Ergonomics study and analysis of workstations in Tunisian mechanical manufacturing

The workers’ performance in the mechanical manufacturing sector is the main factor for the improvement of productivity and quality. At present, it seems that the available information on the ergonomics and the working environment of the mechanical manufacturing actors is scarce. This study deals with the relationship between the working method and the workstation in injection mold manufacturing. An original methodology, based on the survey of operators using participatory ergonomic tools, is proposed in order to evaluate the ergonomic performance of 3 workstations: milling, turning, and drilling. The surveys concerned 3 operators. Obtained results showed that ergonomics play a key role in improving mechanical manufacturing. The results obtained from the analysis showed that ergonomics has a key role in the quality of the various tasks performed by operators. Using the Rapid Entire Body Assessment (RULA) and Rapid Entire Body Assessment (REBA) investigation tools, the examination of the workstations revealed 4 machining operations and 12 operator postures that have a direct influence on the performance of all machining stations. In addition, data from the analysis conducted on injection mold manufacturing revealed that neither the workstations were ergonomic nor the operators complied with the ergonomic rules. Based on the results obtained, a new standardized score is proposed for the RULA and REBA calculations. This score was applied and validated through another study conducted in a leaf spring manufacturing plant. The results of these studies were concretized by proposing the digital factory where CATIA software was used for the virtual design of the ergonomic workstations and their environments.     

Investigation of musculoskeletal symptoms and ergonomic risk factors among female sewing machine operators in Turkey

This cross-sectional study aimed to identify the prevalence of musculoskeletal symptoms and ergonomic risks in female sewing machine operators at a textile company. The study sample comprised all female sewing machine operators in the company. The sample included 283 sewing machine operators. Data were collected through the use of the adapted Nordic Musculoskeletal Questionnaire and by direct observations via the rapid upper limb assessment (RULA) to determine ergonomic risks. RULA is a validated tool for assessment of ergonomic risks. The mean age of the women was 30.2 (SD: 8.4) and the mean number of years of employment was 13.4 (SD: 5.5). The highest prevalence rates for the women’s musculoskeletal symptoms were in the trunk (62.5%), neck (50.5%), and shoulder (50.2%). Of the women, 65% had experienced musculoskeletal pain or discomfort over the last 6 months. Pain intensity of these symptoms was assessed with a visual analogue scale. The average pain intensity of the women was found to be 3.5 (SD: 2.8). Results of the RULA scores were found to be quite high. There were no employees who received RULA scores of 1–2, which indicates acceptable postures (all scores >5). The final RULA scores of 6.9 indicate that the participants’ postures at their work stations need to be investigated immediately.

Relevance to industry

This study based on the RULA method allowed to perform a rapid and quite correct evaluation tolls for SMOs. For this research population, the research findings provided fundamental data on the prevalence of musculoskeletal symptoms and ergonomic risks among Turkish female SMOs.     

Many model thinking in systems ergonomics: a case study in road safety

In complexity science, the many models thinking philosophy argues for a multi-method approach to complex problems. This article investigates whether the use of multiple systems ergonomics methods to examine the same problem is useful, or whether using different approaches creates incompatible analyses. Five systems ergonomics analyses of road trauma are examined and their key insights extracted. The extent to which these insights are compatible with one another and can be integrated when attempting to reduce road trauma is assessed. The findings indicate that applying several systems ergonomics methods to the same problem is useful, as multiple insights are developed and deficiencies in one approach are countered by the others. Importantly, the case study demonstrates that the insights gained are compatible and support the development of holistic systems thinking-based interventions. In conclusion it is recommended that a many systems ergonomics model thinking approach be adopted by ergonomists working in complex problem spaces.

Practitioner Summary: Many model thinking uses multiple methods to understand complex problems. We explore whether this is beneficial in systems ergonomics. Five models of road trauma, developed using five systems ergonomics methods, are examined. The findings demonstrate that a many model systems ergonomics approach produces a diverse but complimentary set of insights.     

Ergonomics risk assessment with digital human models in car assembly: Simulation versus real life

This study investigated how well ergonomics risk assessments on simulations with digital human models (DHM) match real‐life assessments obtained on a car assembly line. Two ergonomists evaluated 20 work tasks in real life and as a DHM simulation using a company‐specific version of the Automotive Assembly Worksheet (AAWS) for assessing static postures, action forces, manual material handling, and extra strains. Results demonstrate that DHM simulations provide good estimations of the workload in real‐life tasks. Additionally, significant correlations were found between AAWS risk assessments and subjectively perceived exertion measured on the Borg scale. Yet, there were also some significant differences in AAWS risk classification and AAWS total scores. DHM simulations appear helpful for reliably detecting static postures and extra strains, whereas action forces are harder to estimate than in real life. It is suggested that comprehensive methods such as AAWS should be incorporated in DHM software for enhancing efficiency and validity of digital ergonomics risk assessment. © 2010 Wiley Periodicals, Inc.     

Impact of multimodal feedback on simulated ergonomic measurements in a virtual environment: A case study with manufacturing workers

The purpose of this study was to evaluate the impact of multimodal feedback on ergonomic measurements in a virtual environment (VE) for a typical simulated drilling task. In total, sixty male manufacturing industry workers were divided into five groups. One group performed the working task in a real environment (RE), and ergonomic measurements for this group were used as the baseline for evaluation. The other four groups performed the same task in a virtual environment with different feedback treatments (visual with or without auditory and/or tactile feedback). Five indices – task completion time, maximum force capacity reduction, body part discomfort, rated perceived exertion, and rated task difficulty – were used to evaluate the measurements of each of the four treatments in VE in comparison to the baseline group in RE. The results indicate that the five indices for each of the four treatment groups were significantly higher than those of the RE group. Moreover, the indices of the visual‐only group were significantly higher than those of the other three groups with auditory and/or tactile feedback treatments. The findings of this study can provide a guideline for ergonomic evaluations of work designs in VE and for establishing a virtual reality simulation system. © 2011 Wiley Periodicals, Inc.     

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.     

Core task modelling in cultural assessment: a case study in nuclear power plant maintenance

This article aims at illustrating the use of core task modelling on a system level and attempts to show its relevance to cultural assessment. The methodology that was used in a case study consists of an iterative process of core task modelling, organisational culture research and organisational assessment. The case study was conducted in a nuclear power plant's (NPP's) maintenance department. The maintenance task, its goals, critical demands and the demands for the working practices were conceptualised by core task analysis. The organisational culture of the maintenance department was explored with interviews, a survey and workgroups. The results show three critical demands and three instrumental demands to be controlled on all levels in the organisation. The maintenance culture must support the activity of balancing between these distinct requirements. The core task model was used in assessing the characteristics of the maintenance culture. This was done through analysing the unity of the personnel's conceptions concerning the organisation, its tasks, goals and values. The relevance of this approach to organisational development is discussed.     

Shortcomings and user requirements associated with cricket helmets currently in use: A study on features for safety and usability

Wearing helmets has reduced the risk of head and facial injury among cricketers. Yet, design gaps are present in the cricket helmets currently being used. The aim of this research was to identify the shortcomings and user requirements pertinent to safety and usability of cricket helmets. The objectives were to explore the design criteria and the drawbacks of state-of-the-art cricket helmets, to identify user requirements for design and to analyse them. To collect data, a three-faceted approach, i.e. a literature review (n = 58), a video-based accident analysis (n = 24) and a user study (n = 42), was used. A frequency analysis technique based on the constant comparative method was used to identify and prioritize the shortcomings and user requirements. Findings from the three approaches were then triangulated to confirm the shortcomings and user requirements. Results revealed that poor fit, inadequate impact attenuation capacity and thermal discomfort are the main categories of shortcomings in the cricket helmets. Research on multi-objective optimisation of features for better fit, impact attenuation and thermal comfort (FIT) is suggested as future work.     

A socio-technical analysis of functional properties in a joint cognitive system: a case study in an aircraft cockpit

Abstract

In a socio-technical work domain, humans, device interfaces and artefacts all affect transformations of information flow. Such transformations, which may involve a change of auditory to visual information & vice versa or alter semantic approximations into spatial proximities from instruments readings, are generally not restricted to solely human cognition. This paper applies a joint cognitive system approach to explore a socio-technical system. A systems ergonomics perspective is achieved by applying a multi-layered division to transformations of information between, and within, human and technical agents. The approach uses the Functional Resonance Analysis Method (FRAM), but abandons the traditional boundary between medium and agent in favour of accepting aircraft systems and artefacts as agents, with their own functional properties and relationships. The joint cognitive system perspective in developing the FRAM model allows an understanding of the effects of task and information propagation, and eventual distributed criticalities, taking advantage of the functional properties of the system, as described in a case study related to the cockpit environment of a DC-9 aircraft.

Practitioner Summary: This research presents the application of one systemic method to understand work systems and performance variability in relation to the transformation of information within a flight deck for a specific phase of flight. By using a joint cognitive systems approach both retrospective and prospective investigation of cockpit challenges will be better understood.

Abbreviations: ATC: air traffic control; ATCO: air traffic controller; ATM: air traffic management; CSE: cognitive systems engineering; DSA: distributed situation awareness; FMS: flight management system; FMV: FRAM model visualize; FRAM: functional resonance analysis method; GF: generalised function; GW: gross weight; HFACS: human factors analysis and classification system; JCS: joint cognitive systems; PF: pilot flying; PNF: pilot not flying; SA: situation awareness; SME: subject matter expert; STAMP: systems theoretic accident model and processes; VBA: visual basic for applications; WAD: work-as-done; WAI: work-as-imagined; ZFW: zero fuel weight     

Ergonomic development work: co-education as a support for user participation at a car assembly plant. A case study

This study deals with the design, trials and evaluation of a co-education programme at the Volvo Uddevalla plant in Sweden. Involving operators, manufacturing engineers and managers, the programme served as a support for the creation of a participatory ergonomics process, intended for continuous use at the plant. It consisted of a basic ergonomics knowledge package, and a dialogue model defining the roles and relations of actors involved. As a practical part of the programme, trial development projects were also carried out by the participants. The main and long term objective of the project was to start the participants cooperating in a continuous change and development process on the shop-floor.

The outcome of the co-education programme was evaluated immediately after the first two regular courses, and, as a longterm follow-up, after seven subsequent courses shortly after the closing of the Uddevalla plant. The co-education programme was shown to be successful. Later on, the expertize of both operators and manufacturing engineers became obvious to everyone at the plant, and the cooperation between operators and manufacturing engineers increased steadily. The main conclusion drawn was that the co-education programme is a good starting point for a process of participation and industrial change work. However, in order to get a permanent impact, the whole organization must nurse and nourish the further development, and implementation of the process.     

Evaluation of procedural learning transfer from a virtual environment to a real situation: a case study on tank maintenance training

Virtual reality opens new opportunities for operator training in complex tasks. It lowers costs and has fewer constraints than traditional training. The ultimate goal of virtual training is to transfer knowledge gained in a virtual environment to an actual real-world setting. This study tested whether a maintenance procedure could be learnt equally well by virtual-environment and conventional training. Forty-two adults were divided into three equally sized groups: virtual training (GVT® [generic virtual training]), conventional training (using a real tank suspension and preparation station) and control (no training). Participants then performed the procedure individually in the real environment. Both training types (conventional and virtual) produced similar levels of performance when the procedure was carried out in real conditions. Performance level for the two trained groups was better in terms of success and time taken to complete the task, time spent consulting job instructions and number of times the instructor provided guidance.     

Simulation-supported change process for product customization - A case study in a garment company

Due to the increasing competition in global markets, many European garment manufacturers have had to undergo significant restructuring and were forced to create leaner value-adding processes. As a result, the majority of the manufacturing operations have been outsourced to low labor cost countries. At the same time, production logistics as well as information and communication technologies have gained importance, in order to keep job functions requiring higher qualifications within Europe. Another challenge concerns the introduction of customized products into the production processes which previously had been designed for manufacturing of large volumes. Prior to implementing such changes, the consequences with respect to production logistics as well as the financial impacts should be examined. The case study presented in this paper uses a simulation tool for these purposes. Different scenarios developed for a garment company were analyzed. Based on the results, recommendations for the further development of the regarded company were deduced.     

Inventory replenishment model using fuzzy multiple objective programming: A case study of a high-tech company in Taiwan

The progress in high technology has led to the wide use of thin film transistor-liquid crystal display (TFT-LCD). The evolution of the manufacturing technology of TFT-LCD keeps increasing the size of TFT-LCD since a larger TFT-LCD allows a larger display application and an improved productivity. However, as the size of TFT-LCD increases, the size of TFT-array substrates and color filter substrates has to increase simultaneously. This leads to a more complicated inventory problem of large-sized substrates. Therefore, this paper considers a color filter replenishment problem in TFT-LCD manufacturing with the consideration of storage space, yield rate, quantity discounts and multiple suppliers. We first formulate the color filter replenishment problem as a fuzzy multiple objective programming, and then a fuzzy multiple objective programming with assigned weights for objectives based on experts’ opinions is proposed. An example with four cases is given to illustrate the practicality for empirical investigation. The results demonstrate that both methods are effective tools for inventory management of color filters for multi-periods. In addition, the methods can be applied or modified for managing inventory in general.     

A fuzzy reasoning and fuzzy-analytical hierarchy process based approach to the process of railway risk information: A railway risk management system

Risk management is becoming increasingly important for railway companies in order to safeguard their passengers and employees while improving safety and reducing maintenance costs. However, in many circumstances, the application of probabilistic risk analysis tools may not give satisfactory results because the risk data are incomplete or there is a high level of uncertainty involved in the risk data. This article presents the development of a risk management system for railway risk analysis using fuzzy reasoning approach and fuzzy analytical hierarchy decision making process. In the system, fuzzy reasoning approach (FRA) is employed to estimate the risk level of each hazardous event in terms of failure frequency, consequence severity and consequence probability. This allows imprecision or approximate information in the risk analysis process. Fuzzy analytical hierarchy process (fuzzy-AHP) technique is then incorporated into the risk model to use its advantage in determining the relative importance of the risk contributions so that the risk assessment can be progressed from hazardous event level to hazard group level and finally to railway system level. This risk assessment system can evaluate both qualitative and quantitative risk data and information associated with a railway system effectively and efficiently, which will provide railway risk analysts, managers and engineers with a method and tool to improve their safety management of railway systems and set safety standards. A case study on risk assessment of shunting at Hammersmith depot is used to illustrate the application of the proposed risk assessment system.     

Multi-agent system for tunnel-settlement monitoring: A case study in Shanghai

Special soil environment and geographic location expose tunnels in Shanghai to a higher risk of asymmetry change and non-homogeneous settlement that could make a threat to passenger safety and tunnel structure stability. Considering work efficiency and costs, current monitoring methods and frequency are not suitable for tunnel monitoring present stage requirements. To make sure tunnel under condition of economic sustainability, environmental sustainability and engineering safety, new technology and instrument for monitoring should be designed to break through. Besides, asynchrony and retardation existing in data acquisition and analysis makes monitoring task cannot reflect tunnel real-time status. This can make people unable to timely detect the occurrence and risk of tunnel disaster. The purpose of this article is to develop a tunnel settlement monitoring system with several intelligent functions for comprehensive evaluating tunnel healthy, generating seasonable warnings and guaranteeing construction sustainability. To facilitate the expansion of the system and data structure, agent techniques and condition based monitoring standard have been applied to establish the system with 9 action parts according to 3 different geospatial. Moreover, web service has also been used to provide human–computer interface and realize visual function, and meanwhile, all the procedure of the system was completed automatically. Additionally, the system was tested with a task in Shanghai tunnel, and the result shows the monitoring system can describe tunnel conditions, prevent tunnel hazards and assist managers to make appropriate decisions with less people and reduced costs.     

Outlier detection in relational data: A case study in geographical information systems

Geographical information systems are commonly used for a variety of purposes. Many of them make use of a large database of geographical data, the correctness of which strongly influences the reliability of the system. In this paper, we present an approach to quality maintenance that is based on automatic discovery of non-perfect regularities in the data. The underlying idea is that exceptions to these regularities (‘outliers’) are considered probable errors in the data, to be investigated by a human expert. A case study shows how the tool can be used for extracting valuable knowledge about outliers in real-world geographical data, in an adaptive manner to the evolving data model supporting it. While the tool aims specifically at geographical information systems, the underlying approach is more broadly applicable for quality maintenance in data-rich intelligent systems.     

Application of implication operators versus regression analysis: A case study of factors influencing differentials in price levels among counties in Florida

The article constitutes an additional case study of the application of implication operators and this time their performance is evaluated in comparison to the performance of linear regression techniques. Both methodologies are applied for the purpose of determining what factors are influencing price level differentials among counties of Florida. Eleven variables were selected as explanatory variables. In the process of applying both methodologies, the advantages as well as disadvantages of each are examined. Utilizing both methodologies, the analysis involved 12 annual cross section runs, as well as one pooled cross section-time series run. the analysis consisted of using traditional linear regression methodologies on the one hand, and four different implication operators, on the other hand. Tables I through XXXV display the results of this empirical case study. the major conclusions could be briefly summarized as follows: Both methodologies show some consistency of results from year to year, but that consistency is limited-as could be expected.

1 The variables utilized in this study are not expected to explain 100% of the variations in price levels. In other words, it could be expected that other factors in addition to the eleven explanatory variables could have impact on the price levels of various counties.

The results of pooled regression analysis display a substantial difference in comparison to annual cross section results. In contrast, the results of year-to-year application of implication operators are fairly consistent with the corresponding pooled results. As the research progressed, it became apparent that conceptual advantages of implication operator methodologies over the regression methods

2 Some very restrictive conditions are required for an appropriate application of regression methods^1-3 but not for the use of implication operators.^4-7

are countered by the incompleteness of research in that area (of implication operators) as reflected by the unavailability of significance indicators. Thus, both methods have some advantages and some disadvantages. The methodology of implication operators has a potential to become the superior method of the two,

3 Because it does not require restrictions on the applications of the implication operators methods in contrast to the regression methods.

once the research and development of these techniques is complete, and the problem of significance tests is solved. But until then, the preferred approach is to utilize both methods to extract maximum information about phenomena under investigation, and then to apply common sense to sort out and interpret the results. As a greater number of relevant but independent methods of analysis are applied to the investigation process, the results could either reinforce one another-if they at least approximately point in the same direction, or call for some caution in the case of contradictory outcome.     

Real-time smart video surveillance to manage safety: A case study of a transport mega-project

There is a tendency for accidents and even fatalities to arise when people enter hazardous work areas during the construction of projects in urban areas. A limited amount of research has been devoted to developing vision-based proximity warning systems that can determine when people enter a hazardous area automatically. Such systems, however, are unable to identify specific hazards and the status of a piece of plant (e.g., excavator) in real-time. In this paper, we address this limitation and develop a real-time smart video surveillance system that can detect people and the status of plant (i.e. moving or stationary) in a hazardous area. The application of this approach is demonstrated during the construction of a mega-project, the Wuhan Rail Transit System in China. We reveal that our combination of computer vision and deep learning can accurately recognize people in a hazardous work area in real-time during the construction of transport projects. Our developed systems can provide instant feedback concerning unsafe behavior and thus enable appropriate actions to be put in place to prevent their re-occurrence.     

Leaf area index measurements in a tropical moist forest: A case study from Costa Rica

The role of tropical forests in sustainable development mechanisms and payments for environmental services is becoming increasingly important. Therefore, there is a greater need for accurate and detailed information about their biophysical characteristics (e.g., Leaf area index-LAI) along different stages of ecological succession. Remote sensing offers the possibility of providing relatively accurate estimations of such biophysical characteristics at a reasonable cost for most regional projects. The objectives of this study are to (1) document the variability of LAI in different stages of secondary growth in a tropical moist forest, (2) estimate LAI from spectral vegetation indices (SVIs), and (3) link LAI to the estimation of other canopy physiognomic characteristics. We found that segregation of LAI measurements by successional stage (early, intermediate, late) contributed to a better definition of the relationship between LAI and the SVIs. In addition, we conclude that the propagation of errors of precision through the SVI formulas must be taken into consideration along with intra-site and radiometric variability when uncertainty terms are calculated. From a linear regression analysis, we found that there is only a minimal difference between the nonparametric Theil-Sen and classical least-squares regressions. We also found that not only does the Lorentzian cumulative transition function describe the relationship between LAI and the SVIs, it also provides an estimate of the range of LAI values to which each index is sensitive.