Multi-fingered grasping of planar objects with desired measure of contact stability

A desirable feature in multifingered grasping of the objects is the ability of the fingers to maintain contact without slipping, known as contact stability. Although strong squeezing of the object improves the contact stability it may reduce the whole grasp stability because of measurement errors and uncertainties in the object shape. Therefore, the equilibrium state should be achieved with as weak forces as possible so long as contact stability is maintained for a given class of disturbing forces. In this paper, computational aspects of a measure of contact stability, introduced earlier, is studied in the planar case. Specifying the stability measures for each contact point is an alternative way to deal with force redundancy when two or more fingers are involved in the grasp. In comparison to internal forces, however, stability measures are more intuitive and easier to assign, because they can be directly related to the maximum disturbing force the grasp can withstand.