A joint-selective robotic gripper with actuation mode switching

Robotic grippers in research and industry make constant trade-offs between payload capacity, dexterity, cost and performance. We try to address all these problems together by developing a dual mode gripper that can switch between a fully actuated precision mode and a grasping mode. In the underactuated grasping mode, the gripper digits conform to the shape of an object and then switches to the fully actuated precision mode, where each joint is individually locked, leading to a fully actuated gripper for handling the grasped object, thus amplifying its payload capabilities. A design concept is presented that combines all planned requirements-a moderate dexterity, a high force and a compact design of the control unit. This concept is based on a frictional locking of the joints via electromagnets. The resulting gripper was rapidly prototyped and tested for the following characteristics: flexibility in operational environments, payload capacity, accuracy and repeatability of operation. This prototype gripper can grasp objects with a force of up to 70N under active control of all degrees of freedom.