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February 9, 2011

Robotic Super Hand

Talk to it.

From IEEE Spectrum:

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German researchers have built an anthropomorphic robot hand that can endure collisions with hard objects and even strikes from a hammer without breaking into pieces.

In designing the new hand system, researchers at the Institute of Robotics and Mechatronics, part of the German Aerospace Center (DLR), focused on robustness.

The DLR hand has the shape and size of a human hand, with five articulated fingers powered by a web of 38 tendons, each connected to an individual motor on the forearm.

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The main capability that makes the DLR hand different from other robot hands is that it can control its stiffness. The motors can tension the tendons, allowing the hand to absorb violent shocks. In one test, the researchers hit the hand with a baseball bat—a 66 G impact. The hand survived.

The DLR team didn’t want to build an anatomically correct copy of a human hand, as other teams have. They wanted a hand that can perform like a human hand both in terms of dexterity and resilience.

The hand has a total of 19 degrees of freedom, or only one less than the real thing, and it can move the fingers independently to grasp varied objects. The fingers can exert a force of up to 30 newtons at the fingertips, which makes this hand also one of the strongest ever built. 

Another key element in the DLR design is a spring mechanism connected to each tendon. These springs give the tendons, which are made from a super strong synthetic fiber called Dyneema, more elasticity, allowing the fingers to absorb and release energy, like our own hands do. This capability is key for achieving robustness and for mimicking the kinematic, dynamic, and force properties of the human hand.

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During normal operation, the finger joints can turn at about 500 degrees per second. By tensioning the springs, and then releasing their energy to produce extra torque, the joint speed can reach 2000 degrees per second. This means that this robot hand can do something few others, if any, can: snap its fingers.

To change its stiffness, the DLR hand uses an approach known as antagonistic actuation. The joints of each finger are driven by two tendons, each attached to one motor. When the motors turn in the same direction, the joint moves; when they turn in opposite directions, the joint stiffens.

The new hand can catch a ball thrown from several meters away. The actuation and spring mechanisms are capable of absorbing the kinetic energy without structural damages.

But the hand can’t always be in a stiff mode. To do manipulation tasks that require accuracy, it’s better to have a hand with low stiffness. By adjusting the tendon motors, the DLR hand can do just that.

To detect whether an object is soft and must be handled more gently, the hand measures force by keeping track of the elongation of the spring mechanisms.

About 13 people have worked on the hand; the hardware for one would cost between 70,000 and 100,000 euros.

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[via Microservios]

February 9, 2011 at 10:01 AM | Permalink


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