Analysis of the Foot-Ground Contact Using an MSD-FEM Co-simulation Approach

The development of realistic contact models is essential for simulating and analyzing human motion, reducing the need for physical measurements and expensive equipment. This information is fundamental for understanding the mechanical principles governing human motion and, developing effective and personalized assistive solutions. This work describes a novel co-simulation methodology for the dynamic and structural analysis of biomechanical systems, integrating a Multibody System Dynamics (MSD) formulation with fully Cartesian coordinates and a generic rigid body, with the Finite Element Method (FEM). The MSD formulation is used to perform the inverse and forward dynamic analyses of the entire system, while a nonlinear and nonsmooth FEM software is employed to realistically characterize the contact phenomena between different bodies. The methodology was applied to the evaluation and analysis of foot-ground contact for the static position and during gait. The results of the gait analysis showed contact pressure patterns consistent with the corresponding experimental data. However, discrepancies between the measured ground reaction forces (GRF) and the estimated contact forces are observed, potentially explained by the simplified friction model used and the mechanical properties adopted for the foot mesh model. The implemented co-simulation methodology suggests that the combination of the MSD formulation’s efficiency with the detailed contact analysis of FEM has the potential to become a successful strategy in describing the contact phenomena between complex geometries.