Normal and Tangential Force Decomposition and Augmentation Based on Contact Centroid

This study presents a simple but effective approach to extract and selectively augment normal and tangential force components from a reaction force when a user interacts with a real object using a probe. The approach first approximates the behavior of a contact area with a single representative point, i.e., contact centroid. We use it to decompose the reaction force into a normal and a tangential force component. For augmentation, the two components are selectively amplified or diminished. For demonstration, we applied the approach in a breast tumor palpation scenario, where inhomogeneity due to hard nodules is amplified for better detectability of abnormality.