On the Stochastic Nature of the Reach of People

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On the Stochastic Nature of the Reach of People

Sen., Dibakar / Reddy, Sarath

In this paper the influence of dimensional variability of the arm on the reach in a given operational space is studied. The arm is modeled as a two-linked planar manipulator using the upper and lower arm dimensions from a public domain anthropometric database. The probability of reach for different points is determined assuming independent distribution, dependent distribution, constant proportion and identical percentiles for the two links in the dyad. The computed probability distribution is then used to understand the implication of these assumptions on the interpretation of reachability of points in the operational space by the given population. Results from the dependent distribution are found to be closest to those obtained from raw data. The quality of reach within the workspace is studied using average condition number corresponding to the reach configuration of different individuals at different points in the workspace. The combined effect of the variation in stature and arm dimensions is also studied and found to be substantial. The study would be useful in developing stochastic digital human models for their effective usage in carrying out the ergonomic analysis of man/machine interfaces.