Shadow Hand
From Wikipedia, the free encyclopedia
The Shadow Dexterous Hand is an advanced robot hand system that reproduces all the movements of the human hand and provides comparable force output and sensitivity. It was first developed by The Shadow Project. This was a research and development programme, managed by Richard Greenhill, whose goal was to develop a complete humanoid robot. The project evolved into a company, The Shadow Robot Company, where the engineers successfully keep improving the Hand. The Shadow Dexterous Hand is commercially available and currently used by NASA, The University of Bielefeld and Carnegie Mellon University.
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[edit] Form factor
The Shadow Dexterous Hand has been designed to be as similar as possible to the average hand of the human male. The forearm structure is comparable in length to the human forearm, although at the base it widens to 146mm.
[edit] Degrees of freedom
The Shadow Dexterous Hand has been designed to have a range of movement equivalent to that of a typical human hand.
The four fingers of the hand contain two one-axis joints connecting the distal phalanx, middle phalanx and proximal phalanx and one universal joint connecting the finger to the metacarpal.
The little finger has an extra one axis joint on the metacarpal to provide the Hand with a palm curl movement.
The thumb contains one one-axis joint connecting the distal phalanx to the proximal phalanx, one universal joint connecting the thumb to the metacarpal and one one-axis joint on the bottom of the metacarpal to provide a palm curl movement.
The wrist contains two joints, providing flex/extend and adduct/abduct.
This means that that the Shadow Dexterous hand has 24 joints all together, with 20 degrees of freedom.
[edit] Actuation
The movements of the hand are powered by a set of 40 Air Muscles in the forearm. The flow of air into and out of each muscle is controlled by eighty valves, also in the forearm. This is done based on the information gathered from the joint sensors.
[edit] Sensing
The hand contains 234 sensors in total.
Position: To determine the position of the fingers, the thumb and the wrist all 24 joints are equipped with a Hall-effect sensor, detecting the angle of the joint.
Touch: Each finger and thumb includes 34 analog tactile sensors in the distal phalanx providing the Hand with even more sensitivity.
Muscle: To determine the pressure in the Air Muscles, each one contains an air-pressure sensor. Combining the information of these two sensors makes it possible to control the stiffness of the Hand.
All data from the sensors are transmitted on a CAN bus, to be read by a host computer, or other parts of the hand system.
[edit] Features
Since the Shadow Dexterous Hand is intended to recreate the functionality of a human hand, it contains several other features that aren't seen in similar robots.
Soft Skin: The fingers and thumb are coated with a soft, but hard wearing layer of Polyurethane. This gives the fingers a reliable grip, and is reported to be pleasing when touched by a human.
Fingernails: Humans use their fingernails for several manual tasks: starting a roll of sellotape, operating small buttons and picking up small objects. Each finger and thumb of the Shadow Dexterous Hand has a fingernail made from Polycarbonate.
[edit] History
The Shadow Dexterous Robot Hand is the first commercially available robot hand from the company, and follows a series of prototype humanoid hand and arm systems. The earlier prototypes were built to study the kinematics and essential features required of such a robot.
