Högskolan i Skövde

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.