To teach a robot how much pain humans can withstand, robotics experts at the University of Ljubljana in Slovenia are experimenting with robotic limbs that punch them in the arm.

A robot doesn't know how much pressure or force stands between touching a human and injuring them, so when trying to adhere to Isaac Asimov's First Law of Robotics, it might shy away from humans entirely.

So now a powerful, industrial robot, borrowed from Japanese production firm Epson, is on the front line of human-robotic interaction to remedy that dilemma -- instead of assembling vending machines, it's pushing, pummelling and attacking six scientists' outstretched arms.

Each volunteer is struck 18 times at different speeds, intensities and impacts, and sometimes with the robot arm wielding a blunt and round object, or a far sharper one. In the extreme cases where the attack could be especially dangerous, an artificial arm was used. After each collision, the researcher would tell the robot just how painful the attack was, ranging from painless or mild discomfort, to horrible and unbearable pain.

Ultimately, the research will be used to limit the speed of a robot when it senses a nearby human, so any interaction or collision, purposeful or accidental, won't injure them.

Conducting robot-human safety research is vitally important for the inevitable robot uprising. Earlier this year, Wired.co.uk reported on a project in Germany that made a knife-wielding robot disengage if it detected soft, human flesh beneath its blade.

Being punched or stabbed by robots doesn't sound like our idea of fun, but at least someone's putting their well-being on the line for the rest of us.