WHISG - A wearable hand to investigate passive stiffness in grasping

Abstract

Wearable robotic hands allow the partial recovery of hand functionality in amputees, and also allow users to investigate the capabilities of the hands. In fact, the human can use his intuition to locate the hand in an optimal position in order to reliably grasp any object. The influence of variable passive stiffness on grasping is rarely explored in the design of hands, since the DLR Awiwi is the only existing hand that provides variable stiffness actuation. However, this hand is not portable due to its weight, and consumes too much energy to be driven by battery only. This work introduces the WHISG hand, a three-finger hand that uses the same variable stiffness concept as the Awiwi hand, combined with low cost servo actuators and rapid prototyping parts, leading to a light, cheap, and robust platform for grasping experimentation. The user can place the portable hand in a convenient position with respect to the object, and can choose the grip stiffness using an adjustment wheel. A trigger is used to initiate the grasp, and fingers are closed while allowing their adaptation to the object shape. Then, the hand sets the chosen stiffness for a reliable grasp.