier. Amongst other things, this enables simulations to be constructed automatically using a library of unit process models. The nature and forms of the various user interfaces are discussed. In particular facilities are available for creating and maintaining databases of rules which are used to identify, classify and rank the events. The system has been tested using data from a number of plants, both hypothetical and real. The primary test facilities have pertained to plutonium nitrate solution storage areas. A hypothetical solvent-extraction and concentration facility has also been considered, to extend the range of applicability of the system. These studies have demonstrated that solution monitoring has the potential to be a valuable aid for inspectors responsible for nuclear materials safeguards

Automatic Qualitative Modeling of Dynamic Physical Systems

This report describes MM, a computer program that can model a variety of mechanical and fluid systems. Given a system's structure and qualitative behavior, MM searches for models using an energy-based modeling framework. MM uses general facts about physical systems to relate behavioral and model properties. These facts enable a more focussed search for models than would be obtained by mere comparison of desired and predicted behaviors. When these facts do not apply, MM uses behavior-constrained qualitative simulation to verify candidate models efficiently. MM can also design experiments to distinguish among multiple candidate models

Real Time Fault Detection and Diagnosis in Dynamic Engineering Systems Using Constraint Analysis

This thesis describes some new ideas and a practically orientated implementation for fault detection and diagnosis in dynamic engineering systems. The method is designed for use on-line, it is model based, and is capable of coping with modelling inaccuracies, noisy measurements from the system and unmeasurable system states. The fault detection system is robust to false alarms, and the fault diagnosis system allows for the possibility that multiple faults may occur simultaneously. A number of system analysis algorithms are presented to extract various system equations from the model of the system. This means that the user need only enter one model of the whole system, and all of the analysis and equation solving is then handled by computer. The results of this analysis are then automatically encapsulated into a fault detection and diagnosis tool. This results in the automatic generation of a specific fault analysis tool for the system entered by the user. A "hypothesis prover" is developed here for the domain of dynamic systems, which is used to test hypotheses. Some of the ideas about multiple faults as developed by de Kleer & Williams and Reiter have been used, but these have been adapted to make them applicable for real-time, recursive, imprecise, diagnosis. (Diagnoses are imprecise because, due to modelling errors and noisy measurement, it is never possible to be 100% certain about anything.) When multiple faults are considered, the number of possible combinations becomes very large, 2N - 1, where N is the number of components. The computation required to prove a particular hypothesis, although not enormous, is not trivial either, making it impractical to prove a large number of hypotheses. To overcome this a method is proposed which involves just proving a subset of the possible hypotheses, and using the information obtained from these to reason about the other hypotheses. This requires much less computational power as the reasoning process is much less intensive than the proving process. This make the diagnosis of multiple faults possible in real-time. The methods developed here are tested on a real, noisy system where approximations are made when producing the systems' model. These tests show the potential of this approach to fault diagnosis