If you threw a bottle, a hammer, and a tennis racket at a typical robot arm, you'd end up with a broken robot arm. Not so with this new mechanical limb invented by Swiss researchers: The device can catch all kinds of flying objects thrown in its direction, reacting in less than one-twentieth of a second.
The robot arm is about 5 feet long, with three joints and an intricate hand featuring four fingers. The researchers at the Swiss Federal Institute of Technology in Lausanne say the device can play catch with projectiles of various irregular shapes. Intriguingly, the inventors did not program their machine with specific instructions on how to catch different objects. Instead, the robot simply imitated how people caught.
Catching a ball is one thing—it's symmetrical and flies in a predictable path. But with a hammer or a racket, the part a human or robot hand wants to catch, the handle, does not always correspond to the center of gravity. In addition, in the case of a half-full bottle in which fluid is sloshing around inside, the center of gravity of an object can shift as it hurtles toward you. These objects not only represented complex shapes, but complex trajectories in space as well.
The robot has a series of cameras located around it to help it model how objects move through space. The researchers first tossed objects several times in the arm's direction so it could learn how to predict their behavior. Next, they manually guided the arm to projectiles a few times so it could imitate how people caught those projectiles and where they grasped them.
In experiments, the robot could position itself to catch items on the fly in just hundredths of a second. In the final milliseconds of the object's approach, the arm refined and corrected its movements for a high-precision capture, synchronizing the movements of its hand and fingers.
This work could help robots not only to catch items, but also to dodge objects if needed — say, a robot car dealing with traffic or pedestrians. The researchers suggest robot arms might not only catch people who are falling or catch objects that might fall on people, but could also serve on spacecraft to help them recover and dispose of debris orbiting Earth.