Underactuated hand with passive adaptation

This paper proposes an underactuated hand with passive adaptation. Although a passively adaptable hand can grasp an object reliably, most hands with passive adaptation can perform only the power grip due to their power transmitting mechanism. In real applications, however, various poses for grasping are necessary and an active control of fingers with motors should be performed in some cases. To cope with these limitations a 4-DOFs(degree of freedoms) hand with passive adaptation was developed. A wire-pulley mechanism was adopted to enable the passive adaptation and was verified with a 1-DOF hand. To enable both power and pinch grip two wire-pulley transmissions are equipped at the palm. Balancing motion is enabled by rotating the thumb in the normal direction to the palm. The hand can be spread out to grasp a large object. Various experiments have shown that reliable grasping can be obtained with the proposed hand.