State-Space Characterization of Low-Speed Friction Regimes in Sliding Contact Using a Fixed Self-Organizing Map

A fixed self-organizing map (SOM) is proposed for comparative characterization of low-speed friction regimes. Tangential resistance force signals were processed by onset alignment, zero-level correction, and repeat averaging, and projected onto a SOM trained on a reference dry-contact series. This provided a common state space for comparing wetting conditions and dry materials under the same normal load. State distributions were described using probabilistic SOM metrics, showing that mean resistance and fluctuation activity provide complementary descriptors of friction behavior.