| 1. |
- Bertilsson, Erik, et al.
(author)
-
Creation of the IMMA manikin with consideration of anthropometric diversity
- 2011
-
In: 21st International Conference on Production Research: Innovation in Product and Production, ICPR 2011; Stuttgart; Germany; 31 July 2011 through 4 August 2011. - : Fraunhofer Verlag. - 9783839602935 - 3839602939
-
Conference paper (peer-reviewed)abstract
- Digital human modelling (DHM) systems are used to simulate production processes and analyse the human-machine interaction, particularly at early development stages. Consideration of anthropometric variation is central in DHM simulations due to the necessity of ensuring intended accommodation levels. This paper describes the process of how digital human models are created and defined within the IMMA software. The process begins with the definition of a number of key measurements, which acts as the basis for the definition of several boundary manikins using a confidence ellipsoid methodology. These manikins represents the appropriate confidence region and hence the anthropometric diversity. Key measurements are then entered into regression equations to define the complete set of measurements for each manikin. These measurements are based on the appropriate ISO-standard. Finally, measurements are used to define the size and alignment of each segment in the biomechanical model of the manikin. The manikins are then used to automatically simulate and analyse human-machine interaction.
|
|
| 2. |
- Fan, Xuelong, et al.
(author)
-
Effects of sensor types and angular velocity computational methods in field measurements of occupational upper arm and trunk postures and movements
- 2021
-
In: Sensors. - : MDPI AG. - 1424-8220. ; 21:16
-
Journal article (peer-reviewed)abstract
- Accelerometer-based inclinometers have dominated kinematic measurements in previous field studies, while the use of inertial measurement units that additionally include gyroscopes is rapidly increasing. Recent laboratory studies suggest that these two sensor types and the two commonly used angular velocity computational methods may produce substantially different results. The aim of this study was, therefore, to evaluate the effects of sensor types and angular velocity computational methods on the measures of work postures and movements in a real occupational setting. Half-workday recordings of arm and trunk postures, and movements from 38 warehouse workers were compared using two sensor types: accelerometers versus accelerometers with gyroscopes—and using two angular velocity computational methods, i.e., inclination velocity versus generalized velocity. The results showed an overall small difference (<2° and value independent) for posture percentiles between the two sensor types, but substantial differences in movement percentiles both between the sensor types and between the angular computational methods. For example, the group mean of the 50th percentiles were for accelerometers: 71°/s (generalized velocity) and 33°/s (inclination velocity)—and for accelerometers with gyroscopes: 31°/s (generalized velocity) and 16°/s (inclination velocity). The significant effects of sensor types and angular computational methods on angular velocity measures in field work are important in inter-study comparisons and in comparisons to recommended threshold limit values.
|
|
| 3. |
|
|
| 4. |
- Fan, Xuelong, et al.
(author)
-
Ergonomic Evaluation of a Prototype Console for Robotic Surgeries via Simulations with Digital Human Manikins
- 2019
-
In: Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018) Volume V: Human Simulation and Virtual Environments, Work With Computing Systems (WWCS), Process Control. - Cham : Springer International Publishing. - 2194-5365 .- 2194-5357. - 9783319960760 ; 822, s. 351-363
-
Conference paper (peer-reviewed)abstract
- Work-related musculoskeletal disorders impact surgical performance, which increase risks for patient safety. A new console has been designed to reduce workload for robotic surgery surgeons. Due to high costs and long waiting time of the production process, a pre-production ergonomic evaluation of the new design is preferable. In this paper, we evaluate if the new console at the pre-production stage by using an US checklist, and the Swedish standard for visual display unit work. A 3D model of the new designed console was introduced to the virtual environment of a digital manikin (Intelligently Moving Manikin, IMMA). The work-ranges of the console were calculated. Various individual work distances of 12 manikins (3 men and 3 women per each of the US and the Swedish population) were “measured”. The data were integrated and used as an objective reference to compare with the Swedish standard, and the US checklist. The result shows that the criteria in the Swedish standard and the US checklist are fulfilled, except for those are related to the adjustable range of the screen view height, the height range of the armrest and the adjustable distance of the pedals. The new console fulfills most of the criteria in the checklist and the standard, but there is room for a few improvements. The DHM tool IMMA provides the possibility for a pre-production assessment. However, the limited virtual measurement tools of IMMA restrained the time efficiency of the ergonomic assessment.
|
|
| 5. |
- Forsman, Mikael, et al.
(author)
-
Inter-ergonomist Reliability in Rating Risk Level - without any Specific Method - in Ten Video Recorded Work Tasks
- 2014
-
Conference paper (other academic/artistic)abstract
- 1. IntroductionRecently, 30 observational methods for assessment of biomechanical exposures at work were evaluated through a literature review (Takala et al., 2010). It was found that several methods are insufficiently tested in terms of validity and reliability. In only in a few cases have estimates of the components of the methods been validated against technical measurements. Also comparisons between methods' resulting risk levels are rare. Swedish Work Environment Authority has recently increased the demands on ergonomic risk assessments. These assessments are usually made by ergonomists in occupational health services (OHS).This study is included in a larger on-going project, with the overall purpose to evaluate six observational methods for assessment of biomechanical exposures of repetitive work in respect of validity, reliability and usability, as well as provide information on which of the methods are best suited for practitioners in risk assessment of repetitive work. The methods' resulting risk levels are compared not only to each other, but also to ergonomists’ “own” risk estimates (i.e., done without any specific method). The specific aim of this sub-study was to investigate the inter-observer reliability of ergonomists’ own risk estimates.2. MethodsNine OHS-ergonomists, all with more than 5 years of experience of general ergonomic risk assessments, made risk assessments of 10 different video-recorded (2-6 minutes) work-tasks (supermarket work, meat cutting and packing, engine assembly, cleaning, post sorting and hairdressing). Video sequences of two or three camera angles were synchronized and showed together. For each work-task, the ergonomists were given data of the work task length (see Table 1), pause- and rests schedules, weights of handled goods, physical factors, and the employees own ratings of discomfort, work demands and own control.The ergonomist could pause the playback as needed, the maximum allocated time per work-task assessment was 20 minutes. The risk of musculoskeletal disorders and need for improvements was rated into green (no risk), yellow (investigate further), and red (immediate risk) categories. Ratings were done for 8 specific body regions: neck, lower back, right and left shoulders, -arms/elbows, and -wrists/hands), and for one over-all risk level.The agreement of the ratings (in percent), and Light’s multi-observer kappa (i.e. Cohen’s pairwise kappa averaged over all pairs; Light, 1971; Cohen, 1960) were calculated per body region and for the over-all risk assessment.3. ResultsFor the 720 (9 ergonomists, 8 body regions, 10 work tasks) risk assessments of the separate body regions, 37% were green, 44% yellow and 19% red. For over-all risk assessments (Table 1), 14% were green, 50% yellow and 36% red.Table 1. Work tasks, hours per work task per work day, and the ergonomists ratings of over risk As seen in Table 1, the consistency between the observers differed markedly. For three of the work tasks all three categories were represented, only in one task all ergonomists rated the over-all risk equally. The average agreement of the ratings were 48% regarding the body regions, and 57% regarding the over-all risk assessments, Light’s kappa was 0.18 and 0.30, respectively.4. DiscussionThe results showed fair inter-observer reliability according to Altman’s table for interpretation of kappa (kappa between 0.21 and 0.40; Altman, 1991). These kappa values will, in the major project, be compared to those of six systematic observation methods.5. ReferencesAltman DG (1991) Practical statistics for medical research. London: Chapman and Hall.Cohen J. A coefficient of agreement for nominal scales. Educational and Psychological Measurement. 1960;20(1):37–46.Light RJ. Measures of response agreement for qualitative data: Some generalizations and alternatives. Psychological Bulletin. 1971;76(5):365–377.Takala EP et al. 2010. Systematic evaluation of observational methods assessing biomechanical exposures at work. Scand J Work E
|
|
| 6. |
|
|
| 7. |
- Forsman, Mikael, Professor, et al.
(author)
-
Mind the gap – development of conversion models between accelerometer- and IMU-based measurements of arm and trunk postures and movements in warehouse work
- 2022
-
In: Applied Ergonomics. - : Elsevier BV. - 0003-6870 .- 1872-9126. ; 105
-
Journal article (peer-reviewed)abstract
- Sensor type (accelerometers only versus inertial measurement units, IMUs) and angular velocity computational method (inclination versus generalized velocity) have been shown to affect the measurements of arm and trunk movements. This study developed models for conversions between accelerometer and IMU measurements of arm and trunk inclination and between accelerometer and IMU measurements of inclination and generalized (arm) velocities. Full-workday recordings from accelerometers and IMUs of arm and trunk postures and movements from 38 warehouse workers were used to develop 4 angular (posture) and 24 angular velocity (movement) conversion models for the distributions of the data. A power function with one coefficient and one exponent was used, and it correlated well (r2 > 0.999) in all cases to the average curves comparing one measurement with another. These conversion models facilitate the comparison and merging of measurements of arm and trunk movements collected using the two sensor types and the two computational methods.
|
|
| 8. |
- Forsman, Mikael, et al.
(author)
-
Reliability in twelve ergonomists’ three-category risk ratings in ten video recorded work tasks.
- 2015
-
In: Proceedings 19<sup>th</sup> Triennial Congress of the IEA, Melbourne 9-14 August 2015.
-
Conference paper (peer-reviewed)abstract
- The Swedish Work Environment Authority has recently increased the demands on ergonomic risk assessments. These assessments are usually made by ergonomists in occupational health services (OHS). Although they are many observational methods that may be used (Takala, Pehkonen et al. 2010), the ergonomists often do risk assessment by sole observation, based on his/her own knowledge and experience, without the use of any specific method.This study is included in a larger on-going OBS project, with the overall purpose to evaluate six observational methods for assessment of biomechanical exposures of repetitive work in respect of validity, reliability and usability, as well as provide information on which of the methods are best suited for practitioners in risk assessment of repetitive work. The methods' resulting risk levels will be compared not only to each other, but also to the ergonomists’ “own” assessments (without any specific method) of the risk of developing musculoskeletal disorders.The specific aim of this sub-study was to investigate the inter-observer reliability of ergonomists’ own risk assessments without any specific method
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
- Keyvani, Ali, et al.
(author)
-
Ergonomic Risk Assessment of a Manikin’s Wrist Movements - a Test Study in Manual Assembly
- 2013
-
Conference paper (peer-reviewed)abstract
- Use of digital human modeling (DHM) tools enables early assessment of ergonomic risks in the production development process. This early risk assessment can indicate needs for preventive actions in order to decrease risks for work-related musculoskeletal disorders. A method for the assessment of physical workload has been developed, for the analysis of wrist joint data produced by a DHM tool. The method is tested in a simulation model of an actual manual assembly station in industry where it is assumed that physical workload problems exist. The results show that the method can be successfully applied on an industrial case. In addition, presumptive risks and possible diagnoses are predicted based on the similarity of the simulated task’s motions with motions from other known work class profiles stored in a database based on epidemiological research.
|
|
| 12. |
- Kjellberg, Katarina, et al.
(author)
-
Comparisons of six observational methods for risk assessment of repetitive work - results from a consensus assessment
- 2015
-
In: Proceedings 19<sup>th</sup> Triennial Congress of the IEA, Melbourne 9-14 August 2015.
-
Conference paper (peer-reviewed)abstract
- During last decades several risk assessment methods for physical ergonomics have been developed. In a literature review 30 observational methods for assessment of biomechanical exposures at work were evaluated (1). It was found that several methods are insufficiently tested in terms of validity and reliability. Comparisons between methods' resulting risk levels are rare. The Swedish Work Environment Authority has recently emphasized the demands on risk assessments of musculoskeletal disorders (2). Practitioners mostly use observational methods to assess biomechanical risks(1). Despite a recent study comparing eight methods evaluating risk factors associated with musculoskeletal disorders (3), there is a lack of knowledge and guidance on which methods are the most effective and valid.This study is part of a larger on-going project, the OBS-project, with the overall purpose to evaluate six observational methods for assessment of biomechanical exposures of repetitive work in respect of validity, reliability and usability. A further purpose is to provide information on which of the methods are best suited for practitioners in risk assessment of repetitive work. The specific aim of this sub-study was to investigate the agreement between six observational methods for risk assessment of repetitive work by comparing the risk levels as assessed by a group of experts.
|
|
| 13. |
|
|
| 14. |
- Nyman, Teresia, et al.
(author)
-
Reliability and Validity of Six Selected Observational Methods for Risk Assessment of Hand Intensive and Repetitive Work
- 2023
-
In: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 20:8, s. 5505-
-
Journal article (peer-reviewed)abstract
- Risk assessments of hand-intensive and repetitive work are commonly done using observational methods, and it is important that the methods are reliable and valid. However, comparisons of the reliability and validity of methods are hampered by differences in studies, e.g., regarding the background and competence of the observers, the complexity of the observed work tasks and the statistical methodology. The purpose of the present study was to evaluate six risk assessment methods, concerning inter- and intra-observer reliability and concurrent validity, using the same methodological design and statistical parameters in the analyses. Twelve experienced ergonomists were recruited to perform risk assessments of ten video-recorded work tasks twice, and consensus assessments for the concurrent validity were carried out by three experts. All methods’ total-risk linearly weighted kappa values for inter-observer reliability (when all tasks were set to the same duration) were lower than 0.5 (0.15–0.45). Moreover, the concurrent validity values were in the same range with regards to total-risk linearly weighted kappa (0.31–0.54). Although these levels are often considered as being fair to substantial, they denote agreements lower than 50% when the expected agreement by chance has been compensated for. Hence, the risk of misclassification is substantial. The intra-observer reliability was only somewhat higher (0.16–0.58). Regarding the methods ART (Assessment of repetitive tasks of the upper limbs) and HARM (Hand Arm Risk Assessment Method), it is worth noting that the work task duration has a high impact in the risk level calculation, which needs to be taken into account in studies of reliability. This study indicates that when experienced ergonomists use systematic methods, the reliability is low. As seen in other studies, especially assessments of hand/wrist postures were difficult to rate. In light of these results, complementing observational risk assessments with technical methods should be considered, especially when evaluating the effects of ergonomic interventions.
|
|
| 15. |
- Rhen, Ida-Märta, 1975, et al.
(author)
-
A possible revival of population-representing digital human manikins in static work situations - exemplified through an evaluation of a prototype console for robotic surgery
- 2021
-
In: Work. - : IOS Press. - 1051-9815 .- 1875-9270. ; 70:3, s. 833-851
-
Journal article (peer-reviewed)abstract
- BACKGROUND: In the 90s, digital human manikins (DHMs) were introduced in planning ofworkstations, by static or semi-static simulations. Modern DHMs can simulate dynamic work and offer a rapid way for a virtual pre-production ergonomic evaluation. Work-related musculoskeletal disorders may affect surgical performance and patient safety. A prototype of an open console, which is contrary to the conventional closed consoles and may be seen as a representative for a new generation, has been designed to reduce workload for robotic surgery surgeons. OBJECTIVE: The aim of this project was to test a new DHM tool with improved usability to evaluate the ergonomics of a console of a robotic surgical system in a pre-production stage. METHODS: The DHM tool IMMA was used together with a 3D model of the prototype console. Twelve manikins who represented females and males from two national populations were introduced. Manikin-console distances, after console adjustments per manikin, were compared with a US checklist and Swedish standard for VDU work. RESULTS: The DHM tool was useful for this case, but the distances of the checklist and the standard were needed to be obtained "manually". The automatic functions of the DHM worked smoothly but were not optimized for VDU work. The prototype fulfilled most, but not all, of the ergonomic criteria of the checklist and the standard. CONCLUSIONS: There is room for improvements of the adjustable ranges of the console prototype. DHMs may facilitate rapid pre-production evaluation of workstations for static work; if ergonomic assessment models for VDU work are built-in, there may be a revival of DHMs in static work situations.
|
|
| 16. |
- Rhen, Ida-Märta, 1975
(author)
-
Development, application, and reliability of methods for ergonomic workload assessments in production evaluation and workstation design
- 2021
-
Licentiate thesis (other academic/artistic)abstract
- Ergonomics assessments of conditions for humans at workstations and in manufacturing processes are necessary to prevent work-related musculoskeletal disorders and enhance efficiency and quality. Many methods can be used for this from systematic observations to direct measurements and simulation. Investigations of the accuracy and reliability of many methods as well as comparisons between them have been performed, but there is still need for further work as well as development of new methods. The inter- and intra-rater reliability of the OCRA checklist was studied through eleven ergonomists’ risk-assessments of ten video-recorded work tasks on two occasions. The statistical analysis included several parameters of reliability of which Cohen's linearly weighted kappa was the primary measure. The inter-rater agreement of the OCRA checklist was 39%, and the weighted kappa was 0.43; the intra-rater dittos were 45% and 0.52. This indicated that the OCRA checklist is a moderately reliable tool. A risk assessment approach for digital human modelling (DHM) was developed. The approach included a reference database of epidemiological relationships between directly measured exposure and related musculoskeletal disorders. For illustration, a case in manual assembly was simulated; exposures were calculated and compared to the reference data to indicate the risk of WMSDs. The application and detailed assessment would be helpful to prioritise among different design solutions. A 3D digital prototype laparoscopic robotic console was ergonomically evaluated using the DHM tool IMMA with 12 manikins representing anthropometries of the Swedish and US population. Work-ranges of the console and the manikins were calculated, compared and ergonomically assessed using the Swedish standards and a US checklist for computer work. The assessment criteria related to the adjustable ranges of the screen height, height of the armrest, adjustable range of the pedals were not fulfilled. The DHM tool IMMA provides the possibility for a pre-production assessment of static work tasks.
|
|
| 17. |
- Rhen, Ida-Märta, et al.
(author)
-
Dynamic wrist exposure analysis of a digital human model
- 2012
-
In: Advances in Human Factors and Ergonomics 2012. - : CRC Press. - 9781466552623 ; , s. 3944-3953
-
Conference paper (peer-reviewed)abstract
- Simulation and visualisation software such as digital human modelling (DHM) tools have been designed to predict and evaluate ergonomics within a virtual environment. Today’s DHM tools typically include observation-based evaluation methods, initially designed for visual observation. Direct measurement techniques enable assessment of quantitative data similar to the information derived from the DHM. Such technique allows detailed and time-dependent risk aspects to be considered in the ergonomics evaluation. No methods in commercial DHM software calculate time-dependent information, which is shown as an important risk factor in the development of work-related musculoskeletal disorder (WMSD). This paper presents and discusses an ergonomics assessment approach based on the theory of a dose-response relationship between exposure and the risk of arising injury. The focus of the approach presented is on the wrist-joint.
|
|
| 18. |
- Rhen, Ida-Märta, 1975, et al.
(author)
-
Ergonomic risk assessment in DHM tools employing motion data : Exposure calculation and comparison to epidemiological reference data
- 2018
-
In: International Journal of Human Factors Modelling and Simulation. - Olney : InderScience Publishers. - 1742-5549 .- 1742-5557. ; 6:1, s. 31-64
-
Journal article (peer-reviewed)abstract
- Digital human modelling (DHM) allows ergonomic risk assessment to be performed at early stages of design and development. Such assessment is typically based on observational methods, which do not take advantage of the potential of DHM tools to provide precise posture and motion data. This paper describes and illustrates an alternative assessment approach employing DHM tools, inspired by risk assessment based on direct measurements. A literature survey established a reference database of epidemiological associations between exposure and wrist-related disorders. This approach is illustrated by a DHM simulation of a car assembly task. Wrist posture and motion were simulated and compared to the database, predicting the prevalence of work-related musculoskeletal disorders on the basis of direct measurements.
|
|
| 19. |
|
|
| 20. |
- Rhén, Ida-Märta
(author)
-
Ergonomics risk assessment methods for creating healthy work environments
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- Risk assessments of ergonomic conditions in pre-production and in field are necessary to prevent work-related musculoskeletal disorders and to increase productivity and quality. Methods for such assessments include simulations, direct measurements and observations. In order to carry out correct ergonomic assessments, which is an important part in the work of creating healthy workplaces, it is vital that these methods are user-friendly, accurate and reliable. However, several methods are insufficiently tested with respect to these factors.The aim of this thesis was to increase the knowledge of some relevant risk assessment methods for the prevention of musculoskeletal disorders. The methods include risk assessments in both planned and existing work environments.A risk assessment approach for digital human modelling was developed. The approach included a reference database of epidemiological relationships between directly measured exposure and related musculoskeletal disorders. For illustration, a case in manual assembly was simulated; exposures were calculated and compared to the reference data to indicate the risk of work-related musculoskeletal disorders. The application and detailed assessment would be helpful to prioritise among different design solutions.A 3D digital prototype of a laparoscopic robotic open console was ergonomically evaluated using the simulation tool Intelligently Moving MAnikins (IMMA); twelve manikins representing anthropometries of the Swedish and US populations were used. The work-ranges of the console and the manikins were calculated and compared. The ergonomics was evaluated using a US checklist and the Swedish standard for computer work. The assessment criteria, which are related to the adjustability of the screen, the armrests, and the pedals, were not fulfilled. The result showed that IMMA, with its built-in functions, provides the opportunity for risk assessment of planned static work tasks. With some improvements, tools like IMMA may increasingly be used efficiently for early assessments of planned products or work environments.The inter- and intra-rater reliability and validity of six observation-based assessment methods, ART, HARM, SI, QEC, OCRA and SWEA, were studied through twelve ergonomists' and an expert group's repeated risk assessments of ten videotaped tasks. The results showed a low to moderate inter- and intra-rater reliability. Both the percent agreement and the reliability differed for the assessments of the methods' overall risk levels. Using a standardised task duration of 3.75 hours (rather than different durations for the different tasks) in the statistical calculations, the reliability of all methods decreased, except for OCRA. The decrease was most evident for HARM and ART, which was due to the fact that the duration of the task has a large impact in the methods' calculation of the total risk level. The validity was similar to the inter-rater reliability for each method.This thesis emphasizes the importance of detailed quantification of exposure and reliable methods to draw accurate conclusions about the risk of musculoskeletal disorders, both in planned and existing work environments.Today's technology, with small and wireless devices for direct measurements and methods for analysing physical exposure, provides opportunities to perform accurate and reliable ergonomic assessments. The possibility of using similar measurement strategies in digital human modelling, allows the discrimination of small differences in exposure which simplifies comparisons of different design solutions as well as between planned and existing work environment. Although the reliability of several observation-based methods was found to be low, observational methods are still important in the risk assessments of physical exposure, in order to include parts of the work environment that are not yet possible to measure. However, observational methods should preferably be used for screening and in combination with technical measurements.
|
|
| 21. |
- Rhen, Ida-Märta, 1975, et al.
(author)
-
Inter- and intra-rater reliability of the OCRA checklist method in video-recorded manual work tasks
- 2020
-
In: Applied Ergonomics. - : Elsevier Ltd. - 0003-6870 .- 1872-9126. ; 84
-
Journal article (peer-reviewed)abstract
- Observation-based risk assessments are often used for evaluation of biomechanical workload and the condition of the workplace ergonomics. However, the inter- and intra-rater reliability of the methods used for the assessments are insufficiently studied. The OCRA checklist method, included as a reference method in the ISO and CEN standards regarding upper limb repetitive risk assessment, was in this study investigated regarding its reliability. Eleven ergonomists were educated within the method. Each ergonomist risk-assessed ten video-recorded manual work tasks, on two occasions. The average inter-rater agreement of the five overall risk levels was 39% and the linearly weighted kappa was 0.43, the intra-rater dittos were 45% and 0.52. Both indicating a moderate reliability, but lower than what could be expected. The levels might be sufficient for coarse surveys. However, for risk assessments before and after an intervention, complementing technical methods should be considered.
|
|
| 22. |
- Rhén, Ida-Märta, et al.
(author)
-
Risk exposure assessment of dynamic wrist motions of a digital human model
- 2011
-
In: Proceedings of NES2011 September 18—21, 2011 Oulu, Finland. - Oulu : University of Oulu. - 9789514295416 ; , s. 386-391
-
Conference paper (peer-reviewed)abstract
- Software tools as Digital Human Modelling (DHM) has been designed to simulate and visualize the human work and to assess ergonomics conditions. No methods in commercial DHM software calculate time-dependent information, which is adequate in defining the relations between exposure and risk of disorders. The paper presents and discusses how an assembly task can be analysed with the help from a DHM-tool. Out comes from the study revealed that it is possible to generate output files with time-dependent wrist exposure data from a manikin in a DHM-tool. However, current evaluation methods do not take time-dependent information into consideration.
|
|
| 23. |
- Rhen, Ida-Märta, et al.
(author)
-
Time dependent exposure analysis and risk assessment of a manikin's wrist movements
- 2011
-
In: Proceedings of DHM, First International Symposium on Digital Human Modeling. - : Université Claude Bernard Lyon. - 9782953951509
-
Conference paper (peer-reviewed)abstract
- The increased computerisation of design and engineering work has led to the development of software such as digital human modeling (DHM) tools. These tools can be used to simulate and visualise human work and for evaluating ergonomic conditions. Observational-based ergonomics methods, such as RULA and OWAS, may be used for characterizing workload and are typically integrated in DHM tools. However, using observational-based methods usually means that ergonomics evaluations are based on assessing static postures, i.e. not taking time-related aspects into account. This is usually also the case when industrial companies choose to customize the DHM software and integrate their own company specific ergonomics methods. Since time-sensitive aspects, such as frequency and angular velocity, are of importance in the ergonomics evaluation, it is necessary to be able to predict these variables also in an early stage of the design process. As observation methods are poor in terms of sensitivity they give rough estimations of ergonomic conditions. Consequently, researchers aim to develop dynamic evaluation methods where also time-dependent aspects, such as repetitiveness, velocity and duration in exposed positions, are considered. The objective of this study is to focus on the assessment of the wrist since a large amount of work related disorders is caused by this joint and also due to the fact that this is a relatively uncomplicated joint to explore from a biomechanical perspective. This paper displays initial findings from the literature for how to adequately and quantitatively assess wrist movements, appropriate evaluation criteria and for how to calculate cumulative load. Moreover, the paper illustrates how time significant wrist exposure data obtained from a DHM may be used for ergonomics assessment. This involves a proposed time consideration concept, based on a combination of modified and established evaluation methods, including suggestions for how to identify fundamental cycles.
|
|
