Experimental assessment of the quality of ergonomic indicators for dynamic systems computed using a digital human model

The growing number of musculoskeletal disorders in industry could be addressed by collaborative robots, which allow the joint manipulation of objects by a robot and a person. Designing these dynamic systems requires to assess the ergonomic benefit they offer. Current assessment methods require physical mock-ups and exclude dynamic phenomena. To perform more thorough assessments, it is proposed to use a dynamic digital human model (DHM) associated with a dedicated ergonomic metric. This paper presents three ergonomic indicators - posture, effort and energy - formulated to meet the requirements of ergonomic evaluations of dynamic systems. Human subjects perform a manual task under different time, load and geometric constraints. Each performance is replayed with a DHM to calculate the indicators. The variations of the indicators are consistent with ergonomic guidelines, and correlate with the strenuousness perceived by the subjects. Moreover, the relevance of an indicator is strongly affected by the task features.