Many ground breaking dexterous robot hands have been developed over the past two decades. These devices make it possible for a robot manipulator to grasp and manipulate objects that are not designed to be robotically compatible. While several grippers have been designed for space use and some even tested in space, no dexterous robotic hand has been flown in EVA conditions. The Robonaut Hand is one of the first under development for space EVA use and the closest in size and capability to a suited astronaut's hand.
Robonaut's hands will be able to fit into all the required places and operate EVA tools like this tether hook. Joint travel for the wrist pitch and yaw is designed to meet or exceed the human hand in a pressurized glove. The hand and wrist parts are sized to reproduce the necessary strength to meet maximum EVA crew requirements. EVA space compatibility separates the Robonaut Hands from many others. All component materials meet outgassing restrictions to prevent contamination that could interfere with other space systems.
Parts made of different materials are toleranced to perform acceptably under the extreme temperature variations experienced in EVA conditions. Brushless motors are used to ensure long life in a vacuum. All parts are designed to use proven space lubricants.
Each Robonaut Hand has a total of fourteen degrees of freedom. It consists of a forearm which houses the motors and drive electronics, a two degree of freedom wrist, and a five finger, twelve degree of freedom hand. The forearm, which measures four inches in diameter at its base and is approximately eight inches long, houses all fourteen motors, 12 separate circuit boards, and all of the wiring for the hand.
The hand itself is broken down into two sections : a dexterous work set which is used for manipulation, and a grasping set which allows the hand to maintain a stable grasp while manipulating or actuating a given object. This is an essential feature for tool use. The dexterous set consists of two 3 degree of freedom fingers (pointer and index) and a 3 degree of freedom opposable thumb. The grasping set consists of two, 1 degree of freedom fingers (ring and pinkie) and a palm degree of freedom. All of the fingers are shock mounted into the palm.