Assessing the differences between numerical methods, CAD evaluations and real experiments for the assessement of reach envelopes of the human body

Numerical models and computer-aided modeling software are tools commonly used to assess the accessibility of an environment, based on static human body dimensions. In this paper, the limits of validity of these approaches are assessed by comparing the reach envelopes obtained by these methods to those obtained experimentally. First, the accessibility areas of forty adult subjects, which may correspond to the distance of reachability of products, were evaluated by performing an accessibility task comprising 168 reach points. Second, anthropometric characteristics of participants were recorded and used to perform the reach assessment by a numerical method, and then by a CAD-based analysis, where the reach was predicted using the software's maximum reach-envelope generation. In spite of the simple nature of the presented design problem (two-dimensional), the results show important differences between the three methods. The study of the number of reached points shows that the CAD-based assessment provides more accurate results than the numerical model. Nevertheless, the shapes envelopes comparison indicates that the maximum reach envelopes obtained with the CAD analysis are not always consistent with those obtained experimentally, closely linked to the hand location. Results indicate that the CAD model used to obtain maximum reaches gave predictions that underestimate the reach ability.