Driving-point mechanical impedance of the human hand-arm system: synthesis and model development

Abstract

A synthesis of the measured values of human male hand-arm impedance characteristics reported in the literature has been performed. The driving-point mechanical impedance data of the human hand-arm grasping a vibrating handle has been compared to highlight the various similarities and differences among the data. Unexplained differences among the results of various studies, conducted independently under nominally equivalent measurement conditions, led to the exclusion of outliers from the analysis. The most probable values of impedance phase and magnitude are defined by lower and upper envelopes of the mean values of the accepted data sets. The mean of the data sets, together with the smoothened envelopes, are used to define the target and range of idealized values of the X h, Y hand Z hcomponents of impedance in the 10–1000 Hz frequency range. A pooling of results from different studies suggests that there is a small dependence of the X hcomponent of impedance magnitude on the hand grip forces. The dependence of the phase of the corresponding impedance component on the hand grip force, however, is insignificant. There is insufficient data from independent sources to establish a dependence of other components of impedance on the hand grip and thrust forces. A four-degrees-of-freedom, lumped parameter model is derived to fit the target impedance magnitude and phase values using a constrained optimization algorithm. The predicted values correlate well with the target values in the selected frequency range.