A powerful robot in Slovenia has been hitting people over and over again in a bid to induce anything from mild to unbearable pain.
But the robo-battering is all in a good cause, insisted Borut Povse, who has ethical approval for the work from the University of Ljubljana, where he conducted the research, reports New Scientist.
He has persuaded six male colleagues to let a powerful industrial robot repeatedly strike them on the arm, to assess human-robot pain thresholds.
It's not because he thinks the first law of robotics is too constraining to be of any practical use, but rather to help future robots adhere to the rule.
"Even robots designed to Asimov's laws can collide with people. We are trying to make sure that when they do, the collision is not too powerful.
"We are taking the first steps to defining the limits of the speed and acceleration of robots, and the ideal size and shape of the tools they use, so they can safely interact with humans," said Povse."
Povse and colleagues borrowed a small production-line robot made by Japanese technology firm Epson and normally used for assembling systems such as coffee vending machines.
They programmed the robot arm to move towards a point in mid-air already occupied by a volunteer's outstretched forearm, so the robot would push the human out of the way.
Each volunteer was struck 18 times at different impact energies, with the robot arm fitted with one of two tools - one blunt and round, and one sharper.
The volunteers were then asked to judge, for each tool type, whether the collision was painless, or engendered mild, moderate, horrible or unbearable pain.
Povse, who tried the system before his volunteers, said most judged the pain was in the mild to moderate range.
The team would continue their tests using an artificial human arm to model the physical effects of far more severe collisions.
Ultimately, the idea is to cap the speed a robot should move at when it senses a nearby human, to avoid hurting them.
Sami Haddadin of DLR, the German Aerospace Centre said: "Determining the limits of pain during robot-human impacts this way will allow the design of robot motions that cannot exceed these limits."
Povse presented his work at the IEEE's Systems, Man and Cybernetics conference in Istanbul, Turkey.