This device was designed to act as an additional gripper for the Kuka Youbot in order to attach an ikea table leg for the class 6.142's automated furniture assembly project. The design not only grips the table leg, and turns it with over 3 n-m of torque, but it allows for great versatility - grasping virtually any object small enough. The claw works by having two circles connected by rubber bands, one is a giant gear and is turned directly be a servo, and the other is attached to a fluid- based damper which drags behind the first one. Some of the benefits to this type of claw are that it can grasp very delicate pieces such as glass rods, grasp complex shapes, such as the grip on a screw-driver, and grasp low friction objects.
This shows the youbot holding the claw and using it to attach the table leg.
This is a more detailed picture of the claw, showing its various components.
This is the inside of the fluid based damper. The damper is necessary in order to get the rubber bands started contracting, before they grasp the part. It also helps to make sure that the claw continually holds that piece. In designing it I tried to have steel spheres dragged through oil by a ring of magnets - this idea kind-of worked. I needed to replace some of the spheres with disk magnets to increase the force, and oil leaked everywhere but the idea in theory did work. This picture shows the inside of the damper before it was bolted together.
This shows one of the possible things that the claw can grasp and spin - look in the videos section for many more different objects!