A review of modeling of soft-contact fingers and stiffness control for dextrous manipulation in robotics

Dextrous manipulation involves a variety of subjects in robotics, including kinematics, rolling and sliding, contact mechanics, grasping planning and optimization, dynamics, and control. It is generally postulated in the literature that contacts in all grasping and manipulation are point contacts or soft contacts. The former can be modeled as either a frictionless point contact or a frictional point contact; the latter, although being a more practical model, has not been commonly utilized. In this paper, the recent progress in the modeling of dextrous manipulation utilizing soft contacts and stiffness control is presented. The result augments the well-known Hertzian contact model from linear elastic contacts to soft contacts. In addition, recent discovery of the conservative congruence transformation (CCT) for stiffness control in robotics, that are often used in dextrous grasping and manipulation, is presented.