“…In detail, F a is the maximum force module and α i,j ∈ (0, 1] is a strictly decreasing sequence of scale factors defined as α i,j (k + 1) = εα i,j (k) (13) α i,j (0) = 1 (14) where ε ∈ (0, 1) and a new value of the sequence is computed every time point z i,j comes out from V. Collecting some terms in the previous dynamic equation of the system, a more compact expression is I,j + k(4 ) = (15) Where, in the expressions, the points with subscript coincides with those with subscripts, respectively. (16) The two poles have to be treated distinctly, due to topological differences, np + (17) For the north pole (np), and sp + (18) For the south pole (sp), (19) Where, is the force vector, is the projection of force , and is the normal unit vector to the surface at point p i . During the action of grasp, the contact points do not always belong to the same plane.…”