"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," Borut PovÅ¡e says. "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."
Seriously, I could quote from this article all day:
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.
"Oh it's horrible. Don't get me wrong, it's absolutely horrible, this pain from the punching robot. But I'm not yet prepared to call it unbearable."