Equilibrium conditions of a rigid object grasped by elastic rolling contacts

This work refers to a planar system of two spherical elastic fingertips grasping a rigid polygonal object under rolling contact constraints at equilibrium. A contact motion model is proposed for elastic-rolling fingertips based on previously reported experimental findings on the rolling distance for a variety of soft materials. The equilibrium conditions are derived from the system dynamics and depend on the deformation and on the kind of elastic material with regard to the fingertip\´s rolling distance characteristics. Equilibrium conditions of the three contacted bodies (elastic fingertips-object) show that in general no-collinear interaction forces act on the object\´s surface and they correspond to the equilibrium of an "internal object" hold by two point contacts with friction.