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Www.Wired.Com - : Image courtesy VintagecomputerFor centuries, people have used the human body, and the hand in
particular, as an inspiration and blueprint for engineering
innovations.
But copying the human hand hasn't been easy. Its complex muscular and
skeletal structure offers a unique, tricky balance: It is dexterous,
stable and precise, but also fast moving, strong and flexible.
Despite the challenges, makers of robot hands have called on a host of
innovations from a variety of disciplines to bring us closer to fully
automated hands.
Considered to be the first working robot hand, the Handyman, developed in 1960 by General Electric's Ralph Mosher, was a two-fingered, heavily jointed claw that set up the foundation for later hands.
The design looks rudimentary now, but the five-pivot segment design in each finger was innovative in its attempt to replicate the human hand's flexible joint structure. A human hand is made up of a set of rigid links (bones and muscles) connected at joints. Each joint can have one degree of freedom (hinging or sliding) or two (rotating or cylindrical). We have four degrees of freedom in each finger, giving us enormous flexibility and the ability to make complex motions.
The Handyman's fingers had three degrees of freedom. But it was the attached mechanical forearm that provided most of the wrist action, as mechanical "tendons" pushed and pulled on the fingers. A technician had to manipulate the hand by placing his arm inside the apparatus like a puppet.
The Handyman's capabilities were limited: It could pinch and hold, but had no sensitivity to what it was holding, limiting it to clawing indiscriminately at things.
: Image courtesy University of RochesterBuilt to study the reaction times of robot muscles, the Utah/MIT hand, built in the early 1980s, is a tendon-based (forearm) system. Electric signals are sent to the knuckles through a complicated cable setup, where one tendon moves each joint, as opposed to the dueling and matching motors of earlier models.
The tendon system was precise because air cylinders allowed knuckle sensors to monitor the angle of the fingers, as well as the tension in the wrists. In addition, the tendons were strong and made the fingers move much faster than previous versions -- the seven pounds of force exerted at the fingertip was the strongest at the time.
But that power sacrificed control and range of the whole hand. If you wanted to move it with any regularity, you had to set up a complicated plan to move the 288 pulleys.
: Designed in the early 1990s by Mark Rosheim, the Omni-Hand is dexterous, rugged and hand-powered by an electric gearbox in the palm. It also was the most life-like and reliable hand that NASA made in the '90s. The space agency's researchers even put a glove on it.
Like the human hand, closing and opening the fingers together laterally (as if you're making Spock's 'V' sign, also known as adduction and abduction) was made possible by a ball-and-socket joint design. This design was also used in the wrist, which enabled pitch (at 110 degrees) and yaw motions (at 70 degrees). Also, each knuckle had built-in stops that limited backwards movements, or hyperextension, just like human fingers.
By using the palm's gear box for sensor placement, tendons became unnecessary and led Rosheim to use stronger hinge materials, like double bearings supporting stronger motor shafts, and he placed flexible sensor wires near the fingers. Finally, every finger was the same as any other, so they could be easily replaced one at a time.
: Photo: Courtesy Gabriel GomezBy 2007, scientists had developed the technology of robot hands to such a degree that they could attach a robot hand to a human forearm. Much of recent research has been split between developing hand dexterity and bridging the connection between flesh and machine.
The robotic hand created by the University of Tokyo's Hiroshi Yokoi is such an arm, and it is tendon-based, similar to the Utah arm. But this time, the tendons don't drive the movements. Instead, the wire currents inside the tendons do the job.
The Zurich/Tokyo hand has 13 degrees of freedom, and each finger is laced with powerful sensors that give it specific joint commands, enabling it, for instance, to simultaneously set a 75-degree angle for one finger and set a specific pressure for another. When the hand was finally attached as a prosthetic device, electromyography signals were used to "interface the robot hand non-invasively" to a male patient. To mimic the tactile feedback of a real hand, scientists sent electrical stimulation through the wires to the test subject's own (organic) sensor and motor system.
: Photo: Glenn MatsumuraThe BH8 BarretHand, built in 2007, is a three-fingered programmable "grasper" known for its great flexibility. Two of the multijointed fingers rotate around the palm (at 180 degrees), and switch positions easily, giving the hand two opposable thumbs.
The hand has its own processor and is controlled by a PC through a serial port. It's also completely self-contained and quite durable, which means scientists no longer have to worry about the force of the tendons or the grippiness of the fingers. It also comes with a clutch mechanism that determines the strength of the grasp.
Robotics experts at Stanford are currently using the BH8 for their Stair 2.0 autonomous robot project, fetching everything from wine glasses to toothbrushes through speech-recognition techniques.
: Image courtesy TouchbionicsThis $65,000 prosthetic robot hand has supersmall motors and five fully articulated digits powered by a two-input myoelectric signal. Doctors place electrodes on the surface of the hand's "skin," which connects to the electrical signal generated by muscles in the remaining portion of a patient's limb.
The i-Limb enables different grips that had not been available to amputees before, such as the key grip (thumb to index finger), and power, precision and index grips (the "we're #1' grip.")
But its realistic dexterity isn't the only good thing about it. Fingers can be easily swapped out with one another, which makes servicing a little bit easier and less expensive.
: Image courtesy SensopacCreated by the EU-funded SENSOPAC group in 2005, the "Robo Habilis" is managed by a software program modeled on the human cerebellum. Now we're really getting somewhere.
An advanced software program coordinates sensations and movements picked up by the hand, getting us a bit closer to intelligent, self-aware robot arms. The SENSOPAC is also covered by sensitive skin made out of a thin, flexible carbon-based material whose resistance changes with pressure. This allows hundreds of tiny sensors to be used as the hand's main information conduits, providing more detailed information on a touch or grip than ever before.
In addition, the attached arm has 58 motors (in opposing pairs) that it uses to create a large range of force. The fingers have 38 opposing motors, allowing it to snap its fingers and even pick up an egg without breaking it.
: Kamen created the Segway, an invention so far ahead of the game that it makes its users look, well, rather dorky. Not so with his robot arm.
Kamen's arm is light-years ahead of the clamping "claws" amputees are used to. It's a fully articulated appendage, with flexible joints and detailed user manipulation called "Gen X - Separate Exo Control." It gives the user the same range of motion (14 degrees of freedom) as a natural arm, and is sensitive enough to pick up a piece of paper, a wineglass or even an olive in a martini.
: The Anatomically Correct Testbed (ACT) hand is all about the accuracy of the human hand's bone/muscle/nerve structure. Yoky Matsuoka, director of the Neurobotics Lab at the University of Washington, designed the autonomous ACT hand to respond to sensors that mirror the brain's neural commands. To do so, she created neuromusculoskeletal copies of the arm's anatomy, including tendon insertion points, specific bone shapes and weight, and supersmall motors that duplicate muscle contraction behaviors. As a result, it is the most human-looking and -moving arm out there.
Like the Handyman and the Utah/MIT hand, the ACT is based on cable "tendons," but those tendons are arranged and attached in a much more human-like manner, giving it a full range of motion.
There's also an uncommon focus on the palm, which is about as important to the human hand's multifaceted nature as its fingers.
: Image courtesy ElumotionThe Sheffield Hand, built in 2002, focuses on the development of "artificial muscle" and sophisticated joints. Powered by telescopic rods throughout the palm of the hand, fingers are pulled and bent in a rotating motion. But it's the detailed phalanges that make it one the most flexible hands and arms, through simple cylindrical disks that produce realistic abduction and adduction.
The hand includes haptic sensors and its hard plastic muscles mimic the flexibility of real human arms. In the process of testing, the scientists conducted arm-wrestling contests between a human and three different versions of the arm.
The Sheffield was also used by NASA's Jet Propulsion Laboratories as a early prototype for the Discovery space mission's 50-foot arm.
: Photo: Jon Snyder/Wired.comYes, this hand looks like it's about ready to start sewing up your undies. But it's actually a very sophisticated Intel project that smartly senses the shape of objects through the magic of electrolocation, used by sharks and other marine animals to detect objects and prey via faint electric fields.
Called the "Shark Hand" or "The Sixth Sense" because of these sonar-like powers of perception, the tips of its fingers emit an "electrical impulse" that detects objects and gives the hand an sense of the shape of objects it is about to grasp.
The hand is part of a larger Intel project on "Pre Touch" technologies, where robots are being laced with internal sensors that are more long-range than the sense of touch, but more short-range than vision.
Check out the video of Wired Science's Alexis Madrigal and Intel researchers playing with the Intel shark hand.
: Image courtesy Shadow RobotThe Shadow Hand has integrated sensors all over its palm and fingers, and can be controlled by different computer systems, which is why several university robotics programs and private contractors are using it. It even has a network option, which means you can torture your coworkers with crazy hand gestures even when you're taking a sick day.
But it is special because it's got more moves than a Moonwalker-era Michael Jackson. Its integrated bank of 40 "Air Muscles" allow it to perform 24 different, large-angle moves, and the fingertips are so sensitive that they can even detect a quarter on the floor. Not only that, but the muscles are soft and acquiescent, which allows it to play with soft and fragile objects.
: Despite almost 50 years of development, these hands are only the beginning. Like notebook computers and MP3 players before them, robot hands will get tinier and ever more complex.
Intuitive Surgical's EndoWrist Instruments are small surgical tools, with 5 mm- and 8 mm-diameter options. With seven degrees of freedom and 90 degrees of articulation, they are the most precise robotic appendages in the medical world. They are widely used by surgeons because they improve the surgeons' own world-renowned dexterity and allows them to perform minimally invasive surgery through teeny incisions.
A doctor manipulates the hand through fingertip controls from a few feet away from the patient, looking into a micro lens. It's hard to believe, but the Endowrist is also strong, and it can handle a variety of forceps, needle drivers, scalpels and any other things needed to cut up a person carefully and safely.
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