Washington, Nov 8 : Scientists have invented a robot which is capable of sensing when it hits someone.

The robot has been made by a research team at the German Aerospace Centre Space Agency (DLR) and is aiming to transform industrial robots from insensitive drones into smart machines that can work alongside humans.

The need for such robots arose after the inability of automated machines to respond to accidents at car factories.

In these car factories, if a person breaches a barrier, sometimes an alarm sounds and the robots stop. But if someone is hit, the robots just move on completely unaware. This led to speculations that an industrial robot could trap or crush a person by being unaware that it had hit them.

Researchers concluded that the next step was to give a robotic arm the ability to detect an impact and react appropriately.

For the first model, scientists used a system similar to specialised stretch receptors in muscles and joints of human beings, which makes them feel the shock of a blow.

Thus, the research team gave the robot arm the same "kinaesthetic" sense by embedding torque sensors in each of its six joints. Made from a collection of metal foil devices that change their electrical resistance when under tension in a particular direction, they give constant feedback on the direction and magnitude of the forces felt by the arm.

In order to see the effectiveness of the new invention, scientists recorded the pattern of torque changes the robot arm feels during normal activity and programmed it to stop moving if it senses something unexpected.

Haddadin, a member of the research team, then put the arm to test, allowing it to hit him in the stomach, chest, forehead and arm at speeds of up to 2.5 metres per second. It performed as expected.

"Once it has stopped, the arm uses its motors and torque sensors to support its own weight. This ensures it doesn't keep moving due to gravity or inertia and cause further harm. Then the arm can simply be pushed aside," said Haddadin. "You give it a push and it just floats away. It feels like it weighs only a few grams," he added. The robot also feels the direction it is being pushed in and uses its motors to help out.

The arm also uses its torque sensors for more sophisticated responses. The direction of an unexpected movement allows it to differentiate a co-worker's guiding hand from an unintended collision, preventing it from stopping unnecessarily.

Meanwhile the magnitude of the movement allows the robot to tell the difference between a big hit and a soft collision. It responds to the latter with a gentle nudge that signals 'get out of my way' to its human co-worker.

"Combining human and robot skills could help a range of industries unable to benefit from existing robots", says Ken Young, who works on industrial robots at the University of Warwick.

Such arms could find uses outside factories too, such as in the home. Also adding magnets and magnetic sensors that track position would allow the arm to perform new factory tasks such as moving objects together.

"What's more, a robot with a feel for its work could speed up the assembly of its own kind," says Haddadin.

A commercial version of the arm will be launched next year by robot manufacturer Kuka of Augsburg, Germany. (ANI)