Towards velocity-dependent nonlinear elasticity of human forefinger soft tissue for specification construction

The impedance properties of the clamped forefinger soft tissue under dorsal contact conditions have been largely overlooked, posing challenges for risk assessment in human-robot coexistence. This study addresses the need for simplicity in elastic modeling to support specification construction. A method for accurately estimating elasticity was proposed, encompassing impact experiment design, nonlinear elastic model development, and subsequent statistical analysis. A total of 117 human participants were recruited to evaluate the effective elasticity of the forefinger soft tissue. Results showed that the proposed three-stage model enabled reliable estimation of tissue response under constant-velocity contact conditions. The tissue's elasticity was dependent on contact velocity but independent of gender and age. Medians and 95th percentile values were summarized to establish a parametric specification. These findings contribute a general approach to the specification of human soft tissues, complement the ISO/TS 15066 standard, and provide valuable insights into machine safety and human-robot interaction research.