Data dependent systems technique: a methodology with an application to human systems

The objective of this paper is to introduce the application of Data Dependent Systems (DDS) methodology to the field of ergonomics. Many current techniques in ergonomics utilize static models, which can have significant limitations. DDS is a stochastic modelling and analysis technique that can be used to capture the dynamics of a system through quantitative analysis of the available data. DDS has been successfully applied to the analysis of manufacturing processes and the surfaces generated by those processes. In this research, DDS was used to analyse time-based hand-skin temperature data for the evaluation of two types of glove liners to be used underneath latex gloves. DDS was able to capture the differences between the two glove liners and the two subjects. The implications of the results and the potential of the DDS methodology are discussed.     

Performing ergonomics analyses through virtual interactive design: Validity and reliability assessment

Virtual interactive design methodology was initially proposed as an integrated environment for digital human model–based ergonomics analysis of human–machine interactions, which uses a motion capture system and virtual environment to realize task simulation. The validity and reliability of this analysis methodology has not been systematically studied. In this article, potential errors are first investigated based on the technology used in the system structure and work process; then, three experimental integration levels are proposed to use different resources for creating manikin postures. Validity and reliability to use this integrated environment for static ergonomics analysis are then assessed by comparing the ergonomics analysis outputs achieved based on the three integration levels. The results indicate that the reliability of this methodology is good; however, the validity of the integrated system is affected by the limitation of the virtual environment used in the testing. © 2011 Wiley Periodicals, Inc.     

Analysis of interaction quality in human-machine systems: applications for forklifts

The aim of the work presented here was to propose a methodology for analysis of interactions between humans and machines. The driver-truck system in a warehouse context was used as a case for empirical evaluation. The work consists of three empirical studies and one analysis of statistical data. In total 29 pallet truck drivers have been involved in the studies which were performed at two Swedish distribution companies. A framework is proposed, where effects on performance, safety, subjective experiences and physical and mental impact on the humans are used as indicators of the quality of interactions. The results show that the methodology proposed supports appropriate input for the evaluation of the interaction quality between humans and technology. One example of this is musculoskeletal loads and discomfort, which could be related to the task and the design of the steering arm. Another conclusion from this work is that many factors outside the warehouse truck affect the interaction in the human-truck system, for example the design of loading ramps. This supports the importance of having a holistic ergonomics view when studying a human-machine system.     

New methodological framework to improve productivity and ergonomics in assembly system design

This work analyses how ergonomics and assembly system design techniques are intimately related. It also develops a new theoretical framework to assess a concurrent engineering approach to assembly systems design problems, in conjunction with an ergonomics optimization of the workplace. Its purpose is to provide professionals with a new and detailed approach to assembly system design procedures that includes ergonomics issues.The methodological framework offered takes into account technological variables (related to work times and methods), environmental variables (i.e. absenteeism, staff turnover, work force motivation) and ergonomics evaluations (i.e. human diversity) to create a comprehensive analysis.At conclusion of the study, the work reports data and insights from two real industrial cases, where an advanced simulation software is used, to validate the procedure and support methodology applicability.

Relevance to industries

This work provides an extremely valuable methodological framework to companies who recognize the link between assembly and ergonomics. The methodology underlines the necessity to analyze and classify the assembly system layout configuration in relation to both technological and environmental parameters- as reported in the framework.     

Computerized task risk assessment using digital human modeling based Job Risk Classification Model

Different from the classical ergonomics analysis, Virtual Interactive Design methodology relies on manikin movements in virtual environment. This platform has been implemented by researchers to accomplish static ergonomic analyses including Rapid Upper Limb Assessment, NIOSH lifting equation and Static Strength Prediction. However, considering only static posture information limits the capacity of ergonomics analysis. In this study, the methodology of performing dynamic ergonomics analysis based on this Virtual Interactive Design platform is proposed. This environment allows velocity and angular velocity of specified body segments/joints calculated for designed tasks to be used to assess the corresponding risk levels based on Job Risk Classification Model. The motion calculation is completed based on the captured interaction between human participants and virtual workplace/mockup. To evaluate the validity and reliability of this upgraded platform, potential errors are analyzed by comparing outputs from several designed experimental conditions.     

Development of ergonomics audits for bagging,haul truck and maintenance and repair operations in mining

Abstract

The development and testing of ergonomics and safety audits for small and bulk bag filling, haul truck and maintenance and repair operations in coal preparation and mineral processing plants found at surface mine sites is described. The content for the audits was derived from diverse sources of information on ergonomics and safety deficiencies including: analysis of injury, illness and fatality data and reports; task analysis; empirical laboratory studies of particular tasks; field studies and observations at mine sites; and maintenance records. These diverse sources of information were utilised to establish construct validity of the modular audits that were developed for use by mine safety personnel. User and interrater reliability testing was carried out prior to finalising the audits. The audits can be implemented using downloadable paper versions or with a free mobile NIOSH-developed Android application called ErgoMine.

Practitioner Summary: The methodology used to develop ergonomics audits for three types of mining operations is described. Various sources of audit content are compared and contrasted to serve as a guide for developing ergonomics audits for other occupational contexts.     

An integrated methodology for manufacturing systems design using manual and computer simulation

Traditional approaches to manufacturing systems design utilize a sequential procedure that focuses on production capacity requirements, with human operator task design developed late in the systems design phase. Implementing manufacturing systems in this way is difficult when operations management must design flexible and efficient processes, with an often incomplete understanding of how people can best perform within the system. This study developed an integrated methodology that uses both manual and computer simulations to evaluate system performance and ergonomic issues early in the system design process. Information about operator performance and ergonomics is obtained in the manual simulations, while estimates of operator utilization and system throughput is obtained through computer simulations. An iterative design process is used, with the results of manual and computer simulations informing each other during subsequent simulations. An industrial case study is presented here to demonstrate the effectiveness of this methodology. The results show that the methodology can be used to design manufacturing systems with significant savings in labor cost and improved manufacturing system flexibility. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 19–40, 2003.     

Input-to-state stability and interconnections of discontinuous dynamical systems

In this paper we will extend the input-to-state stability (ISS) framework to continuous-time discontinuous dynamical systems (DDS) adopting piecewise smooth ISS Lyapunov functions. The main motivation for investigating piecewise smooth ISS Lyapunov functions is the success of piecewise smooth Lyapunov functions in the stability analysis of hybrid systems. This paper proposes an extension of the well-known Filippov’s solution concept, that is appropriate for ‘open’ systems so as to allow interconnections of DDS. It is proven that the existence of a piecewise smooth ISS Lyapunov function for a DDS implies ISS. In addition, a (small gain) ISS interconnection theorem is derived for two DDS that both admit a piecewise smooth ISS Lyapunov function. This result is constructive in the sense that an explicit ISS Lyapunov function for the interconnected system is given. It is shown how these results can be applied to construct piecewise quadratic ISS Lyapunov functions for piecewise linear systems (including sliding motions) via linear matrix inequalities.     

Expert systems in ergonomics: requirements and an approach

Abstract

Industry currently fails to derive maximum benefit from ergonomics. This is mainly due to an imbalance between the large amount of ergonomie knowledge available and the limited amount actually applied. The use of the methodology of expert systems in ergonomics is one possibility for reducing this imbalance. This paper presents basic requirements for the development of expert systems. The particular requirements for the application of expert systems in ergonomics are also derived. Finally, the stage of development of an expert system for assessing lifting and carrying tasks is presented, and practical examples for the application of the system are discussed.     

Evaluating models in systems ergonomics with a taxonomy of model attributes

A model, as the term is used here, is a way of representing knowledge for the purpose of thinking, communicating to others, or implementing decisions as in system analysis, design or operations. It can be said that to the extent that we can model some aspect of nature we understand it. Models can range from fleeting mental images to highly refined mathematical equations of computer algorithms that precisely predict physical events. In constructing and evaluating models of ergonomic systems it is important that we consider the attributes of our models in relation to our objectives and what we can reasonably aspire to. To that end this paper proposes a taxonomy of models in terms of six independent attributes: applicability to observables, dimensionality, metricity, robustness, social penetration and conciseness. Each of these attributes is defined along with the meaning of different levels of each. The attribute taxonomy may be used to evaluate the quality of a model. Examples of system ergonomics models having different combinations of attributes at different levels are provided. Philosophical caveats regarding models in system ergonomics are discussed, as well as the relation to scientific method.     

Comparison between low-cost marker-less and high-end marker-based motion capture systems for the computer-aided assessment of working ergonomics

The paper deals with the comparison between a high-end marker-based acquisition system and a low-cost marker-less methodology for the assessment of the human posture during working tasks. The low-cost methodology is based on the use of a single Microsoft Kinect V1 device. The high-end acquisition system is the BTS SMART that requires the use of reflective markers to be placed on the subject's body. Three practical working activities involving object lifting and displacement have been investigated. The operational risk has been evaluated according to the lifting equation proposed by the American National Institute for Occupational Safety and Health. The results of the study show that the risk multipliers computed from the two acquisition methodologies are very close for all the analysed activities. In agreement to this outcome, the marker-less methodology based on the Microsoft Kinect V1 device seems very promising to promote the dissemination of computer-aided assessment of ergonomics while maintaining good accuracy and affordable costs.     

网络化手势运动跟踪系统设计

设计了一种基于微机电惯性传感器的数据手套.根据惯性导航和刚体动力学原理,构建了基于微型传感器的体感网络,并通过多传感器数据的融合解算以获取运动姿态信息,实现对手指各关节运动数据的捕获.结合计算机图形技术构建三维虚拟手捕获系统进行性能对比评估,实验结果表明:所设计的系统具有良好的稳定性和适应性,能够对手运动信息进行实时有效地捕获.     

Simulation of industrial man-machine systems

In the design of large industrial processes, ergonomics designers can benefit from the use of computer simulation of man/machine systems when on-site studies are too risky or costly and laboratory studies alone have questionable generalization. This paper provides an illustration of this methodology for a hot strip mill in the steel industry and a demonstration of ergonomic design applications. A special simulation package which was developed for small military systems was adapted to this large industrial case and applied to an older manually-controlled mill of the 1930s. The simulation model was then modified to reflect automation and manning changes found in the mills built in the 1950s and the simulation results verified the actual performance differences between these mills. Experiments in further design and manning changes were made in order to demonstrate the usefulness of simulation as a design-aiding technique.     

Safety performance of gloves using the pressure tolerance of the hand

Two prototype gloves have been designed and developed at the University of Nebraska-Lincoln. The aim of this study was to evaluate the safety performance of the developed gloves. An experiment was conducted to assess the discomfort threshold level at 12 zones on the palmar surface of the hand for five hand conditions--bare hand, single glove, double glove and two prototype gloves. Prototype I consisted of a glove with an extra layer of glove material applied selectively to critical areas of the hand; while prototype II had up to four layers applied to critical areas. This design increases protection in critical areas without increasing bulk, provides performances comparable with single glove, and improves grip strength. The study was conducted using an algometer device to apply pressure to each of the 12 zones, for all hand conditions. The results indicated that for pressure tolerance, prototype II had the highest pressure-discomfort threshold, while prototype I had a threshold similar to the double layer glove. Pressure discomfort tolerance threshold is greatly increased by the use of gloves, and pressure-discomfort thresholds are raised by 25-65%. The two prototype gloves, although much less bulkier than the double glove, have pressure thresholds that are equal to or superior to that of a double glove. The algometer can be used to assess the safety of glove from mechanical trauma. Hence, the generalizability of the results is somewhat restricted. However, the method of selective protection, without compromising performance appears to be promising and is worth pursuing by glove designers.     

Applying incremental Deep Neural Networks-based posture recognition model for ergonomics risk assessment in construction

Monitoring and assessing awkward postures is a proactive approach for Musculoskeletal Disorders (MSDs) prevention in construction. Machine Learning models have shown promising results when used in recognition of workers’ posture from Wearable Sensors. However, there is a need to further investigate: i) how to enable Incremental Learning, where trained recognition models continuously learn new postures from incoming subjects while controlling the forgetting of learned postures; ii) the validity of ergonomics risk assessment with recognized postures. The research discussed in this paper seeks to address this need through an adaptive posture recognition model– the incremental Convolutional Long Short-Term Memory (CLN) model. The paper discusses the methodology used to develop and validate this model’s use as an effective Incremental Learning strategy. The evaluation was based on real construction workers’ natural postures during their daily tasks. The CLN model with “shallow” (up to two) convolutional layers achieved high recognition performance (Macro F1 Score) under personalized (0.87) and generalized (0.84) modeling. Generalized CLN model, with one convolutional layer, using the “Many-to-One” Incremental Learning scheme can potentially balance the performance of adaptation and controlling forgetting. Applying the ergonomics rules on recognized and ground truth postures yielded comparable risk assessment results. These findings support that the proposed incremental Deep Neural Networks model has a high potential for adaptive posture recognition. They can be deployed alongside ergonomics rules for effective MSDs risk assessment.     

Crossing levels in systems ergonomics: A framework to support ‘mesoergonomic’ inquiry

In this paper we elaborate and articulate the need for what has been termed ‘mesoergonomics’. In particular, we argue that the concept has the potential to bridge the gap between, and integrate, established work within the domains of micro- and macroergonomics. Mesoergonomics is defined as an open systems approach to human factors and ergonomics (HFE) theory and research whereby the relationship between variables in at least two different system levels or echelons is studied, and where the dependent variables are human factors and ergonomic constructs. We present a framework which can be used to structure a set of questions for future work and prompt further empirical and conceptual inquiry. The framework consists of four steps: (1) establishing the purpose of the mesoergonomic investigation; (2) selecting human factors and ergonomics variables; (3) selecting a specific type of mesoergonomic investigation; and (4) establishing relationships between system levels. In addition, we describe two case studies which illustrate the workings of the framework and the value of adopting a mesoergonomic perspective within HFE. The paper concludes with a set of issues which could form part of a future agenda for research within systems ergonomics.     

Stimulated recall methodology for assessing work system barriers and facilitators in family-centered rounds in a pediatric hospital

Human factors and ergonomics methods are needed to redesign healthcare processes and support patient-centered care, in particular for vulnerable patients such as hospitalized children. We implemented and evaluated a stimulated recall methodology for collective confrontation in the context of family-centered rounds. Five parents and five healthcare team members reviewed video records of their bedside rounds, and were then interviewed using the stimulated recall methodology to identify work system barriers and facilitators in family-centered rounds. The evaluation of the methodology was based on a survey of the participants, and a qualitative analysis of interview data in light of the work system model of 30 and 35. Positive survey feedback from the participants was received. The stimulated recall methodology identified barriers and facilitators in all work system elements. Participatory ergonomics methods such as the stimulated recall methodology allow a range of participants, including parents and children, to participate in healthcare process improvement.     

Safety performance of gloves using the pressure tolerance of the hand

Two prototype gloves have been designed and developed at the University of Nebraska-Lincoln. The aim of this study was to evaluate the safety performance of the developed gloves. An experiment was conducted to assess the discomfort threshold level at 12 zones on the palmar surface of the hand for five hand conditions — bare hand, single glove, double glove and two prototype gloves. Prototype I consisted of a glove with an extra layer of glove material applied selectively to critical areas of the hand; while prototype II had up to four layers applied to critical areas. This design increases protection in critical areas without increasing bulk, provides performances comparable with single glove, and improves grip strength. The study was conducted using an algometer device to apply pressure to each of the 12 zones, for all hand conditions. The results indicated that for pressure tolerance, prototype II had the highest pressure-discomfort threshold, while prototype I had a threshold similar to the double layer glove. Pressure discomfort tolerance threshold is greatly increased by the use of gloves, and pressure— discomfort thresholds are raised by 25–65%. The two prototype gloves, although much less bulkier than the double glove, have pressure thresholds that are equal to or superior to that of a double glove. The algometer can be used to assess the safety of glove from mechanical trauma. Hence, the generalizability of the results is somewhat restricted. However, the method of selective protection, without compromising performance appears to be promising and is worth pursuing by glove designers.