Advancements in control system technology have quickly outpaced understanding of how operators use the control systems. To date, there is incomplete knowledge about how operators scan their instruments, integrate the information and use it as a knowledge basis for making control decisions. For example, little is known about what the attributes of an expert operator are, or what differences there are between an expert and novice operator in the way each monitors instruments. Knowing these differences would aid in operator selection, training and display system design.
Fortunately, research is being conducted which has begun to shed light on the operator-control system interface. One recent experiment, (J.D. Lee, N. Moray, Operators' Monitoring Patterns and Fault Recovery In The Supervisory Control of Semi-Automatic Process, Proceedings of the Human Factors Society 36th Annual Meeting-1992, page 1143), tried to isolate operator control system monitoring strategies which correspond to successful mitigation of process plant upsets. In the experiment subjects controlled a simulated semi-automatic pasteurization process. The researchers tracked the subjects' instrument monitoring patterns, control actions, and their success in mitigating simulated process upsets.
The experiment found that differences in operators' instrument monitoring patterns during normal operation of the plant corresponded to differences in their ability to mitigate process upsets. Expert operators, those who could mitigate the simulated process upsets, were found to monitor the system more frequently and make fewer control moves than the novice operators. The experiment also found the expert operators do not randomly sample the instruments, but rather, their observations follow regular inspection patterns, with subsequent observations influenced by the current plant conditions.
The experiment also found that some operators only monitored a limited part of the process. This instrument monitoring strategy provided the operators with an impoverished view of the process. This monitoring strategy enabled these operators to successfully control the system during normal operation but they were unable to handle the process during upsets.
Copyright © 1992 Beville Engineering, Inc. , All Rights Reserved
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