iFEM2.0: Dense 3-D Contact Force Field Reconstruction and Assessment for Vision-Based Tactile Sensors

Vision-based tactile sensors offer rich tactile information through high-resolution tactile images, enabling the reconstruction of dense contact force fields on the sensor surface. However, accurately reconstructing the 3-D contact force distribution remains a challenge. In this article, we propose the multilayer inverse finite-element method (iFEM2.0) as a robust and generalized approach to reconstruct dense contact force distribution. We systematically analyze various parameters within the iFEM2.0 framework, and determine the appropriate parameter combinations through simulation and in situ mechanical calibration. Our approach incorporates multilayer mesh constraints and ridge regularization to enhance robustness. Furthermore, as no off-the-shelf measurement equipment or criterion metrics exist for 3-D contact force distribution perception, we present a benchmark covering accuracy, fidelity, and noise resistance that can serve as a cornerstone for other future force distribution reconstruction methods. The proposed iFEM2.0 demonstrates good performance in both simulation- and experiment-based evaluations. Such dense 3-D contact force information is critical for enabling dexterous robotic manipulation that handles both rigid and soft materials.