It doesn't take long for humans to learn knife safety. From an early age, parents drill into the kids that knives are sharp and if you aren't careful you can cut or stab yourself. One significant cut with a knife also serves as a significant learning experience for most people. Robots don't benefit from parenting so it's up to researchers to help train robots how to use knives safely around humans.
Researchers from Cornell University are using human trainers to help teach robots to not make stabbing motions with knives around humans. The researchers created a video showing a robot checking out items at a grocery store, including a knife.
In the first sequence, the robot passes the knife very close to the human standing in the checkout lane. The video shows the human trainer hitting a large stop button when the robot gets too close to him with the knife and readjusting the robotic arm. The robot then updates its heat maps that show how close it is to the human and tries the process again.
Over a process of trial and error, the human is able to teach the robot how close they can get with a knife without scaring or hurting humans nearby. The learning algorithm used in the robot allows the researchers to teach the robot in small increments and refine its trajectory over time. The robot can also learn a different trajectory for different types of items. That would mean the robot to learn that it has to be more careful with a carton of eggs than it does with a box of cereal.