In the context of geometric Impulsive Mechanics of systems with a finite number of degrees of freedom, we model the roughness of a unilateral constraint ${ \mathcal S\/}$ by introducing a suitable instantaneous kinetic constraint ${ \mathcal B\/}\subset { \mathcal S\/}$. A constitutive characterization of ${ \mathcal B\/}$ based only on the geometric properties of the setup and on the dry friction laws can then be introduced to model the frictional behavior of ${ \mathcal S\/}$ in an impact of the system. Such a model restores determinism and avoids the analysis of frictional forces in the contact point, with all its associated theoretical problems of causality. Three examples of increasing complexity, showing a natural stick--slip behavior of the impact, are presented.
Categories: math-ph math.MP