Development and evaluation of a monitoring-aid system for a nuclear power plant in control room system manipulation.

BACKGROUND: In an advanced nuclear power plant (NPP), the operators are responsible for monitoring a massive number of alarm parameters. OBJECTIVE: To assist the operators, a monitoring-aid system (MAS), that applies four quality control chart methods, was proposed and evaluated. METHODS: Two types of MAS, namely, text and graph marks, were proposed and compared with the original display. To validate the proposed MAS, 17 professional engineers and operators were invited to join an experiment. Two different system states, normal and abnormal, were simulated. The operators were asked to manipulate the system, monitor the critical parameters, search for operational procedures, and deal with other secondary tasks. The primary and secondary task performance and heart rate were measured. After each task was conducted, three subjective rating questionnaires, namely, mental workload, situation awareness, and preference ratings, were implemented for the proposed MAS and the original system. RESULTS: With the assistance of the MAS, the alarm detection rate, secondary task performance, and subjective mental workload demonstrate significant improvements. The proposed MAS helps the operators monitor critical parameters. CONCLUSIONS: Therefore, the MAS should be considered for implementation with the control panel to increase the safety of NPPs. Furthermore, the MAS could reduce the mental workload might decrease the health hazard of the operators.

Applications of integrated human error identification techniques on the chemical cylinder change task.

This paper outlines the human error identification (HEI) techniques that currently exist to assess latent human errors. Many formal error identification techniques have existed for years, but few have been validated to cover latent human error analysis in different domains. This study considers many possible error modes and influential factors, including external error modes, internal error modes, psychological error mechanisms, and performance shaping factors, and integrates several execution procedures and frameworks of HEI techniques. The case study in this research was the operational process of changing chemical cylinders in a factory. In addition, the integrated HEI method was used to assess the operational processes and the system's reliability. It was concluded that the integrated method is a valuable aid to develop much safer operational processes and can be used to predict human error rates on critical tasks in the plant.

Development of an expert system for abnormal operating procedures in a main control room.

The study was conducted from the perspective of human factors engineering in order to compare the process that operators originally used to diagnose potential and actual faults with a process that included an expert system for diagnosing faults. The results of the study indicated that the existence of an expert system for fault diagnosis makes the task of fault diagnosis easier and reduces errors by quickly suggesting likely Abnormal Operating Procedures (AOPs).

The effects of platform motion and target orientation on the performance of trackball manipulation.

The trackball has been widely employed as a control/command input device on moving vehicles, but few studies have explored the effects of platform motion on its manipulation. Fewer still have considered this issue in designing the user interface and the arrangement of console location and orientation simultaneously. This work describes an experiment carried out to investigate the performance of trackball users on a simple point-and-click task in a motion simulator. By varying the orientation of onscreen targets, the effect of cursor movement direction on performance is investigated. The results indicate that the platform motion and target orientation both significantly affect the time required to point and click, but not the accuracy of target selection. The movement times were considerably longer under rolling and pitching motions and for targets located along the diagonal axes of the interface. Subjective evaluations carried out by the participants agree with these objective results. These findings could be used to optimise console and graphical menu design for use on maritime vessels. STATEMENT OF RELEVANCE: In military situations, matters of life or death may be decided in milliseconds. Any delay or error in classification and identification will thus affect the safety of the ship and its crew. This study demonstrates that performance of manipulating a trackball is affected by the platform motion and target orientation. The results of the present study can guide the arrangement of consoles and the design of trackball-based graphical user interfaces on maritime vessels.

Assessment of human color discrimination based on illuminant color, ambient illumination and screen background color for visual display terminal workers.

Human performance on color discrimination in visual display terminals may be affected by illuminant colors, the level of ambient illumination and background colors of the monitor. Few studies have focused on this topic. This study investigated human color discrimination ability in a simulated control room. Ten subjects were recruited as participants to perform a series of experimental tasks. A complete factorial (2 x 3 x 3) within-subject design was used. The independent variables were three illuminant colors (red, blue, and white), two ambient illumination levels (50 lux and 300 lux), and three background colors (black, blue and brown); the three dependent variables were the color discrimination ability (error scores), completion time and subject preference. The results showed that the illuminant colors and the screen background colors both significantly influenced human color discrimination ability (p<0.01). The result of this research can be used in control room design when considering the effect of color.

Investigation of legibility and visual fatigue for simulated flexible electronic paper under various surface treatments and ambient illumination conditions.

This study employs simulated electronic paper to investigate critical issues and focuses on improving legibility of display and reducing users' visual fatigue. Three critical factors--choice of surface treatment, ambient illumination, and bending curvature--are evaluated through the method of a letter-search task. The results show that subjects performed better on legibility and felt less visual fatigue with an anti-glare treatment. Choosing the better anti-glare treatment instead of the anti-reflection series can save significant cost for manufacturers. In addition, ambient lighting of 1500 lux is more appropriate for reading on electronic paper than an environment with extreme illumination (e.g., 8000 lux). The present study also found that curvature had no impact on legibility or visual fatigue. These evaluations of simulated electronic paper may provide manufacturers useful information in fulfilling ergonomic requirements for product design.

Effects of input device and motion type on a cursor-positioning task.

Many studies have investigated the performance of using nonkey-board input devices under static situations, but few have considered the effects of motion type on manipulating these input devices. In this study comparison of 12 mens' performance using four input devices (three trackballs: currently used, trackman wheel, and erectly held trackballs, as well as a touch screen) under five motion types of static, heave, roll, pitch, and random movements was conducted. The input device and motion type significantly affected movement speed and accuracy, and their interaction significantly affected the movement speed. The touch screen was the fastest but the least accurate input device. The erectly held trackball was the slowest, whereas the error rate of the currently used trackball was the lowest. Impairments of the random motion on movement time and error rate were larger than those of other motion types. Considering objective and subjective evaluations, the trackman wheel and currently used trackball were more efficient in operation than the erectly held trackball and touch screen under the motion environments.

The effects of in-vehicle tasks and time-gap selection while reclaiming control from adaptive cruise control (ACC) with bus simulator.

This research aimed to find out the effects of in-vehicle distractions and time-gap settings with a fix-based bus driving simulator in a following scenario. Professional bus drivers were recruited to perform in-vehicle tasks while driving with adaptive cruise control (ACC) of changeable time-gap settings in freeway traffic. Thirty subjects were divided equally into three groups for different in-vehicle task modes (between subjects), including no task distraction, hands-free, and manual modes. Further, time-gap settings for the experimental ACC were: shorter than 1.0 s, 1.0-1.5 s, 1.5-2.0 s, and longer than 2.0 s (within subjects). Longitudinal (mean headway, forward collision rate, and response time) and lateral control (mean lateral lane position and its standard deviation) performance was assessed. In the results, longitudinal control performance was worsened by both shorter time-gaps and heavier in-vehicle tasks. But the interaction indicated that the harm by heavier in-vehicle distraction could be improved by longer time-gaps. As for the lateral control, it would only be negatively affected by shorter time-gap settings. This research indicates the effects of time-gaps and in-vehicle distraction, as well as the interaction. Proper time-gap selection under different in-vehicle distractions can help avoid accidents and keep safe.

Design and evaluation of computerized operating procedures in nuclear power plants.

A small-scale virtual system has been developed in this study to enhance operators' understanding and operating performance. For this, a computerized graphical interface based on Dynamic Work Causality Equation (DWCE) has been designed to transform the operating procedure into a flowchart. Furthermore, the Programmable Logic Controller (PLC) was installed to connect the signboard (proposed system) with the computerized graphical interface. An experiment was conducted to verify the effect of computerized graphic interface, indicating that the computerized system significantly decreases learning time and improves operational performance.