A bio-mechanical designed under-actuated hand and force control schemes

In order to mimic the natural appearance, motion and perception of the human hand, a biomechatronic approach to design an anthropomorphic Under-actuated hand-HIT/DLR Under-actuated Hand has been presented. It reproduces human hand in its fundamental structure such as appearance, weight, dimensions and inertia. Its thumb can move along a cone surface in 3-D space. Similar with humans', it combines with abduction and adduction from palmar position to lateral position. Actuated by only one motor, the mid finger, ring finger and little finger can envelop complex objects. Furthermore by applying dynamics model, the force-based impedance control can realize more accurate and stable force control during grasp. Experiments displays dynamic control can make the finger grasp with more smooth and precise trajectory and stable grasp force, these would be particularly helpful for the widely application of underactuated hand.