Information Aids for Diagnosis Tasks Based on Operators’ Strategies 김 종 현

INFORMATION HIERARCHY Abstractive Information aid – information integration

Classes of IDSSs Input Information Overload (IIO) –Too much information –Filter the information and remove the redundant or superfluous parts Incomplete information –The information that is missing or ill-defined –Provide the missing default information or reason with incomplete information Insufficient information –The additional information exists potentially, but a separate and specific effort is required to bring it out. –Extrapolation, prediction, calculation evaluation, and trend

Information Aid Systems for MCR Operators Monitoring/ Detection Monitoring/ Detection Situation Assessment Situation Assessment Response Planning Response Planning Response Implementation Response Implementation Alarm System Instrumentation System Instrumentation System Control/Protection System Control/Protection System Plant Fault Diagnosis System Fault Diagnosis System Computer-based procedure Computer-based procedure Implementation System Implementation System Display System

Information Aid Systems for MCR Operators FeaturesDisadvantage or Problems Alarm System Need: information overload Features: alarm definition, alarm processing, alarm prioritization, alarm display, and alarm control and management Lack of positional information Fault diagnostic system Need: fault propagation, PRA, accident management Features: on-line and off-line, component and plant-wide Limitation in capability of the systems Lack of supporting operators’ diagnostic strategies Computer- based procedure system Purpose: to guide operators’ actions in performing their tasks in order to increase the likelihood that the goals of the tasks would be safely achieved Features: automatic identification of procedure, automatic calculation of procedure-referenced valued, etc. Lack of supporting operators’ dynamic operation strategies

Information Aid Systems for MCR Operators Underlying causes of the problems –Lack of understanding operators’ dynamic strategies of the tasks Providing hypotheses and computerizing procedures are not enough to support MCR operators –Ambiguity in allocating roles to operators and support systems in the tasks Defining the roles or relationship between two agents (operator and support system), that is automation level, is vague.

Paradigm Change in Decision Support Systems ProsthesisInstrumentAgent

Automation Levels of OSSs Level 0 It refers to the classical paper operation manual, computerized or not. The OSS is reduced to to a simple knowledge database Level 1 It is characterized by an OSS connected to the system being controlled. It helps by determining possible situations (contexts) which the operator then select. It is able to start a process of analytical reasoning, interacting with the operator. The operator answers the questions, applies to the procedures or not, and can stop the reasoning at any time Level 2 It determines contexts and suggests one which the operator should follow. All possible contexts are presented with a likelihood judgments. Some questions are automated, i.e., the OSS checks the truth of the corresponding request information, and presents the selected answers to the operator Level 3 It selects a context automatically. It presents procedures to apply and the operator approves or not. The OSS applies the procedure and sends the message ‘executed’ to the operator Level 4 All the questions which do not necessitate operator confirmation are totally automated. The procedures are applied automatically. The situation recognition part is totally automated. Level 5 Everything is automated.

Requirements for OSSs Building systems –Accuracy –Coverage Strategy supporting –Task analysis –Strategy analysis –Role defining –Transparency

Process to Develop Support Systems in MCRs The operational tasks that must be performed A model of human performance for these tasks A model of how control room features are intended to support performance

Operational Task: Diagnosis Normal Operation Abnormal operation Emergency operation monitoringaction Immediate response diagnosis Corrective action Immediate Response (safety parameter) diagnosis Corrective action

Operational Task: Diagnosis Diagnosis –Monitoring –Decision making (determination of the plant status and the corresponding procedure) Control –Goal-oriented tasks –Tuning plant parameters, making changes in plant mode (e.g., startup, shutdown, intermediate power change), performing switch over, etc. –The feedback is important.

Diagnostic Strategies: Two Aspects Bottom-up process –Data-driven process or Forward reasoning –Observations to hypothesis –Early in the information processing –Familiar faults Top-down process –Hypothesis (goal)-driven process or Backward reasoning –Hypothesis to observation –Novel faults

Diagnostic Strategies Topographic search

Diagnostic Strategies Symptomatic search Pattern recognition

Diagnostic Strategies Symptomatic search Decision table search

Diagnostic Strategies Symptomatic search Hypothesis-and-test strategy

Diagnostic Strategies A comparison of the resource requirements of the various diagnostic strategies Performance factor Topological search Recognition Decision table Hypothesis and test Time spent -Low-- Number of observations HighLow- Dependency on pattern perception -High-- Load of short-term memory Low High Complexity of cognitive processes Low -High Complexity of functional model Low--High General applicability of tactical rules High--Low Dependency on malfunction experience LowHigh-Low Dependency on malfunction preanalysis --high-

Information Aid Systems from the Viewpoint of Diagnostic Strategy Alarm system Fault diagnostic system

Information Aid Systems from the Viewpoint of Diagnostic Strategy

A Proposition for Information Aids in Diagnosis Tasks “Computational technology should be used to aid the operator in the process of solving his problem,” and therefore, should support the operator along with his/her diagnostic strategy FeatureProcess to be supported Alarm processing Topological search, pattern matching in symptomatic search, bottom-up process Hypothesis+model of function in hypothetical failed system + reference symptom pattern Hypothesis-and-test strategy, decision table search, top-down processing

Further Study Experiment –FISA-2/PC : Visual display unit –Alarm processing module –Fault diagnosis module