Friction and Deformation Behavior of Human Skin During Robotic Sliding Massage Operation

This study investigates the friction and deformation behavior of the skin in contact with a rigid massage ball and its influencing factors. Pressing and stretching experiments were conducted using a collaborative robot experimental platform. The experiments encompassed a loading normal force range of 2 N to 18 N and a sliding speed range of 10 mm/s to 20 mm/s. The friction response curve exhibits two different stages: static stick state and dynamic stick-slip stage, both of which have been mathematically modeled. By analyzing the experimental data, we analyzed the effects of elastic modulus, sliding speed and normal loading force on skin tangential friction and tensile deformation. The results indicate that as the normal load increases, both friction and deformation exhibit an increase. Conversely, they decrease with an increase in elastic modulus. Notably, while deformation diminishes with higher sliding speed, friction force remains relatively unaffected by velocity. This observation can be attributed to the strain rate sensitivity resulting from the viscoelastic characteristics of the skin under substantial deformation. This study advances the understanding of friction and deformation behavior during skin friction, offering valuable insights to enhance the operational comfort of massage robots.