Researchers at the Institute of Robotics and Mechatronics, part of the German Aerospace Center (DLR), have created what may be the toughest and strongest robotic hand ever made. The fingers can exert a force of up to 30 newtons at the fingertips, and is tough enough to withstand repeated blows from a hammer, as shown in the video below.
The hand is fully anthropomorphic, with five articulated fingers powered by a set of 38 tendons, each attached to a individual motor encased in the forearm. The full DLR Hand-Arm System "mimics the kinematic, dynamic and force properties of the human arm using variable passive compliance actuators" and has a total of 52 drives and more than 100 sensors.
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 operate the hand, the researchers use special sensor gloves or simply send grasping commands. The control system is based on monitoring the joint angles. It doesn’t need to do impedance control, says Markus Grebenstein, the hand's lead designer, because the hand has compliance within the mechanics.
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.
“In terms of grasping and dexterity, we’re quite close to the human hand,” he says
Robert Heinlein directed our attention to robotic hands in his 1956 novel The Door Into Summer. When designing Flexible Frank, the all-purpose robot, great attention was paid to the manipulators provided to the robot:
Hands I could order from the atomics-engineering equipment companies who supplied Hired Girl's hands, only this time I would want the best, with wide-range servos and with the delicate feedback required for microanalysis manipulations and for weighing radioactive isotopes...
(Read more about Heinlein's robot hand)