The development of a model and simulation of an aviation maintenance technician task performance

This paper describes the model of an aircraft maintenance technician (AMT) behaviour working in a real world environment and the application of this model in a computer simulation. The model was derived from the combination of two existing models of cognition (SHELL and RMC/PIPE), based on the paradigm of an information processing system. The simulation structure was developed by transforming the model into an action-execution structure and implementing this model in a computer program based on an object-oriented programming language. An error generation system was coupled to a simple taxonomy of causal correlations between socio-technical and contextual factors operating in an environment defined by a comprehensive task analysis. The simulator can be applied to many aviation maintenance tasks to assist in the design of aviation maintenance training systems through the analysis of the interaction of performance influencing factors and possible AMT performances during the execution of normal maintenance operations. A number of sample outputs from the simulator show the potential of the results to assist in training development. A discussion is also made of other potential applications and the future directions the simulator structure can take.     

Probabilistic safety assessment and reliability based maintenance policies: application to the emergency diesel generators of a nuclear power plant

This study is performed on the four 2.5 MWe emergency diesel generator (EDG) sets of Hydro-Quebec Gentilly-2 Nuclear Power Station. EDGs are safety related systems for the case of the loss of off-site power. This study establishes the basis of an enhanced preventative maintenance and periodic testing program with the objective of improving the long-term reliability and availability of the EDG. It is also the first step to a PSA program based on the real historical data of the system.     

Timeliness and task specification in designing for human factors in railway operations

Human error is often related to flaws in system design which might have been avoided had greater attention been paid to human factors knowledge and methods as the system was developed. The paper considers the role of human factors in system design and argues that adopting an operational perspective in identifying human factors issues ensures that subsequent human factors advice is focused upon real needs and is consistent with how managers and engineers choose to manage their systems. It also considers the issue of timeliness of human factors input. Failure to consider human factors issues at a time when other design decisions are being taken often means that it is less straightforward to accommodate changes. Thus, managers and engineers may resist dealing effectively with potential human factors problems for reasons of cost and delay in meeting project milestones.     

A case study of a human reliability assessment for an existing nuclear power plant

This paper concerns a Human Reliability Assessment (HRA) carried out over a period of two years as part of a Nuclear Power Plant Probabilistic Safety Assessment (PSA). The HRA involved all elements of the HRA process, from problem definition and task analysis, through error representation and quantification, to impact assessment, error reduction, quality assurance and documentation. The aim of this paper is to show the methodology of HRA as applied in a real PSA, highlighting various elements of the HRA, and how the HRA interfaced with the PSA. Comments are also given on practical aspects and impacts of the various approaches, and the usefulness of a hybrid HRA/PSA team approach.     

Workload measurement using physiological and activity measures for validation test: A case study for the main control room of a nuclear power plant

In design of safety-critical and social-technical systems such as a nuclear power plant, practitioners are required to conduct a performance-based Integrated System Validation (ISV) test to verify that the system design could support the safe operation of the plant. Measurement of workload should be included. However, subjective workload measurements could not provide detailed information and continuous monitoring of the changing workload. This study compared physiological (heart rate difference, heart rate variability, respiration rate and breathing wave amplitude) and activity (number of walking steps, peak acceleration, activity level, and inclination) measures with workload defined as intensity of task demand and estimated with a task complexity measure in an ISV test. The test was conducted on a full-scale simulator using a beyond design-basis accident scenario. The results show that heart rate difference and respiration rate are positively correlated with the estimated workload, while heart rate variability and breathing wave amplitude are negatively correlated with the estimated workload. For operations using traditional panels, high workload is accompanied by larger number of walking steps, higher activity level, and smaller angles of inclination. It is suggested that continuous monitoring of cardiovascular, respiration, and activity measures can detect workload change during the ISV test. Relevance to industry: This study provides recommendations for continuous monitoring of workload during an ISV test of a nuclear power plant. The identified physiological and activity measures can be applied in detecting workload change. The findings are supportive in meeting regulatory requirements and improving system design in the nuclear domain.     

An overview of a nuclear reprocessing plant Human Factors programme

This paper presents a case study of a large Human Factors programme applied in the nuclear fuel reprocessing industry (1987-1991). The paper outlines the key Human Factors issues addressed, as well as the impacts achieved, and gives an indication of the resources utilised (approximately 15 person-years of effort). It also considers the starting point of the programme, in terms of the factors that led to the need for such an extensive programme. Some general lessons learned are given at the end of the paper.     

Relations between task and activity: elements for elaborating a framework for error analysis

The notion of error, when applied to an activity or the result of an activity, implies the notion of task: it expresses the deviation between the activity and the task being considered from an angle which is judged to be relevant. The task and the activity are the object of representations for the analyst (or specialist) and for the driver. Four representations are dealt with in this paper: the task and the activity for the specialist and the task and the activity for the driver. An interpretation is proposed for these tasks, and they are illustrated using some of the work already carried out in this field. The signification of deviations between these representations is then discussed, together with the advantage of studying these deviations in order to clarify error-producing mechanisms. Analysis in terms of task and activity raises methodological and practical problems which are touched upon; it does not exclude referring to psychological theoretical frameworks to which it is worthwhile linking it. This perspective raises questions which make it possible to enhance the study of errors: it could be completed at a later date by extending it to include other representation categories.     

Comparison between conventional and digital nuclear power plant main control rooms: A task complexity perspective,part I: Overall results and analysis

Digitalization is a trend in safety-critical complex systems. It changes the way human interacts with systems. We have less empirical knowledge about its potential negative effects on human. In our study, we compared conventional and digital main control rooms (MCRs) in nuclear power plants (NPPs) from a task complexity perspective. Complexity factors in MCRs were quantified in terms of three aspects, frequency of occurrence, complexity induced by their being, and impact caused by them. A total of 69 licensed operators participated in the study. The study consists of two parts. In Part I, overall results and analysis were reported. Generally, operators in digital MCRs perceived higher frequency and higher impact of complexity factors than those in conventional MCRs, no matter in abnormal/emergency or normal situations. Operators in digital MCRs perceived higher complexity than those in conventional MCRs in abnormal/emergency situations. These findings suggest that operators in digital MCRs experience higher complexity and workload which may reduce their reliability. These findings imply that we should caution the side-effects of ubiquitous digitalization in complex industrial systems.Relevance to industryDigital technologies are widely deployed in the nuclear industry. They change the working environments in which operators interact with NPP systems. There is insufficient research on operator experience on the changes brought by technological developments in NPP control rooms. Our findings imply that we should take care of the potential negative effect of digitalization on operator working environments.     

Comparison between conventional and digital nuclear power plant main control rooms: A task complexity perspective,Part II: Detailed results and analysis

Part II of this study aims to provide detailed, diagnostic information about the complexity difference between conventional and digital main control rooms (MCRs) in nuclear power plants. Complexity factors were classified according to task components and complexity dimensions. The effects of operator experience and plant type on complexity factors were statistically analyzed from three levels, i.e., task components, complexity dimensions, and individual factors. Interface management complexity factors were compared with other factors in digital MCRs. The results suggest that generally operator experience had effects on several task components and complexity dimensions only in abnormal/emergency situations. Plant type affected several task component and complexity dimensions in both abnormal/emergency and normal situations. Complexity factors in the affected task components and complexity dimensions had higher frequency, complexity, or impact in digital MCRs than those in conventional MCRs. Factors related to crew activity and the dimensions of overabundance, temporal demand, and variability had relatively high frequency, complexity, or impact. Compared with other factors, interface management complexity factors had marginally higher frequency, but significantly lower complexity and impact.Relevance to industryThis study quantitatively addresses the complexity difference between conventional and digital MCRs in detail. It may provide rich information for how to improve operator working environments in NPPs. It may also contribute to other applied domains, such as human reliability analysis and interface design.     

Human reliability analysis and optimization of manufacturing systems through Bayesian networks and human factors experiments: A case study in a flexible intermediate bulk container manufacturing plant

Human reliability analysis (HRA) and optimization in manufacturing systems are effective to reduce system failure. The purpose of this study is to examine the HRA and optimization through a Bayesian network (BN) model and human factors experiments (HFEs). This study was applied to a flexible intermediate bulk container manufacturing plant. The human physiological and psychological factors consisting of personal abilities of flexibility, coordination, memory, and attention were regarded as the only performance shaping factors in this study. With the BN model, the relationship between human factors and human errors was described qualitatively and the impact of the human factor on system failures was judged quantitatively. Then the workers’ abilities training with HFEs based on the fault diagnosis results was carried out. The total numbers of errors have been decreased by 69.06% and the system failure rate has been reduced significantly after training.     

Development of a systematic checklist for the human factors evaluation of the operator aiding system in a nuclear power plant

In the safety systems review of the Korean nuclear power plants, the Human Factors Program Plan for the OAS (Operator Aiding System) has been executed mainly by an expert review. The reviewers had to integrate all the relevant sources of information and make judgement based on their own criteria. Consistency and thoroughness of this process was always in question and a systematic approach to correct these problems was in need. The purpose of this work was to design a methodology for supporting an effective and efficient ergonomic evaluation of the user interface of the OAS. By collecting and systematically structuring all the critical considerations in the human factors review process, an ergonomic evaluation checklist for the CFMS (Critical Function Monitoring System) in an MCR (Main Control Room) was designed and implemented in this study. Application of the developed checklist was used during the licensing review process for the CFMS of the Ulchin unit 3&4. Efficiency and effectiveness of the human factors review process was enhanced significantly with the aid of the integrated checklist and the standardized evaluation format developed in this study.

Relevance to industry

Human factors review process is an integral component of the safety of a nuclear power plant. The methods and procedures developed in this study will provide valuable support for the enhancement of the safety and usability of the human interface of the nuclear power plant.     

Progress in systems ergonomics: a selective review

Abstract

The 1967 conference on the Human Operator in Complex Systems identified several developments required in systems ergonomics. Progress in four areas requiring development is reviewed, based on information from workshops and surveys of applications of systems ergonomics in military systems. It is concluded that there has been less progress than might have been hoped in the use of systems relevant criteria in systems ergonomics. Few applications have involved trade-offs between selection, training and equipment design. Task analysis techniques have not advanced, although their use may be changing. Although there appears to be general agreement on the major activities associated with systems ergonomics, the emphasis placed on those different activities may be changing as a result of technological developments. However, these technological developments are now providing opportunities for systems ergonomists to improve their tools and techniques.     

Ergonomics risk assessment among maintenance operators in a Tunisian railway company: A case study

Railway truck maintenance plays a crucial role for rail transport. It aims at ensuring the availability of the equipment and the safety of the operations. However, maintenance activities often involve uncommon work and nonroutine tasks and it is obvious that maintenance operators are more threatened than other employees to be exposed to various hazards in their workplace. In Tunisia, the prevalence of occupational accidents and injuries among maintenance workers is not well documented. The target of this cross‐sectional study is to assess ergonomics risks associated with maintenance activities in a railway company. Data collection was carried out through a self‐administrated questionnaire and via direct observations. The Body Parts Symptom Survey (BPSS) was used to identify the discomfort level of the workers. More than 100 maintenance operators working in nine different workshops were involved in this study. From BPSS results, this paper proposed a new method to calculate the discomfort index related to each body part in order to calculate the global discomfort index (GDI) for each workshop. Results showed that the most hazardous workshop was rail‐car maintenance workshop (GDI = 43.06). Four main tasks were assessed with normalized score. Final scores were found to be extremely high. To remedy the raised problems, new adjustable workstations were proposed, which showed a considerable improvement on workers’ postures.     

The effect of information availability in a user interface (UI) on in-vehicle task performance: A pilot study

When performing an in-vehicle operation, the information display is a crucial element that decides the operator's control behaviors. The interaction between information presentation and operator's in-vehicle task performance is critical for vehicle safety. The question arises: What is the optimum availability of information? The aim of this study is to investigate the relationships between different information availabilities and operation performances as operators interact with an in-vehicle user interface (UI) to complete a simulated train driving task. The results show that some types of information significantly affect the operator's task performance. Information that improved the task performances were closely associated with specific task requirements. The participants' task performance indicated that they had a better awareness of a task situation and were better at controlling their virtual vehicle when completing time and process-restricted tasks with limited, relevant information. These results support the conclusion that more information does not always promote accuracy and safety during the task completion.Relevance to industryThis study presents a unique insight into the information display of in-vehicle UI design for vehicle control. The information available within an in-vehicle interface should be optimized by performance assessments to provide more useful information; this has significant positive effect on operator performance from an accuracy and safety perspective. Thus, this study provides advice for designing an in-vehicle UI.     

Mechanical exposure implications of rationalization: a comparison of two flow strategies in a Swedish manufacturing plant

The aim of this case study was to (1) investigate differences in mechanical exposure (i.e. mechanical forces arising in the body of the operator) between two production strategies: long-cycle parallelised flow assembly (OLD) and conventional serial flow assembly (NEW), and (2) estimate potential changes in job exposure as a consequence of waste reduction when rationalising a line system. Data on postures, movements and whole body exposure were collected during an ordinary working shift, by means of video recordings synchronised to direct technical measurements of six professional operators. The results revealed the machine paced NEW system to have slower movements with less time spent in movements of high velocity compared to the self-paced OLD system. No significant differences were found between time-median posture levels. 'Disturbances' in the NEW system offered lower mechanical risk exposures compared to direct assembly work. Modelling the removal of wasteful 'disturbances' revealed both an increase in risk-implying fast movements and decrease in recovery-implying periods at low velocity - effectively isolating a work intensification. This study helps expose the complex relationship between rationalizations and mechanical exposure for system operators.     

Optimal design methods for a digital human–computer interface based on human reliability in a nuclear power plant part 1: Optimization method for monitoring unit layout

This is the first in a series of papers describing the optimal design method for a digital human-computer interface of a nuclear power plant (NPP) from three different points based on human reliability. The purpose of this series is to propose different optimization methods from varying perspectives to decrease human factor events that arise from the defects of a human–computer interface. The present paper mainly discusses the optimization method for the layout of monitoring units.The layout of relative positions among different functional blocks in a digital human–computer interface influences the time required to search information. The risk of an event increases with increases in the time required to search for information because of the limited time available during a nuclear emergency. To avoid the risk of such an event, the authors propose an optimization method for the layout of monitoring units based on human reliability for a digital human–computer interface of a NPP. In the optimal design process, the authors propose a linear reversal genetic hybridization method that uses the Bayesian method as an adaptive function and takes human reliability as the optimized criterion. To quantitatively obtain the probability of human reliability, the authors use dynamic simulative functions including time and human factors. Finally, an experiment is conducted. The results indicate that the linear reversal genetic hybridization method has good stability and sensitivity and that the proposed optimization method has good accuracy and convergence.     

Selection of diagnostic techniques and instrumentation in a predictive maintenance program. A case study

Predictive maintenance programs (PMPs) can provide significant advantages in relation to quality, safety, availability and cost reduction in industrial plants. Nevertheless, during implementation, different decision making processes are involved, such as the selection of the most suitable diagnostic techniques. A wrong decision can lead to the failure of the setting up of the predictive maintenance program and its elimination, with the consequent economic losses, as the setting up of these programs is a strategic decision. In this article, a model is proposed that carries out the decision making in relation to the selection of the diagnostic techniques and instrumentation in the predictive maintenance programs. The model uses a combination of tools belonging to operational research such as: analytic hierarchy process (AHP) and factor analysis (FA). The model has been tested in screw compressors when lubricant and vibration analyses are integrated.     

Effects of data quality and quantity in systems modelling: a case study

When constructing a probability distribution from incomplete and imprecise data, the effects of the quantity and the quality of the data are of serious concern in practical applications. Consider a situation when one is building a matrix of a joint probability distribution. For some events, the probabilities are available only approximately, and for the majority of the events they are not available at all. Traditionally, if the known values are exact values, this type of problem is dealt with by maximizing the Shannon entropy of the distribution while using the known values as constraints. In this case, however, the available information is approximate and represented by fuzzy numbers. A multi-objective optimization method is proposed that employs the well-known principles of maximum and minimum uncertainty. In this method, the Shannon entropy is maximized and, in addition, the known elements whose membership grades are as high as possible are searched for. The method is applied to the construction of an origin–destination (O–D) table of a transit from incomplete and imprecise data. The behaviour of the solution with respect to quantity and quality of available data is tested with sensitivity analysis using real-world data of four transit lines. This analysis reveals how changes in the quantity and quality of data affect the acceptable level of an O–D table. Furthermore, the issue of how to combine O–D tables developed on the basis of different sets of approximate values is examined using a method that minimizes the sum of the relative Shannon entropies.