Simulation and impedance control of the grasping of a spherical object with soft contact surfaces

Soft- tips, in human fingers, plays a great role in object grasping; specially, when we talk about isotropic and elastic matters. By other word, stability of a typical grasping is really dependent on contact conditions. Well, rolling is the type of constraint approached by this feature and focused in this paper. Grasping an elastic sphere-formed ball by a pair of soft-tip parallel fingers is presented. For starters, by modeling objects as a mass-spring system, dynamic and kinematic systems of equations are derived. Then, a position-based impedance control is developed for the supposed system. To implement and validate the suggested controller, a pair of soft-tip fingers, holding an elastic ball, simulated in ADAMS; this software begets a control block in the Simulink software as a plant of the control system. As a consequence, the process of grasping under the effect of controller can be simulated in real time. The result of the simulation shows the ability of controller in appropriate tracking fingers till making contacts with ball and more importantly, by graphs, stability of grasping is guaranteed.